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

[6spdg37s]

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-

[WildBillyT]

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

[sweetbmxrider]

Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the Powertrain Control Module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage, from the underhood fuse block. The ground path is provided at G106.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 3 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 3 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.

LS1
The PCM commands low speed fans on under the following conditions:

Engine coolant temperature exceeds approximately 108°C (226°F).
When A/C is requested and the ambient temperature is greater than 10°C (50°F).
A/C refrigerant pressure exceeds 1482 kpa (215 psi).
After the vehicle is shut off if the engine coolant temperature at key-off is greater than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:

Engine coolant temperature reaches 112°C (234°F).
A/C refrigerant pressure exceeds 1710 kpa (248 psi).
When certain DTCs set.

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?

[MDSheds_SS]

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

Ls1 Camaro

[NJ Torque]

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

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

[6spdg37s]

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

[sweetbmxrider]

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?

[6spdg37s]

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

[sweetbmxrider]

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.

[6spdg37s]

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

[sweetbmxrider]

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.

[BonzoHansen]

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

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

[6spdg37s]

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.


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

[sweetbmxrider]

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.

[6spdg37s]

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)

[6spdg37s]

....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...

[WildBillyT]

....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:

[6spdg37s]

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

[sweetbmxrider]

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

[6spdg37s]

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