1995 E 320, automatic, SW, AC compressor not engaging
Thread Starter
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Joined: Dec 2005
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From: I am United Arab Emirates
E 240 model 1999 Station wagon
1995 E 320, automatic, SW, AC compressor not engaging
My climate control was working just fine yesterday, but today I have no air conditioning. When I set the climate control to warm temperatures I get heat, and when it's on cold temperatures I only get outside air blowing in with no air conditioning. When the vents are set to windshield defrost (the button on the far left) it only blows hot air regardless of the temperature setting of the climate control (is this normal? I hadn't noticed this until now.) I checked the Poly V belt and it's fine; it seems that the A/C compressor just doesn't engage. The fan(s) that usually turn on when the A/C is running don't come on at all.
In my car the moment i turn the air blower switch the AC compressor use to engage. The question is this normal? But now as mentioned above the AC compressor is not engaging. The freuon gas is ok.
Any ideas as to what may have gone wrong? I've search this forum but was unsuccessful in finding info on this problem. I would appreciate any help I can get before I start poking around under the hood tonight.
In my car the moment i turn the air blower switch the AC compressor use to engage. The question is this normal? But now as mentioned above the AC compressor is not engaging. The freuon gas is ok.
Any ideas as to what may have gone wrong? I've search this forum but was unsuccessful in finding info on this problem. I would appreciate any help I can get before I start poking around under the hood tonight.
Thread Starter
Almost a Member!
Joined: Dec 2005
Posts: 47
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From: I am United Arab Emirates
E 240 model 1999 Station wagon
I took the car to an AC Mec. He had checked the switch mounted on the AC filter bottle through a tester. It was not getting the current. (On which one can see the gas flow as there is a transparent window). So after that he just pulled a relay as shown in the pic. This relay was behind the battery having around 8 pins or so. While he was pulling the relay I heard the compressor getting engaged for a second. So he just cleaned the legs of the relay and plugged it back to its place.
For the whole day my car AC was working very fine. I asked the tec that what was the defect. He laughed and said even he never knew what was it……………… But thanks God the AC is working till now………
For the whole day my car AC was working very fine. I asked the tec that what was the defect. He laughed and said even he never knew what was it……………… But thanks God the AC is working till now………
Junior Member
Joined: Dec 2006
Posts: 60
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From: South River NC
OK, this is the same problem I'm having now. I too jumped all the pressure switches in the refrigerant lines and the crompressor still doesn't engage. I have pulled the MAS relay like pictured above without luck.
I understand this relay controls the fuel pump as well. If I pull it out with the engine running, it dies.
I suppose the AC side of this relay could be bad, but how often does this occur?
Anyone have one for sale?
Thanks, Perri
I understand this relay controls the fuel pump as well. If I pull it out with the engine running, it dies.
I suppose the AC side of this relay could be bad, but how often does this occur?
Anyone have one for sale?
Thanks, Perri
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Joined: Dec 2006
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
I don't think this is one of those DIY things. It could be getting an out-of-range signal from the OA sensor and think it's too cold outside. The sensor is located at the inlet to the airbox. It could be a fried controller. Could be a fried HP switch. Without going through a ladder diagram who knows? I would start with R and R all the fuses. The connections sometimes get loose.
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MBWorld Fanatic!
Joined: Dec 2006
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
I would love to upload the .pdf for the explanation of how the climate control system works from the service manual but it's 15.2 Mb. That's a HUGE document. This is a complicated system. Even the wiring diagram is 5 Mb. Due to modern micro processor technology, they are much simpler now. But I was serious when I said you should remove and re-install all the fuses.
Junior Member
Joined: Dec 2006
Posts: 60
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From: South River NC
Zorro, I found the answer! Can't you read? I started at the climate control and worked my way to the compressor.
Want to know which terminals at the MAS to jump to determine compressor viability?
This system is similar to my 2 Cadillac climate controls. Except the Cadillacs have a BCM that talks to the PCM. The Caddy systems are quite a bit more complicated though.
Want to know which terminals at the MAS to jump to determine compressor viability?
This system is similar to my 2 Cadillac climate controls. Except the Cadillacs have a BCM that talks to the PCM. The Caddy systems are quite a bit more complicated though.
MBWorld Fanatic!
Joined: Dec 2006
Posts: 1,042
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
I'm not sure what sort of FM goes on inside this MAS relay. If I get some time this weekend I will dig into the wiring diagrams and see what I can find. It's like 14°F and snowing here; hard to think about air conditioning. But I realize that we can't all live in paradise.
