Yeah eliminate the harness from the equation completely and just work with 42blue and 33 red. That way you are working strictly with the PCM and no other equipment can be to blame... unless your volt meter is broken

 

Check this out, I have two fans and each one has its own relay but i run my ground signal to both from pin 42, which should inturn make both fans come on at the same time.... Butttttt one fan runs constantly whether the truck is on or off and the other fan will come on with the truck started!!! I can figure it out just tired of jacking with it today and watching yall to see if there is anything im missing

 

Yours is simple, the one that is on during the truck being off is a bad relay or is wired wrong...Just check that relay and make sure its wired right, if its not a wiring problem then replace it. The other relay that is working when the truck on, is it turning on at the programmed on time in the tune!?

 

the fan that was running constant even with the key out of the truck.... i took off the ground wire from the relay thats going to # 42 and it quit!... I need to go back and check the tune because last time i saw it i belive it was accidently put on 160 to come on and 180 to go off, 160 degree stat

 

Yeah a couple things... one, if the same ground works well for one relay and doesnt for the other then the relay that is acting funny is either 1 of three things:

1. Wired incorrectly or
2. Failed relay internally or
3. The wrong relay style! It may have an open switch by default and use the ground supplied to close the switch! Make sure the relays are exactly the same or you will get different results.

As for the tune if you use a 160 tstat your on temps should be like 180 then turn off at 175

 

Engine off/ING on - 33 Grounded -- 42 nothing
Engine off/ING off - 33 shows very slight ground -- 42 nothing


Here's the nifty part, I think I have a bad relay possibly... Pull pin 33 and the wire spliced from it to the other relay, fan shuts off, hook it back up, fan stays off, until the Ignition is turned back on, then the fan stays on until you pull those wires again. I'm also wondering if the light ground that I'm seeing is being back fed from another relay, it's dark now so I'll have to check it tomorrow.

Edit : I couldn't wait and made the girlfriend hold a flashlight. I do have a slight ground on 33 at all times, it's enough to trip the first relay "Cooling Fan 3 relay"

So I'm still at square 1. As long as I want to pull the wire from the relays every time I get out of the truck, then I'm done! lol. Not only is that fan on all the time, it's on high.

 

Ok if youre seeing a ground signal from 33 then your problem could lie somewhere with the Pressure sensor switch. Try removing the #17 Wire (Im pretty sure its a blue wire) from the RED harness. Then plug the harness back in the pcm, put the ground back on the battery, and key on eng off test it again. If it goes away then you have a pressure switch issue or the switch could possibly be correct and you have a high pressure issue with the A/C.

 

I'll pull the PCM back apart tonight, make absolutely sure that I spliced into the correct wire. It was solid green if anyone can verify for sure. I didn't have a Volt/Multimeter last night, so I was testing with a test light... I'd guess it's showing -3 to -5V all the time on 33, truck on, truck off, key in, key out... doesn't matter.

If I am spliced to the right wire coming out of the red connector, I'll check the pressure switch.

 

You can't splice into the wire coming off of pin 33. In stock configuration, that wire controls the HVAC recirculation actuator which is also controlled by the HVAC controller. They are spliced together somewhere around the actuator. To do a proper e-fan swap, you have to use that wire coming off of the PCM to exclusively control the relay. If you don't, you can get a ground from the HVAC module which could activate your relays.

 

So can I just cut the wire off from the rest of the HVAC system? I think I remember reading somewhere that you can do that since that specific function is also controlled by the HVAC module.

The fan on pin 42 is operating correctly. It comes on at around 200* engine temp.