Air conditioner change in speed

CARPETMAN1759

MEMBER
2001 CHEVROLET S-10
4.3L
V6
4WD
AUTOMATIC
118,000 MILES

I turn air conditioner on to max and it works great. It blows hard and strong but when I hit the gas it slows down like you turned the knob back down to regular air conditioner setting on the knob. Once you let the gas off it comes right back to max and blows like it should. This happens every time I pull out into traffic or leave from a stop sign.

11 Replies

HMAC300

MECHANIC
48,601 POSTS

Check for dirty battery terminal ends and check belt and tensioner they should be replaced at 60,000 miles.

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Thursday, August 18th, 2016 AT 6:14 AM

CARPETMAN1759

MEMBER
81 POSTS

Maybe I did not explain it correctly. It does not shut off. It just slows down, like if you were to turn the switch from MAX to regular air conditioner. All terminals are clean and the tensioner is ten days old and working great.

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Thursday, August 18th, 2016 AT 10:35 AM

KEN L

MASTER CERTIFIED MECHANIC
42,895 POSTS

There is a check valve in the vacuum line that is located in the engine compartment which feeds the climate control system. Locate the vacuum line headed into the firewall and then remove the check valve and try to blow in it. It should only blow one way.

Please let me know what you find.

Best, Ken

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Thursday, August 18th, 2016 AT 4:30 PM

CARPETMAN1759

MEMBER
81 POSTS

Pulled check valve today. The part has three ports on it. Two of them tie together. Air will only blow one way, so this valve is OK. When I blew on it oil came out of it. But it still works. What can I try next? I have already replaced the vacuum valve behind the glove box which operates the doors and also the vacuum control swich on the dash.

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Friday, August 19th, 2016 AT 6:36 PM

HMAC300

MECHANIC
48,601 POSTS

This isn'nt a vacuum problem have the control head scanned for codes it may be screwing up see if you have oil in hvac control head line if it is the transfer case vacuum switch as it may be sucking oil into the control head. But I think ifyou scan it you'll find a problem with that. Also clean ground at right rear of cylinder head finally check blower relay under hood and see if corrosion on prongs if there is try cleaning that off as well as fuse box and use dielectric grease on prongs when reinstalling. It's about $2 on counter at auto parts.

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Saturday, August 20th, 2016 AT 5:40 AM

CARPETMAN1759

MEMBER
81 POSTS

There can't be no wire contact problem because I removed all the wires and cleaned them. Both battery cables and EVERY single ground on this truck. I cleaned them and there contact spots. Charging system works like new. What are you talking about the control head scan and where is the transfer case vacuum switch? There is oil in the vacuum tank in the inner fender plus the 4 wheel drive vacuum actuator. It must have to do with a vacuum door that opens when you turn the A/C switch from regular A/C to max. When I step on the gas it looses vacuum and shuts the door.

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Saturday, August 20th, 2016 AT 8:36 AM

HMAC300

MECHANIC
48,601 POSTS

Control head is the where you turn the a/c on or heat on and move to different areas of the truck you only have to replace the tcase switch if there is oil in vacuum line at control if not don't change it. The aC switch from max to regular is in the control head the vacuum closing door is because the vacuum switch you said had oil in it is not working correctly and you lose vacuum when you accelerate and it closes the door because vacuum operates the door. But tht wold not have anything to do with the blower losing speed to a lower speed because that is electrical and controlled by the head which can be scanned to see if anything is wrong with it. Check for burnt wires or a bad switch even in control head. If blower slows down when door closes then it's not electrical it's a vacuum problem with either broken hoses /cracked/ or the vacuum tank that just holds vacuum and it would probably be under hood is bad.

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Saturday, August 20th, 2016 AT 10:14 AM

CARPETMAN1759

MEMBER
81 POSTS

I am sorry HMAC300 you mite of not under stood me. My fault! The fan does not slow down, it happens like this. You put the controls on max and it works great, blows a lot of air. When I hit the gas it is like I turned the knob from max to regular A/C it still works but not as powerful as on max but, as soon as I let of the gas it comes back to max again. The whole A/C head control unit is new and there was no oil in it. Just oil in the vacuum tank in the fender and the 4 wheel drive actuator. Where do you think this oil is coming from?

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Saturday, August 20th, 2016 AT 11:27 AM

HMAC300

MECHANIC
48,601 POSTS

What I told you a couple of replies ago it should be easy to find it's either on the axle or case you could have a broken door as well but it sounds like the one door or a couple are changing due to a vacuum loss. Which can be anywhere in the vacuum system try holding the fresh air door closed so it only pics up air from the cab that is what max air does besides speed the blower up. That would tell you it's a vacuum leak or see if the hose was not connected or connected to wrong place.

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Saturday, August 20th, 2016 AT 1:05 PM

CARPETMAN1759

MEMBER
81 POSTS

Thank you so much HMAC300 I found the small leak in the orange tube going to the recirculation actuator behind the hvac control panel. Now I will check the transfer case vacuum switch out next. Thanks again!

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Saturday, August 20th, 2016 AT 7:32 PM

KEN L