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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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Discussion Starter #1
Yep you read that right. New compressor installed during a water pump job (one of those "while I'm in there"). The A/C was working just fine and the reason for the new compressor was a front seal leaking so a failure with metal in the lines was not an issue. During the reassembly of everything the power feed wire was pinched/shorted which blew the #5 fuse. The wire was repaired and now when the car is running the compressor also runs no matter which button on the Climate Control is pushed, even "OFF" it runs. I pulled the plugs from the pressure switch, no joy so I unplugged the compressor so I can run the car. I did a search on the CCU and found nothing, like I said the system was working before the W/P job. Is there an additional relay that controls the compressor. Does anyone have the wiring diagram of the A/C and compressor circuit ? Thanks
 

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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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Discussion Starter #6
Thanks guys. Actually I didn't think of the Klima relay until the morning after I posted (mindset was still on the reassembly and if I did anything else stupid :confused:). I've got another Klima on the way, no spare unit here but I'll be sure to get an extra. In the meantime she's driveable and the weather has cooled off quite a bit

And Thanks John for the PDF
 

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1985 300 TD 1981 300 SD
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318 Posts
When you go to install the new klima why not open up the old one and have a look, if the contacts are fused you may be able to free them up.
 

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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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Discussion Starter #8 (Edited)
Yeah Kev, I'll do that in a few. I took my old FPR apart (thought they were epoxied together) a while ago (intermittent operation and was changed with a new one with fuel pumps and filter), I didn't see any burned spots on it, had another FPR from parts car I never checked and popped it in just long enough to see it works so now have a good spare. So far a spare EZL ignition control, alternator with a new regulator, an additional new voltage regulator, spare FPR that ride in the boot in a box

Popped the Klima cover off, no moving parts I could see and don't have any diagram of the circuits, no burned spots
 

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Two '87 570SECs, one '87 560SEL
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Good ideas - I'll go find my spare Klima and try it in my "AC Always On" SEC too.
 

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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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Discussion Starter #10
Update, the Klima relay got here and I popped it in after cleaning the pins with an pencil eraser (old Army trick), anyway, no joy, it didn't work. Now comes the part I've never understood about electronics, after lightly thumping it on my workbench I put my old Klima back in (remember the other day the compressor wouldn't kick out/off) and it worked like it should :unsure: kicking in and out depending on the button pushed. Now waiting for FedEx to deliver the switches, was supposed to arrive Saturday but they changed the delivery date to today (Tuesday) and here it's 8:25pm and still not here, they did this once before making me wait 3 extra days for my skid plate (n)
 

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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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Discussion Starter #11
Well finally this job is done, new A/C switches installed today (I did have to pull one back out and install a different Oring, holds vacuum now) and A/C charged. Water pump and new hoses have no leaks and the cooling system "burped" itself, running Zerex G05 again, engine temps at just under 80 and nudges up a hair with A/C running. Aux fan kicked in at 80 with 42 degree air blowing inside. This has been one of those jobs I don't expect to have to do again (I hope)

Smoke in the pic is where I shot a can of Seafoam down the throat, let is soak for an hour instead of just the 10 minutes, cleaned her innards out good but probably not that dirty anyway because Seafoam goes in the tank every 3rd fillup

I'm wondering what that little fuse holder next to the main fuse box powers, it has two slots but only one fuse in it
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1990 350SDL, "Grandpa's Roadster" Project Car
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I'm wondering what that little fuse holder next to the main fuse box powers, it has two slots but only one fuse in it
Cabin fan?

So, what was making the compressor stay on? Seems all the switches are there to shut it off, not keep it on.
 

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'91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
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Discussion Starter #13
Cabin fan?

So, what was making the compressor stay on? Seems all the switches are there to shut it off, not keep it on.
Cabin fan is the 30amp flat fuse over on the 2nd firewall, yes ? This box is over betwixt the main fuse box and the fender.

I still don't know why the compressor stayed on even with the Climate Control in the off position. Perhaps the relay coil (?) in the Klima was hung until I gave it a thump on the bench. I remember sometimes radios I worked on in the Army we'd go through everything by the book (and not just me) and couldn't get them to work quite right until we gave them a thump on the bench, started working like they should
 
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