Mongo

For about 3 hours last night i tried to troubleshoot why the heck my fans weren't coming on properly on my car sitting in downtown traffic. The temperature pegged the red and the "holy ****" light came on. What was strange though was when i goto to the freeway, and got up to speed 60+ mph the temperature dropped drastically down to the 1st hash mark. When my friend and I got to his place we checked the car out again and the fans weren't coming on either unless I hit the AC button...

I hung out there for about 10 min, came back home, had a talk with Eyal onthe phone about the cooling issue. But, to my surprised the fan on the drivers side came on when the temperature hit the 2nd hash mark and lowered the temp back down to half!!! WTF, first the fans wouldn't come on, then they come on? Actually the driver side fan only is working, and I think my passenger side fan is shot.

So, I have some questions below:

1. If the driverside fan intermittently comes on to cool the engine down, but doesn't the other 5% of the time the car starts up, could this be the fan switch?

2. Would a bad relay be the cause of the fan not coming on unless I hit the AC button?

3. When is the passenger fan supposed to turn on for these later model cars??? Because, mine isn't turning on and I think the fan is dead...I'd hate to spend 175 dollars not knowing if it's really dead or not...

If anyone knows what's the cure, please post here. I'd like to get this issue diagnosed today and I have a fan switch i'll be installing on my car tomorrow.... thanks for your help.

Andy

Mongo

ok I just got this from Kevin Gross' FAQ on the car:

Check the fan operation - there are two. There are two relays that affect fan operation. One controls the one fan during normal operation and another that controls the other fan when the A/C is on. Only one fan operates when the A/C is off, turning on the A/C activates the other fan. Neither fan is necessary for highway cooling (in fact, they get in the way) so you may only notice over heating in stop and go traffic. The fan switch in the radiator can fail with the fan off, or on. If the fans won't run under normal conditions (sitting in traffic while your temperature climbs) the switch is probably stuck off. If your fans continue to run long after you turn off the car, draining your battery, the switch is probably stuck in the on position.

Where is this second relay They are talking about? All I see is the large one in the G10 spot that is about $175 bucks to fix...

Andy

GOBOGIE

The majority of times it is the thermal temp switch located on the drivers side top corner of the radiator (back side of the radiator). Local parts store will run you under $40. My '86 did this also. I went as far as getting a spare G10 relay (used) and spending $65 instead of checking the thermal fan switch first.

This was mostly my pre-Rennlist days and I wasn't asking for assistance like you are now. I spent a whole summer trying to diagnose this problem... what a knuckle head!!!

Rennlist rules.



Cory

IceShark

I agree it is probably the thermo fan switch in the radiator. If you go to Clark's Garage he has the testing procedure. You remove the plug from the thermo fan switch and jumper the connectors under a couple conditions and see what the fans do. Pretty simple but you need to take off a belly pan to get your hand up there. Then you will know if it is the switch rather than just buying a replacement and crossing your fingers.

Oh, and you are probably going to have to buy a deep throat socket to fit the switch if you need to change it out .... I think an 1 1/8" or 1 1/16" inch will fit it, I forget exactly what the dimensions were.

Porsche-O-Phile

What they said - about $20. Good luck.

Robert D

I'd replace the fan switch first as well. However, when mine went bad the fans were on all of the time. If you know of someone who owns another 944, I'd try to swap the relay with theirs and see what happens. Good luck.

Mongo

i'm gonna get my hands on a relay as well as install the switch on Wed. to see if this solves the problem. Hopefully that passenger fan will work too or I'm gonna be out a lot of $$$ just in parts.

Andy

Mongo

ok guys here's the update:

I got the cooling fan on the passenger side to work. The connections on the fuse "cooling fan 1 terminal 15" were corroded and i replaced the fuse. Problem solved for that issue.

BUT...I took the car out today and got the car up to the second hash before red and the fans never came on. When I pulled into a Walmart parking lot the temp almost was at red, still no fans. I shut it off and let it cool down for 15 min to look inside. Then, I come back out and take the car home. And what happens? The fans come on and cool it down!!! When I get home, I turn it off and wait about 10 min and start it back up, I get the car back up to second hash again and slightly past and the fans again don't come on!!! WTF...

Is this still a fan switch issue here???? this is really frustrating...


Andy

Mark Lue

Love your avatar(s) !

If you found one coroded contact you may have more. Check the ground near the rad and the ones going to the thermofan switch.

The thermofanswitch is mechanical as is the cooling fan relay, you should follow the advice that was given before to use the instructions at "Clark's Garage" to check out or iliminate the thermofan switch before spending $ on a relay.

Mongo

well i definitely know its not the relay. The harness going to the fan switch does look worn. Is there any way I can replace that too or make my own???? I know it has that 3-pin thing, but how about cutting one off a wrecked car and splicing it in?

Andy

Devia

temp switch. Get a low temp one! I got one, fans kick on at the halfway mark, love it!

Saved my engine last month, when the fools sticking on my tires messed with my radiator cap, and left it loose by 1/4 turn.

Mongo

ok guys, fans are still acting up, but at least the passenger fan works now. I changed the fuse again on that side because it looked funky. The temp still jumps into the red with still no fans...but the next startup the fans turn on at second hash mark below red.... I got my fan switch and will install tomorrow morning if I have toruble I'll be back posting on here...

Wish me luck...

Andy

Mongo

bump

tomc_85.5_944

So what did you find out when testing the thermo switch. mine did the same thing yours did, from working to not working to working all the time. Switched out the switch, AFTER testing with Clarks diagnosis, and all is good....

Chris_924s

My "lazy" fans were due to the grounds being oxidized- It was causing an intermittent ground on one fan.

It couldn't hurt to clean up then grounds.