WOT with A/C on
Thread Starter
Advanced
Joined: May 2013
Posts: 66
Likes: 1
From: Pittsburgh PA
WOT with A/C on
Hey guys. Should my LT4 shut the A/C compressor off during wide open throttle? My compressor runs under full throttle conditions and every other vehicle I had always shut the compressor off.
If it should is there a wot relay somewhere? If not there will be soon
If it should is there a wot relay somewhere? If not there will be soon
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
4 volts or greater from the TPS should remove ground from the Compressor Clutch Relay which is also PCM driven. How do you know it's not cutting out? OBD2 cars are fairly seamless when it comes to compressor engagement/disengagement.
Thread Starter
Advanced
Joined: May 2013
Posts: 66
Likes: 1
From: Pittsburgh PA
I get a vibration at wot at higher rpms only with the a/c on. I have checked all the compressor brackets and they are good. If I shut the climate control off it is smooth all the way to redline. I would assume the compressor is engaged causing the vibration at high rpms.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
OK, but,
where is the TPS/pedal at that time? You can get wot without going to the floor...it may need some TPS adjustment. I'd get a scan to see and KNOW. At least set TPS with a dvm and test the range of the potentiometer.
where is the TPS/pedal at that time? You can get wot without going to the floor...it may need some TPS adjustment. I'd get a scan to see and KNOW. At least set TPS with a dvm and test the range of the potentiometer.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
No TPS adjustment for an LT4. Hook up a Scanner (or download an APP for you Cell and get a Cable) and datalog. You do want to see TPS voltage and the A/C Request fields (which should be off or no at WOT). Engaged or not, there shouldn't be any vibration. Remove the belt and see if you can turn the outer hub by hand. There should be some resistance, but if you need a wrench to turn the compressor shaft, the compressor is shot. Otherwise, possible Tensioner problem or it may just need a new belt.
Thread Starter
Advanced
Joined: May 2013
Posts: 66
Likes: 1
From: Pittsburgh PA
No TPS adjustment for an LT4. Hook up a Scanner (or download an APP for you Cell and get a Cable) and datalog. You do want to see TPS voltage and the A/C Request fields (which should be off or no at WOT). Engaged or not, there shouldn't be any vibration. Remove the belt and see if you can turn the outer hub by hand. There should be some resistance, but if you need a wrench to turn the compressor shaft, the compressor is shot. Otherwise, possible Tensioner problem or it may just need a new belt.
Safety Car
Joined: Apr 2011
Posts: 3,660
Likes: 22
No TPS adjustment for an LT4. Hook up a Scanner (or download an APP for you Cell and get a Cable) and datalog. You do want to see TPS voltage and the A/C Request fields (which should be off or no at WOT). Engaged or not, there shouldn't be any vibration. Remove the belt and see if you can turn the outer hub by hand. There should be some resistance, but if you need a wrench to turn the compressor shaft, the compressor is shot. Otherwise, possible Tensioner problem or it may just need a new belt.
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Drifting
Joined: May 2007
Posts: 1,426
Likes: 165
From: Motor City
Not to hijak, but I also have a similar issue when my compressor is running. Anything above 3k (at any load) with the ac on will cause a vibration. Brackets are all ok as well. Havn't figured it out yet.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Check updated Bulletins. Chevy did issue a Bulletin reporting that some LT engines had a mid range vibration which could be verified with the vehicle in neutral, the clutch and brake depressed, and then bringing the engine up to 3500 rpms. They had no answers other than it wasn't the driveline. Dealers were to seek assistance from Chevy's Technical Network.