I can feel the AC system drag on the engine...

[Roadster Guy]

Since I've owned my Vette (7 years now) I've always accepted the fact that when I set the climate control to auto cool, say at 68F, I can feel the compressor (or AC system) cut in and out as I drive. By that I mean I can feel it drag on the engine or performance as it cuts in and then more power returns when it cuts out. It is a bit subtle, but there none the less. It is more noticeable at low speed. None of my other cars has this happen where I can feel what I assume is the compressor cutting in and out.

The climate control works great and cools well in any heat and even when crawling around the city it maintains the set temperature. The engine runs at the proper temp in all temperatures and driving conditions. The engine starts and runs beautifully. Because of this I've always just figured the AC drag was ok.

Is something not right here or does this happen in other Vettes with Climate Control as the system tries to maintain the temp?
RG

 

[6 Shooter]

RG - My 96 LT4 did the same thing, never gave me any issues but you could really feel it turn on & off.

L8TR - D

 

[compyelc4]

My '95 has always done the same thing. Only car I've ever owned that does this. You'd think 300hp would not even hiccup with the AC but it does. I emptied 1/2 can of freon in her although she was cooling like a mutha. I do believe I do not feel as much of a momentary lag now when the AC cycles.I believe your problem is just about normal for the C4.

 

[Roadster Guy]

Well thanks guys for that. Yeah, I can feel it alright and it does strike me as strange you can feel it cycle on these engines. Must be lots of C4 owners who have noticed this and accepted it as normal as I did. I've never seen a thread relating to it before. AC works like a charm, but still may try adding some freon, though hate to tamper with anything that cools so well!
RG

 

[LT4man]

My A/C does not drag down my LT4 engine as it cycles. During its life I have had my freon changed with an A/C recycling machine.

I would not just add freon to your system. I would find a shop with a recycling machine and have the freon removed and reinstalled through the machine.

These later systems (R-134 especially) need EXACTLY the exact amount of charge to operate at an optimum level.

Hope this helps you!

AFTER RECHARGING YOUR A/C, BE SURE TO SAVE THE !

 

[Roadster Guy]

My A/C does not drag down my LT4 engine as it cycles. During its life I have had my freon changed with an A/C recycling machine.

I would not just add freon to your system. I would find a shop with a recycling machine and have the freon removed and reinstalled through the machine.

These later systems (R-134 especially) need EXACTLY the exact amount of charge to operate at an optimum level.

Hope this helps you!

AFTER RECHARGING YOUR A/C, BE SURE TO SAVE THE !

Thank you LT4man, this does help. So you are saying the freon level is the issue. Maybe with the wrong (low) freon level the system cycles more too. Do you feel absolutely no drag at all when the system is on?

By the way, I assume yours being a CE it is equipped with the electronic climate control. I say this as I was wondering if this dragging on the sysem was maybe only an electronic climate control issue versus a standard heat/cool system.
RG

 

[LT4man]

So you are saying the freon level is the issue. Maybe with the wrong (low) freon level the system cycles more too. Do you feel absolutely no drag at all when the system is on?

Yes, a low freon level will cause the A/C compressor to cycle more often. Also, a defective low and/or high pressure switch will make the compressor cycle more.

I must add the following: I have quite a few bolt-on mods to my engine, including a dyno-tune. At this time, I feel absolutely no drag on my LT4 while the A/C is operating. When I purchased the Vette new in March of 1996, I do not remember the A/C causing a fluctuation in idle speed. To be completely fair, that was over 13 years ago and over 111,000 miles. In June '96, I started modding the engine. So, I did not have many miles on it when I starting installing performance enhancements.

By the way, I assume yours being a CE it is equipped with the electronic climate control.RG

BTW, you are correct. My Vette is equipped with C68, the electronic controls for A/C. These controls only impact how the driver chooses the A/C commands. Technically, this would not affect the specific A/C operation of the compressor, condenser, evaporator and fan speeds.

AFTER CHECKING YOUR A/C OPERATION, BE SURE TO SAVE THE !

 

[Curious George]

Since I've owned my Vette (7 years now) I've always accepted the fact that when I set the climate control to auto cool, say at 68F, I can feel the compressor (or AC system) cut in and out as I drive. By that I mean I can feel it drag on the engine or performance as it cuts in and then more power returns when it cuts out. It is a bit subtle, but there none the less. It is more noticeable at low speed. None of my other cars has this happen where I can feel what I assume is the compressor cutting in and out.

The climate control works great and cools well in any heat and even when crawling around the city it maintains the set temperature. The engine runs at the proper temp in all temperatures and driving conditions. The engine starts and runs beautifully. Because of this I've always just figured the AC drag was ok.

Is something not right here or does this happen in other Vettes with Climate Control as the system tries to maintain the temp?
RG

From your description, your A/C system is working fine. You do not need any refrigerant (R-134). Freon is R-12. My '92 C4 acts the same way. I bought it with the original R-12 (in the system) and my clutch went out, so when I replaced the compressor, I converted the system to R-134. The compressor still behaves the same way. I suspect all C4 Corvettes behave slightly differently (compressor variances, clutch, etc) than others in this manner. C5's use a variable output compressor, which do not cycle on / off. They work very well and it is nice not to have the cycle effect, but not a big deal to me when driving the C4.

CG

 

[Roadster Guy]

Ok, thanks LT4man. All points noted.
RG

 

[Roadster Guy]

Curious George, your post came up while I was reading LT4man's post.
Seems to me then that this is pretty common on C4's and mine is working fine. Like LT4man said, it has been a long time since his was stock so he may not recall the cycle effect.

It is no big deal for me either when driving. I just wanted to put it out there and see if it was unique to my Vette or if (as it turns out) it is a pretty normal C4 thing. Seems as more and more people chime in that I'm not alone. Anyway, thanks for the info.
RG