5.3 swap fan wiring problem
 

Here's what I got..... 01 2wd truck harness and pcm, 04 5.3 and 4l60e. It's swapped into a 1990 c1500 regular cab short bed 2wd. I got everything figured out by either info I found on here, lt1swap.com, or just trial and error. The truck runs and drives great I just can't figure out what is going on with my electric fans:mad: I've got fan 1 wired to pcm blue pin 42 for relay ground and fan 2 to red pin 33. The hot trigger wire for my fans is key on power only. When the engine is cold I turn the key on all is good, no fans running. As soon as I start the truck fan 1 comes on (blue pin 42). Fan 2 works perfect. I have wired up plenty of stuff using relays before, I've double and triple checked all my wiring. Btw, my fans are wired very simple.... one relay per fan. They're either on or off when the relay sees key on power and a ground. Why is blue pin 42 grounding as soon as I start the engine? Also, at the moment a/c isn't tied into this. The fans should only come on at a given ECT. I've consulted with my tuner (blackbear tuning) and I'm pretty sure he feels like it's not in the tune, but I don't know what else it could be.

The Red/Blue Trucks don't use primary fan from the factory. When you inserted a wire in there you probably realized there wasn't a wire to begin with. You need to check the tables in the tune. I'm not sure what happens with a stock tune if you put a wire in the spot without adjusting. So check the tables if you can

I don't have a way to check anything, but I'm using a reputable tuning service. He seems pretty sure that he knows what he's doing, but I can't help but think that it's in the tune. Is there anyone that can give me some advice on what to ask the tuner to kinda double check him?

which OS is he using? Camaro (F-body) or Truck? With the truck OS, unless you do a segment swap - your not going to get the 2nd fan to kick on.

Gotcha. I know on the Truck operating systems you can enable a second fan within programming on HP Tuners. However, this guy has an issue with primary fan I believe.

The 01 truck pin out shows that pin 42 doesn't have a wire on it, but 41 is a ground. Makes sense that when you turn your key on the fan runs, as it could be pinned to the ground.

As for pin 33, that is the pin to the recirculation door. Your tuner needs to look in the tune file and toggle recirc. door to fans, then it should work for the second fan.

Post #13 on the link below has the pinouts for a 2001 truck...

https://ls1tech.com/forums/conversio...swap-faqs.html

More on the subject....

https://ls1tech.com/forums/conversio...lp-please.html

And one more with more detail...

https://ls1tech.com/forums/conversio...ctic-fans.html

T,

Correct, but I added a wire to pin 42 where there wasn't one before. Pin 42 is supposed to be fan one relay control from what I've read. I suggested a segment swap to my tuner and he said, "it would likely create more problems than it would resolve." Since I have no idea what a segment swap is, I can't argue with him. So since my secondary fan operates correctly I just had him lower the temps on it and I'll just operate both fans off one trigger wire for now. :|