Twin Aux fans problem
09-18-2006, 06:07 AM
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Twin Aux fans problem
Okay, I've got a 91 300CE-24V which has been getting a bit hot in traffic, not too bad, as it never goes into the red, but I prefer to see the needle rock solid in a car, or at least below 90.
Anyway the aux fans werent kicking in. I've got aircon, but no gas in at the moment, so the pressure switch wouldn't kick in which is fair enough, but the temp switch didn't seem to work either. I jumped the temp switch (two wire switch on stat housing) and one fan kicked into life - so there's power going down there if the circuit is made. I can live with one fan working in UK climate and figure out how to get the other working at a later time. However here is the mystery. When I took out the jumper wire the fan stopped fine, then I left the plug unattached to the sender, but after a while the fan kicked back in, and cooled down the motor, and cut out, then kicked in again when it got hot. So basically the fan is working when the plug is not plugged into the sensor, but doesn't work when it is!! Anyone got any ideas?
Anyway the aux fans werent kicking in. I've got aircon, but no gas in at the moment, so the pressure switch wouldn't kick in which is fair enough, but the temp switch didn't seem to work either. I jumped the temp switch (two wire switch on stat housing) and one fan kicked into life - so there's power going down there if the circuit is made. I can live with one fan working in UK climate and figure out how to get the other working at a later time. However here is the mystery. When I took out the jumper wire the fan stopped fine, then I left the plug unattached to the sender, but after a while the fan kicked back in, and cooled down the motor, and cut out, then kicked in again when it got hot. So basically the fan is working when the plug is not plugged into the sensor, but doesn't work when it is!! Anyone got any ideas?
09-18-2006, 08:34 AM
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The fans do go bad ....I have been seeing many folks lately on many forums asking questions to as why theirs aren't working on their W124s. Me too recently.
Is your wiring harness all good? Relays compentent? Not sure if your car has the dropping resistor behind the left side headlite (like a 500E does)....but the wires to it often get cruddy.
One fan is for the a/c when its on, low speed ...the other is for the high temp of the coolant, runs at high speed. Sorry if I'm re-stating the obvious.
Spin the fans by hand when the car is off and cool....it should spin freely, if not then they may be done. Find the power connector for them and directly power them up to be sure.
Is your wiring harness all good? Relays compentent? Not sure if your car has the dropping resistor behind the left side headlite (like a 500E does)....but the wires to it often get cruddy.
One fan is for the a/c when its on, low speed ...the other is for the high temp of the coolant, runs at high speed. Sorry if I'm re-stating the obvious.
Spin the fans by hand when the car is off and cool....it should spin freely, if not then they may be done. Find the power connector for them and directly power them up to be sure.
09-18-2006, 09:14 AM
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Its not the fact that they aren't working, I can sort out the one that isn't working, it may well be that it kicks in with the AC although I hadnt heard that one was aircon and the other coolant cooling. Its just the RHS fan works perfectly cycling in and out when its disconnected from the temp sensor, whats switching it with the heat if its disconnected?
