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Buick Grand National Charging issues Pages: 12

mad_trbo on Wed June 23, 2010 4:19 PM User is offlineView users profile

Year: 1987
Make: Buick
Model: Regal
Engine Size: 3.8
Refrigerant Type: R134
Ambient Temp: 90
Pressure Low: 30psi
Pressure High: N/A

I recently got my A/C up and running. I performed a retro to r134a and thought I had everything working well.

My original installation involved charging the system with approximately 2.7lbs of r134a which resulted in a low side reading of 30-31psi, unfortunatley I never got a high side reading.

I took about an 1.5 houe long trip with the A/C running the entire time, vent temperature started out at 39 degrees or there about and after about one hour the temperature started creeping up. it creeped Until it reached 55 degrees. We reached our destination after 1.5 hours of travel with the reading of 55 degrees at the vent. Trip home same results started out cold and faded to about 55 degrees.

I put the guages on the car when I got home and I couldn't get a high side reading and now I don't recall my low side reading. At any rate I found my retro fitting was causing the problem on the highside(not allowing the manifold guage to depress the schrader) so I installed another fitting at which time I heard the schrader valve leaking. So I went to replace the valve only to find a portion of the valve remained in the line. I worked that out and charged the systme back up only to have the compressor continuously cycle on and off. I figured I wasn't getting enough charge so I bridged the low pressure cycle switch inlet.

With this low perssure was dropping down to 10 - 15 psi and I noted the expansion tube frosting heavily with no coolness to the evaporator outlet and suction line like usual. Highside was about 210 - 220.

Ambient temp had to be low to mid 90's.

What hole have I dug myself into.

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

Edited: Wed June 23, 2010 at 4:19 PM by mad_trbo

padgett on Wed June 23, 2010 6:56 PM User is offline

a) sounds like you have lost some 134, at 90+F low side should be in the 30-40 psi range, high 220-270. Cycles should be at least 15 seconds on but if you have shorted the low switch it may not be cycling at all.

b) but cold when starting out and creeping up as you drive, then cold again in morning sounds like not enough air frow across the condenser, are your fans working properly ? Is anything obstructing the air flow ? Lower air dam missing ?

c) even further out would be a creeping hot/cold diverter valve

but first correct the freon level.

Many Carpets

mad_trbo on Wed June 23, 2010 7:48 PM User is offlineView users profile

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

mad_trbo on Wed June 23, 2010 8:05 PM User is offlineView users profile

More information on my current status.

I drew the system down to the requisite 29 inhg and held it there for a period extending beyond 3 hours.

I then hooked up a 30lb bottle of r134a with the system off and high side closed. The car off and low side opened up I let the system draw in the freon. It stopped at approximately 70 psi both sides(lo/hi) close to being equal.

Ambient temperature around 90 degrees.

I turned the car on with the a/c on high. The compressor cycling frequently, the evaporator inlet tube slightly cool to the touch while the evaporator outlet tube is equal to ambient temp.

I manually cycle the compressor on so it stays on.

I see a low side pressure of 5 psi and a highside of 150 psi. Again the evaporator inlet tube freezes up under this condition and I get very little temp change on the outlet evap tube. Interior temp doesn't change...

I am thinking I am low on freon but I am leaving the freon flowing waiting for the sytem to pull more in. What am I missing, I am way off in left field I know.

Odd is I had the system working fine at least for short trips.

To answer previous questions,

I am using a FAL fan system number 298 which claims it moves over 4600 cfm. Has no problem keeping the car at no more than 195. But like mentioned I was getting below 40 and that was while sitting at idle.

The fans are continuously running when the air is on.

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

HECAT on Wed June 23, 2010 9:34 PM User is offline

So you charged into a vacuum until the vacuum decayed. 70 psi is meaningless other than it is enough for the pressure switch to allow the compressor run and suck the remainder of the proper charge in. Your cylinder is on a scale, right? System performance and diagnostics are useless without the proper full charge (weight) of refrigerant installed.


HECAT: You support the Forum when you consider for your a/c parts.


Edited: Thu June 24, 2010 at 6:23 AM by HECAT

mad_trbo on Thu June 24, 2010 7:28 AM User is offlineView users profile

I'll be honest and I am probably trying to be to smart for myself.

I don't have a proper scale, so I theorized I should be able to charge the system based on the results obtained on the manifold guages. Everything says I should see about 30-35psi on the low side and 2 to 2.5 times ambient on the high side. Can I not use this method charge until the guages read properly according to the properties of the freon?

Shouldn't the system pull a charge with the compressor running until it gets to a point where it doesn't cycle? As previously mentioned it doesn't seems to be pulling in the freon??

I used this method before and the car cooled well upto an hour on the road and then the cooling ability began to degrade.

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

NickD on Thu June 24, 2010 7:52 AM User is offline

For a Buick Grand National, problem would have been better off to use "Freon", DuPonts tradename for R-12. Typically for an R-134a conversion the amount of R-134a used is 90% of the recommended Freon. R-134a does have better heat conductive properties and you may learn your tube and fin condenser can't handle this addition heat, that translates into greater high pressures. Also need to change the cycling switch to an R-134 compatible unit, low side pressures run an average of 5 psi lower than Freon, more in the 24-25 psi range.

To really get good cooling your liquid line needs solid liquid in it, bubbles don't cool very well. Yet another factor is with 23 year old vehicle depending on mileage, is your compressor and clutch may be getting tired. R-134a makes your system work a lot harder than Freon.

One of the greatest difference between a new and an old vehicle is dirt, 23 years can collect a lot of debris, all that should be cleaned up first. You will never get the correct pressures if you system is not moving air. Air is very much apart of AC, that A stands for air.

mk378 on Thu June 24, 2010 8:44 AM User is offline

Charging by weight is essential to know where you stand. You have a number-- it worked pretty well with 2.7 lbs in-- so you should try to get back to that point. If you don't have a scale you could use 12 oz cans of refrigerant instead. Next time you have the system empty, inspect the orifice tube. The symptoms you have now (low low side and little to no cooling) suggest a blocked orifice. Also if you're still running the 1987 accumulator drier, it's useless. Replace it.

The gradual loss of cooling could have been a freeze up, either on the outside of the evaporator or inside the orifice (due to water in the refrigerant). Or it could be an air control problem inside the car causing reheating.

Edited: Thu June 24, 2010 at 8:46 AM by mk378

mad_trbo on Thu June 24, 2010 9:28 AM User is offlineView users profile

Determined to get this figured out and back to the point where I was at least getting cool air in the car for short trips. One hour or less.

Other Facts:

Accumulator dryer was replaced
Compressor was replaced
condensor was cleaned during body restoration
Cold air 39 - 40 at vent sitting at idle. After one hour driving highway speeds vent temp up to 50 degrees. This is where I started traveling backwards and ended somewhere in left field. disappointed in myself.

Upon further inspection of the orifice tube after the first inspection I came to discover the metering portion of the orifice remained inside the expansion tube upon extraction- will replace. Am I right in thinking this truly should not have caused an issue, the metering tube was still in place so it was able to do it's job???

Last night I vac'd down and drew in r134 unknown amount, shorted low cycle switch. Low side 10psi and highside 150 psi - could this be a sign of a faulty compressor?

Equalized static leads me to believe orifice blockage is not at issue and further review shows orifice was not blocked just seperated.

When i charge should I charge with liquid or gas?

Next steps:

Replace accumulator
Replace Orifice
purchase 4 cans R134 and use this method for charge

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

bohica2xo on Thu June 24, 2010 12:02 PM User is offline

Step one:
Throw the shorting wire in the trash. If you have not killed the R4 with it yet it will be a miracle.

Stop charging unknown amounts of refrigerant into the system. Put a scale under that 30 lb tank.

A broken orifice tube does not meter well. The loss of cooling over a long drive sounds like icing of the evaporator.

Once you have the system evacuated, with the engine OFF you can start charging. Charge liquid through the high side. Running liquid into an evacuated system should let you get 50% of the charge in before you equalize pressures. Watch the scale, and don't put more than 75% of the charge in with the engine stopped.

Now, close the high side valve. This should remain closed for the rest of the charge. Start the engine, set the cabin fan to high, and let it idle. The compressor should cycle - LET IT CYCLE.

Since this is a conversion, you will need to add the balance of the charge slowly while observing the system. Add gas through the low side. Add a small amount, and wait a minute for the system to stabilize. With a 90f ambient and the cabin fan on high (doors open) it should stop cycling when the high side approaches 200 psi.

Once the high side is 180 to 200 psi, raise the engine rpm to 1500 & hold it there. After 5 minutes, record the pressures & vent temps - and post them here.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

mad_trbo on Thu June 24, 2010 1:22 PM User is offlineView users profile

Thanks and will do.

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

mad_trbo on Thu June 24, 2010 2:26 PM User is offlineView users profile

Ambient temp - 95
Vent temp - 80
Lo-side 25
Hi-side 230

Two cans 12oz dupont r134 through high side, started car and stopped with about
4oz as gas through lo-side.

Orifice changed out with gm correct part
Accumulator changed out
Vac'd and held one hour

No sweat on evap out line, but evap in line cool and sweating.

Do I need to add more r134?

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

bohica2xo on Fri June 25, 2010 2:48 AM User is offline

You are close on the refrigerant. If those numbers are at 1500 engine, you can go as far as 250 ~ 260 psi on the high side safely - at 1500 engine rpm & 95f.

The low side looks better, but could come up a couple of psi. You don't need to add much at this point, an ounce or two probably.

The vent temps can reflect all sorts of things, like blend door issues, reheating etc. The fact that the suction line is warmer than the evaporator inlet says it is recovering a lot of heat.

Add a little refrigerant, and take it for a drive. See if the vents improve with the car above 40 mph & 1500 rpm.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

mad_trbo on Fri June 25, 2010 7:18 AM User is offlineView users profile

I hear what you are saying, but something has to be up. I say this because one week ago I had vent temps where they should be and the evap exit and suction lines were sweating bb's.

Couple of questions:
Do the pressure numbers indicate a healthy compressor?
If the compressor were bad it couldn't produce those numbers right?
Additionally if I had a blockage, say in the evaporator line? would my lo- side be extremely lo and high side be high due to the fact that the system couldn't pass the r134 from oneside to the other

One other point, the evap inline looks frosty cold, never really paid attention to this before. I don't know what the freezing properties of r134 are but again it doesn't look like a block because of pressure readings. But I am trying to use logic here not expertise and experience.


Ambient 82 degrees

I just performed an experiment based on a comment about how much heat the system might be removing and the fact that the evap exit and suction lines weren't sweating.

I removed the blower and cycled the A/C on, the accumulator/ evap exit and suction lines immediately got frosty.

Could this mean that as suggested I needed to take the car for a ride. The interior of the car was simply overwhelming the ability of the evaporator? Yesterday during testing the interior of the car had to be at least 120 degrees according to the vent thermometer I was using.

Last question and I'll wait for a response: How much of a temp drop should you see between the cabin ambient and the vent temperature? Just on average as I am sure there are factors that play into this that may cause a change humidity etc....

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

Edited: Fri June 25, 2010 at 8:42 AM by mad_trbo

iceman2555 on Fri June 25, 2010 10:23 AM User is offlineView users profile

NickD said it best several post ago.....USE R12 !!! The system was designed for this refrigerant and will work best with this refrigerant.
However, it seems that 134a is the refrigerant of choice. If that is truly the path choose, then forget the 75%, 82.777333999 % or 91.6%....the system has to be charged with a sufficient amount of refrigerant to 'flood' the evap. If this takes..what ever the amount.....this is what it matter what the pressures are....this is what is required.
It is assumed that the system is clean inside....the correct amount and type of lubricant has been added to the system and the engine cooling system is fully functional.
Charging with a scale is preferred...simply because it give a reference to amount of refrigerant within the system.
Evac the system.....if a charging machine is not available....and one must charge with cans (small) or one can (large 30 lb) so be it. Keep in mind that the entire time the system is charging the compressor is operating without sufficient lubricant get this charged as rapidly as possible.
bohica2xo suggestion of getting as much refrigerant into the car at one time is valid. My only concern is check the location of the high side service port. Insure that it is between the condenser and orifice tube. If the high side is between the compressor and condenser.....then it is quite possible to flood the compressor with liquid...and this is not a good thing.
One good method to insure that the compressor does not become flooded with liquid during this process......operate the engine during the evacuation process. This places a tremendous amount of heat in all AC components and will insure complete 'boil off' of any liquid refrigerant added to the system.
Keep in mind that the job of the compressor is not to 'pull' refrigerant into the system....that is your the immortal words of a great mind....'git'erdone'....or words to that effect.
Place the vehicle in the following conditions: MAX COOL...HIGH BLOWER....ENGINE AT IDLE....DOORS OPEN!!!! Highest heat load on the system...and no you can not over ride the evaporator.
Acquire a method to measure surface temperature of metal. Sears sells a small multimeter with a temp probe for less than $50.00 or check with AC Kits..they may have a tool to use....what ever...get one.....!!!!
Suggest to start with an approximate recharge of 90% 134a into the system. Keep in mind that it takes app 3-4 oz to initially pre charge your AC manifold and hoses.
Once this has been added to the system...engage the compressor....allow the system to operate for app 5-7 minutes...this allows the system to stabilize.
Utilizing the newly purchased temp measurement device....measure the inlet and outlet temps of the evap. Inlet is the cold side of the orifice and outlet is before the accumulator. These temps should be equal...the change....although you may allow 3-5 degrees.....this is acceptable. If the outlet is warmer than the inlet by more that 6-8 degrees...add 2 oz of refrigerant......allow system to re stabilize...and retest. Gotta get these temps within that range. Any adjustment to refrigerant level.....add or subtract requires re stabilization of the system.
Once the evap floods...the system is properly recharged.....the kicker.....NO MATTER WHAT YOUR PRESSURES INDICATE...this is the charge rate. If an excessive (perceived) pressure is too high...then more condenser cooling is needed. Do not remove refrigerant.....this will hinder system performance...and most of all reduce lubricant flow to the compressor (bad). With the fan set up you are is doubtful that this will be an issue. However, if it is...the condenser of your vehicle may need to be undated to a more efficient unit.
Next step...check the inlet and outlet temps of the condenser....should be app.....25-28 degrees.
Measure ambient temp app 1 foot in front of the vehicle....condenser level. Measure vent temp (probably center) that is close to evap air outlet. Temp drop should be 25-30 degrees. between ambient and vent.
Keep in mind that a very low vent temperature will not be available at this time.....remember the doors are open.....max heat load...!!!!
If these temps do not fall into the range stated.....measure the outlet temp of the evap once more. This indicates the app temp of the evaporator core. It is possible to experience a temp increase between evaporator air outlet temp and vent temp of 5-7 degrees. If temperature is not within range.....evaluate system for possible heater/blend door heat leakage.
Once the system is functioning....CLOSE THE DOORS...MAX AIR....ENGINE 1200-1500 RPM....REDUCE BLOWER SPEED to 2nd or 3rd level. This will allow for testing of cycling devices.
The compressor will not cycle during the OPEN DOOR test....unless the system is undercharged. This operational condition will give you that much need boost of seeing a vent temp that one likes.....COLD!
Remember that you are using 134a in a system that was never designed for the pressures/temperatures of 134a. Normal R12 pressures (perceived) have little to no bearing with a retro fit. The key to system performance is the proper charge....then increasing condenser efficiency or cooling to maintain suitable operational pressures.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

NickD on Fri June 25, 2010 11:39 AM User is offline

Was adding those leaky R-134a adapters mentioned, plus a HPCO switch in series with the clutch coil? The latter is a very common sense thing to do to prevent blowing up your system, along with a lable that the system was modified.

All pressure tests are done at 1,500 rpm, doors open, blower at max, and yes, the AC turned on. Key pressure is always the low side, at 90*F have to keep it high enough to prevent excessive cycling, shoot for 30, you already change the cycling switch to an R-134a compatible type. But can't ignore the high either, may even go up to 300 at 90*F, that is head scratching time and that is also why you have a HPCO switch installed. Hey, how old are your hoses, they tend to rot and get brittle, could be a problem. And didn't know you were stuck with an R-4, that was a problem when new. Putting two large disks with two large O-rings on it inside of a tin can was never a good idea. Dissimilar metals and rubber that can dry up are the reasons, you will have higher pressures, no way of getting around that, can expect that to be the straw that broke the camels back.

Not being sarcastic, feel its more experience. The big question for you is, is your car worth putting money into it? The AC system is usually the first to go, hopefully your evaporator is in good shape, but would consider replacing the rest of it, doing the work yourself, maybe 5-600 bucks worth, but then you will have something. Would even do that with R-12, especially R-12, if your condenser is in good shape, can keep that, but still would be concerned about that compressor and those hoses. Rubber here is the key element, even if not used, it ages.

bohica2xo on Fri June 25, 2010 12:59 PM User is offline


I spent years here telling people to keep R12 vehicles R12. I got tired of arguing with them, being called names etc. Screw it. Let them convert. All I can offer is suggestions to approaching the correct charge.

I do not believe that it is possible to flood (washdown) a piston compressor from the high side, regardless of the location of the service port. The discharge valves should keep the refrigerant moving toward the condensor, as they were designed to do. Charging liquid through the LOW side however can wash all of the oil out of a compressor very easily - seen it done on FS10's in fox bodies...

It is important to get as much charge in before starting the compressor to promote oil circulation. I think jumper wires kill more compressors every year than low charges do. At least if it is cycling there is some high speed flow to move the lubricant.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

iceman2555 on Fri June 25, 2010 5:57 PM User is offlineView users profile

The issue of 'wash down' is not my major concern with adding refrigerant to the liquid side of the system. Liquid refrigerant in the hands of a 'newbie' scares the heck out of me.....I see the results of compressors that have been subjected to liquid ingestion all the time.
That being said...the issue with 12 seems to come up each day. Received a call yesterday, early model GM with POA AC system, the customer is all prepared to convert to 134a. A suggestion to stay with 12, however, he assures me...he knows what he is doing and precedes with the procedure. Another call today...same customer complaining that the compressor does not cool the vehicle properly. Does not wish to hear the issue with the POA adjustment...simply that the compressor does not cool the system. Still in his mind, the retro will work.

There is total agreement on the amount of refrigerant into the system prior to start up...esp with a CCOT system.....unfortunately too often these retro fits are charged to a perceived acceptable pressures. About 3-4 weeks later the compressor is returned for warranty because it is noisy or locked up. Naturally no lubricant is found in the compressor......but what the heck it was cooling great for awhile.

It is a known factor that most all do not like 4s compressors....and I can say I agree...but for entirely different reasons.....the retro craze almost put 4s in the ground. I was employed there during this period and one can not believe the number of units that were returned as 'defective' and upon inspection, the major issue was a total lack of lubricant, either completely dry or suction side was dry and discharge side was lubricated. All these issues were directly related to the amount of refrigerant or refrigerant flow within the system. For some unknown reason, I am getting an abnormal amount of retro fit questions this year.....can not understand why.

If this customer were to change his condenser, recharge to OE specs he should have a very good system. The engine cooling system far exceeds the OE units ability to cool.
Looking forward to the results of his procedure.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

mad_trbo on Fri June 25, 2010 6:03 PM User is offlineView users profile


I appreciate the assistance, I finally got things back within the center of the field. I got so far into left field running the fan on hi, not sure why my system won't handle high, but it seems to work fine at one and two

Iceman, I also appreciate your write-up. That was very helpful as well.

With the system at 2 i get vent temperatures of 45 degrees currently, good enough for now

Ambient temp of 96 degrees
lo-side 29
High side 220

I think I still need to add R134, but it seems to be doing ok currently.

Any further advice?

How much will changing out the condenser to a newer unit help? I didn't see the previous post about a new condenser i must have been typing as you were writing iceman. I am very curious to know how much a new condenser will help I am not beyond replacing the old unit.

Thanks again this has been an incredible learning experience.

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

Edited: Fri June 25, 2010 at 6:10 PM by mad_trbo

NickD on Fri June 25, 2010 8:08 PM User is offline

The newer parallel flow condensers have a much lower thermal resistance between the refrigerant and the air flow, far more surface area is the reason for that than the older tube and fin type. Superior heat transfer results in much lower high side pressures.

Is it really even possible to charge by liquid with a can? For that refrigerant to stay a liquid, the rest of the system would have to be around -30*F, but if its warm, as soon as that liquid hits the charging line, it will evaporator into a gas, thats why those charging lines get cool.

mad_trbo on Fri June 25, 2010 10:27 PM User is offlineView users profile

K now I need to go back and take a physics class.

If thermal resistance is lower and the highside is lower, does this actually convert to cooler cabin temperatures or simply a system that is more efficient from the stand point of compressor run time.

Seems like with a lower high side you'll have a lower lo side which will cause the low pressure cycle switch to turn the compressor off??

Unless the real benefit comes under extreme heat conditions. Is that the case? With the new condensor you can theoretically expect the system to cool as efficiently at an ambient of say 95 as it would at an ambient of 85. Where now with the old style condensor the system can't cool as well under the ambient of 95.

Am I getting anywhere with this?

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

ACProf on Fri June 25, 2010 11:56 PM User is offline

TO address some of your physics (thermodynamics) related AC questions.

THe whole idea of the condenser is "heat exchange". The heat in the refrigerant in the condenser needs to be "exchanged" to the air going through the condenser.

Physics Thermodynamics RULE: Heat only flows from a hotter object to a colder object.

Also: THe more surface exposure of the refrigerant to the air, the more heat exchanging can take place.

The PF condenser has MANY more paths than tube and fin for the refrigerant to flow and increases the amount and exposure of the refrigerant to the air (through the aluminum fins, of course).

THe compressor takes the heat laden vapor refrigerant it got from the evaporator and compresses it to make it HOTTER than the air coming into the condenser (See Thermo RULE above). THe higher the pressure (within operating range) the more heat will leave the refrigerant in the condenser and exchange into the cooler air.

Once cooled, the now liquid refrigerant goes back to the evaporator by way of the Otube or expansion valve to absorb more heat.

THat's about it in a nutshell.

To increase cooling:
Larger condenser area and more refrigerant paths to exchange heat to the air.
More (and cooler) air through the condenser. Not much for cooler air in AZ!
Hotter refrigerant (higher pressure) into the condenser to transfer more heat to the air-> this has other wear and tear consequences.
Larger orifice tube opening or larger TXV flow metering device of refrigerant into the evaporator > but not flooding it with liquid!
Larger evaporator (to absorb more heat into the refrigerant) from the cabin air going through it.
Larger capacity compressor to flow more refrigerant through the system. -> without overloading the condenser or evaporator, of course. THe A6 was a 12 cu in compressor and nearly bullet proof!

Low side pressure is controlled by the metering device (Otube or TXV) - not the high pressure value. TXV valve adjusts for best results - Otube is "set" for best opeation at cruise RPMs. If the higher pressure causes the low side to go up, the system is probably overfilled and refrigerant is being force fed through the metering device instead of being controlled.


mad_trbo on Sat June 26, 2010 9:29 AM User is offlineView users profile

Thanks AC Prof

Now getting back to my original issue.

I really think the evaporator must have frozen on that hour long ride.

Would an improperly adjusted low pressure switch cause this to happen, meaning if it is not cycling at 30 psi and instead say 20 psi would this cause the compressor to run continuously at very low temperatures that would freeze moisture being pulled from the air?

What is the difference between Max cool and normal cooling onthese cars, is it compressor control or blend control...

1993 GSX Eclipse - This is the small Stick
1987 Buick Grand National - This is the big stick if you take out the Eclipse which is rare

NickD on Sat June 26, 2010 12:10 PM User is offline

If your evaporator did freeze up, your blower air would slow down to nothing and your air will have a stagnant odor to it. Besides low charge, a cycling switch set way too low can cause this problem. Max and normal is the difference as to whether the recir door is opened or closed, in recir mode in max, air comes from under the windshield grille in normal.

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