My Aux fan doesn't come on, My Temp RARELY rises above 85, and my Compressor is dead, but the system has charge.

can the motor in the fan be renewed? is the AC compressor likely a bad clutch, or switch? And are my temps the result of a stuck open themostat?

I've jumped the AC dryer switch and nothing, and put power directly o the fan and nothing...

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RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

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FACEBOOK: PANZER450

You've got two different problems.

If the fan won't run when you apply 12V and ground directly to the fan leads, then it's the culprit. It needs to be replaced. I recall that someone actually rebuilt it with replacement brushes at some point in the past.

If the compressor clutch won't engage, you need to apply 12V and ground directly to the clutch and see if it's a control problem or a clutch problem.

aux. fan bearing replacement: http://www.peachparts.com/shopforum/showthread.php?t=98493&highlight=fan

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

---------check your wiring through your Dessicant . One set of connections is the Pressure Switch, which lets the compressor run. Another set of connections is a temperature switch, which lets the Aux Fan run. If you switch , or cross connect the two pairs, to the incorrect sensors, like I did earlier this spring, you will get this problem.

I know because I did this.

As a test you could jumper the two sets together. Your aux fan should run and your compressor should click.

Also apply 12 V to your AC compressor and let me know if you get cold air!

Mr. Got the Benz,

Yes, the aux fan motor is apparently readily-repairable... I've got mine apart as we speak, and am currently looking for the right brushes. (Does anyone know a source for these?) they are apparently of a roughly .340" square stock, about 3/4" long, with a side-facing pigtail. The electronics plate is held in with two rivets. Am planning to grind these out, effect an easy repair, secure with two peened-over rivets - done! Many $hundreds saved!

How to diagnose? If it's the brushes which are the culprit, the fan motor will sometimes start with a little backward pressure - careful! - on the fan body itself.

For the record, have already rebuilt my ventilation blower motor, and a window lift motor or two, with new brushes - saving a couple hundred bucks, certainly.

Lou