Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

Poor Performance

bigwingboy on Wed September 12, 2007 3:43 PM User is offlineView users profile

Year: 1990
Make: BMW
Model: 325i
Engine Size: 2.5
Refrigerant Type: R12
Ambient Temp: 105
Pressure Low: 55
Pressure High: 270

I've been fighting with this project for a while now. I replaced the entire system in this car with the exception of hoses, so everything that matters is new. I flushed the hoses; they have no mufflers on them. I decided to keep R12 in the system since I had a few cases sitting in the garage and figured it would perform better then R134. However, when I charge the system (capacity of 2.15 lbs.), the low and high side pressures get very high (low 75, high 325). Too high. A soon as I added one 12oz can of freon, the low side went to 55 and the high went to 260! Adding more freon just makes the pressures go higher. I should be able to get another can and a half of freon in the system. Anyway, I charged the system with 12oz of freon and it gets cold as long as the engine RPM is above 1500, as soon as the engine goes to idle the vent temps rise 20 to 30 degrees. Appears like an undercharge. There are lots of bubbles in the sight glass. I tried charging until the sight glass cleared, but that resulted in some really high pressures and high vent temps.
The expansion block that I installed was R12 and R134 compatible. The fan works properly and the shrouds are in place. I tried putting my swamp cooler in front of the condenser, but the vent temps don't change. I'm wondering if there is some kind of restriction in the system, or the expansion block I installed is faulty. Help!

Thanks, Curt

Chick on Wed September 12, 2007 4:43 PM User is offlineView users profile

I don't see mention of a vacuum being pulled?? Was it?? Is the fan(s) working properly? One can should not raise the pressures like that, and since they are both high, but have a large differential, it looks like air in the system...

-------------------------
Chick
Email: Chick

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

Freedoms just another word for nothing left to lose

bigwingboy on Thu September 13, 2007 12:57 AM User is offlineView users profile

Vacuum was pulled for almost 2 hours. I had other things to do so I left the pump on it while I was busy. I'm about ready to pull the system apart again to make sure there isn't some junk stuck in the expansion block or condenser. I hate to do it since I have to rip out a bunch of the interior to get to the expansion block.

Edited: Thu September 13, 2007 at 1:03 AM by bigwingboy

bigwingboy on Thu September 13, 2007 1:00 AM User is offlineView users profile

Vacuum was pulled for almost 2 hours. I had other things to do so I left the pump on it while I was busy. I'm about ready to pull the system apart again to make sure there isn't some junk stuck in the expansion block or condenser. I hate to do it since I have to rip out a bunch of the interior to get to the expansion block.

Sorry, didn't mean to post twice.

Edited: Thu September 13, 2007 at 1:04 AM by bigwingboy

TRB on Thu September 13, 2007 1:11 AM User is offlineView users profile

Pressures are off by a good margin.

Low side: 15 to 30 PSI
High side: 1485 to 205

Pressures listed at 95 degrees ambient.

Refrigerant capacity R12: 33.6 ounces
Oil capacity: 5.7 ounces

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

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

bohica2xo on Thu September 13, 2007 2:48 AM User is offline

If the high side went to 260 psi with 12 ounces of refrigerant, I would not be digging for the TXV just yet...

Where is the high side service port located - before or after the condensor?

I would be inclined to drop a couple of thermocouples on the inlet & discharge of the condensor to see how well it is working.

B.

-------------------------
"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.

bigwingboy on Thu September 13, 2007 10:27 PM User is offlineView users profile

The high side service port is located on the passenger fender integrated in a metal high pressure line that goes directly to (or comes from) the TXV and evaporator and hooks into the receiver-drier. The condenser is brand new. It is a serpentine type whereas the old one (factory) was a tube and fin. I don't have thermocouples, but I do have an infrared thermometer. Since it is new I would think it is OK, but you never know. I'd rather find something under the hood than have to rip out the interior to get at the TXV.

Went out and ran the car at idle and 2000rpm.

condenser inlet temp: Idle--165F, 2000RPM--260F

condenser outlet temp: Idle--155F, 2000 RPM--165F

Suction line temp in engine compartment, 2000RPM -- 121F

High Pressure line temp in Eng compartment, 2000RPM -- 165F

Line temp into and out of receiver drier: 2000RPM -- 163F

I hooked the gauges up to get some pressures and found some interesting facts.
At idle the low side was 90 and the high side was 205.
At 2000 rpm the low side was 30 and the high side was 225
Ambient Temp 105F

The compressor is only a couple of months old. I added 6 oz. of mineral oil when it was installed. There has never been more than 34 oz of r12 in the system at any time, so I know it has not been overcharged. All parts were clean and new. Could the compressor be going bad already? Nippondenso 10P15E bought at AMA.


Edited: Thu September 13, 2007 at 10:28 PM by bigwingboy

TRB on Thu September 13, 2007 11:32 PM User is offlineView users profile

What are you best vent temps. Did you drain any shipping oil out of the compressor?

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

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

bohica2xo on Fri September 14, 2007 2:09 AM User is offline

Ok, so if I read this right your high side port is between the receiver/dryer & the TXV. I hate to think of what the compressor discharge reading is.

Your condensor is not doing so well, especially at idle - it has a 10 degree delta. With 165 degree refrigerant headed for the TXV, you can't say there is anything wrong with it yet.

Start by spraying a mist of water on the condensor @ 2000 rpm, while monitoring your pressures. If it drops like a rock, you have a condensor issue - either an airflow problem, or defective condensor.

A system with way too much oil can also act like this, but it takes a lot of oil to make the pressures jump that high with just 12 ounces in the system.

B.

-------------------------
"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.

bigwingboy on Fri September 14, 2007 2:27 AM User is offlineView users profile

Tim, I did drain the PAG oil out of the compressor and replaced it with mineral oil. I was going to leave the PAG oil in, but someone on the forum suggested I use mineral oil since that's what was used with R12. I let it drain for over 30 minutes then turned it over by hand to help any remaining oil out. I did NOT use any flush in the compressor. Thanks for the how-to flushing article on the forum. I didn't measure how much I drained out, but I Added 6 ounces of mineral oil. I did measure that. Since the rest of the system was flushed (hoses, no mufflers) or new I am certain of the oil quantity.
I didn't measure the vent temps today, but at idle it felt like 80+ degrees, at 2000 rpm maybe 55 degrees. It seems like it is slowly getting worse. I'll measure them tomorrow.
What really baffles me is how the low side rises from 30 to 90 when the engine goes to idle, the high side doesn't swing much.

Thanks, Curt

Edited: Fri September 14, 2007 at 2:30 AM by bigwingboy

bigwingboy on Fri September 14, 2007 2:48 AM User is offlineView users profile

Quote
Originally posted by: bohica2xo
Ok, so if I read this right your high side port is between the receiver/dryer & the TXV. I hate to think of what the compressor discharge reading is.

Your condensor is not doing so well, especially at idle - it has a 10 degree delta. With 165 degree refrigerant headed for the TXV, you can't say there is anything wrong with it yet.

Start by spraying a mist of water on the condensor @ 2000 rpm, while monitoring your pressures. If it drops like a rock, you have a condensor issue - either an airflow problem, or defective condensor.]



Thanks, for the reply! Could the 10 deg. delta across the condenser at idle have something to do with the low side abruptly rising from 30 to 90 with the high side dropping from 225 to 205? It appears a lot of compression is disappearing at idle. When the engine RPM is raised from idle to 2000 there is approximately 100 degrees delta.

I spray the condenser tomorrow and see what happens.

My apologies if my questions seem uninformed. I'm no AC expert, but I have been wrenching for 30 years. I like to do things right, I do my research, and I'm always willing to learn from those that know more than me. I truly appreciate the help form everyone!

Curt

Edited: Fri September 14, 2007 at 2:56 AM by bigwingboy

bohica2xo on Fri September 14, 2007 3:26 AM User is offline

The compressor is a positive displacment pump - it displaces the same ammount each revolution. Maximum output happens around 3,000 compressor rpm - this is why we keep telling folks to test @ 2000 engine rpm. Most factory service manuals require testing at 1500 to 2000 engine rpm. As compressor speed increases, the low side should drop like it is doing - but it is too high to start with.

Idle testing does not tell you a lot. Testing @ 2000 engine rpm, doors open, cabin fan on highest speed is a worst case load - the same load as a heat soaked car leaving the parking lot at 5pm.

Your condensor discharge is awfully hot. The 100f delta sounds good, but it should be greater. I don't have the right book within reach, but I believe your vehicle has a mechanical fan. If it is equipped with a viscous clutch, that may be some of your troubles. How does the system work at road speed? Connect the gauges, and tape them to the windshield - then go for a drive...

Try the water mist first. If you suspect a bad fan clutch, either take it for a drive, or use the testing procedure in the FAQ's.

B.

-------------------------
"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.

bigwingboy on Fri September 14, 2007 12:28 PM User is offlineView users profile

Quote
Originally posted by: bohica2xo
The compressor is a positive displacement pump - it displaces the same amount each revolution. Maximum output happens around 3,000 compressor rpm - this is why we keep telling folks to test @ 2000 engine rpm. Most factory service manuals require testing at 1500 to 2000 engine rpm. As compressor speed increases, the low side should drop like it is doing - but it is too high to start with.


Idle testing does not tell you a lot. Testing @ 2000 engine rpm, doors open, cabin fan on highest speed is a worst case load - the same load as a heat soaked car leaving the parking lot at 5pm.


Your condenser discharge is awfully hot. The 100f delta sounds good, but it should be greater. I don't have the right book within reach, but I believe your vehicle has a mechanical fan. If it is equipped with a viscous clutch, that may be some of your troubles. How does the system work at road speed? Connect the gauges, and tape them to the windshield - then go for a drive...


Try the water mist first. If you suspect a bad fan clutch, either take it for a drive, or use the testing procedure in the FAQ's.



B.


Thanks for the reply. The car has both an electric fan and a viscous fan clutch. I have been going through this car and fixing it up. The viscous fan clutch is no more than 1 yr old and works as it should. There are no overheating issues with the car. In fact the temp gauge never gets above 1/2, even when sitting in traffic with 112 degrees outside. The electric fan works properly. I have tested it per the Bentley manual. I even hard-wired it on high speed to see if it made any difference in vent temps. None. There's lots of air going through the condenser.

I agree with your statement about pump output, but I've never seen a system that started out with 90 on the low side at idle, and dropped abruptly to 30 with RPM. The system works pretty good on the highway, fair on the local streets, and not at all when stopped.

Oh well, I'm off to mist.

Thanks again, Curt

bigwingboy on Sat September 15, 2007 1:05 AM User is offlineView users profile

I misted the condenser today with the engine at 2000 rpm the high side pressure dropped form 240 to 160. The vent temps dropped from 65 degrees to 56 degrees.

2POINTautO on Sat September 15, 2007 3:50 AM User is offlineView users profile

It works fine at speed and the HI side pressure seems to be about 2.5 ~ 2.7 times ambient. At idle with fans working as long as the temp drop across the condensor is less than 50 ~ 55F then there is no real restriction, of course your concern here is only 10F drop, condensor is not dropping enough.

I am also unclear if you have put all the freon in yet, it sounds like you are still a can and a half shy, did I miss something there. It also sounds like you replaced the condensor, I would compare the new to the old and count how many tubes there are and anything less on the replacement is a cause of poorer cooling. Re-read and see you put in a different type condensor, I am sorry but you are going to have to go back to the tube and fin type.

You mentioned pulling a vacuum, did you have your freon hooked up during the vacuum and then service directly into the vacuum or did you hook up the can after the vacuuming, this will allow air in.

Without a good condensor and a full system, you cannot diagnose yet, I hate to say that this aftermarket condensor is ok, put the garden hose back on it and fill it full 33.6 oz of freon and let us know temps and pressures one last time. The clutch fan should blow small kittens out of the engine bay at 2000 RPM.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

2POINTautO on Sat September 15, 2007 8:53 AM User is offlineView users profile

Go over to the ODD COMPRESSOR NOISE thread and look at the pic and see my comments below it, its near the bottom of the thread.

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

bigwingboy on Sat September 15, 2007 6:01 PM User is offlineView users profile

Quote
Originally posted by: 2POINTautO
It works fine at speed and the HI side pressure seems to be about 2.5 ~ 2.7 times ambient. At idle with fans working as long as the temp drop across the condensor is less than 50 ~ 55F then there is no real restriction, of course your concern here is only 10F drop, condenser is not dropping enough.



I am also unclear if you have put all the freon in yet, it sounds like you are still a can and a half shy, did I miss something there. It also sounds like you replaced the condenser, I would compare the new to the old and count how many tubes there are and anything less on the replacement is a cause of poorer cooling. Re-read and see you put in a different type condenser, I am sorry but you are going to have to go back to the tube and fin type.



You mentioned pulling a vacuum, did you have your freon hooked up during the vacuum and then service directly into the vacuum or did you hook up the can after the vacuuming, this will allow air in.



Without a good condenser and a full system, you cannot diagnose yet, I hate to say that this aftermarket condenser is ok, put the garden hose back on it and fill it full 33.6 oz of freon and let us know temps and pressures one last time. The clutch fan should blow small kittens out of the engine bay at 2000 RPM.

The condenser is different. The old type was tube and fin; the new type is serpentine. I'm assuming the serpentine holds less freon since placing a full charge in the system rendered some high pressures (low around 75, high around 300) and high vent temps.

I did add a can of freon yesterday to bring the system up to 24 oz. The low side went to 55 and the high side went to 250. Ambient was 103F. Vent temps at 62F with the engine at 2000 RPM. The vent temps did come down about 8 degrees. Adding more freon caused the vent temps to rise. Then I misted the condenser. The high dropped from 250 to 160. The low side went down to 35 from 55 , and vent temps dropped to 54F.

Lots of air is blowing in the engine compartment. I can hear when the viscous clutch kicks in.
I did not have the freon connected when pulling the vacuum. The vacuum pump was hooked to the service hose. When I charged, I loosened the the charge hose at the gauges and let air escape until a small amount of freon came out. Then I tightened the service hose and charged into the vacuum. I doubt there is air in the system.

I see the serpentine condenser as an upgrade to the tube and fin.

Thanks, Curt

bohica2xo on Sat September 15, 2007 7:31 PM User is offline

Curt:

It looks like you have an airflow problem, with your latest information. Yes I know the fans blow like the devil, but the symptoms say that the air is not going over the condensor.

Since you have a different condensor, look carefully at the interface with the body/radiator/support. Is there ANYPLACE that the air entering the fan intake could be bypassing the new condensor? Even a small gap can be enough to cause this, because the serpentine units tend to have high fin densities compared to the tube & fin units.

Your highway speed data, and the misting drop point to a condensor that can do the job - IF it gets enough airflow.

Keep at it, you will win this one eventually. The high pressures indicate a healthy compressor, and the highway cooling says the TXV is ok.

B.

-------------------------
"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.

JJM on Sun September 16, 2007 12:04 AM User is offline

Assuming those temps are accurate (a thermocouple is better), a drop from 260F on the condenser inlet to 165F on the condenser outlet almost certainly points to a partially restricted condenser. Anything over a 40-50F drop is suspect for me - you're looking at 95F!

Your A/C is a heat exchanger. With a 95F drop over the condenser - discounting efficiency losses - you should be looking at 10F vent temps at 105F ambient, but you obviously ain't gettin' that.

Run your infrared thermometer gradually over the condenser from side to side towards the bottom, inlet to the outlet, at 2,000 RPM. The temperature drop should be gradual, and at no point should it be lower the final condenser outlet temperature. If there are any "cold" spots, that indicates a restriction. If it's bad enough, there will be icing in the area.

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com




2POINTautO on Sun September 16, 2007 1:14 AM User is offlineView users profile

As I mentioned, 50 ~ 55F drop or more is not good but I was refering at idle, I am sorry I just do not remember testing the drop at RPM, the others may be correct and it may be too much with a 100F drop but my memory doesnt serve me at RPM, why not drop a lot, with more airflow, dont take my word for it, a restriction is a restriction and it should drop more than 50F at idle. Additionally, your HI side test port is after the condensor so you cannot tell if there is a restriction. Sorry to be persistant, I am not a guru, I admit it, I still think that with misting and a full charge, it will work, if it does, I would go back to the original type condensor and add an extra fan to the front (pusher).

-------------------------
Give all the dirty details
and dont forget the LO & HI pressures
Year, Make & Model would be nice too

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.