surging with ac on
Thread Starter
Burning Brakes
Joined: Nov 2017
Posts: 1,060
Likes: 80
From: Fort Mill, SC
surging with ac on
I noiticed when on auto or manual the car would surge with ac on. I charged it to the correct suction pressure; same problem. at idle and even whey at steady 2000 rpm it the ac clutch doesnt cycle.. any ideas?
Oil Producer
Joined: Apr 2014
Posts: 9,363
Likes: 2,734
clarify please:
do you mean the compressor is cycling on / off? or do you mean the engine is surging rpm up and down when hvac is calling for ac ?
can you describe a bit better and i can recommend one test to check compressor function at least.
do you mean the compressor is cycling on / off? or do you mean the engine is surging rpm up and down when hvac is calling for ac ?
can you describe a bit better and i can recommend one test to check compressor function at least.
Thread Starter
Burning Brakes
Joined: Nov 2017
Posts: 1,060
Likes: 80
From: Fort Mill, SC
Clarification:
Cool air is coming out of the vents but a feel a very slight surge as though th ac is cycling. It would seem to me it wouldnt be felt in a 300hp v8? Im worried that the clutch of the ac is getting hot and releasing then engaging. I had this happen in my 99 f250 and all I had to do was remove a shim and it solved it.. but in that case cooling would stop inside the pass compartment and then come back on..
So I guess Im asking if a very very slight surge of power loss and gain is felt while driving my 96 corvette is normal.
At idle I see the clutch is engaged all of the time when its 95f ambient.
Cool air is coming out of the vents but a feel a very slight surge as though th ac is cycling. It would seem to me it wouldnt be felt in a 300hp v8? Im worried that the clutch of the ac is getting hot and releasing then engaging. I had this happen in my 99 f250 and all I had to do was remove a shim and it solved it.. but in that case cooling would stop inside the pass compartment and then come back on..
So I guess Im asking if a very very slight surge of power loss and gain is felt while driving my 96 corvette is normal.
At idle I see the clutch is engaged all of the time when its 95f ambient.
Last edited by barchetta1; Jun 21, 2018 at 09:09 PM.
Thread Starter
Burning Brakes
Joined: Nov 2017
Posts: 1,060
Likes: 80
From: Fort Mill, SC
Thread Starter
Burning Brakes
Joined: Nov 2017
Posts: 1,060
Likes: 80
From: Fort Mill, SC
Well.. its not normal.. It surges with great frequency and then at about 75mph after about 5 min it stopped..blew edit: WARM air. then after awhile I decided to turn it off and put it back in auto mode.. started to blow cold air and surge with frequency again.. anyone?
Last edited by barchetta1; Jun 22, 2018 at 09:32 PM.
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Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,072
From: Lansing MI
Well.. its not normal.. It surges with great frequency and then at about 75mph after about 5 min it stopped..blew edit: WARM air. then after awhile I decided to turn it off and put it back in auto mode.. started to blow cold air and surge with frequency again.. anyone?
On the rare chance the evap core is not sealed to the case, go run the car and the ac, then without shutting the car or the ac off, open the hood and see if you have frost on the low side lines.
Last edited by PatternDayTrader; Jun 23, 2018 at 10:33 AM.
Thread Starter
Burning Brakes
Joined: Nov 2017
Posts: 1,060
Likes: 80
From: Fort Mill, SC
I just charged it but will check again and also do a subcool test on it and see what I see. I think its a bad pressure sensor either low or high side.
Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,072
From: Lansing MI
Just make sure you notice if you have heavy frost on the low side lines. I had a 95 model car while back that sort of did what you are describing, it was full of refrigerant, and it would never really get very cold. Sometimes the compressor would cycle somewhat erratically, and if you turned the system off, then restarted it a few minutes later it would seem to cure itself for a short amount of time before reverting back to not very cold air and the compressor cycling again. Several different people tried to fix this car but never could figure out the problem. Ultimately I noticed something that others did not, that being frost on the low side lines all the way to the compressor. The refrigerant was not evaporating in the evap core, because the seal around the core had come apart and the blower motor air was going around the evap core.
Last edited by PatternDayTrader; Jun 23, 2018 at 12:42 PM.
Thread Starter
Burning Brakes
Joined: Nov 2017
Posts: 1,060
Likes: 80
From: Fort Mill, SC
Yesterday I found that if I turned the fan up all the way and put the system on recirculate the car would not surge anymore and blew very cold air.