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I am ready to buy an engine and trans for my project, a fullsize Jeep with factory air (Vintage Air) type system and want some input before I fork over the cash and back myself into a corner.

I want to retain the simple Jeep factory air and I believe I should buy the Vintage Air LS compressor mount and run a Sanden compressor.

My plan was to buy a complete LM7 or L59 and 4X4 4L60E, does the newer serial data ECM have a wired AC input that will add rpm? I believe the answer is no.

If not, do I need the older ECM that has the wired AC input and if so, will it work with the newer 01-06 harness or do I need an older harness as well?

Express Van ECM and harness or ECM only?

If so, what year models?

F-Body, if so, what year models?

ls1nova71

iTrader: (4)

First and foremost, what year/model is the Jeep? Secondly, you say it has factory air, but then put Vintage Air in parentheses right next to it? Factory is factory and Vintage is aftermarket, so I assume you mean just the factory installed A/C. A lot depends on the year and how it was originally wired.

As for the serial data controlled A/C request, it's really not needed. A lot of people hear PCM controlled A/C and think the computer works some kind of black magic that makes the air better. In reality, without the PCM controlling the A/C, if an additional load is placed on the engine, the computer will compensate for it. There may be a slight delay, but in all honesty it's really not that noticeable. The other feature that people just HAVE to have the PCM do is to cut the compressor off at WOT. This is a good feature, but again it's not needed, if you're going to be full throttling it, just turn the air off for a second. What people don't realize is if you go to, say 95% throttle, the A/C is still on, so full throttle cut off really isn't all that important. If it is, you could mount a limit switch on the pedal, but in my opinion, more trouble than it's worth.

That said, there is a way to convert the serial data to 12v request, BP Automotive does it, but I guess what I'm trying to say is don't sweat it, it really isn't that big of a deal. What ever you do, don't try the older harness and PCM thing unless you plan on getting the older throttle body and TAC module to go along with it as the 03-07 TBs and TACs won't work with the older PCMs/OSs.

243

Thanks, I have a 78 Cherokee with a 360/T400/Quadratrac with factory AC. The system has the underdash plenum and a firewall mounted evaporator and blower similar to 80's Chevy's and a York compressor.

I am not interested in PCM control of the AC system, my only concern was having idle compensation when the compressor is engaged due to the negative reports here and the basis for my questions.

I recently installed a TBI system on my 258 CJ and without the idle compensation it would stall on a regular basis.

I did read where BP Automotive can modify the PCM to provide a 12v signal but my understanding is this requires they modify the harness too. That is a huge expense for my build when I planned to modify my harness on my own.

garys 68

iTrader: (1)

I'm running an L59 and LQ9 with aftermarket air, no AC request to ecu. No problems at all. If you're running electric fans use a trinary switch to control one.

BP Automotive

iTrader: (3)

Even if you do not run PCM controlled a/c run the pressure switch.

There are a TON of advantages to running PCM controlled air. On of the main ones is the High RPM shut off function.

Bill

243

What are the advantages?

BTW, I sent a PM requesting a quote.

gofastwclass

iTrader: (2)

I think the advantages vary a bit by PCM choice.
The high RPM / throttle position threshold is the first that comes to mind.
Another is being able to run the fan by AC pressure and engine coolant temp vs. blindly being on when the AC is on and off when it's off.

BIll, if you know of others I missed I would love to know about them.

243

I plan to run a mechanical fan.

I do see the advantage of the PCM turning the fans on and off based on conditions.

A mechanical AC system has not been a problem in the past and it appears to me adding parts and pieces to an existing system to allow the PCM to control the AC complicates the project.

I am not closing my eyes to the possibility but I want to understand both sides before I say yes or no.