Automotive Air Conditioning Information Forum (Archives)

mytoy on Mon August 23, 2010 5:16 PM

Year: 1996
Make: Camry
Model: LE
Engine Size: 2.2
Refrigerant Type: R134

What controls cycling of compressor? I doubt if my compressor is cycling, seems to
stay engaged all the time. No bubbles appearing thru the sight glass when running.
Cooling is fine for 10 minutes after starting car, then effectiveness dropps off. Still works but
not as cold as first 10 minutes. I've posted reems of info about this problem past month
or so. Eveything has been replaced, problem persists. Now dealer says "all lines need to
be replaced", says restriction must be soemwhere. Want another $900 to replace all the lines.
Have already dumped nearly $2000 on this. Compressor, Evap, Cond, Exp Valve, Dryer, Thermistor.

My question is simply what controls cycling of compressor?

-------------------------
...Bob

bob234 on Mon August 23, 2010 5:37 PM

Sounds like the condenser fan is not working. The reason it blows cold the first 10 minutes is because the engine bay is not hot then, heating up the condenser right in front of the radiator. Your problem is lack of air flow, making high head pressures. By the way $900 to replace just the lines is a complete rip off. I did the ones on my truck in less than a hour. High and low side ones. You can just pay someone $20-50 to evacuate it for you, and install them yourself. Just replace the o-rings on every connection you remove. Then when you are done, take it to a A/C shop and have it recharged because it has to be vacuumed first.

ACProf on Mon August 23, 2010 5:38 PM

This vehicle contains a "AC Amplifier" controller that controls power to the clutch coil. This controller makes decisions on the clutch power by receiving and analyzing inputs from a dual pressure switch, evaporator temp sensor, and two additional inputs from the engine control module section of the emission control computer.

mytoy on Mon August 23, 2010 7:11 PM

Quote
Originally posted by: bob234
Sounds like the condenser fan is not working. The reason it blows cold the first 10 minutes is because the engine bay is not hot then, heating up the condenser right in front of the radiator. Your problem is lack of air flow, making high head pressures. By the way $900 to replace just the lines is a complete rip off. I did the ones on my truck in less than a hour. High and low side ones. You can just pay someone $20-50 to evacuate it for you, and install them yourself. Just replace the o-rings on every connection you remove. Then when you are done, take it to a A/C shop and have it recharged because it has to be vacuumed first.

The cooling fans seem to be working normally. I tried feeling with my hand on the condensor wherever
I could an reach and its not hot. I priced the cost of the lines from Toyota(parts), they say its $620.
High Pressure Line and Suction Lines from Compressor and the two aluminum refrigerent lines. Was
considereing canging the two lines from the compressor(High pressure and Suction) myself as you suggest.
They are relatively easy, the others are far more involved. Go back to the firewall.

I appreciate your input.



-------------------------
...Bob

mytoy on Mon August 23, 2010 7:15 PM

Quote
Originally posted by: ACProf
This vehicle contains a "AC Amplifier" controller that controls power to the clutch coil. This controller makes decisions on the clutch power by receiving and analyzing inputs from a dual pressure switch, evaporator temp sensor, and two additional inputs from the engine control module section of the emission control computer.

Is it conceivable AC amplifier or the ECU could contribute to the problem I decribe about diminished cooling
after 10 of 15 minutes? These items are about the only things not replaced thus far. As stated, dealer
is going down the road of line restiction somehere after the system run for awhile. I'm dubious.

Really appreciate your thoughts...

-------------------------
...Bob

ACProf on Mon August 23, 2010 8:08 PM

Not unless the the AC amplifier is releasing the clutch.

mk378 on Mon August 23, 2010 8:12 PM

After it stops cooling, you need to pull over, leave the engine and the A/C on, open the hood and check if the compressor and condenser fan are running or not.

The high pressure line from the compressor to the condenser normally gets hot, often too hot to touch, whenever the compressor is running. If it is ambient temperature, that suggests an electrical problem is shutting the compressor down completely. It could also be the clutch gap, a very common reason for the compressor to fail to engage after the engine warms up.

Edited: Mon August 23, 2010 at 8:14 PM by mk378

mytoy on Mon August 23, 2010 8:59 PM

Quote
Originally posted by: mk378
After it stops cooling, you need to pull over, leave the engine and the A/C on, open the hood and check if the compressor and condenser fan are running or not.



The high pressure line from the compressor to the condenser normally gets hot, often too hot to touch, whenever the compressor is running. If it is ambient temperature, that suggests an electrical problem is shutting the compressor down completely. It could also be the clutch gap, a very common reason for the compressor to fail to engage after the engine warms up.


Yes, the compressor is engaged even when the cooling diminishes. Seems that it never
disengages when a/c is on(doesn't cycle). One line from the compressor is very hot, other
is cool with slight condensation on the line to whiich it connects running towards firewall.

-------------------------
...Bob

bob234 on Tue August 24, 2010 1:03 AM

bob234 on Tue August 24, 2010 1:15 AM

Sorry for the blank post above, don't know why it did that. Well now that you mentioned that one side is hot and one side is cold, I think it might be a problem with your evaporator. I had a vehicle a while back, that had a evaporator that was so full of crud that air was only blowing through a small part of it. After a few minutes it would ice over due to not enough air flowing through it, and then I would get no air through the vents at all. If it was a restriction in the lines as that dealer was describing, the A/C wouldn't work at all. I had a plugged orifice tube one time(Yours has a expansion valve instead). The compressor would engage and immediately disengage. Once I flushed the system good, and replaced the compressor that was shredding itself, it was ice cold again.

mytoy on Tue August 24, 2010 10:36 AM

Quote
Originally posted by: bob234
Sorry for the blank post above, don't know why it did that. Well now that you mentioned that one side is hot and one side is cold, I think it might be a problem with your evaporator. I had a vehicle a while back, that had a evaporator that was so full of crud that air was only blowing through a small part of it. After a few minutes it would ice over due to not enough air flowing through it, and then I would get no air through the vents at all. If it was a restriction in the lines as that dealer was describing, the A/C wouldn't work at all. I had a plugged orifice tube one time(Yours has a expansion valve instead). The compressor would engage and immediately disengage. Once I flushed the system good, and replaced the compressor that was shredding itself, it was ice cold again.



-------------------------
...Bob

mytoy on Tue August 24, 2010 10:44 AM

Quote
Originally posted by: mytoy
Quote
Originally posted by: bob234
Sorry for the blank post above, don't know why it did that. Well now that you mentioned that one side is hot and one side is cold, I think it might be a problem with your evaporator. I had a vehicle a while back, that had a evaporator that was so full of crud that air was only blowing through a small part of it. After a few minutes it would ice over due to not enough air flowing through it, and then I would get no air through the vents at all. If it was a restriction in the lines as that dealer was describing, the A/C wouldn't work at all. I had a plugged orifice tube one time(Yours has a expansion valve instead). The compressor would engage and immediately disengage. Once I flushed the system good, and replaced the compressor that was shredding itself, it was ice cold again.


Litterally everything(except lines) has been replaced and still not fully resolevd this diminishing cooling issue.
Compressor&clutch(new Denso), Evaporator, Condensor, Dryer, Thermistor. Now dealer says change the lines!
Claim there must be a clog somewhere??? I'm close to giving up on this. Till now I flet this car(96 Camry) was
absolutely fantastic car. Just can't fathom why this should be such a difficult problem.

I appreciate your input...

-------------------------
...Bob

jglanham on Tue August 24, 2010 12:07 PM

Sounds like it might be a heater problem. First 10 minutes, engine is coming up to temp. After engine warms up, problems in heater valve, blend doors etc. could be adding heat to your vents through the heater core. Clamp off the heater hoses and see if the problem goes away.

-------------------------
johnl

mytoy on Tue August 24, 2010 2:55 PM

Quote
Originally posted by: jglanham
Sounds like it might be a heater problem. First 10 minutes, engine is coming up to temp. After engine warms up, problems in heater valve, blend doors etc. could be adding heat to your vents through the heater core. Clamp off the heater hoses and see if the problem goes away.

Just called the shop, they said they tried that. Dam, I had hoped your suggestion might be the
resolution. Now i'm being told its possible its the compressor again. This would make it the
third(3) new compressortrying to get this solved. I bought the compressor from a comapany over
the web, sell New/DENSO's or rebuilts. I bought new. Shop said they felt first compressor
was faulty, gave fluctuaiting pressure readings. Sent it back, they replced with another new one.
Now after changing all the other stuff the shop is not discounting possibility its another faulty
compressor. This whole thing has become rediculous....



-------------------------
...Bob

mk378 on Tue August 24, 2010 3:51 PM

The next step would be to read pressures when it is not cooling.

Are you sure the TXV has been properly installed? Edit: never mind, it's a block type, they're rather idiot-proof.

Edited: Tue August 24, 2010 at 3:55 PM by mk378

mytoy on Tue August 24, 2010 5:04 PM

Quote
Originally posted by: mk378
The next step would be to read pressures when it is not cooling.



Are you sure the TXV has been properly installed? Edit: never mind, it's a block type, they're rather idiot-proof.


Just talked with the company from whom I purcahed the two compressors. Explained the entire ordeal to them
again. Explained the shop here is now suspect again of possible faulty internal valving in the compressor. in other
words...another faulty compessor. They're good guys, they're very understanding, however they said they have had
"very" few NEW Denso''s come back. They agreed its not impossible but just seems weird. They asked exactly same question
as you....get the pressure readings and call them back. They're fully in agreemant to ship another, just want to hear the
readings first...preferably when cooling poorly(as you suggested). Shop will take reading tomorrow afternoon. I'll fill
you in what happens tomorrow. It'll be winter before this gets concluded....

-------------------------
...Bob

Edited: Tue August 24, 2010 at 5:55 PM by mytoy

mytoy on Mon August 30, 2010 8:29 PM

Quote
Originally posted by: mytoy
Quote

Originally posted by: mk378

The next step would be to read pressures when it is not cooling.








Are you sure the TXV has been properly installed? Edit: never mind, it's a block type, they're rather idiot-proof.





Just talked with the company from whom I purcahed the two compressors. Explained the entire ordeal to them

again. Explained the shop here is now suspect again of possible faulty internal valving in the compressor. in other

words...another faulty compessor. They're good guys, they're very understanding, however they said they have had

"very" few NEW Denso''s come back. They agreed its not impossible but just seems weird. They asked exactly same question

as you....get the pressure readings and call them back. They're fully in agreemant to ship another, just want to hear the

readings first...preferably when cooling poorly(as you suggested). Shop will take reading tomorrow afternoon. I'll fill

you in what happens tomorrow. It'll be winter before this gets concluded....



Well here's the latest update....

Had pressure reading done today after running the car for about 1/2 hour when the a/c looses
its cooling effectiveness. High ranged 155 to 160, Low ranged 4 to 9. Talked with the company
I bought the compressors from, fellow at first said he thought pressures indicated the compressor
is working correctly. Said this based on the differential between the two numbers. I asked if its
possible the compressor they sold me is not perfoming to spec for a 96 camry 4cyl. He said they
will discuss and call me tomorrow with one of their specialist/techs. He at first said it clearly a
exp valve issue. Told him two its been replaced twice. Once withn the exp valve they sold me and
one by the Toyota dealer. Enough with the exp valve theory!!!

I'm no further along with this dam thing..... HELP!!!!!


yt



-------------------------
...Bob

Tennessee_Timmy on Mon August 30, 2010 9:39 PM

Quote
Originally posted by: mytoy
Quote
Originally posted by: mytoy
Quote

... Had pressure reading done today after running the car for about 1/2 hour when the a/c looses

its cooling effectiveness. High ranged 155 to 160, Low ranged 4 to 9.


If you mean 4 to 9 psi, that's way too low. the system may be losing it's effectiveness when the evaporator becomes a block of ice?

-------------------------
Good Luck 2 ya,
Timmy

iceman2555 on Mon August 30, 2010 10:25 PM

A suggestion would be to locate a very good AC shop that can diagnosis a problem instead of throwing more parts at it and hope one works.
There are several areas of concern.
If the low side is as low as indicated, then the temperature of the refrigerant at that point is about the same. This indicates a possible failed thermostatic switch in the system. If not mistaken, this is located in the evap core. Some of these Toys have an access door for this switch. Secondly, the pressures indicate a possibility of a seriously undercharged system. There is not mention of the ambient temp....but for this time of year and most temps in the US...these pressures seem a bit low. How was the system recharged?
On this vehicle....one of the lines entering the evaporator (the high side liquid) should be hot or warm to the touch. The return line (low pressure gas) should be cold. A bit of condensation is acceptable.
Is the TXV on this vehicle an OE Toy unit or an aftermarket unit? There have been some issues with aftermarket valves on Toys and Hondas. Just a thought.
First and foremost...it must be known that the system is totally charged. Supply this info please.
Statement that the condenser had been replaced....everything except the hoses.....is the condenser an EXACT duplicate of the OE unit? If there are any changes please list them...or supply a photo of the condenser. There are some aftermarket suppliers that are shipping serpentine condensers as replacements for the PFHE.
Just came to mind, is this condenser a unit with the internal rec/drier or do you have a separate rec/drier?
There is nothing wrong with the compressor...nor is it believed that the other units were at fault. A compressor is not a primary cooling unit in the AC system...it is simply a pump....the evaporator and condenser are the two heat exchangers. True a compressor must be able to build pressure...but this one is surely accomplishing this....an increase of 150 psi is acceptable.
How much lube as added to this system?
Also, were the lines flushed and cleaned? What failure occurred with the original compressor or why did you replace the compressor?
If possible test the inlet and outlet temps of the condenser....post results.
This does not seem to be an insurmountable problem...just takes some thought....and insure that certain perimeters are met....but first...gotta know if the system is properly charged!

-------------------------
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

mytoy on Tue August 31, 2010 11:13 PM

Quote
Originally posted by: iceman2555
A suggestion would be to locate a very good AC shop that can diagnosis a problem instead of throwing more parts at it and hope one works.

There are several areas of concern.

If the low side is as low as indicated, then the temperature of the refrigerant at that point is about the same. This indicates a possible failed thermostatic switch in the system. If not mistaken, this is located in the evap core. Some of these Toys have an access door for this switch. Secondly, the pressures indicate a possibility of a seriously undercharged system. There is not mention of the ambient temp....but for this time of year and most temps in the US...these pressures seem a bit low. How was the system recharged?

On this vehicle....one of the lines entering the evaporator (the high side liquid) should be hot or warm to the touch. The return line (low pressure gas) should be cold. A bit of condensation is acceptable.

Is the TXV on this vehicle an OE Toy unit or an aftermarket unit? There have been some issues with aftermarket valves on Toys and Hondas. Just a thought.

First and foremost...it must be known that the system is totally charged. Supply this info please.

Statement that the condenser had been replaced....everything except the hoses.....is the condenser an EXACT duplicate of the OE unit? If there are any changes please list them...or supply a photo of the condenser. There are some aftermarket suppliers that are shipping serpentine condensers as replacements for the PFHE.

Just came to mind, is this condenser a unit with the internal rec/drier or do you have a separate rec/drier?

There is nothing wrong with the compressor...nor is it believed that the other units were at fault. A compressor is not a primary cooling unit in the AC system...it is simply a pump....the evaporator and condenser are the two heat exchangers. True a compressor must be able to build pressure...but this one is surely accomplishing this....an increase of 150 psi is acceptable.

How much lube as added to this system?

Also, were the lines flushed and cleaned? What failure occurred with the original compressor or why did you replace the compressor?

If possible test the inlet and outlet temps of the condenser....post results.

This does not seem to be an insurmountable problem...just takes some thought....and insure that certain perimeters are met....but first...gotta know if the system is properly charged!


Thanks very much for the thoughful and thorough comments. To serve as update to this issue, the company from whom
I purchesed the compressor called me back today. They contacted DENSO and explained the entire issue and the pressures
I obseved. They felt as you, these pressures don't indicate a bad compressor. They had interesting advice. Said 1994, 95's, 96's
which were beginning years using r134 and had some rare but not uncommon internal refrig hose breakdown. Supposedly
these hoses had a internal coating that didn't react well to r134. Sometimes caused walls to alligator or break loose and cause retricted flow. I know I've been way down the changes-parts road but I'm goning to bite again. So today I orded both hoses coming off the compressor today(Suction and Delivery). Shoud have them Friday, will put them in asap and report back. Everyone and I mean everyone involved in this issue wants to hear what happens when these hoses are replaced. We'll see!

-------------------------
...Bob

Edited: Tue August 31, 2010 at 11:18 PM by mytoy

iceman2555 on Wed September 01, 2010 8:19 AM

If, indeed, this is a issue, I would like to see or obtain the hoses. Detailed micro photos will suffice, but the real thing would be great.
We encounter some issues with Toy hoses before, however, it was not with the inner liner breaking down as posted, the inner liner would actually break and form a 'flapper' valve. However, we only encountered a few of these items.
It does seem a bit 'odd' about this statement. These hoses are made by various mfger's and should show up on various model vehicles....but the failure does not seem to be an issue. Anyway, let me know what you discover.
Good luck!

-------------------------
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