My turn for AC funnies 300TE - PeachParts Mercedes-Benz Forum

psfred · #1 08-11-2007, 03:21 PM

Finally got all the leaks fixed on the TE, and now the compressor will not activate!

Here's what I have done:

Compressor operates fine jumpered at the KLIMA (so not clutch problems, etc).

No voltage at the pressure switch, either side (i.e. control unit not turning compressor on).

All temp sensors within spec

Used Pushbutton unit doesn't work either (but no absolute guarantee it's good either). All other functions work fine.

Continuity between pushbutton control and pressure switch, but have not check for ground on the wire yet -- shows 140 mV pretty consistantly).

I'll be making a code pulse reader this weekend to check for stored codes.

Any thoughts other than a bad pushbutton unit? I don't believe I have two with the same defect, and yes, I unplugged the aux water pump for the second one (shouldn't be on in 98 F degree weather anyway).

thanks -- this one is driving me nuts and my mother is cooking in the car....

Peter

larry perkins · #2 08-11-2007, 05:06 PM

fred i dont think you are looking in the right area,sounds like the ccu is doing its job to pull the compressor enable input down to the .140 v dc.
to comfirm, pull both wires off the ref pressure sw and see if one side has batt voltage and the other side is near ground.with key on in run position of course.
larry perkins lou ky

psfred · #3 08-11-2007, 05:45 PM

Does it ground the input or provide 12V? Diagnostics says you should have >11V at the connection when energized using the "Y" cable from Benz.

I know they say ground, but 12V ain't ground in my electrical book. Who knows what the Germans mean, though.....

Easy enough to check, I'll get the DMV out tomorrow and see if the pushbutton unit is grounding the line, then figure out what the ..... is wrong with the KLIMA. Have a spare for that, too....

And no, it does not come on even for a split second, no clutch movement at all unless I jumper the socket -- runs fine then.

Peter

larry perkins · #4 08-11-2007, 06:18 PM

dont know the y cable,but the kilma supplies the high dc to the sw and if the sw is closed and the ccu ask for compressor on then the line is pulled down to the .1-.2 volts you seen.
larry

psfred · #5 08-12-2007, 02:30 AM

KLIMA is bad then, or one of the other inputs is out of spec.

I have a spare off eBay, maybe I'll try it again, and will do the troubleshooting program for the KLIMA.

Peter

psfred · #6 08-12-2007, 09:11 PM

Replacement KLIMA fixed the problem, but now the red fuse blows after a few minutes.

What should the resistance of the clutch coil be? I suspect I need a new one.

Peter

saumil · #7 08-13-2007, 12:36 AM

On my 87, 260E, the current drawn by compressor is about 4A. So I think the resistance should be no less than about 3 ohms.

Does the fuse also blow if you short terminals 5 and 7 in the Klima socket ?

Do you have sufficient oil in the compressor ?

psfred · #8 08-13-2007, 08:48 PM

Compressor hp requirement won't change the clutch coil draw, and since the fuse only blows when the compressor is running, I don't know what else it could be. Will check tonight if I get a chance. I suppose the KLIMA could be shorted, it's a used one.

Peter

chrislk02 · #9 08-13-2007, 09:48 PM

I have a compressor on a 1985 190E with the same symptoms. I can force the compressor on however after a few seconds of running, the fuse blows. I have traced to what I am guessing is a problem somewhere on the compressor however ran out of troubleshooting time this weekend.

saumil · #10 08-15-2007, 05:22 PM

Tons of current is flowing to blow this fuse, nothing inside the Klima on its control side can withstand such current without smoking. Most likely it is the clutch coil. Shorting terminal 5 and 7 in the Klima socket can distinguish between the coil and the Klima possibilities. If it is something shorting in the Klima relay only, the fuse will not blow when 5 and 7 are shorted.