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Discussion Starter #1
Hi,

I have an '05 ZX3.
My A/C cuts out when the engine revs up. Is this normal?
I don't have a tach so I don't know @ what RPM this happens. I mostly notice when revs spike between shifts on aggressive accelerations. It is quite apparent during these 100+ degree days we have been having. The first time it happened I thought it had gone out, and I almost cried (seriously)[mecry]
Thanks[:D]
 

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im pretty sure its designed to do this to give better aceleration when its on.
 

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Discussion Starter #4
I figured it was normal. I thought it might do it to spare wear on the A/C compressor. I probably wouldn't even notice if I wasn't living in south hell.
 

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Almost all cars do this, the A/C is cut during W.O.T. (wide-open throttle).

I think the common consensus is to say it's because you need full power to pass or go uphill (hence, you're using WOT).

But it could be for another reason as stated above, I dunno. On an old '78 Granada I had with the straight-six, the A/C cutout did not work properly, and the belt would squeal like mad when the trans kicked down a gear and RPMs would jump.
 

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V8s don't.
 

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Discussion Starter #7
My buddy's V6 F-150 doesn't either which sort of debunks my theory. The car is hardly an Aston Martin, but it doesn't seem to need the help. The cut out probably wouldn't be noticed in sub-triple digit temps [}:)].
BTW, I have NEVER held any car @ WOT (OK, there was that one time [:D]). I have too much mechanical sympathy (and it scares me because it is noisy and I am a baby). I don't have a tach, but I don't think I have ever gotten near redline. It is usually after riding the revs too high in first (going 20 mph instead of 10) or giving too much gas when shifting [driving] . I would guess it is <3000 RPM.
 

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"My buddy's V6 F-150 doesn't either which sort of debunks my theory"

My 1992 Ford Explorer V-6 4.0 Cologne engine does. In fact, that was the only warranty repair it required -- the "WOT Relay" was stuck so that I had no A/C and it had to be replaced.
 

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OK, so it's off-topic, but I need to poke a little fun at......

slaphappyjacko said:

BTW, I have NEVER held any car @ WOT (OK, there was that one time [:D]).
[:D]You need an SVT[:D]

j/k

I did some Googling, it looks like all modern cars do this WOT cutout regardless of engine.

What we really need is an automotive engineer to explain this one to us so we're in the know.
 

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alos if there is not enough refergerant in the a/c system it will cause it to cylcle on and off. If your really worried just go have the a/c check they will hook some gauges to to see if it is within spec or holding enough.
 

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Compressors don't like being spun at speeds faster than 5k rpm, which is more than the rpm that yours cuts out at. Of course, the compressor rpm is higher than the engine rpm- so that makes up some of the difference. The reasons have already been listed: longer AC system life, more engine power at WOT, and maybe a little lower fuel consumption.

This is cool stuff that everyone should enjoy. AC compressors have really come a long way from when Chrysler was mounting those monsterous twin piston V compressors on the tops of motors. Although I must admit that the factory AC in my 64 Dodge worked flawlessly- but OH what a drag on the engine!!!
 

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pspringe said:
V8s don't.
Yes they do..... I know for a fact that 99 and up F150's and Mustang GT's both have the WOT AC cutout.... my Cobra did as well ( before I totaled it)
 

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Just about all Ford's since the early 70's have had some form of WOT (wide open throttle) cut out for the a/c system. Designed to cut the a/c compressor off under hard acceleration.
 

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Why is it that my acceleration suffers when passing with the AC on then? It takes about 1.5 sec longer to pass than when the AC is off. Now I understand that there are variables here but it really does seem to make a difference. If the relay is hooped, would it throw an OBD code, and if not, how do I determine if it's serv?
 

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Hard to say.
 

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<Why is it that my acceleration suffers when passing with the AC on then?>

Well, it is a "WOT" system, i.e., it does not necessarily cut out the A/C unless you floor it... moderate acceleration while passing may not cut out the A/C.

Or, your WOT A/C cutout may be malfunctioning. As I noted earlier, the WOT relay on my Explorer stuck such that I didn't have any A/C at all. I would assume it could malfunction the other way such that the A/C is not cut out with WOT.
 
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