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'91 300CE M104 and '86 560SL
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237 Posts
Discussion Starter #1
I was having a problem with no AC coming out of the center vents - common problem and one that I had previously fixed on this car by replacing the Center/Defrost vacuum pod. So, today I took the radio out and the AC/Heater control panel, the glove box and pulled out my vacuum pump. I got the center vents working, but I think I have a vacuum leak somewhere - NOT in the new pod I replaced, but a slow leak in the one that's in the heater box...

Anyway, after I do all of my troubleshooting, I put things together and now the AC compressor won't engage at all. It was working fine just earlier today - before I did all of this "fixing"!

Any suggestions? I suppose it's possible that it's a coincidence...but could I have accidentally disconnected something?

ryan
 

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US spec MB560SL 1986, Audi A4 and A6, Ford Taunus 1964 17M and 2.0 1975
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1,419 Posts
In the center concole area are inside/dash temp sensor and of course the AC panel. I would first check if their wires and connectors are properly at their places.

Check AC fuses 7 and 8.
 

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'91 300CE M104 and '86 560SL
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237 Posts
Discussion Starter #3 (Edited)
Put gauges on it today and residual pressure evened out at 100 psi...jumped the low pressure switch and still couldn't get the clutch to engage. Checked all the fuses and they are fine.

Found the following PDF on Programa's web site and steps 1-3 checked out, but I'm not sure at step 4. Testing between pins 6 and 3 of the right side connector gives me infinity resistance - yes it's larger than 35 ohms, but I;m not sure....

Actually, I'm not sure about anything! The AC and compressor has always worked great in this car - I just went to check out the vacuum issue with the center vents (which I have fixed before a couple of years back) and now it won't come on.

Any ideas as to why the clutch isn't engaging? Also, the clutch doesn't come on when running the Defrost...

ryan
 

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1978 450SL--117K
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1,374 Posts
Make sure your klima is seated properly. If it is and still no go when jumpering the compressor pressure sensor, remove it and jumper the pins for 12V in and 12V out together and see if the compressor engages. If it does, and all else is well (Gluek's test procedure) then it's most likely the Klima relay.
 

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'91 300CE M104 and '86 560SL
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237 Posts
Discussion Starter #5
Installed another Klima relay today and still no go...can't figure out what's going on here. I will try and build the connector as described by Glueck and go from there.

It seems obvious to me that I have disconnected some connection in removing the AC control panel when I was looking for vacuum pod related issues to there being no air from the center vents...but, I've looked and looked and can't figure out what I might have done.

ryan
 

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'91 300CE M104 and '86 560SL
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237 Posts
Discussion Starter #6
I know it's been a while since I last posted on this thread, but I have made no progress - and it's coming up on summertime in Oklahoma.

Anyone help?

Ryan
 

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Previous: 1989 190E 2.6, 1997 E420, 1985 380SL, 1975 450SLC
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747 Posts
In my experience it's almost certainly something you impacted with your earlier repair. I'd retrace your steps being mindful of things that may have become disconnected and/or stressed during disassembly. You did check the A/C fuse..?
 
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