cosmo04

Start out by saying hello, I am new to the board. I recently purchased a 04 cosmo purple gto. Within a week of having it, I notice it getting relatively warm. Turns out, the fans stopped turning on. So I started checking certain things, I changed the temp switch, didn't fix it. But does turn on when you unplug it. The fans come on if you turn the ac on. But they won't come on if the car gets to the middle and keep climbing. All the fuses are good. The fans work. Now I'm stumpped. Anyone have any ideas?

hrcslam

How high does the temp gauge actually get? Some GM vehicles let the temps get uncomfortably high before the fans come on, it's normal for them. But I'm not sure if the GTO is the same.

cosmo04

It gets to the red.

hrcslam

That's more than relatively hot, lol.

Weird issue for sure. I'd try another temp sensor.

cosmo04

Haha yea,. I had a buddy of mine put it on the scanner and he can turn it on from there. But I thought about putting another temp switch on it. You never know.

Cpt.Derrek

iTrader: (13)

My Buddies LT1 Camaro has the same exact issue, let us know if a new temp sensor fixes the issue.

hrcslam

The LT1 F-body's are different. Those have 2 sensors, 1 on the water pump for the PCM the other on the drivers side head for the dash Guage. The dash guage does not go to the PCM at all. Has he hooked up a data logger to confirm the dash gauge is accurate? What year is the car? If it's 1993-1995 there's a free data logger available that can manually actuate the fans, abs, idle, etc. You'll only need a laptop and the ALDL cable.

Also, for LT1 F-body there are two different ways the fans are wired from the factory. 1 with a 2 relay set up, another with a 3 relay set up.

Cpt.Derrek

iTrader: (13)

Oh awesome!! Thanks for the info! I'll look into that.

hrcslam

Also, if he's a 94-95 car, he only needs the ALDL cable, Tuner Pro RT (free) with the correct definition files (free), Scan9495.exe (free, Google it), and WinFlash from TunerCat and he can tune everything on his car as many times as he wants. Should run less than $80. He'll also need a laptop of course, but who doesn't have one of those already.

smitty2919

For LT1 guys you can also download TTS DataMaster on a laptop for 10 free trials to simply read live values from the engine.

As far as the OP, have someone hook up a scanner to it and read the engine temp values and compare it to the temp gauge. I'm not 100% at what temperature stock GTO fans are meant to kick on. Getting into the red and not coming on is an issue. Like you said, it seem like a triggering issue. Fans come on when the AC is called upon, but not when temps get high.

If I remember the temp sensor is on the driver side front of the head. You could also use a voltmeter to test these sensors if they are bad or not. It's a little confusing that the fans come on when you unplug the sensor...unless that is a safety measure programmed into the car if it get no reading from the temp sensor.

senicalj4579

iTrader: (41)

Could it be a relay?