Replaced servo and amp, working heat for a few days then intermittent now no heat. Fuses good, seems amp fried but no melted parts in amp, but a few darker spots on board. Is there a way to test amp, I have power to yellow red wire at amp plug, it still gets warm when fired up, was going to check aux pump as well, ideas?

I was made aware that the aux pump behind the right headlight can seize and cause a meltdown in the controls; you might confirm your pump is working. If it Was seized, from what I understand it will Not stop heat from flowing...

G/L

Thx G/L I will check the aux pump, it is next to my servo in this car and I also found a loose resistor on the acc amp board so will solderit as well.

The OP has the early climate control system ACC II with the vertical pushbutton control panel. The aux pump doesn't cause a control unit meltdown on that system.

The later system used 81->, ACC III, has that issue.

OP: you say the fuses are fine, do you mean you have checked the little glass inline 2A fuse under the black cover on the driver fenderwell?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

Wrong! The aux pump will fry the amp, there is no fuse in the circit and this is a good cause for the people who have a bad evil servo system...

Remove your aux pump and test it at the battery, if it doesn't work...then that is your issue....they can be if not rusted shut, taken apart, cleaned, greased and reinstalled.

Another issue, can be caused by the foam temp sensor tube, behind the glove box...this has now turned to dust and needs replacing..

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thanks all, I will send back my amp and get a replacement as the seller on ebay said he would replace it. One of the big grey resistors is loose and the welds are cracked, I thought a replacement would be better than soldering the welds. will see..cooljay, how do you know if the foam temp sensor tube is bad, all I see is the copper tube and the rubber intake tube from the dash sensor?

First of all, let's all take the time to read before we light our boxers on fire and bring down the wrath of Valhalla:

I was answering the other responder, who related something about the later system and the aux pump frying the controls (CCU). I never mentioned the amp in my reply.

Look at a wiring diagram. Explain to me how the aux pump, as it's wired into that system, could possibly fry the servo or the amp.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

I'm out, I don't want to play the back and forth game at the moment...you win no way possible, nope never notta...all good to go...peace...

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OK folks, I got a new amp and water pump, put it n the amp and no servo action, did my servo fry? Can I test my servo somehow with jumpers? Dam frustrating..