944 Radiator Fan Doesn't Turn On.

[cjkacp]

I'm having an issue with my 83' radiator fan that is an A/C model. I have tested the relay, sent power directly to the fan, and swapped fuses so none of them are the issue. I did unplug and relog in the the relay one time and then it proceeded to work for 2 days. However, in general the primary cooling fan does not turn on whether the car is on or off, the only one that does is the a/c one if you turn it on while the car is running and when you switch the car off automatically to cool it down.

I'm thinking its either a wiring issue, ground issue, or its the temperature sensor. Though again that unplugging and replugging made it work for those two days.

[originalowner]

Just clariying, you have one fan that never runs, and you have one fan that runs with the A/C on or while the engine is cooling off when hot.

Questions:
1) Does the fan run fast with the A/C on, or slow? Fast = very noisy, slow = somewhat less noisy.
2) Does the fan run fast with the engine cooling down, or slow?
3) Or does it run at the same speed, and you can't tell if fast or slow.
4) With the hot engine off, A/C off, and the fan running in cool down mode, turn the ignition on.
a) Does the fan speed up?
b) Does the fan stay the same?
c) Does the fan stop.

This info will help pin down the problem.

[Michigan944]

OriginalOwner has a pretty good list for you to start with. The more information you can give on the issue the easier it will be to track down.

When you were testing the fan, how did you send power directly to it? When my radiator fan switch failed several years ago I unplugged the two wires from it and connected them using a jumper wire. Fans should kick on by doing that. (Can't remember if just one or two should kick on). If nothing happens with the fans, then the issue is elsewhere. Those switches failing is pretty common though.

[walfreyydo]

Cooling fan operation can be narrowed down to these main things:

-cooling fan relay
-cooling fan temp switch (sensor in the radiator)
-cooling fan resistors
-cooling fan's themselves (bad wiring or bad fans)

Testing procedure for all the above is on clarks
http://www.clarks-garage.com/shop-manual/cool-01.htm

[Matt at Pelican Parts]

Hi cjkacp, I tried to see if i could do some research on the subject. I did find this old thread with similar symptoms. On post #23 they note that changing the fan cut-on switch located on the radiator seemed to do the trick. You may want to investigate that!

https://forums.pelicanparts.com/porsche-924-944-968-technical-forum/11140-fan-trouble.html

[Monkey Wrench]

Just thinking that the thermal switch an probably be checked for resistance at different temperatures
If it just goes open or closed it could be jumped or disconnected to test that and see if fan runs.
The contacts in the relay might be blackened in a pinch you can usually carefully open them and clean the contacts up, or just replace. Sure clean up all the related connections grounds fuses etc just disconnect the battery and clean them, then put a bit if dielectric grease on them.

[walfreyydo]

Originally Posted by Monkey Wrench

Just thinking that the thermal switch an probably be checked for resistance at different temperatures
If it just goes open or closed it could be jumped or disconnected to test that and see if fan runs.

From the clarks link I posted above:

Testing the Early Thermofan Switch

Tools

· Thermometer (which goes to at least 200 °F)

· Multimeter

Procedure

1. Connect a Multimeter across the contacts on the thermofan switch. The thermofan switch contacts should be open (i.e. infinite resistance on Multimeter).

2. Suspend the thermofan switch in a pan of water and heat the water on a stove. Insert the thermometer into the water to monitor water temperature.

3. When the water temperature reaches 198° F, the contact in the thermofan switch should close (i.e. zero resistance reading on the Multimeter).