MooreBoost

track car. passenger fan always runs with key on and fan switch unpluged. driver side doesnt come on at all. put power to driver side fan and it works. i did clarks diagnose and only pass fan works. tried replacing relay and still same thing. i took out heater, ac and relocated fan resistors.

help!

MooreBoost

oh and passenger fan is always on high speed. i jumped switch and it comes on slow for 2 sex and then goes high speed

MooreBoost

im going to look into the resistors

Bri Bro

The resistors are used to change the high speed to low speed. Test at the fan relay, all the connections that control the fan are there.
Lots of info in this link: https://rennlist.com/forums/944-turb...?highlight=fan

951mcomm

I think i have the same prob, i diagnosed that it is the thermo fan switch. It is plugged into the radiator, they do go bad and hve the same symptoms.

MooreBoost

it has a new switch less then 3 months

smokin_944

944CHM944, do you have an early car or a late one?

931guru

They make bad switches, some take 20 years to fail, some are DOA.

Test it first.

MooreBoost

read first post. fans come on with switch unpluged

smokin_944

You say you replaced a fan relay in your first post. Not knowing what year car makes it difficult to troubleshoot because the cooling systems are different from early cars to late cars, the fuse boxes and relays are different, the wiring is different. On early cars only one fan comes on at slow speed, on late cars, both come on. If it is an early car and you don't know the difference between say the AC relay and the fan relay you may have swapped the wrong relay out. This would mean the problem continues. Need more info.

MooreBoost

late car. i swaped relay from a late car also.

smokin_944

Excellent, on the late cars the 2 fans come on at once. I read a post a while back at 944online, in the tech section. IIRC, the problem in a case similar to yours was the 2 resistors responsible for the slow speed function. Corrosion had attacked the contact points to such a degree the slow speed function stopped working. They had to be rewired. This might be a good place to start looking. A less likely scenario is that you have a short in the fan harness wiring/fuse setup. Let me know what you find, we'll take it from there.

M758

Since you have a track car just wire the fans directly and run then off a switch or two. Much easier than tracking down electrical issues and it allows you to control the fans when you want. My early car has 2 5 blade fans with each fan on its own switch. Thus I can choose which fan to run at what temp and for how long. If I run both fans on a cool down lap it really sucks the heat out of the motor. The circuit is simple to with two 20 amp switches, an inline fuse for each and some wires. If it failes it is due to the fan motor, fuse, switch or break in the wires. Plus since I have two independant circuits if one fails I still have at least on fan. I only need both fans in the warmest air temps.