A/C won't draw in R12... - Page 2 - PeachParts Mercedes-Benz Forum

Merkey · #16 06-09-2010, 01:22 PM

Evap, expansion valve and dryer replaced, lines and condensor flushed. Compressor flushed.
Correct amout of Ester oil added to each componant.
Both climate control unit and the klima was swapped with his 300TE unit that works fine...

rrgrassi · #17 06-09-2010, 01:22 PM

IIRC, The pressure switch makes or breaks the grounding connection for the compressor clutch. One lead should have continuity to ground and the other traces back to the compressor.

I could be wrong about that, someone else can confirm it.

Merkey · #18 06-09-2010, 01:27 PM

LOL, you guys are so fast...
Trying to catch up with your responses!
Larry:
No offence taken... trust me, I have made every stupid oversight in the book, feel free to ask or question anything or everthing!
You here a click and the front bell of the compressor engages and spins with the pulley... and the aux fan kicks in.

rrgrassi · #19 06-09-2010, 01:29 PM

Are you supposed to use Ester Oil with R-12? I thought you were to use mineral oil. I do know that PAG will not mix with R-12.

Merkey · #20 06-09-2010, 01:30 PM

Wow...
Ok, just tested the pressure switch...
With my MM set to ohms both pins read OL to ground...

Merkey · #21 06-09-2010, 01:31 PM

We checked with people over on his evap replacement thread over in the Tech section and found that they agreed Ester works and is compatable with both..

Merkey · #22 06-09-2010, 01:51 PM

Reading again the charging procedure, I left the jumper on pins 5 and 7 of the Klima, and with the compressor running, I tried to charge it again..
The can is draining, and getting cold... I put in about half of it and checked the Interior vents ambient temp is about 75 here in my garage... and vent temp was reading 62... so something is working...
Happy with that and looking at the pressures, I pulled the jumper and put the Klima back in... No compressor engagement again..

Merkey · #23 06-09-2010, 02:38 PM

Thanks Larry, my boy said it should take 3 cans, so thats what I will put in..
Anyone tell me if the pressures look ok, with 75 deg ambient?

Mazootpusher · #24 06-09-2010, 02:47 PM

I am thinking the rpm sensor could be at fault,also the problem could be;
(1) the KLIMA relay or (2) the AC control unit or (3) the RPM signals provided to the KLIMA relay.
A common failure is the RPM sensor in the compressor.
replacing it will mean removing the gas from the system and removing the compressor from the car,
You can test the sensor between pins 9 and 11 of the KLIMA relay socket,
with engine off it should have resistance between 550 and 650 ohms.
With engine on at idle you should see about 0.3 volts AC between pins 9 and 11.

Merkey · #25 06-09-2010, 11:06 PM

Quote:

Originally Posted by Merkey

The compressor kicked in and the pressure reading were 160psi High side, and 35psi low side...

This reading...

vstech · #26 06-10-2010, 12:11 AM

165 and 35 sounds low. 165 sounds low, but at only 75 it's hard to tell. 35 is also low, for a 65F output. but if your charge is low by weight, then it'll not be cooling properly, and the expansion valve could be trying to compensate.
it's best to just put in the correct volume of refrigerant, and then determine off the air temps what's going on.
165 and 35 at least show the compressor is doing something.
verify volume of refrigerant, and then report temps outside, and inside. with the blower on high.

ps2cho · #27 06-10-2010, 01:42 AM

Well it took all 3 cans. No idea why the sudden change, but it did, so I'll take it what it's worth....Final reading is 45psi low and 215psi high. Sound about right?

Ambient temperatures were ~75F and I was reading a low of 45F at the vents. Sound about right also?

Now..with the klima back in (no jumper/bridging), the compressor is not kicking on still. I have swapped both the Klima and the CCU with the one from my wagon (in which the A/C works fine), so can I rule both of them off as the culprit? What is the next thing to check? The RPM Sensor as stated above?

nhdoc · #28 06-10-2010, 06:32 AM

Quote:

Originally Posted by ps2cho

Well it took all 3 cans. No idea why the sudden change, but it did, so I'll take it what it's worth....Final reading is 45psi low and 215psi high. Sound about right?

Ambient temperatures were ~75F and I was reading a low of 45F at the vents. Sound about right also?

Now..with the klima back in (no jumper/bridging), the compressor is not kicking on still. I have swapped both the Klima and the CCU with the one from my wagon (in which the A/C works fine), so can I rule both of them off as the culprit? What is the next thing to check? The RPM Sensor as stated above?

The low side pressure is a little high and the vent temp is too. IIRC you should be seeing closer to 30-35 PSI and vent temps in the mid to high 30s if it is only 75F out with the setting on max cool. I'd guess that if it gets really warm you might have a hard time keeping the car cool with that system and with R12 that should never be the case. You might have a problem with the expansion valve which might have been why you had trouble charging it in the first place. You might try tapping it lightly with a screwdriver handle and seeing if it changes the pressures. Also, make sure the small sensing bulb and capillary tube is properly routed and hasn't gotten detached.

vstech · #29 06-10-2010, 08:14 AM

go for a drive and report the temps at the vents.
it's kinda hard to determine pressures and temps at idle.
are your fans working? did the aux fan come on with the jumpered kilma?

ps2cho · #30 06-10-2010, 09:44 AM

Yes aux fan was on. The dealer put a relay down there by the drier and it kicks in automatically as soon as the A/C is on.

The expansion valve was brand new...what could be wrong with it?
I also put the oil in with the expansion valve not attached, was this wrong? The FSM does not state any oil should be put in the expansion valve.

What is the sensing bulb and capillary tube?

The fresh air door should close for both the A/C settings and open for Econ, correct?