Radiator Fan Won't Come On Need Some Help

[streetoreca]

Been dealing with this little headache since a recent track day.

The car overheats when it is sitting in traffic but cools back down on the highway. I have checked and the fan is not coming on. Swapped fan relays and the relays appear to be OK but still no fan action. Took out the intake to see that the wiring to the radiator fan all looks good and the fan spins freely.

I have read all the threads I could find but none of them really seem to provide any answers except swap the relay or water pump and I dont think either of those are my issue.

96 gts with 14k miles if that helps, all fluids are fresh and I take pretty meticulous care of it. One thought I had was to just wire the fan to be on all the time but I don't know how to do that and it's not really the right way of doing things. Another thought I had was that maybe there is a coolant temp sensor not transmitting the right signal to get the fans to turn on. I know something like that exists but don't know where to go looking for it on the motor.

Thanks in advance for any help, this forum is awesome to read through and be a part of.

 

[Mutts02GTS]

I just checked the service manual and it states: Electric fan inop possible causes: Fan relay, powertrain control module, coolant temp sensor defective... The engine coolant temp sensor threads into the front of the drivers side cylinder head... look like it is just outboard of the upper radiator hose goose neck, cylindrical with a locking electrical connector on the top. Let me know if I can help out with anything else... Jeff

 

[whitebluevipe]

mine was a thermostat. call chuck tator

 

[dave6666]

Sending unit or coolant too low.

 

[dave6666]

Also pull the relays back out and check down in the sockets for burning or whatever. Obviously there are fuses too that should be checked.

 

[dave6666]

mine was a thermostat. call chuck tator

That kept your fan from coming on?

 

[streetoreca]

I just checked the service manual and it states: Electric fan inop possible causes: Fan relay, powertrain control module, coolant temp sensor defective... The engine coolant temp sensor threads into the front of the drivers side cylinder head... look like it is just outboard of the upper radiator hose goose neck, cylindrical with a locking electrical connector on the top. Let me know if I can help out with anything else... Jeff

Jeff, That was an awesome post, I was trying to figure out where the temp sensor relay was and just had no idea where to look since I am a relatively new owner and jut haven't gotten the service manual (coming this weekend).

I actually asked Sean Roe over at Roe Racing whether buying his relay kit with the adjustability would bypass the stock relay and he said it would/would run in parallel but to run a wire from positive on battery to the green wire of the radiator fan first to see if the fan/fan motor turn on (indicating fan and fan motor are good). I was really impressed that they replied to me so quickly and he was great to talk with and wanted to make sure if I bought the part that it was going to be the right solution for me.

I believe I have it narrowed down to either the fan/fan motor or the temp sensor. I will make sure to post back after more troubleshooting tonight so we can have a solution to this. Thanks again everybody

 

[streetoreca]

the car has a fluidyne radiator and the fan looks pretty substantial to me. This car has substantial upgrades so I am sure the cooling system was addressed.

I jumped a wire from the positive to the fan power and confirmed the fan and motor are ok.

I checked and the fan does come on when the a/c is tripped. Once I figured this out I decided to go for a drive. Happily, the car stays cool if the a/c is on. When it is not on the car will begin to slowlly heat up when sitting in traffic. Nothing alarming tonight.

I am suspecting that I either need to burp the system or it is a bad temperature sensor. For tonight I am just glad I got a chance to drive her around and that I have a way if I need to drive it somewhere I can cool it. I think for 15 bucks the easiest thing to do next is go get the temperature sensor, if I am correct it's pretty easy to get to and should just unscrew and drop a new one in.

I'll keep an eye on the thread if anyone has any other thoughts and will report back once I get a new sensor and continue the saga until it's fixed. Thanks again for all of the input.

 

[streetoreca]

So part of the issue with burping the system is that it looks like a fairly complex procedure. I have read on here that the front end has to be jacked up so the radiator is higher than the block, the bleeder is in a hard to get to place, etc. Would a truly simple solution to burping the system be to spend the 30 bucks for the roe racing upper radiator hose bleeder kit?

Also, one other thing I forgot to mention is that the car does not have heat for some reason. It never seemed to be an issue before as I live in Florida, but if burping the system would solve that issue too then 30 bucks is a no brainer. Am I thinking in the right direction?

 

[whitebluevipe]

That kept your fan from coming on?

i meant sending unit.

 

[Dan Cragin]

Check the connection at the fan, these burnt up on the 96-97 models.

 

[dave6666]

I think the horror of burping the Gen 2 cooling system is over rated. I have had my cooling system drained way more times than I would like to have, and have never "burped" the system. It is self purging of air to an extent so fill it up and allow the stat to open then fill it up more. Put the radiator cap on and drive it. The level in the fascia bottle will make up the fluid as the air is purged by driving. I've done this many times and my playground is the 110 degree days of Texas. You just have to make sure the pressure cap is good, the hose to the overflow is good, and that you have coolant in the overflow. Top off the overflow after a few runs and it is that simple.

 

[gsav69]

I had a similar issue and chased my tail for a while. I'm doing this from memory but I believe it was the hi/lo fan relay if I'm not mistaken. The issue that made it difficult to idenitfy was regardless of temperature, the car needed to be running for the fan to come on. I would put the key on and try and diagnose it and it wasn't enough. Once I realized the car needed it to be running, locating the issue was a lot easier!