LS with A/C

[BigBird05]

I am trying to think this whole swap thru before starting on it. How are you configuring the A/C? How can I use the LS compressor and hook it up to the stock 72 Evaporator? Do you use the stock in dash lever switch to activate the A/C? Does that send a signal to the computer to increase the engine speed at idle? Do I need to install the LS A/C inline switches? Have I missed or not thought of anything?

[Davidf]

Quick answer is yes, you can use all the stock A/C components and controls. But, if you do so, you will have a compressor that runs 100% of the time when A/C is being requested. Not sure the LS compressor is designed to operate in such a manner. The issue is that the factory system is not designed to cycle. But, it you want to try it, I suggest you simply use the factory 12v a/c compressor wire and connect it to the LS PCM (pin 17), then power the compressor via the PCM (pin 43, ground output) through a relay. Previous assumes early truck donor (i.e. '99 - '02, later years are harder as the PCM is looking for serial data input from the HVAC module). Wiring as mentioned will allow the PCM to control the compressor and thus idle speed compensation.

What I did was take the opportunity to upgrade the evaporator to the orifice type with an accumulator. The accumulator has the low pressure cycling switch to control the compressor. I used all the a/c circuits from the donor LS harness and wired accordingly. I added condenser fans controlled via relays triggered by compressor signal.

If you purchase Hooker Blackheart engine stands, you can retain the stock truck compressor location with no interference issues. You will need to have custom a/c hoses made.

Hope this helps.

[mtdave2]

i retained the stock ac. it is not a variable pressure compressor so it could be used with a vintage air system. my truck had original ac, but I decided to get rid of the old bulky crap and go with vintage air. was easy to install.

there is a clearance issue with the low-hanging ac compressor.. i ended up notching the frame, and the hoses were a challenge but I was able to build my own.