72 LT-1 with A/C - rpm drops signifcantly with the a/c compressor on

[Ed H.]

Re: 72 LT-1 with A/C - rpm drops signifcantly with the a/c compressor on

Thank you Kevin for giving yours a run. Yep, this sounds like mine with about 100 to 150 rpm drop and yes after it has warmed up mine will stall with the a/c on as well.

[Ed H.]

Re: 72 LT-1 with A/C - rpm drops signifcantly with the a/c compressor on

Thank you Michael. This is helpful and sounds like the exact same behavior as mine. The a/c compressor and clutch were recently rebuilt and working fine. Congratulations on your success at 2014 National convention.

[Duke W.]

Re: 72 LT-1 with A/C - rpm drops signifcantly with the a/c compressor on

Kevin, thank you for the pictures. Mine does not have the TCS solenoid on the right side. From what I have read the late model 72 LT1s did not have it (mine was built in June 72). What rpm drop are you seeing with the a/c turned on ?

Once emission certification was obtained GM could not change the configuration of the emission control system without recertifyilng, which is an expensive process, so it's very unlikely that any changes were made to '72 configurations once they were certified. The TCS system is part of the emission control system.

This is a simple problem to solve - simply go through the idle speed/mixture adjustment procedure with the compressor engaged (the fan on high and turn on the lights and high beams to add more load) and select the lowest idle speed that will provide a stable idle.

Then with the compressor not engaged the idle speed will increase 100-200 revs. So be it! That's the way it was back then. You did what you had to do to get the car to run right. Dealers had a steady stream of customers in the service lane with driveability complaints on early emission controlled cars, and the techs learned that some simple tweaks to timing, idle speed, and idle mixture would usually solve the problem and keep the customer happy.

Duke