HVAC turns off under boost

thbjcb

Member
Joined
Apr 3, 2005
Is it normal for the HVAC to turn off the blower fan under boost? Any time the boost goes above 0 the HVAC fan stops blowing and It’s really annoying when u want the ac on and trying to merge into traffic
 
Car makers almost all turn off the ac compressor at high throttle openings. Its bad for it to turn high rpms. It would shorten the life of it and risk blowing apart the serpentine belt at the high load and high rpm. The compressor clutch would also be at risk due to trying to engage and or disengage constantly at said rpms.
 
I am not romping on it I am simply easing into it and the second +1 psi occurs everything turns off. Don’t understand the fan stopping either. Just want to know if this seems normal. I am having problems with ac blowing on my feet and out the vents when on max.
 
My 1st GN, an 86 w/ electronic touch climate control, had a bad fan controller from the factory.

Bought it in Palm Springs CA and drove it back to Phoenix, AZ with the A/C going out every time I accelerated or got above 75 MPH..... miserable trip, to say the least.

Could be your issue......
 
The fan stops completely. This is not the touch version. Where would the check valve be located?
 
Believe check valve is behind coil pack. Is there constant vac on purple line at controller. Disconnect it and check. Then pull other lines at controller and check for vac. Also check canister at left frt wheel well area.
 
first he says stops blowing .. thats not something that should occur , the ac compressor clutch will disconnect through the ecm under heavy throttle when the ecm disconnect the ground to the blue wire at the ac compressor clutch relay on passenger fender
when the ac clutch is disconnected will also cause the high speed to radiator relay fan to disconnect because compressor isnt running .. but nothing in the system should shut down the the blower fan

then he says it blows on his feet could be the blower is just being diverted and going someplace else making it seem like it stopped

theres a leak in the HVAC system causing it to not store vacuum to hold the HVAC doors in position when vacuum drops and changes at wot .
things to check

- HVAC 3port check valve behind driver valve cover by firewall , (the most common failed component)
-splits or breaks in the hose from the 3port valve to the reservior ball under front of driver fender
-vac hose connections at the Y fitting before hose goes into fender by horns
, if cruise check hose from the Y fitting to the cruise servo
broken plastic line from 3port valve to HVAC controller

if the check valve before the egr solenoid is bad and the hvac check failed then boost can get by and the hvac controller could see boost and parts can be damaged (popped) because its not built to take pressure
broken leaking 9port valve at back of hvac controller
broken leaking 2port heater control valve at hvac controller
broken or disconnected line to heater coolant diverter valve by rear of pass valve cover
 
Have vacuum to the purple line on HVAC controller. I don’t hear any leaks if I go through any settings. Have vacuum to the canister center line. Vacuum line to the ball was not on very far and could use a replacing as it is somewhat rotted. I don’t have an EGR see pics of current setup. Checked over all other hard plastic vacuum lines but did not find anything. Going to replace ball vac line and see if that fixes it.
 

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Have vacuum to the purple line on HVAC controller. I don’t hear any leaks if I go through any settings. Have vacuum to the canister center line. Vacuum line to the ball was not on very far and could use a replacing as it is somewhat rotted. I don’t have an EGR see pics of current setup. Checked over all other hard plastic vacuum lines but did not find anything. Going to replace ball vac line and see if that fixes it.
Did you check to see if this check valve is any good? How about the one up against the firewall that goes to the vacuum ball and A/C system?
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in your pic theres what looks like a tee where you are supposed to have a 3port HVAC check valve ..without that check valve the system wont hold vacuuum .
simple test start engine then shut off , wait a minute or so and pull hose from reservior ball ..you should hear a hiss indicating it was holding vaccuum ..no his you either missing the proper check valve or theres a leak
 
One routing from the tee goes to a y that goes to the cruise and to the ball. The other end of the tee has a line that goes under the blower. Check valve works before tee. Started engine for 30 seconds waited a minute and unhooked ball hose No hissing noise. Tried it but unhooked the cruise vacuum line..... nothing
 
Looking closer at your picture....it looks like you have the vacuum check valve in backwards.
I'm taking my comment back! The picture you posted is from over the top of the engine from the right side. It made everything look backwards. OOPS!
 
Accidentally hit send. What does the three port check valve look like and and how do I hook it up with the egr removed? To prove this Is the problem I could pinch off this line then turn the car off to see if it holds vac.
 
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