Finally getting to the AC on my 1991 V6 Firebird... I've done the R4 to Sanden FLX7 swap, but I'm having an issue with the clutch. For some reason the ECM isn't grounding the AC clutch relay to engage the clutch.
Mine is a Vin T car and per the diagram here: http://austinthirdgen.org/mkportal/m..._continued.gif I've checked for power in the relay plug and have 12v on both the PNK/BLK wire and the LT GRN/BLK wire, but the clutch never engages despite the ECM reporting an A/C ON state (I use an EBL-P4).

I tried manually grounding DK GRN/WHT and the clutch engages. It also cycles normally, and the engine RPM adjusts like it should. Without this being manually grounded, the clutch never engages.

So I have two questions:
1.) Does anyone have any insight as to what might cause the ECM to not ground this pin on the relay like it's supposed to?
2.) What (if any) problems may arise from leaving this relay always grounded manually? From what I can tell, it appears to effectively be how the vin E, F, etc. cars were wired and the clutch seems to behave normally (cycling, hvac controls working, etc.). Obviously ECM features like high-rpm AC cutoff won't work, but that shouldn't be a problem. I find it odd that the V6 cars were the only ones to use a relay for the clutch, so I thought I'd see if anyone had any helpful info...

 

Check with Rbob. It maybe shut off in ebl. My guess would be used for higher idle enable with the ac on but your guess of wot cutoff makes plenty of sense. (Lower output engine, need more available power?) Whether the relay is needed or not is unknown to me, I don't know why the v8 cars didn't use it but I'm guessing the answer is somewhere on the boards

 

Strange coincidence...I'm considering EBL (and slightly terrified of it). I've been attempting to read this 100 page thread on EBL tuning. Somewhere in the first 4 pages that I've gotten through there was a member with this issue. It "might" help to thumb through it.

https://www.thirdgen.org/forums/diy-...uning-ebl.html

 

I would test the Light-Green Wire with Black Tracer for continuity.
Test from the Relay to the PCM Connector (where this Wire is Terminated).

If that is GOOD... That Ground Circuit in the PCM is most likely no longer working properly.
I would disconnect that Dark-Green Wire with White Tracer from the PCM.

Instead...
Install a Relay that will Ground the Dark-Green Wire with White Tracer to a Chassis-Ground Point.
You can activate the Relay with a Vacuum Switch that gets tied-in to the Vacuum for the HVAC Control-Head.
T-into the Vacuum Line that will hold Vacuum, when the HVAC Control-Head is set to the AC Norm/ AC Max Settings.

Relay use was very Minimal (relatively) at this point in time (1980s through Early-1990s)... especially for our Third-Gens.
Non-VATS cars only used a Starter Motor Relay for Anti-Theft purposes...
Meaning our Cars did NOT even use a proper Starter Motor Relay!
NO Relays for the HeadLamp Switch, Dimmer Switch, and so much MORE!

Any way...
Our cars ONLY used a Relay for the Refrigerant Compressor, if the PCM had to Active the Compressor Clutch Circuit.
The ECM can NOT pass a High-Amperage needed for this Circuit.
This is the purpose of a Relay... Active a High-Amperage Circuit with a Switch (PCM in this case) that can NOT handle High-Amperage.

Most all of my Customers Cars have been updated...
I install Relays for over a Dozen Circuits that did not use one.
I recommend this highly!
The #1 Circuit that I recommend doing... is the Starter Motor Solenoid Circuit.

Install a Relay near the Battery.
Run a short 8AWG Cable (2 Ft) from the Battery to the Relay...
And then another short 8AWG Cable (4 Ft) from the Relay to the Starter Motor Solenoid.

The Original 10AWG Purple Wire that was on the Starter Motor Solenoid...
Will now be the Trigger Circuit for the Relay.
Extend the 10AWG Purple Wire with more 10AWG Purple Wire to the Positive side of the Relay Coil.
Ground the other side of the Relay Coil to the Chassis-Ground Point.

All finished!
The Engine should start a bit more easily (Less Wire length, Less Resistance, more Voltage and Amperage available) and more reliably.

 

Good find! Looks like the EBL Flash requires a pin moved and an option checked when using it on a vehicle with an A/C relay. Unfortunately I have the EBL-P4 and that option isn't available. Might have to send RBob a message about this because there's several Option Words pertaining to A/C who's function I cannot ascertain. I've already verified continuity between on the LT GRN/WHT wire between the relay and the ECM.

I have nothing but good things to say about my EBL-P4 so far. It's made tuning my supercharged V6 very easy. There's a pretty steep learning curve though...

 

A supercharged V6-60! Very cool. Glad you are enjoying the EBL too. So much going on with that, it makes my head spin.

Yeah, there seemed to be differences between the ECMs also. Probably best to check with him.