I have been working on an idle problem with my 99 xk8 for quite some time and at this point I think it is ironed out. However, the A/C has a problem.

With the A/C on I noticed it did not cool down like it has in the past and it would produce an uneven idle problem. The gauge showed that the low side was low and the high side was high so I elected to drain the system and pull a vacuum and recharge to specs.

When I recharged the system I got High pressure (80lbs) on the low side and (75lbs) on the high side and no cooling. I should mention I had only one code on the A/C and that was the pressure switch and it cleared. So I elected to drain and refill the system again taking my time and double checking the process, high pressure closed and the low pressure open on the manifold when recharging. The low side at 105lbs with needle bouncing and the high side at 125lbs cleared the low pressure code and still no cool air. Not the results I was looking for so I drained the system again and pulled a vacuum and that is where I am now.

I am not well versed on the A/C system but I am about to get a replacement compressor but I keep thinking about expansion valve that is located in the heater/air conditioning unit that is in the car but never heard of one failing. I feel that the bouncing was generated by the compressor. I do not hear any additional noise from the compressor that I think is abnormal. Things I read say low pressure high, high pressure low and needle bouncing look at a defective reed valve and/or compressor.

I checked again and the only code I get is 23 and that is generated every time I pull a vacuum on the system.

A/C is not my strong point so any input would be greatly appreciated.

I am on hold right now to see if I am on the right track so any input would be greatly appreciated.

 

How about anyone that can help Gus to resolve his issues?

A chance for someone to help one of the legends of the forum.

Hope you get it sorted soon Gus
Best

Jim

 

Bump!

 

Gus,

Have you listened to your running compressor using a mechanic's stethescope? When my 2005 S-Type's A/C system began to lose cooling effectiveness back in May 2010, the compressor sounded normal to my unassisted ears. But when I touched my scope to its case, it sounded like a cement mixer full of gravel. The bearings were in the process of dying. This confirmed that the compressor was indeed my problem. A new one resolved the issue and the car's HVAC system has been normal ever since (furiously knocking on wood right now)....

If you are still running your original compressor I will not be surprised if that is indeed your culprit....

Best of luck and keep us posted....

 

Hi Gus - what were the high and low side pressures before you recharged the first time? - you say the high side was high and the low side low? At 75F ambient you should be around 35/45 low side and 150/170 on the high. The pressures you have now sound to me like static pressure - i.e. compressor not running or pumping. If you had a blockage in the system you would likely get high discharge pressure until the high pressure switch cuts the feed. As you say, expansion valves rarely fail - they can block with debris or moisture(which freezes in the orifice) but as I say that would give high discharge pressure.Same if the receiver/drier was blocked. I would imagine you have checked for leaks? Will the system hold a vacuum overnight?(that's also good for removing moisture from the system.) Did you notice a deterioration in the cooling performance before the present work? My guess is the compressor - either worn out or broken valve - if you remove it from the car you could bench test it - just check whether it pumps. Be sure to cap all open ends whilst the system is being worked on - moisture from the air is not desirable. If it's the compressor change the receiver drier as well and be sure to replace any oil you lose. If the expansion valve was defective that could also cause low discharge pressures - but as said they are pretty reliable.

 

Jon - I have not listened to the compressor but will get it in the air and see what I can hear.

Batroute - I did not record the readings at the first test but the temperature was 90⁰ with the low psi on the low side and the high psi on the high side.

I do agree that I am looking at static pressure now.

I have checked for leaks and pulled a vacuum and it did not move for a full 24hrs so I am comfortable with stating no leaks. Yes the car did not cool as it has in the past and the compressor did cause additional idle problems.

I have a buddy that is going to help me this weekend. He many years of experience with residential A/C systems (has his own company) and with a little luck we will come to an agreement on the cause of this auto A/C system.

Thank for the input, I am going to check things again and see what I can come up with and as you know I will let you know what we find.

 

Parts are on order and will update you when I get them installed.

 

After vacuuming out, how did you put the oil in the system?

Did you use the right type and weight?

Also, are there any codes?

Problem with vacuuming out the system is that you took out most of the oil, but not all and if the system calls for 2 oz. and you put in 2 oz., but the system still had an 1 oz., you see my point?

Not having the correct oil weight and type and amount can play havoc on an A/C unit, especially on a unit that is weak to begin with.

Also, is the clutch engaging, if not either the clutch or compressor, or electrical fault is the problem. High pressure on the low side, usually means the compressor is not engaging or your ECM is not telling your compressor to engage.

 

Good points randyb but how do you know how much oil is in the system?

 

No I did not add oil! When I pulled a vacuum I did not see evidence of oil nor did I see the level of the vacuum pump oil increase. I will know when I replace the compressor.

The only code I had was one indication low 134A pressure and I cleared it. I should also mention the clutch engaged when the 134A pressure was acceptable.

I should also mention that the A/C worked but was not a efficient and the gauges were not reading correctly and the low side was bouncing.

 

Most systems that vacuum out the freon have accumalators for oil and you can measure.

Note, putting a new compessor on and not putting the correct oil in before charging is a sure fire way to make sure you will replace it again in the not to distant future. Also, prime the compressor after adding oil and before starting engine, same thing you do for a new engine.

Good Luck and OP sounds like a bad compressor!!

 

I have a new compressor and plan the check the oil type and volume. I am on hold to flush the system. This is new ground and need to do it correct. I am reading a lot on flushing the system because I do not want to do it again.

Gus
www.jagrepair.com.