1989 300E Aux Fan - PeachParts Mercedes-Benz Forum

LoveLEE143 · #1 05-29-2007, 01:25 PM

I know I am beating a dead horse.

1989 300E

OK so I am trouble shooting my aux fan as it doesn't work. I have search through many other threads but have not seen one with pictures. Different people have been using different names for the same part which has lead to some confusion.

First I have put 12 volts directly to the fan plug and the fan spins.

I checked with volt meter that 12v is running across the fuse in the fuse D. Which is the fuse for the aux fan.

I checked with volt meter that 12v is running across the strip fuse.

I jumped the AC dry receiver together. I get a clicking noise from the relays behind the fuse box.

I jumped the temp switch and I get a clicking sound from the relay behind the fuse box.

I tested the resistor and got no voltage. I tried jumping the wires and still got not voltage.

I am not sure what else to check. I prefer not to trace every single wire in the whole system. Thanks for your help in advance.

Mike D · #2 05-29-2007, 01:50 PM

You have a problem between the fan itself and the relay. You say you can hear the "clicking" when the fan is triggered (by either the A/C or the remp sensor). Check the plug on the voltage relay. I've seen the slip-on connector corroded and also have seen the wire melted at the connection. The melting is usually caused by corrosion at the connection.

Could just be a bad relay.

LoveLEE143 · #3 05-30-2007, 10:42 AM

OK I put wire straight from the battery to the resistor in the last picture. If I put it on the top of the resistor then the fan spins at a low level. If I put it on the bottom side then the fan spins at a high level.

brewtoo · #4 05-30-2007, 11:15 AM

So now you know the resistor is good and the fan is good.

The problem must be the relay or the wiring between the relay and the fan, like Mike D said above.

I bet it is the relay.

LoveLEE143 · #5 05-30-2007, 12:39 PM

But will the relay make a clicking sound if it is bad?

Arthur Dalton · #6 05-30-2007, 01:15 PM

Quote:

Originally Posted by LoveLEE143

But will the relay make a clicking sound if it is bad?

The click simply means the relay is pulling the fan contacts IN..if the contacts are bad , you get no power to the resistor..many times , the wires are burnt under the relay.
Also check for power to the relay from the load fuse.

david s poole · #7 05-30-2007, 05:23 PM

youve got two relays one for low speed and one for high,try switching them.