Cooling fan issue
07-14-2012, 01:25 PM
#1
Rennlist Member
Thread Starter
Cooling fan issue
I have looked through the archives but have not really found what I was looking for. If anyone has good threads saved if you would post me a link. Such as testing and normal operation.
From what I gathered with AC and ignition on, both run at low. And with car running, both at high. I gather both run at high when engine temp gets hot. Not sure about normal low temp operation.
My problem is currently with the ignition on, both fans run. One at low and the other alternates from low to high. Seems to do them same running or when engine temp high. Not sure what to look for.
Thanks for any and all help.
From what I gathered with AC and ignition on, both run at low. And with car running, both at high. I gather both run at high when engine temp gets hot. Not sure about normal low temp operation.
My problem is currently with the ignition on, both fans run. One at low and the other alternates from low to high. Seems to do them same running or when engine temp high. Not sure what to look for.
Thanks for any and all help.
07-14-2012, 01:49 PM
#2
Three Wheelin'
It sounds like the relay is bad. But here is a fan check procedure you can go through.
During normal operation, and you have the factory rated thermostat, the coolant temperature gauge should read at or near the lower white line (80 degrees C) and will creep up to the mid-point between the upper and lower white lines when sitting still in traffic. The upper white line represents 100 degrees C. If the temperature normally runs above the mid-point, you need to investigate immediately.
There are several temperature ratings of the thermo switches, so it is hard to say at what point they should turn on for your car. If they are not both running at high speed when the temperature is above 90, you might have a problem.
The fans are controlled by the cooling fan relay which is in turn controlled by the thermo switch, and the a/c system. Whenever they are closed, both fans should run at the same speed at the same time. If only one is working or you only get high speed operation, there is a problem.
You should always have power available to the relay, so the fans can run at any time. Remove the cooling fan relay. It is the large rectangular silver relay in the back of the panel. Check the diagram on the fuse panel cover for the exact location. All of the following checks can be made at the fuse panel. You will need a bright light to see the markings on the fuse panel.
1. In the Bosch world, a terminal designation of “30” means it is un-switched battery voltage. Check for voltage at positions 30 M1 and 30 M2. You should get 12v + at both positions. If no voltage, check the wiring from the battery, the connections to the fuse panel, and the fuse panel itself. You will have to pull the fuse panel up, but disconnect the battery before messing around under the fuse panel.
2. Check for continuity between ground and the temp switch positions "TS" and "TF" on the fuse panel. If you have continuity, the thermo switch is calling for fan operation. If the car is cold, the thermo switch is bad.
3. Fabricate a jumper wire with flat blade connectors on each end, and a 20a fuse in the middle.
4. Connect the jumper between M1 30 to M1, the drivers fan should run at high speed. If the fan does not run, check for voltage in the connector at the fan motor, if you have voltage but the fan does not run, replace the fan motor.
5. Check the passenger fan by connecting the jumper between M2 30 and M2, the passenger fan should run at high speed. If not, the same drill.
6. Next connect the jumper between M1 30 and V1, the drivers fan should run at low speed. If not the resistor or wiring is bad. Check for voltage at the radiator fan connector and then check the resistance across the resistor.
7. Next connect the jumper between M2 30 and V2, the passenger fan should run at low speed. If it does not run, check the wiring and resistor.
If the car is still running hot and the fans are working properly, you have other issues, like a clogged radiator, water pump failing, air bubbles, bad thermostat, or a bad head gasket.
The other positions on the fan relay are:
X = battery power to the logic board in the relay
31 = Ground for the logic board in the relay
AC = AC freeze protection switch
During normal operation, and you have the factory rated thermostat, the coolant temperature gauge should read at or near the lower white line (80 degrees C) and will creep up to the mid-point between the upper and lower white lines when sitting still in traffic. The upper white line represents 100 degrees C. If the temperature normally runs above the mid-point, you need to investigate immediately.
There are several temperature ratings of the thermo switches, so it is hard to say at what point they should turn on for your car. If they are not both running at high speed when the temperature is above 90, you might have a problem.
The fans are controlled by the cooling fan relay which is in turn controlled by the thermo switch, and the a/c system. Whenever they are closed, both fans should run at the same speed at the same time. If only one is working or you only get high speed operation, there is a problem.
You should always have power available to the relay, so the fans can run at any time. Remove the cooling fan relay. It is the large rectangular silver relay in the back of the panel. Check the diagram on the fuse panel cover for the exact location. All of the following checks can be made at the fuse panel. You will need a bright light to see the markings on the fuse panel.
1. In the Bosch world, a terminal designation of “30” means it is un-switched battery voltage. Check for voltage at positions 30 M1 and 30 M2. You should get 12v + at both positions. If no voltage, check the wiring from the battery, the connections to the fuse panel, and the fuse panel itself. You will have to pull the fuse panel up, but disconnect the battery before messing around under the fuse panel.
2. Check for continuity between ground and the temp switch positions "TS" and "TF" on the fuse panel. If you have continuity, the thermo switch is calling for fan operation. If the car is cold, the thermo switch is bad.
3. Fabricate a jumper wire with flat blade connectors on each end, and a 20a fuse in the middle.
4. Connect the jumper between M1 30 to M1, the drivers fan should run at high speed. If the fan does not run, check for voltage in the connector at the fan motor, if you have voltage but the fan does not run, replace the fan motor.
5. Check the passenger fan by connecting the jumper between M2 30 and M2, the passenger fan should run at high speed. If not, the same drill.
6. Next connect the jumper between M1 30 and V1, the drivers fan should run at low speed. If not the resistor or wiring is bad. Check for voltage at the radiator fan connector and then check the resistance across the resistor.
7. Next connect the jumper between M2 30 and V2, the passenger fan should run at low speed. If it does not run, check the wiring and resistor.
If the car is still running hot and the fans are working properly, you have other issues, like a clogged radiator, water pump failing, air bubbles, bad thermostat, or a bad head gasket.
The other positions on the fan relay are:
X = battery power to the logic board in the relay
31 = Ground for the logic board in the relay
AC = AC freeze protection switch
07-14-2012, 02:21 PM
#3
Rennlist Member
Thread Starter
Thanks for the post,
I did find that one of the larger resitors was bad, so swapped it out. And both fans run at slow with ac on but with car running they did not seem to run at high with AC on. Not sure if they should unless engine temp is high.
I will play with it some more this afternoon.
Steve
I did find that one of the larger resitors was bad, so swapped it out. And both fans run at slow with ac on but with car running they did not seem to run at high with AC on. Not sure if they should unless engine temp is high.
I will play with it some more this afternoon.
Steve
07-14-2012, 11:29 PM
#4
Three Wheelin'
I had a similar issue that proved to be the resistor. The fans should run on low speed with a/c running. High speed is temperature related. Sounds like your ok.
07-19-2012, 09:42 AM
#5
1st Gear
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I have a similar issue with my wife's 1988 944 automatic (Right Hand Drive here in Australia), and I want to check the resistors out. I have seen a couple of posts which suggest they are located under the windscreen edge on the passenger side of the car, however they are definitely not there, another suggested under the dash again on the passenger side, I have removed the dash and glovebox, however no joy there either. Can anyone help me with the location on a RH drive vehicle? Ours is a non turbo btw.
Many thanks
Many thanks
