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Air Conditioner blower control question

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drcevin
Posts: 59

Air Conditioner blower control question

Post#1 » Tue Mar 31, 2009 6:44 pm

I was told by the P.O. that the AC didn't work. After playing with it i found that the freon was a tad low but the compressor kept cutting off when it shouldn't. I discovered that if i turned the round blower control knob off and back on that the compressor kicked back on. Then the compressor would quit working again, once again i turned the fan blower off and back on and the compresor started back up. I assume at this point that it's a contact in the fan control knob itself. Does this sound like a possible diagnosis? Is this a common problem?

Thanks,
Doc

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inkblotz
Posts: 5735

Re: Air Conditioner blower control question

Post#2 » Thu Apr 02, 2009 4:25 am

I would think a good test would be to bypass the switch connecting the 2 wires to see if the clutch of the compressor is working properly. If the clutch grabs hold and remains on (the compressor spins) then the switch would be suspect.

Not having one in front of me I do not truly know the feasibility of this test.

Mark

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jonathan joseph
Posts: 494

Re: Air Conditioner blower control question

Post#3 » Thu Apr 02, 2009 5:01 am

A/C compressors generally rely on the refrigerant to carry lubricating oil through the system. They have a low pressure sensor to shut the system down in the event that refrigerant is lost and therefore the compressor is not getting lubricated. This could be you problem. I'm not sure if that system is switched on by the blower switch or not but what "might" be happening is that every time you turn it on it tries to go but when correct pressure isn't reached it gets shut down. Better get it checked out. I wouldn't just keep turning it on and off.

Jonathan

Theo85
Posts: 109

Re: Air Conditioner blower control question

Post#4 » Tue Jun 23, 2020 4:09 am

Reviving this old thread as I seem to have the same problem with the A/C. When i turn the fan on the compressor kicks on but the air turns warm a few seconds later.

I was thinking of buying a freon refill kit, but I have no idea if that's something that is possible to use on the G. Is there a refill nozzle thats accessible in the engine bay? 96 G320 LWB btw.
Hilda - 1996 G320 LWB
Ottawa, Canada

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AlanMcR
Posts: 5281

Re: Air Conditioner blower control question

Post#5 » Tue Jun 23, 2020 8:49 am

R124 or R12 based? That year is near the cutoff.

I know where they are on my 1996 diesel, but it may not match up with your system. Refilling is at best a short term solution since the gas that was there must have leaked out. It it leaked very very slowly then you have some chance of cooling happiness.
...Alan

Costa G
Posts: 19

Re: Air Conditioner blower control question

Post#6 » Wed Oct 14, 2020 9:34 am

I had the same issue with my ‘96 G320. Everything checked out (as far as Freon charge, fan switches, etc). I thought I was having an issue with the main control relay, so I started checking all the inputs and outputs. Everything looked good here as well except for one input. I believe only the the 463 had this feature, but it turns out that the a/c compressor has a rpm sensor (on the back side , opposite the clutch) that measures the difference between engine rpm, and compressor rpm. If any differences are detected, the main control relay reads this as a sign of belt slipping, therefore cutting out the compressor. Most times, you can just turn the ignition off, then restart the car, turn the a/c back on, and all is well. Turns out my compressor has a bit of a hard spot sometimes, which kicks in this safety feature. New compressor solves this. Hope this helps.

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AlanMcR
Posts: 5281

Re: Air Conditioner blower control question

Post#7 » Wed Oct 14, 2020 11:21 am

As far as I can tell the 1996 diesel had all of the new electronics, transmission, and R134a based AC, a year earlier than the gas version. The R134 AC is much simpler than the earlier R12 versions. A couple of dumb relays and some sensors. No RPM sensor. So, I think that your experience was with the the older system, or perhaps specific to gas versions.
...Alan

Costa G
Posts: 19

Re: Air Conditioner blower control question

Post#8 » Wed Oct 14, 2020 1:16 pm

Mine is a factory R134a system.

User avatar
AlanMcR
Posts: 5281

Re: Air Conditioner blower control question

Post#9 » Wed Oct 14, 2020 5:41 pm

Interesting. Both gas & diesel made the change over in 1996, but used different AC control systems.

No RPM sensor on mine, before or after the compressor replacement. It could have used a sensor. The compressor seized up and the belt kept turning the pulley. Turned the clutch into a smoking cinder.
...Alan

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