I have replaced engine coolant temp unit and gauge sending unit and the fan relay and the fan will not come on when she heats up. the fan comes on when the ac is turned on. any ideas???

 

fan switch - pass side head between #6 & #8 cylinder. remove the connector, and with key on, ground it - if fan comes on, then the switch is bad. watch eyes/face when replacing, coolant comes out there!

 

Without knowing what engine you have, we cannot give you any answers (no matter how much we'd love to guess).
TBI/TPI? Year?

To save yourself trouble of repeating this information in every post, simply fill out your profile with your car's info.

Lou

 

It is my dads car. He has a 1991 camaro rs. It has the tpi v6. I believe it is the 3.1.

 

Not sure if you are the original poster (two different user names) but the posts sounds like it. *shrug*

Anyway, on the V6 MPFI engines, there is no overheat switch in the passenger side head. The ECM is the only thing that controls the fan on this engine.

If the A/C turns the fan on, that means that the fan circuit functions correctly all the way from the ECM to the fan.

What temperature did you let it heat up to? The ECM is programmed to kick the fan on at 238 degrees Farenheit, if my memory serves me right. So yes, your dash gauge should be showing 240 for the fan to kick in. If it gets to 250 and still nothing, I'd check the actual engine temperature with an infra thermometer. At that point, I'd also ohm out the coolant temp sensors (both, for the ECM and for the dash gauge).

Let us know.
Lou

 

I replaced the coolant temp sensor under the nose of the throttlebody and the gauge sensor on the pass. side of block, and also the fan relay on the firewall.

 

How hot did you let the engine get?

Lou

 

I t seems the temp gauge goes all the way to the red zone. had it checked by a mechanic and said that the gauge was goo but sensor was bad

 

I just bought this car two months ago and can't get used to the high temps these thing run at

 

Hmm, at this point, I'd put a laptop on the ECM and check that it reads the engine temperature correctly and sets the fan request as needed.

Is the engine harness hacked up in any way? Previous owners do stupid things with our cars.

Lou

 

no car was owned by a 48 yo women that was the original owner. that is the only thing that I can think might be wrong something in the wiring.