AC on idle issues

[Accelo]

I have a mostly stock LS1 with an automatic in my 70 C10. The ls1 does have a small camshaft installed. Advertised as No converter necessary.
I am having idle issues when the Air Conditioner is on. There an input to the ECM that tells the motor when the air conditioning is activated. I can see it when I scan the computer but there isn't a wire from the A/C connected to the ECM in any way. However, I am not exactly sure of the function of the "A/C is on" parameter. Does it increase the idle?
Just wondering if it’s required or would help my solve my idle issues, the motor dies with the air on.

[v30crewcab]

yes you need to wire it to the transducer that is on the back of the stock ac compressor. if you dont have a stock compressor you can add a fitting inline to put it in. that tells the computer to compensate for ac on.

[Davidf]

If you're talking about the A/C request wire, then you only need to apply 12v to that input. However, the 12v should only be present when the a/c compressor is on. So, the easiest method is to simply tie into the a/c compressor clutch activation wire.

The better method is to let the ECM control the a/c compressor...which means the A/C request is activated when a/c is on...then the computer, through a relay, activates the compressor clutch. The pressure sensor on the back of the stock compressor is just inline of this signal and interrupts the power to the clutch if the pressure goes too high. The cycling switch is also inline.

[Accelo]

Thanks for the input.
I should have mentioned the air is a Vintage Air setup and is difficult to integrate with the stock ECM as it has it's own. I will see if I can identify the pin for the 12V input and add it as an input from the clutch. I have since had a bad tune rectified and will see what difference that makes. One would believe if an idle speed is specified the ECM would just attempt to keep the correct idle speed no mater what the load is. However, I acknowledge the AIR input it wasn't added as a whim.
Thanks

[Rich84]

Originally Posted by Accelo

I have since had a bad tune rectified and will see what difference that makes. One would believe if an idle speed is specified the ECM would just attempt to keep the correct idle speed no mater what the load is. However, I acknowledge the AIR input it wasn't added as a whim.
Thanks

You should not need it. ECM increases idle as you noted it would. The tune was probably your issue.

[Davidf]

It is my understanding that the ECM can react quicker to compensate for the added a/c load than the IAC valve alone. Also, if you have low vacuum, then I believe the IAC valve cannot compensate alone for the a/c load. Others may need to confirm this.

Best practice is to use at least the 12v a/c control input.

[Davidf]

Originally Posted by Accelo

Thanks for the input.
I should have mentioned the air is a Vintage Air setup and is difficult to integrate with the stock ECM as it has it's own. I will see if I can identify the pin for the 12V input and add it as an input from the clutch. I have since had a bad tune rectified and will see what difference that makes. One would believe if an idle speed is specified the ECM would just attempt to keep the correct idle speed no mater what the load is. However, I acknowledge the AIR input it wasn't added as a whim.
Thanks

System type/manufacturer should not matter. All systems have a 12v signal to activate the compressor clutch. Just route that wire through the ECM (utilizing a relay on the output. The output is a ground reference signal) and done.

[87chevy.com]

Originally Posted by Accelo

Thanks for the input.
I should have mentioned the air is a Vintage Air setup and is difficult to integrate with the stock ECM as it has it's own. I will see if I can identify the pin for the 12V input and add it as an input from the clutch. I have since had a bad tune rectified and will see what difference that makes. One would believe if an idle speed is specified the ECM would just attempt to keep the correct idle speed no mater what the load is. However, I acknowledge the AIR input it wasn't added as a whim.
Thanks

what do you mean, it has its own? the vintage air just gives 12v to compressor yes, is that what the facotry GM ecu needs? then send that 12v to the ecu and wire the a/c circuit like factory.... just that easy

[Accelo]

I want to thank everyone for their input.
I plan on putting some miles on it this summer. I really have only drive the truck 35 miles since the tune and most of that was on the highway without the Air on. My plan is to give the air conditioning a try as it is around town. Getting more of the bugs out every day. This month it was the first time this truck moved on it's own in over 15 years. At least I have a plan, adding the computer input, if I still have idle issues.
Cheers.

[Davidf]

Originally Posted by 87chevy.com

what do you mean, it has its own? the vintage air just gives 12v to compressor yes, is that what the facotry GM ecu needs? then send that 12v to the ecu and wire the a/c circuit like factory.... just that easy

Yes, the factory ECU takes the 12v compressor clutch signal directly. So, you can simply tap off the Vintage Air compressor wire and send directly to the ECU "A/C Request" input.

Or, you can reroute the Vintage Air compressor wire FROM the compressor and straight into the ECU "A/C Request" input. But, then you have to use the a/c control (output) from the ECU to power a relay which sends 12v to the compressor. The ECU a/c output is a ground reference signal (used to ground the control input of the relay).

Simple. I believe ECU "A/C Request" input went away when a/c control function became part of the control/bus network...maybe 2002 or later.

[87chevy.com]

Originally Posted by Davidf

Yes, the factory ECU takes the 12v compressor clutch signal directly. So, you can simply tap off the Vintage Air compressor wire and send directly to the ECU "A/C Request" input.

Or, you can reroute the Vintage Air compressor wire FROM the compressor and straight into the ECU "A/C Request" input. But, then you have to use the a/c control (output) from the ECU to power a relay which sends 12v to the compressor. The ECU a/c output is a ground reference signal (used to ground the control input of the relay).

Simple. I believe ECU "A/C Request" input went away when a/c control function became part of the control/bus network...maybe 2002 or later.

Your "or" is what was implied, no monkey tapping into rigging mumbo jumbo... wire the vintage air signal to gm computer if its gen3 and wire it like a factory gen3. If its gen 4 or 5, similar just need the module to interpret and then send signal to GM ECU.. thats what i do for the genV ac signal request.
Vintage air signal to interface to stock gen5 ecu and works just fine. Why this big company is in the iceage on this is a joke.

Clint

[HYPR]

Originally Posted by 87chevy.com

If its gen 4 or 5, similar just need the module to interpret and then send signal to GM ECU.. thats what i do for the genV ac signal request.
Vintage air signal to interface to stock gen5 ecu and works just fine. Why this big company is in the iceage on this is a joke.

Clint

Clint, As you and I have spoken I am still not sure why someone like PSI don't already have a fix for this. Mind you I haven't already spoken to Tony about this point yet so it is possible he already has it resolved so that this is a plug and play. Look as I already stated I am by no means an AC guy, just not in my skill set.
I agree, it is a head scratcher why Vintage Air doesn't already have this resolved. Perhaps because they are more interested in selling you a new Compressor. A one size fits all solution in their minds?
As for me, I have no interest in installing my compressor up high and moving everything else around to accommodate this. On another note why one can't buy a Sanden SD7 NON Variable with the 4 rib compatible pulley already installed is another head scratcher (they do offer a Variable version as a direct replacement). I looked at the SD7 in my '56 and it should fit easily into the stock LT mount location.

[Rust-O-Matic]

Originally Posted by Davidf

I believe ECU "A/C Request" input went away when a/c control function became part of the control/bus network...maybe 2002 or later.

This is correct. '03+ receives a serial data signal from the BCM rather than a 12v request like the older gen 3s.

I'm gonna give this solution a whirl on mine:

https://ls1tech.com/forums/conversio...c-request.html