Painless Harness fan trigger wires?

[dme922]

I am using a painless harness on my 5.3 swap and i cannot get the fan trigger wires to start my fans. How can i check the fan trigger wires to see if they are working at the ecm set temps?

[mongocanfly]

was your ecm setup to run fans?...I had issues with mine and they had to go back in and fix it in the program..

[dme922]

The guy that did mine said the ecm was set for the fans to come on at 205 and off at 190.

[homemade87]

Originally Posted by dme922

I am using a painless harness on my 5.3 swap and i cannot get the fan trigger wires to start my fans. How can i check the fan trigger wires to see if they are working at the ecm set temps?

The fan trigger wires are a ground trigger for the relays . If you have the temp gauge plugged in the ecm should see what temp the engine is . Once the temp gets up the ecm will ground that wire . I would think you could use a meter on the trigger wire ( ground ) and to a +12 and see it come on . Green for low speed and blue for high speed .

[Hart_Rod]

Originally Posted by dme922

I am using a painless harness on my 5.3 swap and i cannot get the fan trigger wires to start my fans. How can i check the fan trigger wires to see if they are working at the ecm set temps?

Do you have HP tuners? If so, you can turn the fan on/off by using their scanner/data logger. But as stated above, the Painless wire provides ground to a relay, that triggers the fans to come on.

[Custom 68]

Great info guys and yes I have seen a few folks assume the computer wire is positive so when they hook up the relays and all the wiring they have two negative wires to the fans and they wont run.

[dme922]

I dont have HP tuners but i do have access to a tech 2 computer. Im going to retrace my wires but i believe i had the ground wires from the relays going to the ecm fan trigger wires. I will double check.

[dme922]

Here is a little more info on my fan issue. The guy that i got my ecm from asked me what year my motor was and i told him an 04. I know not many if any 04 5.3 had electric fans but after initially having this issue i asked him if the ecm was programmed for electric fans and he said it was set to come on at 205 and off at 190. That being said a friend of mine hooked it up to a tech 2 computer and the ecm was getting the engine temp but was not grounding the trigger wires at the set temp. I contacted the guy that i got the ecm from and he sent me another ecm but i am having the same issue. Any suggestions?

[ls1nova71]

Did you try and command the fans on with the TechII, and if so, did they come on? Also, how do you have them wired up? What I would do is pull both PCM connectors off, then turn the ignition to "on", obviously don't start it . Then find pin #42 on the blue connector and touch a wire from it to ground, the fans should come on "low" if wired like stock. Then find pin #33 on the green connector and ground it, fans should come on high. If none of this makes them come on, you need to look into your wiring, either bad ground, not getting power or something just isn't wired up correctly, barring that the fan itself isn't just dead. If they do come on when you try this, then it's almost got to be a tune issue, and it sounds like maybe you need to find another tuner.

[dme922]

Today i used my dads snap on computer and i can force the fans on. It also showed me the engine temp and when it reached the set points the tuner told me the fans didnt come on. So it does sound like a tune issue since my ecm is getting a temp reading and the fans will run by being forced on.