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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: ROARING 455 on September 08, 2023, 05:13:16 pm

Title: Gen 4 A/C PCM Questions
Post by: ROARING 455 on September 08, 2023, 05:13:16 pm

So I’ve read that the gen4 pcm are different and that the AC isn’t able to be programmed into the pcm for an ls swap build to help boost the rpm’s when it’s on and running. Is this true? If not could someone please point me the right way on any post or info as to which pin in the pcm is it that I need to keep in my harness?

Title: Re: Gen 4 A/C PCM Questions
Post by: JohnnyPopper on September 09, 2023, 07:23:56 pm

nei...not enough information

Year, model, yada... ;)

Is that a Mano Cornuto symbol?

Title: Re: Gen 4 A/C PCM Questions
Post by: ROARING 455 on September 10, 2023, 11:53:14 am

Gotcha. So donor truck is a 2008 Chevy Silverado with a 5.3 4l60e transmission and I literally got everything I need from the donor in good condition and it’s going to be going into a 1974 gmc square body. I’ll be starting a build forum eventually but right now I’m just trying to put some numbers together after knowing what I’ll be using from the donor truck.

Title: Re: Gen 4 A/C PCM Questions
Post by: ROARING 455 on September 10, 2023, 11:59:13 am

Oh and yes that is correct. MANO CORNUTO lol I had to look that up

Title: Re: Gen 4 A/C PCM Questions
Post by: ehjorten on September 12, 2023, 09:19:02 am

What I understand is that in later years the A/C control was moved to the BCM and as such you are unable to control the A/C activation with the PCM. You need a pre-2003 PCM to do that.

https://www.lsenginediy.com/upgrading-gen-iii-ls-series-pcm-air-conditioning-guide/

Title: Re: Gen 4 A/C PCM Questions
Post by: Mike81K10 on September 12, 2023, 01:44:01 pm

I have a Vintage Air, Gen4 system in my 81 K10 and the system is self contained. Just supply the power.

Title: Re: Gen 4 A/C PCM Questions
Post by: ROARING 455 on September 12, 2023, 04:47:42 pm

Quote from: ehjorten on September 12, 2023, 09:19:02 am

What I understand is that in later years the A/C control was moved to the BCM and as such you are unable to control the A/C activation with the PCM. You need a pre-2003 PCM to do that.

https://www.lsenginediy.com/upgrading-gen-iii-ls-series-pcm-air-conditioning-guide/

Oh ok. That’s kinda dumb that Chevy did that on the gen4s. Thanks for the link also definitely lots of info on there that I’ll revert to for sure. So just out of curiosity tho, couldn’t I just use the bcm from the truck, depin it, but the ac pins and find some one to program the bcm at the same time I have my ecm done?

Title: Re: Gen 4 A/C PCM Questions
Post by: ROARING 455 on September 12, 2023, 04:52:44 pm

Quote from: Mike81K10 on September 12, 2023, 01:44:01 pm

I have a Vintage Air, Gen4 system in my 81 K10 and the system is self contained. Just supply the power.

Oh dude I wish I had the vintage ac setup also. Kinda expensive and at the moment I’m about to be doing the 5.3 rebuild with some new goodies. Eventually I’d love to buy one tho, but at the same time if I can get the OG one to work with my swap correctly I’ll just go that route and save myself a grand to put into something else.