AC Pros - a little help with AC diagnosis?
10-13-2016, 12:11 PM
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1995 Mercedes C36 AMG
AC Pros - a little help with AC diagnosis?
Vehicle: 1995 C36 AMG
Consolidating this thread from the C36AMG forum - seeking more help:
I was getting intermittent a/c. Lots of hot air. Trying to narrow the diagnosis before I go to the Indy, charge system or replace parts. I'm a novice, but enjoy trying to DIY. Crawled a bunch of threads, help from forum & YouTube. Model variants lead to confusion. Took a while to nail down onboard diagnosis. Also tooled up with HF guages, vacuum, ...
First diagnosis:
Here's my results: (the car had not been run and was outside at 58degree)
01 - 59 In-car temp
02 - 55 Outside temp
03 - 57 Heater core sensor temp
05 - 59 Evaporator sensor temp
06 - 58 Engine coolant sensor temp
07 - 03.3 Refrigerant Pressure in Bar
08 - 15 Blower control voltage
09 - 03 Software status
15 - 72 Selected in-car temp
20 - 02 Version code
21 - 00.0 Engine speed RPM
22 - 00.0 A/C compressor speed
23 - 00.0 Vehicle speed
50 - 74.0 Not used
51 - 00 Number of Current poly belt slip
52 - 00 number of stored poly belt slip
The onboard Diagnosis returned:
dl R current
End
dl.R stored
60. A/C Compressor Electromagnetic Clutch Short Circuit intermittent
End
del
The gauges returned:
at 59 degrees ambient temp.
Low Press side: 30psi Normal Range: 25-35psi
High Press side: 75psi Normal Range: 135-155psi
So, I had a Normal low side and a LOW High side.
Suspecting low refrigerant and being environmentally cautious, I had the AC evacuated at a shop. They only found .26lb of Freon.
I went home and vacuumed the system a couple more times. Then freshly charged to the 29oz spec. The car does hold vacuum pressure of -24psi for one hour.
Ran another diagnosis and here's the results:
Low Press side: 30psi Expected: 25 - 35psi
High Press side: 200-210psi Expected: 135 - 155psi
Diagnosis chart suggests: Expansion Valve or Orfice tube obstruction
The car does chill to 35F now and it operates at 15 Bar at idle. I've cleaned the engine/underside and continuing to observe for leaks.
Your thoughts? Before I go chasing parts or changing the expansion valve which looks like a PITA. Thanks.
Consolidating this thread from the C36AMG forum - seeking more help:
I was getting intermittent a/c. Lots of hot air. Trying to narrow the diagnosis before I go to the Indy, charge system or replace parts. I'm a novice, but enjoy trying to DIY. Crawled a bunch of threads, help from forum & YouTube. Model variants lead to confusion. Took a while to nail down onboard diagnosis. Also tooled up with HF guages, vacuum, ...
First diagnosis:
Here's my results: (the car had not been run and was outside at 58degree)
01 - 59 In-car temp
02 - 55 Outside temp
03 - 57 Heater core sensor temp
05 - 59 Evaporator sensor temp
06 - 58 Engine coolant sensor temp
07 - 03.3 Refrigerant Pressure in Bar
08 - 15 Blower control voltage
09 - 03 Software status
15 - 72 Selected in-car temp
20 - 02 Version code
21 - 00.0 Engine speed RPM
22 - 00.0 A/C compressor speed
23 - 00.0 Vehicle speed
50 - 74.0 Not used
51 - 00 Number of Current poly belt slip
52 - 00 number of stored poly belt slip
The onboard Diagnosis returned:
dl R current
End
dl.R stored
60. A/C Compressor Electromagnetic Clutch Short Circuit intermittent
End
del
The gauges returned:
at 59 degrees ambient temp.
Low Press side: 30psi Normal Range: 25-35psi
High Press side: 75psi Normal Range: 135-155psi
So, I had a Normal low side and a LOW High side.
Suspecting low refrigerant and being environmentally cautious, I had the AC evacuated at a shop. They only found .26lb of Freon.
I went home and vacuumed the system a couple more times. Then freshly charged to the 29oz spec. The car does hold vacuum pressure of -24psi for one hour.
Ran another diagnosis and here's the results:
Low Press side: 30psi Expected: 25 - 35psi
High Press side: 200-210psi Expected: 135 - 155psi
Diagnosis chart suggests: Expansion Valve or Orfice tube obstruction
The car does chill to 35F now and it operates at 15 Bar at idle. I've cleaned the engine/underside and continuing to observe for leaks.
Your thoughts? Before I go chasing parts or changing the expansion valve which looks like a PITA. Thanks.
10-13-2016, 04:37 PM
#2
Out Of Control!!
If you had a faulty expansion valve it would show up as a fluctuating needle on the AC gauges-----does the needle fluctuate---simply yes or no??
10-13-2016, 06:50 PM
#3
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1995 Mercedes C36 AMG
The High Press side moved between 200-210psi once completely recharged, but that's about it. I can retest. What am I looking for - which gauge - how much fluctuation? Thanks.
