Pin 13 and Pin 25 off of the ECM goto your AC amplifier on the D connector.

13 should be a blue black wire.. 25 should be blue yellow wire


Which ac do you have the manual one ? or the automatic ? ( what does your dash controls look like? They levers or digital)

Basic manual AC.

You’re correct on the wire colors. I just picked up a used ECM for 75.00.

Ok. I was going to give you the pinout on you ac amplifier so you can verify the wires have continuity. However, I know your going to try that other ecm.

Good job on not giving up as you will fix it and learn alot from this process.



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I did the continuity test awhile ago. For some reason, I didn’t probe the ECM circuits.

I don't know which signal is which but that is part of the secondary communication between the AC amplifier and the ECU. You are on to something there.

One signal is the "AC wants to be on" from the amp and the other is the "Turn off the AC" signal to the amp.

-Charlie

I did get another ECM and nothing changed on the clutch side, but….now it blows hot air.

I’m beyond angry.

Good grief...:/

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Does the ac clutch even kick in with the other ecu?

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No, it did the same thing, only when the throttle is depressed.

Good thing I can return it.

Not the ecu then left with wiring and bad amplifier. That entire thing is crazy.


You still have pressure and referent in the system?

As you could have a leak and the 134a gone.

I had one do that to me that I need a new ac line for. As my actual line itself is damaged leaking the refrigerate.


I never seen your issue before. Now I greatful to have to only deal with the leaks problems.

I knew I should have grabbed that ac amplifier out of that 1999 ...

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I have another amplifier. I swapped that too and no difference.

Does it work with you original ecu? If not I trace those 2 wires that go from the amplifier to the ecu as something got worse here.



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I put my original ECM back in an it was working on the gas pedal as usual. Today the clutch wouldn’t engage and I put the gauges on. It’s about 15 psi on the low side and 5 psi on the high side. The only part that glows is the manifold the the hoses connect to.

Maybe the compressor gave up the ghost? It wasn’t my original, in fact it was an aftermarket one

You have a refrigerate leak on top of everything else. 15 is too low your pressure switch opened the safety switch so the compressor won't turn on.


Very possible the compressor has an issue as well. As 5 psi isn't good at all.

When my one compressor blew it was the same pressure on both sides. :/

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Just want to take a minute to update everyone on this issue.

I have been working with a local AC and radiator shop and I believe we are getting closer to an answer.

To date I have replaced the following:
-Condenser
-Receiver
-Evaporator
-Expansion Valve
-Pressure switch
-Thermistor
-Amplifier
-Swapped compressor ( my original is back due to a failed seal on the reman)
-I tried a new ECM with no effect.

As of today, the system does cycle, but only on the throttle. I went back to my FSMs and looked through the trouble chart again. One component I overlooked, the main heater relay. According to the manual, terminals 2-4 and 3-5 should have continuity. 3-5 did not get a beep. The relay energized when I put battery voltage to those terminals. Not sure how it’s possible. The manual states to replace the relay if it fails any of the tests. I have one coming in tomorrow.

I’ll let you know what happens….

Scott