LS stalls when AC turns on

[camcojb]

Originally Posted by aany001

Wondering if anybody has come across this issue. Did an LS swap on my 69 camaro and when I kick the Vintage Air AC on the idle doesn’t bump up and it stalls. Any tips that can remedy this would be greatly appreciated.
Thanks
Steve

Seems like the IAC is either improperly set so it's so far open just to hold a normal idle there's nothing left when you add the load with A/C. Or it isn't working at all. Need to see what the IAC counts are at idle with no A/C and fully warmed up. You want the IAC to be mostly closed down at a warm idle so it can open further and bump the idle speed when the engine gets a load like A/C. Usually and IAC count of 20-40 at a warm idle and no load is in the range. If the IAC is at 160+ it's pretty much all open and can't do anything.

If it's too high you will have to bump the idle screw on the throttle body until you can maintain a hot idle desired speed, and the IAC can close down so it'll actually function when you need it. If it's DBW then ignore everything I just typed lol.

[Musclerodz]

The bump up has to be tuned into the ecu, especially if its not a factory ecu. They sometimes provide a pigtail, but its not always turned on in the ecu. You can also over charge the ac system and put enough load on the compressor to kill the motor as well. Also make sure you have a large enough alternator to handle the amp spike when the fans kick on. That can also cause accessory load issues as several of the front drive kits out there only come with 140 amp alternator or less and that won't cut it.

[aany001]

Originally Posted by Musclerodz

The bump up has to be tuned into the ecu, especially if its not a factory ecu. They sometimes provide a pigtail, but its not always turned on in the ecu. You can also over charge the ac system and put enough load on the compressor to kill the motor as well. Also make sure you have a large enough alternator to handle the amp spike when the fans kick on. That can also cause accessory load issues as several of the front drive kits out there only come with 140 amp alternator or less and that won't cut it.

Mike Im gonna check the pressures for sure..... good point! Also gonna load test my alternator and see whats going on? Im running a factory corvette alternator as well as the accesory drive.
Thanks guys!

[aany001]

Originally Posted by camcojb

Seems like the IAC is either improperly set so it's so far open just to hold a normal idle there's nothing left when you add the load with A/C. Or it isn't working at all. Need to see what the IAC counts are at idle with no A/C and fully warmed up. You want the IAC to be mostly closed down at a warm idle so it can open further and bump the idle speed when the engine gets a load like A/C. Usually and IAC count of 20-40 at a warm idle and no load is in the range. If the IAC is at 160+ it's pretty much all open and can't do anything.

If it's too high you will have to bump the idle screw on the throttle body until you can maintain a hot idle desired speed, and the IAC can close down so it'll actually function when you need it. If it's DBW then ignore everything I just typed lol.

Jody Im gonna grab my scanner and check when i get home and see what the IAC is doing. OH and yes its a drive by cable.
Thanks