R134 Conversion Done - No Compressor Engagement? - PeachParts Mercedes-Benz Forum

Cummmins · #1 07-20-2013, 03:37 PM

Hi. I just got done with my R134 a/c conversion. Pressures and temps are perfect. BUT, the a/c compressor will not turn on with the climate control. I have to hot wire the compressor to get the system to work. There is no power at the compressor connector. The temp sensor on the dryer is turning on the fan. The low pressure switch is closed. I have the climate control set to the coldest setting (i can hear it make some kind of sounds when i do this), and the button pushed with the up and down arrows both filled in. I also have the fan on high. What is the best way to go about diagnosing this system from where I am at? Any relevant help would be appreciated!

Mike D · #2 07-20-2013, 07:44 PM

First question.
A. Did it work before?
Second question.
Why did you change the system.
Third question.
How did you convert it? Just feeding a couple of cans of R134 into an old, non-working R12 system just wont cut the mustard.

Cummmins · #3 07-21-2013, 12:09 AM

No, the system did not work before. I have owned the car for a couple of months, and it didn't work when I bought it.

I changed the system because it it was completely inoperable, and r134 is a "good" replacement for r12.

It appears as though you have assumed that I tried to do a hack job - which I do not appreciate. The system was evacuated, and flushed. All o-rings were replaced. Schroeder (sp?) valves were replaced, along with the dryer and expansion valve. Conversion valves were installed. The compressor was drained, and refilled. The temp sensor and pressure sensors were tested. Fan operation was tested. The system was vacuumed down and tested for leaks. The system was charged and tested.

I do not have a complete wiring diagram to help me track down what is going on. I do not know if there are any other electronics (modules etc.) that are involved.

tilac1 · #4 07-21-2013, 07:15 AM

I had the same problem, it was the KLIMA relay behind the battery. I found one on Ebay.

What are your vent temps on a hot day? My 134 conversion is not cold enough....

Mike D · #5 07-21-2013, 08:41 AM

Didn't mean to ruffle your feathers.

I was trying to determine the process you went about to convert the system. You didn't give us enough information to even begin to diagnose your problem.

You've read some of the threads which go on for 4 pages and it turns out the poster failed to mention one critical step he skipped.

As an example, it would be convenient to know what type of car you are working on.

engatwork · #6 07-21-2013, 08:44 AM

Quote:

it would be convenient to know what type of car you are working on

That is what I was wondering.

Cummmins · #7 07-21-2013, 10:36 AM

Sorry about that -I really need to fill in my signature. It is an 85 300D.

Feathers not ruffled. I had just spent a lot of time on it if you know what I mean. No worry's.

My vent temp was right at 60* when it was 101* in the garage. What is a KLIMA?

Mike D · #8 07-21-2013, 11:39 AM

KLIMA voltage relay found on the W126's and other models. Big honking relay usually found on the firewall, interior RHS bulkhead or inside the fuse compartment depending on the model.

Cummmins · #9 07-21-2013, 01:09 PM

Just did some reading on the KLIMA relay, then did some troubleshooting. It looks like I have a bad relay. But, I would like confirmation on this. With the car running and the ac turned on I have 12.4v on pins 5 and 7. 5.96v on pin 2. 9.1 ohms on pin 7 (resistance of compressor clutch I am guessing. Pins 6 and 4 are open. When the wide open throttle switch is closed, or the micro switch on the valve cover is closed pin 4 goes to ground. Pin 31 is grounded.

engatwork · #10 07-21-2013, 02:54 PM

Somewhere around here is the schemactic for the Klima. It may even be printed on it. Try jumping the two pins that supply power to the compressor. You can run it like that but keep in mind it won't drop out if it starts to lock up.