A/C stops blowing under mild acceleration

**LAWS6** · 07-19-2007, 11:40 AM

I know the clutch on the compressor is supposed to disengage under hard acceleration but even at say 1800 rpms it shuts off not only the compressor but the blower also. It seems like it may be a vaccum problem but I had it checked out as thorough as possible and the system is holding vaccum.
Any thoughts into this issue would be greatly appreciated.

**Wesman** · 07-19-2007, 12:00 PM

Perhaps the clutch on the compressor is going bad, and under acceleration, it starts slipping and therefore the compressor stops turning. Something to check out.

**MikeSomething** · 07-19-2007, 12:19 PM

Sounds like a bad diverter valve.

**SeVeReDiStOrTiOn** · 07-19-2007, 04:08 PM

The HVAC fan shuts off also?

**LAWS6** · 07-20-2007, 06:35 AM

Yes, I thought that was unusual. I am trying to determine if I can feel some cold air directed at my legs when this happens. When the air from the dash vents shuts off it does feel like there is cold air from under the dash near the console. So maybe if the air is that cold then the compressor is not shutting off but the vent doors are freaking out.

**SeVeReDiStOrTiOn** · 07-20-2007, 03:26 PM

Check the vaccum switch thingy to the rear and on the driverside of the intake manifold. You'll know it when you see it...it's not very big and has several vaccum lines going to it.

**greatwhiteZ28** · 07-20-2007, 05:32 PM

its somewhat normal casue mine does it when i turn the steering wheel hard or brake hard, not sure which onw it effects but it turns off for like a milasecond

**SeVeReDiStOrTiOn** · 07-20-2007, 06:23 PM

it shouldn't...check all your vaccum lines and that switch mentioned earlier

**slims00ls1z28** · 07-21-2007, 04:42 AM

Blower shouldn't be cutting off because of vacuum. I might divert it from dash to vent or something like that but it shouldn't cut off thats electrical. If the blower cuts off I'd check around for loose grounds somewhere.

**Fastcar** · 07-21-2007, 05:22 AM

Originally Posted by MikeSomething

Sounds like a bad diverter valve.

Mike hit it right on the nose: what causes the A/C to stop blowing out of the dash vents is caused by low vacuum on acceleration. The A/C works fine when you start cruising again, right? I had the same problem, but my system failed completely and blew air out of the heater (foot) and defroster vents only, all of the time. My vacuum diverter valve cracked and caused a big enough vacuum leak to create this condition. The replacement valve worked for about a week, then cracked again! My mechanic didn't know why that happened, so he put in a metal valve: the factory part is plastic. Worked fine after that; my mechanic explained that the heater/defroster vent default operation was designed that way for safety. If your vacuum system malfunctioned during the wintertime, you would still have defrost to keep the windshield clear. You may have a small vacuum leak; even after the repair, my A/C still does the heater/defroster vent operation under hard acceleration. I guess that if you want to eliminate the problem completely you'd have to install a vacuum reservoir.

**Anthracis** · 07-22-2007, 08:58 AM

Mine has a gremlin too and I can't figure out the problem. I wonder if my compressor is going out. My AC whines when driving slow in the city and stops cooling. Only hot air blows. But on the freeway, it blows cool air. But sometimes it blows hot air. Other times the belt whines like its slipping when the AC is on but when I turn off AC, its fine. WTF? Can anyone help?

**LAWS6** · 07-23-2007, 03:34 AM

Originally Posted by Fastcar

Mike hit it right on the nose: what causes the A/C to stop blowing out of the dash vents is caused by low vacuum on acceleration. The A/C works fine when you start cruising again, right? I had the same problem, but my system failed completely and blew air out of the heater (foot) and defroster vents only, all of the time. My vacuum diverter valve cracked and caused a big enough vacuum leak to create this condition. The replacement valve worked for about a week, then cracked again! My mechanic didn't know why that happened, so he put in a metal valve: the factory part is plastic. Worked fine after that; my mechanic explained that the heater/defroster vent default operation was designed that way for safety. If your vacuum system malfunctioned during the wintertime, you would still have defrost to keep the windshield clear. You may have a small vacuum leak; even after the repair, my A/C still does the heater/defroster vent operation under hard acceleration. I guess that if you want to eliminate the problem completely you'd have to install a vacuum reservoir.

My mechanic changed the diverter valve and the car has a vacuum canister on it from the factory. The system pulls and holds vacuum as it should. I will agree that it is a vacuum problem and I'm wondering if when the previous owner installed the headers they took off some vacuum lines and put them on incorrectly. BTW the cold air does come from the heater and defrost vent. I was wondering why on a humid night the winshield kept fogging up by the vent.

**Fastcar** · 07-23-2007, 09:41 PM

Yep. You have a vacuum problem somewhere.

**IronBird** · 08-10-2007, 05:30 AM

Originally Posted by Fastcar

Mike hit it right on the nose: what causes the A/C to stop blowing out of the dash vents is caused by low vacuum on acceleration. The A/C works fine when you start cruising again, right? I had the same problem, but my system failed completely and blew air out of the heater (foot) and defroster vents only, all of the time. My vacuum diverter valve cracked and caused a big enough vacuum leak to create this condition. The replacement valve worked for about a week, then cracked again! My mechanic didn't know why that happened, so he put in a metal valve: the factory part is plastic. Worked fine after that; my mechanic explained that the heater/defroster vent default operation was designed that way for safety. If your vacuum system malfunctioned during the wintertime, you would still have defrost to keep the windshield clear. You may have a small vacuum leak; even after the repair, my A/C still does the heater/defroster vent operation under hard acceleration. I guess that if you want to eliminate the problem completely you'd have to install a vacuum reservoir.

Where did you get the metal valve? I keep breaking/cracking the plastic ones too.....

**Chaos** · 08-10-2007, 12:09 PM

well shit, my car has been doing that since new. blows out the vents and at a certain point while accelerating the air is diverted to the feet, then returns when I back off the throttle. I thought it was normal this whole time. so it's not? lol

**Fastcar** · 08-11-2007, 11:47 PM

Originally Posted by IronBird

Where did you get the metal valve? I keep breaking/cracking the plastic ones too.....

I think that my mechanic somehow adapted or substituted a metal tee that would fit in place of the valve. I was a bit concerned that it wasn't a true valve, but he said that the vacuum system would still work fine (which it does to this day, more than 4 months since he put in the metal tee). I guess that he was right, and I've had no problems since.

**IronBird** · 08-14-2007, 10:58 AM

I started to just "tee" it, but did not know if it would damage anything without the actual "valve" part. I always wondered though...what that valve was "checking"....to much suction? With my luck, if I tried without it, it would suck the hvac into the intake!

Thanx for the 'gitbak man.