Electric Cooling Fans

[JPVortex]

Ok, wouldn't I need to give power to the part that goes into the PCM too aswell as ground aswell? Or wait actually the relays would give it power.

And to ground it would I just splice into the wire and run it to a good ground?

Or I could probably just put an alligator clamp on the connector

 

[Fless]

You might think about pulling both PCM connectors off to inspect for water migration and pin fitment. IIRC the fan pins are at the bottom of the connector and that's where the water goes if it gets in. Just something to check.

 

[JPVortex]

You might think about pulling both PCM connectors off to inspect for water migration and pin fitment. IIRC the fan pins are at the bottom of the connector and that's where the water goes if it gets in. Just something to check.

Yeh thatd be a good idea, I'll first test the connector by sending ground with those wires

 

[JPVortex]

Another thing to test could be unplugging the connector from the fan harness to the PCM. Then on the end that runs to the relay box you can ground the green wire for low speed or blue for high. That should tell you if it is harness/relay related.

Do you have a picture of which connector goes to the PCM?

Also from what you said I'm guessing that the way the PCM turns the fan on and off is by cutting ground? Since I'd be grounding the wire?

 

[mattbta]

The connector with the two small gauge wires in the middle of this picture is what I’m talking about. Disconnect that connector. You will want to ground to the relay side (left in the pic), take a spare wire and touch to negative battery terminal and then to one of the pins inside that connector. Green for low or blue for high.

The two small wires with tiny pins in the picture go to the PCM. Don’t do anything with that side of the connector. (The PCM supplies, not cuts, ground when the fans are activated.)

If the fans turn on, then it’s not the relays or harness.

Make sure to plug it back in.

 

[JPVortex]

View attachment 391236The connector with the two small gauge wires in the middle of this picture is what I’m talking about. Disconnect that connector. You will want to ground to the relay side (left in the pic), take a spare wire and touch to negative battery terminal and then to one of the pins inside that connector. Green for low or blue for high.

The two small wires with tiny pins in the picture go to them PCM. Don’t do anything with those. (The PCM supplies, not cuts, ground when the fans are activated.)

If the fans turn on, then it’s not the relays or harness.

Make sure to plug it back in.

Ok thank you very much. I will perform this test tomorrow as itll be like 45 farenheit out compared to 15 lol.

 

[JPVortex]

Did run out quick to test the temp sensor. Fans did not kick on with it unplugged, kind of expected that

 

[JPVortex]

Well heres an update yall, did the test and the fans do kick on! So it's some sort of PCM issue. I have a spare PCM but it might be for a pre 2005 truck that doesnt have electric fans.

also wondering if my pcm was replaced at one point and the electric fans weren't enabled in it.

 

[Rocket Man]

Have you removed the connectors at the PCM and looked for corrosion? It’s fairly common like @Fless mentioned. The PCM is located under the battery and has 2 large connectors with 8mm screws holding them on iirc. You’ll have to loosen those and wiggle the connector to get them off. Disconnect the battery first of course. There’s an o-ring on each one but sometimes water still gets in. You should be able to tell if the PCM has been swapped by looking at it. If it’s undisturbed looking then it’s probably original.

 

[JPVortex]

Have you removed the connectors at the PCM and looked for corrosion? It’s fairly common like @Fless mentioned. The PCM is located under the battery and has 2 large connectors with 8mm screws holding them on iirc. You’ll have to loosen those and wiggle the connector to get them off. Disconnect the battery first of course. There’s an o-ring on each one but sometimes water still gets in. You should be able to tell if the PCM has been swapped by looking at it. If it’s undisturbed looking then it’s probably original.

Yeah I have the PCM off right now. I see no corrosion what so ever on it.