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View Full Version : air conditioning a/c not working after swap?



The Captain
04-07-2012, 12:42 AM
I have a 93 vert with an early Gen 2 3S-GTE swap. My third plug on the 5s ECU had 12 pins. My a/c worked fine before the swap, but not after.

If you have a GTS with the auto a/c system, it should be plug and play. If it doesn't work, it's the engine harness that has a problem somewhere. I had a failure at J/B no#2 from the harness that I had for the 3s. Drove me nuts but I found it.

I think I may have found the key. In order for the 5s a/c amp to command the a/c magnetic clutch to engage, it needs various signals. ATS is one of these signals and it's provided by the 5s ECU. Guess what? The 3s ECU doesn't have this signal to provide. I think it's "A/C Temp Signal" but I'm not sure. If you were smart(I wasn't), you'd have measured this signal BEFORE you removed your 5s. Then you may be able to fool the a/c amp with a fake signal.

So the other day I was at good ole Pull A Part and I found a GTS. I removed the a/c amp and harness. That was weeks ago. Today I decide it's time to look. So I compare the original 5s a/c amp and an "auto" a/c amp. THEY WERE IDENTICAL except for the damn ATS input.

Long story short, I simply plugged in the "auto a/c amp" to the original harness and voila, my compressor kicked on!

I unplugged the a/c thermistor and pressure switch and the a/c kicked off. Tells me the amp is protecting the system.

I spent weeks trying to figure this out. I had everything right. I could ground the L-Y wire and the a/c clutch would engage. The amp just wasn't commanding it. I think I paid $5 for the amp and PAP. Almost as good as finding my vert boot for $4.67 there.

I can only provide for 5th gens. I have no idea on the others.

joe's gt
04-07-2012, 11:36 PM
That's what I noticed too. The 3s ecu was 1 pin short. I just set up a cyclical time switch for the compressor, but never worked quite as good as the original a/c. Then my a/c developed a leak and I just gave up on it for good. So all that is necessary is to replace my GT a/c amp with the GTS one as long as it has auto a/c? Great work! Definitely will help future swappers with their troubleshooting.

4thgenceli
04-08-2012, 12:15 AM
A/C?

What's that?

The Captain
04-08-2012, 03:04 AM
A/C?

What's that?
Short for Aircraft.

Or, a heat removal system that prevents malodorous conditions that make you offensive to the rest of us. Also improves the success with the opposite sex on a hot day/night.

4thgenceli
04-08-2012, 03:20 AM
Short for Aircraft.

Or, a heat removal system that prevents malodorous conditions that make you offensive to the rest of us. Also improves the success with the opposite sex on a hot day/night.

Oh that.

I don't have that in my swap. The pure sexy sight, noise and power of my swap gets me that all night long.

The Captain
04-08-2012, 12:50 PM
That's what I'm missing!

alltracman78
04-08-2012, 09:27 PM
Interesting...
Great info man! :)