W124 air conditioning problems, wife’s 1995 E-320. I have replaced the expansion valve due to leak, system fully charged, cools only to about 80 degrees. System low side pressure seems high, about 60 where experience would suggest 30, high side pressure low, 225 instead of around 300, but otherwise appears normal, no bubbles in sight glass, auxiliary fans working, dashboard climate control functions OK. The symptoms seem to suggest expansion valve stuck open, which seems unlikely since I just replaced it, or a weak compressor, which I don’t know how to check. I am hoping somebody knows more about this than I do (shouldn’t be hard) and can help me figure out what to fix or steer me in the direction of someone who, for a reasonable price, can.
I think I can do the work, once I know what’s needed. I have replaced compressors before, 1986 300E, 1999 BMW 323i, replaced a compressor shaft seal, and lots of other mechanical maintenance from water pump to fuel injection and, with a friend who definitely knew his stuff, replaced the cylinder head and timing chain on that ’86 300E..
My wife thinks the W124 is the best Mercedes-Benz ever, perfect combination of sophistication and simplicity, a beautifully driving car with outstanding steering, ride, and driveability, and I’m inclined to agree. We know the 1995 E-320 series ends the W124, 300E era. I will say, though, while my car, 2000 C240, is much more “Chryslerized,” the a/c works extremely well.
This is my first forum post ever. I hope I did OK and hope someone can help my wife and me out. Thanks.
Mine works well at 25-30 psi on the low-side . I agree with your ideas maybe the compressor is going. I was thinking over charged ,but your high side "should be" higher.
Perhaps jump the clutch to run steady and watch your pressures to get a max , to see what the compressor can do. Keep a water hose ready to cool the condenser .
I waited until spring then replaced the compressor and it did not help at all. So I finally did the smart thing and had a shop check the a/c out (only $85). They said the problem is a blockage in the fuel cooler, a fitting on the hose from the expansion valve back to the compressor. This would explain the low side too high -- high side too low symptom. Now my question is, with a replacement hose (manifold set) at $500+ (Adsit Co.), could I just cut the fuel cooler out of the system and replace it with a section of a/c hose? I'm very sure this would fix the a/c but I don't know if it's safe to jettison the fuel cooler.
The car has been terrific except for the a/c problems: leaky expansion valve, leaky evaporator (and one huge job to fix), and now a needlessly replaced compressor. I am still money ahead, of course. Having a dealer or shop replace the evaporator would have been a couple of grand or more.
Maybe I am at last on the road to a fix. July in Kansas City, so I sure hope so. Thanks for all the help.
Last edited by Ken8911 : 07-13-2007 at 11:53 AM.
Reason: misleading before, better heading now
Can you measure the temperature of the low pressure hose ? May need a special thermometer that wraps around but this is an inexpensive part and wothwhile to have.
Turn on the car, turn on the a/c on high fan, recirculate mode, let it run for about 5-10 minutes. If you could, then read the temp of the low side hose, near the valve somewhere. Then from the gauge, read the temperature corresponding to the pressure, there is a dial for the refrigerant that you have (R134a). If the temp on the hose is more than 20 deg lower than the temp from the dial, you are overcharged. Reduce the low side pressure till you get the temp diff to be between 15 and 20 deg. This works for home a/c because the air flow is constant, in cars it is variable so there are some variations, but this will still be a good rule for high blower speeds, for lower blower speeds it may appear to be slightly overcharged. Hope this helps. And high side pressure between 180-220, even as low as 160, is o.k., dont need 300, 300 is way high.
Saumil: Thanks for the speedy response. The shop that diagnosed this said they identified the blockage at the fuel cooler because the temperature on one side was 76 degrees, and on the other 34 degrees. This makes me think if the diagnosis is right I have three alternatives: replace the hose set (expensive), try to clean out the fuel filter blockage (unlikely to work) or bypass the fuel cooler (seems likely to work, but violates manufacturer's specs and might not be safe. When I charged up this system last weekend, it never cooled much, not when first charging, not later on either. I'm guessing overcharging is not the problem, but let me know what you think if you would please. Thanks!
I am lost, where did the fuel come into the picture from ? What are the two sides that you are talking about ? Low pressure and high pressure side ? There must be some misunderstanding here !!
Linear Mode
