fan wires

[kglowacky]

Started my LS2 today for the first time.

Motor ran well for about ten minutes then it shut off.. heres what s is happening. The fans (neither one) will will turn on. Then after about 10 minutes the pcm shuts off the relay to the fuel pump. I think the problems are related. My question is is the fan wires from the pcm hot wires when they get the signal from the pcm and therefore act as the positve side of the relay or are they the negative side of the relay? I think the pcm reads a hot engine and shuts off the fuel??? Help your thoughts

[mongocanfly]

What was the coolant temp?
And what relays are you using...
And at what temp are your fans programmed to turn on?
Is this a DIY harness or store bought
I've never had the ecm shut off the fuel when engine gets hot..

[mongocanfly]

This is how my psi relays are wired..
The ecm makes the ground side of the relay to engage 12v to the fan

[kglowacky]

I wired mine the same way except I assumed the pcm was supply power to the relay so when the pcm sent the ground to the relay I had grounds on both sides. never triggering the relay. I am going to fix it to look like yours in the morning. My harness was done by someone in California and it looks like he did a great job. he used my old one and just cleaned it up. as far as fan temp turn ons he set them a little high for me in texas.
fan 1 226 on 219 off
Fan 2 234 on 227 off

I am thinking of lowering them to 200/193 and 208/201

I hope he can reprogram the pcm without me sending the harness. ''
I will udpdate if this fixes the problem in the next few days,

[mongocanfly]

He wont need the harness to reprogram...
I know that sounds high, but LS engines seem to run at higher temps than the smallblocks..
My 13 runs at 215..
My fan temps on my 81/lq9 are set a 175 and 180...I've never had a issue..
If your running dual fans you need 2 relays..one for each fan..not sure of your setup

[kglowacky]

two relays one for each fan no third relay at this point. Will add if needed after I get the it on the road. And you meant harness not ecm i assume

[mongocanfly]

Ooops ..correct...he wont need the harness...my bad..
I changed it
On my ecm it was only setup for 1 fan from the factory..they had it programmed wrong when I had the ecm done..I had to send mine back and get it reset for 2 fans...

[kglowacky]

update. Switched the pcm fan wires to the neg side of the relays (running two fans) and they work perfectly. As far as the fuel relay shutting off do to the high temp MONGOCAN FLY was correct. It had nothing to do with the temp. The one relay wire had slide down in the plug to where it was making bad contact. still deciding on what temps to adjust my turn on turn off temps. Until I get the ac hooked up I wont make that decision.
Only question my mechanic has is it is only running at 13.5 amps. When I turn on the high beams drops to 13.3 When I increase speed the amps do not increase. We are not sure if the alt is not charging correctly or the pcm is holding it back or if this is normal.
'Any thoughts

[mongocanfly]

amps? or volts?...mine puts out around 12-1/2to13 volts according to my volt gauge

[kglowacky]

volts