lets play a game... why is my car running hot...
 

Pretty much here is the rundown...anyone that can help feel free to chime in... let me start by saying im a mechanic lol this has me stumped

-cam goes in
-we notice it seems like 1 fan is down (driver side)
-then it seems like its working again
-car is tuned for 160 thermostat
-temp goes up to around 212 without A/C on , around 228 with A/C on
-diagnose as a bad fan, replace the fan assembly
-fan kicks on
-car is still running hot, and driver side fan is not on
-replace all 3 relays... discover that there is a non factory jumper wire from the bottom of fan relay 1 to the middle of the wire harness running in front of the car
-when I did the cam also did an ASP underdrive pulley setup
-58k miles on the car

I'm not sure if this is an electrical problem, or if the fans are behaving correctly and its a water pump problem, or if the water pump simply cant handle the smaller pulleys so its not operating at efficiency

what are the fan sequences, my understanding is driver side is LOW fan, Passenger side is HI fan, but when the car is getting hot BOTH fans should be on ?

thanks-

You don't have a signature... what car/engine is this?

I would confirm the tune didn't foul up fan operations first. Then, observe the data stream and see if and when the fans are being commanded on. If its good on the pcm side, we'll get into checking the wiring. You could always jump the relays to test the fans or jumper straight to them if you are unsure of wiring that may have been altered. If its overheating at idle, the water pump shouldn't have trouble keeping up. Coolant is full and bled and coolant temp sensor for computer is working correctly?

Ls1 Camaro

What pulley is on the car, 10% or 25% UD?

Are you using a actual temp gauge or the stock dummy?

Running temp off my scanner ... He reflashed the car when he noticed the fan issue ...

Commanded them with the snap on scanner and they worked

If everything is working as it should with a scan tool then your pcm either isn't seeing the signal to turn them on, coolant temp sensor, or the tune isn't telling them to turn on. Do they come on with a/c on? Or is a/c gone?

Hi fan on pass side comes on with ac , driver side does not

Seems problem is only driver side

Maybe my coolant temp sender is bad who knows ... Gonna have to play around with it see if I can get w reading with my IR thermometer

Didn't you say you commanded them on with the scanner and they worked? You have to be a little clearer with what you post up info wise, its not easy diagnosing over the internet :lol:

Best way to check coolant sensor is to let the car sit overnight so the coolant reaches ambient (air) temp. You then read the datastream and compare the coolant temp with the intake air temp. They should be within 4 degrees of each other. You can then let the car warm up and see if the pcm commands low and high speed fan operation at their respective turn on temps.

I did command it with my scanner but it's possible there is a short somewhere

I'm not sure what you mean by short. If the scanner makes it work, that means the circuit from the pcm to the relays, to the respective powers and grounds are good. The inputs to the pcm are most likely your issue, you are bypassing them and commanding the fans manually instead of the pcm processing the data and commanding them normally.

This is assuming you commanded both low and high speed fans, had no jumper wires etc, and everything worked when you asked it to.

shorts blow fuses or make smoke, now an open circuit....

So when I commanded them on they went on.

Now I found a jumper wire someone had run (previous owner I assume) from the pin on relay 1 to mid wire harness ... Why I'm not sure but assuming maybe they had an issue with input from pcm at some point ?

I need to play with it when it's in front of me don't have it with me right now

Ok so it was working when commanded, did you then remove the jumper and then find the fans no longer working as expected? It does sound like there is some issue that was present before.

I left everything as it was. We just noticed it was running hot when we were tuning it, and we noticed that the left (driver side) fan was not working. I am not sure why that wire is there but that is actually the high fan wire and that is functioning correctly.

Okay so I went to my shop today and did some testing...

-relay 1 command, low fan goes on
-relay 2,3 command high fan goes on
-I checked the low and Hi fan signal wire that run from the PCM to the relay box, they both commanded the fans on as well
-once the car got to the temperature that was supposed to trigger both low and Hi fans, the corresponding low and high fan wires from the PCM had ground (fans are ground triggered)

then car starts heating up and low fan (driver side) did not come on. the car went up to 238, it does not come on with the A/C on or the A/C off. but the signal wire is sending the ground to the relay. The relays are new.

what stumps me is that the fan works when commanded or probed

unless there is a break in a wire between the relay for the low fan and the actual low fan pigtail, and it makes contact and doesn't (fan going on n off)

....and a broken wire it is... I can't even begin to describe how I discovered this... just kept following wires and diagrams and digging...

Yeah, but you DID find it. Gotta count for something! :mrgreen:

yeah lol. only took me 5 hrs so i guess not bad. I hate electrical gremlins/problems though they are extremely hard to diagnose/fix

I was starting to think intermittent connections, you definitely had me thinking hard on this. What wire was broken? Clean break?

Clean break .. The orange that gives power to relay 3 and the ground signal wire