99 Silverado e-fans

[97 SS 383]

I read a post somewhere about Nelson tuning programming electric fans to work using the truck computer, I was wondering if that programming also makes them come on when the A/C is switched on, or if it is only by temperature.

[02P3wZ71]

Mine is set to turn on by temperature. I don't think that it can be tuned to turn on with the A/C as well. It just isn't possible to wire it up to do all of that. That is what was explained to me, maybe Allen can work magic!

[97 SS 383]

If he can, I may have plenty of work for him.

[badseed91]

How does the computer on the camaros know the ac is turned on? Im sure that it cant be that hard to find a way to hook the a/c into the cycle to get the fans to come on once the a/c is turned on.

[farmtruc]

The truck pcms are setup to turn the fans on, but only one output is available, I just got the latest version 1.4 edit and there is an update on the second output temp control, I'll have to play with this.
Most ppl complain the fans come on at the same time and drain the truck for a sec, having that second output would be nice. One fan at at time.

As far as the ac. Check the pinouts, the trucks also have an output or sense line for the ac. It's not necessarily meant to turn on the fan when the ac comes on, but any wire/pcm pin, that changes from 0 to 5, or 5 to 0volts when the ac comes on will work. You're just looking for a signal change

I'll keep you guys updated on the second pin output.

later,

allen

btw, you do need edit to change the fan temp settings in order to activate the fan output/control line.

[GMCwantsLS1]

On the Camaros the switch on the dash sends a positive 12V to the PCM then the PCM tunrs on the compressor. The PCM then senses the high side pressure and when it gets high enough it turns on the fans. I think all you need to do is turn on the fans when the compressor is on. Just tap into the compressor 12V+ wire and use that to trigger your fan relay.

[97 SS 383]

The problem is not making the fans come on when the A/C comes on using extra wirin and relays, I have done that for years. What I would like is to not have to do that anymore. If someone can actually have the computer do it, that would be cool.
I didn't realize you were using LS1 edit for all of this, I thought you actually had the GM computers and programming skills. I have had great luck thus far with Fastchip/Ed Wright, I thought maybe you were doing something like him.

[GMCwantsLS1]

On mine I have the PCM "AC Request" on my truck hooked to the wire that goes from the controler on the dash that turned on the old compressor. I had to add the high side pressure switch so the PCM can sense the AC pressure and turn on the cooling fans. Works just like the camaros do, in other words the PCM controls all fan functions for temperature and AC! Most don't do it like this and say it is too much trouble, but I like it working like the factory intended it to.