Electric Cooling Fans

[JPVortex]

I tried swapping in the other pcm, did not work either. But with this different pcm the truck is in limp mode or something, shifting horribly. When revving in park too it feels different and is slow to come back to idle.

 

[Rocket Man]

I tried swapping in the other pcm, did not work either. But with this different pcm the truck is in limp mode or something, shifting horribly. When revving in park too it feels different and is slow to come back to idle.

You can’t just swap in PCM’s without programming them to your VIN and doing a VATS relearn. First thing- we need more info, the more the better. Have you owned the truck for a long time and the fans recently quit working or did you just buy it? Were the fans ever working that you know of? Why do you have 2 PCM’s? Is the Fan turned on in the PCM tune (s)? Is a Tech2 available? Any info you can provide will be of help.

 

[JPVortex]

You can’t just swap in PCM’s without programming them to your VIN and doing a VATS relearn. First thing- we need more info, the more the better. Have you owned the truck for a long time and the fans recently quit working or did you just buy it? Were the fans ever working that you know of? Why do you have 2 PCM’s? Is the Fan turned on in the PCM tune (s)? Is a Tech2 available? Any info you can provide will be of help.

The second pcm is vats relearned.

Ok that makes sense, and that I know of the fans have never worked, I've never heard them come on when me or my mother owned the truck. I have a second pcm because it was leftover from a friends partout so he gave it to me among other parts.

Not sure if the fan is tuned for it or not, and no I dont have access to a tech2 unfortunately.

I used a test light for ground on the pcm connectors, but since it's not grounded unless the fan is running that's useless I realized.

 

[JPVortex]

This is looking a bit suspect. A bunch of electrical tape and corrosion, but it worked when I put ground to it so I doubt it's a problem

 

[Rocket Man]

The second pcm is vats relearned.

Ok that makes sense, and that I know of the fans have never worked, I've never heard them come on when me or my mother owned the truck. I have a second pcm because it was leftover from a friends partout so he gave it to me among other parts.

Not sure if the fan is tuned for it or not, and no I dont have access to a tech2 unfortunately.

I used a test light for ground on the pcm connectors, but since it's not grounded unless the fan is running that's useless I realized.

Did you do the relearn after you installed the PCM because that’s how it needs to be done unless you mean it’s had VATS disabled. And if it isn’t tied to your VIN it has no way of knowing what engine, trans and options your truck has so it might just go into limp mode.

 

[JPVortex]

Did you do the relearn after you installed the PCM because that’s how it needs to be done unless you mean it’s had VATS disabled. And if it isn’t tied to your VIN it has no way of knowing what engine, trans and options your truck has so it might just go into limp mode.

Yeah that makes sense and oh I'm stupid all I did was pair the key with the pcm so itll start I didnt do a vats relearn lmao.

For this fan issue I may end up having to go to the dealer for them to add the fan to the pcm in tech2, not sure how much itll cost.

Other alternative is to convert it to a clutch fan lol

 

[mattbta]

What we know with certainty is, it isn’t the relays. (The harness looks fine to me.)

As @Rocket Man said in post #9, if you had access to a Tech2 (not sure if other bidirectional tools can do the same, they very well may) you could command the fans on via the PCM. If that doesn’t turn them on it could indicate issue with PCM. Otherwise, might be a myriad of issues not allowing the the PCM to think they need to be turned on.

BTW, tossing a random PCM in and running the truck is potentially disastrous. You would need to know what OS and calibrations are on this spare and that they match what came from the factory.

Good luck.

 

[JPVortex]

What we know with certainty is, it isn’t the relays. (The harness looks fine to me.)

As @Rocket Man said in post #9, if you had access to a Tech2 (not sure if other bidirectional tools can do the same, they very well may) you could command the fans on via the PCM. If that doesn’t turn them on it could indicate issue with PCM. Otherwise, might be a myriad of issues not allowing the the PCM to think they need to be turned on.

BTW, tossing a random PCM in and running the truck is potentially disastrous. You would need to know what OS and calibrations are on this spare and that they match what came from the factory.

Good luck.

I know tuning software like hptuners can be used. What else would cause the pcm to not turn them on? Honestly I'm close to wiring a manual switch to them lol

 

[Scottydoggs]

I know tuning software like hptuners can be used. What else would cause the pcm to not turn them on? Honestly I'm close to wiring a manual switch to them lol

you need to pretty much just turn the fans on in the tune via hpt. and plug it all in of course.

years ago after burning 3 clutch fans up. i did a efan swap in my 03 gmc 2500 hd rand dual relays one for each fan used a temp probe, as well as a manual on/off switch in the cab. ran cooler and the ac was never colder.

 

[JPVortex]

So I decided I would direct wire the fans with switches. The switches are working but its not toggling the ground on and off. I had the ground for the fan on the middle of this.

 

[ivin74]

So I decided I would direct wire the fans with switches. The switches are working but its not toggling the ground on and off. I had the ground for the fan on the middle of this. View attachment 391670

You need to wire it like the diagram shown below

 

[Fless]

Wired like that will switch the B+ (12v+), won't it? How are you sending power to the fans? Constant, with the ground switched? I'm confused.

If the power to the fans is constant, and you want to switch the ground, you'll need to run the ground through the two conductors that go to the red wires on that diagram.

Using that to switch ground will probably mean that the LED won't light up, even if you put 12v to the terminal that has the black wire. Polarity matters with LEDs. I could be wrong.

 

[ivin74]

Wired like that will switch the B+ (12v+), won't it? How are you sending power to the fans? Constant, with the ground switched? I'm confused.

If the power to the fans is constant, and you want to switch the ground, you'll need to run the ground through the two conductors that go to the red wires on that diagram.

Using that to switch ground will probably mean that the LED won't light up, even if you put 12v to the terminal that has the black wire. Polarity matters with LEDs. I could be wrong.

Not sure how he is wiring it, if it was me I would wire it like the image shown below with a relay. I would run the switch thru pin 86 on one end of the switch to power and the other end ground. Pin 85 needs to be grounded to the chassis of the suv. Pin 87 is power to the fans.

 

[Fless]

He shows a 20a switch and I'm not sure that's going to survive without using a relay. Not sure how much current the fans draw.

 

[JPVortex]

I was trying to use the stock harness with relays just controlling turning the grounds on and off with a switch instead of the pcm

 

[JPVortex]

Wired like that will switch the B+ (12v+), won't it? How are you sending power to the fans? Constant, with the ground switched? I'm confused.

If the power to the fans is constant, and you want to switch the ground, you'll need to run the ground through the two conductors that go to the red wires on that diagram.

Using that to switch ground will probably mean that the LED won't light up, even if you put 12v to the terminal that has the black wire. Polarity matters with LEDs. I could be wrong.

So pretty much I'd put a ground for the switch itself and then run the ground wire from the fan?

 

[Fless]

Need to figure out which two terminals on that switch are the actual contacts for the switch. (Normally if you're going to switch power, the only reason that ground lug is there is for the LED, so it can be ignored.

You'd run a ground to the switch, then the other terminal of the switch goes to the fan relay ground. In order for that to work the relay would need to have a constant power (12v) and the switched ground.

 

[JPVortex]

Need to figure out which two terminals on that switch are the actual contacts for the switch. (Normally if you're going to switch power, the only reason that ground lug is there is for the LED, so it can be ignored.

You'd run a ground to the switch, then the other terminal of the switch goes to the fan relay ground. In order for that to work the relay would need to have a constant power (12v) and the switched ground.

ok thanks! I'll see what happens

 

[ivin74]

He shows a 20a switch and I'm not sure that's going to survive without using a relay. Not sure how much current the fans draw.

The switch is going to burn up, the fans draw about 40amps

 

[Fless]

If you know which wire is the ground that needs to go to the PCM, that would be your relay ground to run through the switch.