Dougs951S

My car has been running a bit hot lately when sitting still, so today I checked to see if both fans were working and of course, the driver side fan doesnt work, even with AC on. I just replaced this fan less than 6 months ago and have put less than 1500 miles on the car since then. The fan spins fine and isnt locked up or rubbing, so I decided to test for power at the connector and with AC on, there is power but I'm only seeing 6.5-7 volts. What does that indicate? I don't know enough about the way the fans are wired to hazard a guess. Could a failing fan relay cause low voltage to just one fan?

Also when I jump the Thermofan switch, I cant get the driver side fan to come on high or low, so Its not the low speed fan resistor.

Dougs951S

I went ahead and decided to pull apart the relay, and immediately I see 3 solder joins on M2 that are suspect. lacking a wiring diagram for the relay, i decided to try to figure it out visually and I believe I found the source of my issues. Pins 30M1 and M1 have continuity when the M1 relay is closed like they are supposed to, but pins 30M2 and M2 do not have continuity when the V2 relay is closed. I believe that those pins should have continuity with the relay closed and that is why the fan is not working. Am I correct in assuming that M2 controls the driver side fan, and did I prove my relay to be bad? If so I'd just as soon try to resolder is before dropping 100+ dollars on a replacement. Thanks in advance all.

Van

The way the fans work, low speed sends a full 12v to those large round resistors so a lower voltage goes to the fans. For high speed, the relay bypasses the resistors.

Also look for broken insulation and corroded wire by the resistors - this is quite common.

Dougs951S

so then power getting to the fan via the relay with the AC on confirms that my fan is bad? its just hard to believe a replacement fan failed in 1500 miles of easy driving for no obvious reason. that means something is killing that fan and I need to find out what or it will keep happening.

Van

To test the fan, use alligator clips and a jump pack to put 12v directly on the fan's terminals.

If it is dead, you're probably right - you've got something else killing it.

Dougs951S

edit: The fans draw current directly off the relay, right? I think I found my fault. I got a hold of a wiring schematic for the relay and took more readings.

Pins 30M2 and V2 have continuity with V2 relay closed = passenger side low speed
Pins 30M2 and M2 have continuity with M2 relay closed = passenger side high speed
Pins 30M1 and V1 are open with V1 relay open or closed = no driver low speed
Pins 30M1 and M1 are open with M1 relay open or closed = no driver high speed.

Driver side fan is number 1, passenger side is number 2. Possible double fault in the V1 and M1 relays? I don't know why I am still seeing voltage at the connector though, and why it isnt a full 12 volts when the high speed circuit is engage.

Ronin-951

Van is being exceptionally polite, as always. Friggen Hell Hole is likely what you'll find, Resister's get HOT and the Wire/Connections will cook.

CurtP

The wire to the ballast resistors are too small - the entire wire gets hot. I've pulled apart several harnesses and every one of them has had deteriorated insulation and conductors inside of the harness. I always recommend abandoning the original wires entirely and build a new harness from the ballast resistors to the relay.

Ronin-951

Just so happens that 944Online is now selling a up-dated Resister harness.

Dougs951S

I just resoldered the connections, seems to be continuity now on both driver side fan circuits. going to throw it into the car and cross my fingers. i will check on the resistors too.

Tom M'Guinn

Good luck. I've often wondered if bad grounds and connections create slower fans than intended and might explain why some cars have temps that creep up more in traffic than others, despite healthy cooling systems.... Let us know if it works and if you notice a difference compared to when they last worked...

Dougs951S

I pulled the fans out of the car and wouldn't you know it, driver side fan is open. If I tap on the back hard while I have a meter on it, I can sometimes pull a reading between 1.4k and 1.8k ohms but its very intermittent. I don't know if I fixed the relay or not for this reason, but I do suspect my resistors are good as they look almost new. Likely the PO replaced them in his attempt to solve the same issue, as I bought the car with an inoperative, locked up driver side fan. Nothing I can see was making the fan bind or touch, and they both spin freely in and out of the car. I sanded down the inside of the shroud where the fans run just to increase the clearance slightly, but I know they were not touching before. Only thing I can think at this point is that its possible I got a bad replacement fan. It was a used unit from Lart I got about 6 months ago, and when I installed it, it worked fine so I simply forgot about it. I have no idea when it stopped working. Its possible that like any other old part, it simply decided to randomly die. I just dont want to chuck another fan at this car and have it eat it too. Anything I should check on before I give Lart a shout?

Tom, makes sense a bad ground or any bad connection along the current's path would slow the speed of the fan down in both high and low speed operation. Its added resistance which would mean less voltage making it to the motor. Same function as the slow speed resistor.

Dougs951S

Bump,


Nothing short of some kind of contact/rubbing that could be causing friction induced overheating of the motor could be killing it, right? Not some strange electrical issue I'm unaware of? Should I just replace the fan again, finish sanding down the inside of the shroud, be sure to tighten the shroud down tight to nothing can move, and call it a day? I really don't want to revisit this again. Cooling has been the main issue with the car since owning it and I thought I finally had it all figured out.

Tom M'Guinn

Have you checked the grounds and/or voltage levels at the connectors? Some electric motors will overheat if the power supply isn't good. Power tools are known to burn out if you use too long of an extension cord for example...

Scott H

Welp, having just pulled most of the wiring in the engine bay today, this is one area I still have yet to address. What gauge wiring would you recommend?