I am goimg to assume you left the sw in the circuit, Correct??

Behind the driver headlamp , find this resistor

http://catalog.worldpac.com/mercedesshop/sophio/image.jsp?title=Aux.%20Fan%20Resistor&url=http%3A//img.eautopartscatalog.com/live/G504051927BER.JPG



bring a jumper from battery pos+ to the side of the resistor that has 2 wires on it...should have high fan

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A Dalton

What is the sw?

Btw, that resistor has one wire on each side.

[QUOTE=higher planes;1877917]What is the sw?

SWITCH

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A Dalton

Okay. Yes, I left the switch in the circuit.

Thank You

Check fuse D and 7


Jumper from Bat to R , should have high and low fan , depending on which side you jumper ..NOTE ..this test is with key OFF

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A Dalton

Checked fuse 7, it's good. Not sure about fuse D. There's a separate fuse box in front of the main fuse box. inside there are fuses A, B, C, & D. And D looks good.

Jumpered the resistor on both sides and low speed fan and high speed fan work.

Whats with post 15 ???

I just happen to notice you made a change ...I do not see those edited changes and they directly effect how I am diagnosing the problem ..

Do NOT do that ! I didn't see that "Lets Back UP "" change.... If there is a change , post it on a CURRENT post..I do not go back and re-read the old postings........................................

Now , please explain that post.

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A Dalton

Ok, sorry about that. One of the first things you had me do is unplug a blue sensor to see if the fan would come on. I told you that i unplugged it and the fan didn't turn on, but I had unplugged the wrong sensor.

Later I noticed the correct sensor, which I unplugged and the fan turned on.

Unreal..

So, then what's your complaint...the High fan is nor programmed to come on until 105C as sensed by that sensor. When I had you unplug it, that is just a test we use that puts the Control Panel into default to test the Fan circuits integrity..your fan circuit has passed the test.

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A Dalton

Ok, i understand that the car passed all the diagnostic tests and whatnot. But the fans don't kick on in real driving situations, when i need them to work. And they will not turn on, no matter what the temperature is. I had the needle nearly hit the 120 mark. That's really my concern.

So what's the deal?

If your fan circuit passed the default test and they do not turn on when coolant temp has exceeded 105C, then the Deal is you need a sensor..
Your earlier post said your concern was you had no fan at 100C.. that is Normal........................

But you may want to test the sensor with a ohm/temp test ...it is a thermistor and the R value decreases with temp increase [ Negative Coefficent Thermistor]
I would test that b/c you could also have an intermittant relay or fuse feed problem [ poor conection]
You also still have a low fan fault b/c you did not get low fan when you did the drier sw jumper test...that is why I had you test Fuse D ..that is low fan relay feed to Resistor,,,so that test has failed but low fan is only a/c high side pressure triggered.

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A Dalton

Ok man, Sorry for any confusion and I really appreciate your help. I'll check the last thing you mentioned and will update you tomorrow. Thanks again.

-D

Very Good

I would also take a serious look at the fan motors themselves...as I see you mentioned in one post that only one fan was running..this indicates a problem b/c BOTH fan should always run in together b/c they are wired in parallel...regardless of which speed is being called for ..so , check that out ..see if they both spin nice and easy by hand and that they always start together.etc.............
Low fan is critical b/c if the a/c is working hard and the low fan is not coming on to relieve the condenser , the radiator gets heated from passive heat of condenser and the results is overheat condition of coolant.. It's a passive thing , but very common and often mis-diagnosed .

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A Dalton