a/c pressure adjust for fans

[jknox]

You can still wire it up like this (factory harness or custom) to have high speed control from the ECU, but the pressure adjust fields would allow us to dial in when high speed would kick on-off a bit better compared to AC pressure.

Not for those of us with '02 or earlier. On my '02 the high-speed pin on the ecm is used for something else...

I'd still like the better controls though.

[4.8t]

'and us guys putting LS1 fans and have wired up their own relays to work like factory.

You can still wire it up like this (factory harness or custom) to have high speed control from the ECU, but the pressure adjust fields would allow us to dial in when high speed would kick on-off a bit better compared to AC pressure.

my truck fans kep blowing the relays on the a/c fans side. it just flat out draws to much current. so i'm gonna try to order the stock harness. its suppose to have way better relays. it sucks when you sit still and the a/c doesn't work because a relay goes. it melts down the insides. i even used some relays i pulled out of a cars fuse box. i think it uses thicker wire too.

[4.8t]

maybe this would fix my problem.?
http://www.jcwhitney.com/webapp/wcs/...atalogId=10101

[jimmyblue]

Relay logic and a few cheapo thermostats would solve it all.
If you like to cobble.

[4.8t]

i like the ecu to control things if i can though. but i did get ahold of some good relays.

[BigKID]

I am another that is using an '02 truck pcm to control my e-fans via pin42 and would be very interested in the ac control.
With my fan circuit it would be nice if it could be set to be set for the fan trigger to be grounded when ever the ac is on whenever in range of the speed on/off control. i.e.... Pin 42 (fan trigger) would be grounded based on coolant temp and/or ac on/off dependent on vehicle speed.

[4.8t]

is on or off dependeant on head pressure and vehicle speed. like if head pressure such and such and you are below say 30mph the fans will be on but at the same head pressure and above 30 mph fans will kick off. but if head pressure is to high or low can't rember off the top of my head, the fans will be off no mater of vehicle speed. then you have the vehicle temp for the other fan and it work same but uses temp and speed.

[BigKID]

A pressure control will work just the same; as head pressure will build quickly if the compressor is on and there is no air flow across the condenser. I just brought up the on/off trigger idea incase it was in easier solution from a coding perspective.

[Wilde Racing]

my truck fans kep blowing the relays on the a/c fans side. it just flat out draws to much current. so i'm gonna try to order the stock harness. its suppose to have way better relays. it sucks when you sit still and the a/c doesn't work because a relay goes. it melts down the insides. i even used some relays i pulled out of a cars fuse box. i think it uses thicker wire too.

Are you having the PCM control both the high and low speeds? Or are you using just one ground pin from the pcm?

[4.8t]

right now i'm just useing one pin to control one fan then i'm useing the a/c relay to control the other and if both are true both fans are on but in low i think. its the nelson harness right now but with better relays to stop the melting realys. but if i ever get hpt to write in the a/c contols for the a/c like the other tuner then i will get the factory harness. stock both fans are on with the a/c on. wether the eng is hot or cold to keep the a/c cool as possible i guess. untill a predetermend speed then the fans shut off. i had two guy start their trucks bone cold and hit the a/c on and both fans came on ad they said they think they were on high. either way they were both on.

[Wilde Racing]

I'm not sure if it will work on the 04 Tahoe’s, But on Silverado’s, I know for a fact you can use the other pin in the PCM to control the fans. Set you fans to "two fans" and the fans will function Just like the fans found on the 05's. This "should" solve your relay burning problem, then just wait for HPTuners to give us more control over the fans......

It's just a matter of hooking the wire you currently have hooked to the A/C circuit to a fused "key on power source" and running the relay ground to the PCM.

[4.8t]

so the a/c side is already programed to run that pin when its turned on? with my harness i think its on the ground side of the a/c relay already so i could just pin it to the ecu. will the fans then shut off at speed? thats what i hate is the fans running all the time with the a/c on. when your driving there is no need.

[Wilde Racing]

so the a/c side is already programed to run that pin when its turned on? with my harness i think its on the ground side of the a/c relay already so i could just pin it to the ecu. will the fans then shut off at speed? thats what i hate is the fans running all the time with the a/c on. when your driving there is no need.

To be honest, I don't know. The truck I helped set-up is down in Arizona and his fans run all the time. He was having overheating problems. (like some do with that set-up). He could only run the fans on high with the a/c on. After we changed it so the PCM has control of both wires. his overheating problems went away. Plus no huge draw and burnt relays everytime the A/C clutch cycles.
FWIW, we tested both grounding pins in the PCM with a tech 2. they both fuctioned properly, so I would guess as long as there are some a/c / fan control tables in the PCM (even if we can't see them), the fans well work as factory.

[4.8t]

now i just have to reread to remember which pins are which and i'll just go test it tommorrow with a ohmmeter. if it grounds with a/c on then i'll try to find a pin. do you happen to have a part number for the pins so i don't have to search for it again. thanks

[WarWagon]

I would love to see Fan support including kickout speed for the Trailblazer LS2. I can't be the only one keeping the EV fan.

That and many would like more control of the electrics they put in.

[4.8t]

just cross our fingers and hope i guess lol.

[SS_bnoon_SS]

Anything new yet? NEEEEEEEEEEEED it before summer gets here...

[4.8t]

maybe it will be in the next release.

[2manytoys]

I was doing some research today on this and ran across the thread on pt.net. I am currently running a spal controller. It works fairly well but I would like to be able to control the fans with the PCM.

[Wilde Racing]

Bump???