When driving on the highway with the a/c on, when I go uphill the air stops blowing out the center vents and blows out the defroster. Once I crest the hill, it returns to the center vents. If it's a long hill or I have the fan on high, I have to slow down to below 55 and set the fan to 1. Is there a spring on the vent doors that could be worn out or broken?
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a/c woes
- Thread starter egotripp
- Start date
JJacobs
NAXJA Forum User
- Location
- Fort Collins CO
Hello, it appears you have forgotten the first rule of OEM Tech, which is vehicle info please!
It is most likely to be a vacuum leak, info on YEAR would help to confirm that.
It is most likely to be a vacuum leak, info on YEAR would help to confirm that.
JJacobs
NAXJA Forum User
- Location
- Fort Collins CO
See, that wasn't so hard, now was it?
The late models can have issues with the doors moving slowly or even not at all.. but your issue is from a vacuum leak, possibly compounded by sticky doors. Find the leak first.
The late models can have issues with the doors moving slowly or even not at all.. but your issue is from a vacuum leak, possibly compounded by sticky doors. Find the leak first.
- Location
- Southern Maryland
Yeah it's a vacuum problem. Have you done anything to the vacuum reservoir behind the front bumper?
I have a custom winch bumper but it is still there. I have had this problem since i bought it 4 yrs ago.
- Location
- Southern Maryland
I'm not intimate with the later years, but the way this is typically setup is with a dedicated accessory vacuum line that has HVAC and cruise control. There's usually a check valve on the line to keep vacuum pressure from leaving the harness, and the bottle under the bumper keeps a reservoir so that vacuum is consistent.
If vacuum pressure on the line drops then the typical symptoms are flopping HVAC outlet (default position is defrost) and cruise control turning itself off. With a large leak, nothing will work right at all. If the HVAC is flopping back and forth then t actually sounds like you don't have any reservoir to keep the vacuum pressure stable. The other possibility is that you have a small leak in the dashboard harness... the vents are controlled by low vacuum pressure and a small leak is enough to cause the flip-flopping. On my 91 I had a very small leak on the back of the HVAC head unit that was causing similar problem, fiexed it by pulling the head unit and coating the seals with silicion dielectric grease.
Probably ought to get yourself a basic vacuum tester ($20ish at any parts stores) and trace for leaks. You can use a check valve on the line that goes into the firewall to isolate that segment
If vacuum pressure on the line drops then the typical symptoms are flopping HVAC outlet (default position is defrost) and cruise control turning itself off. With a large leak, nothing will work right at all. If the HVAC is flopping back and forth then t actually sounds like you don't have any reservoir to keep the vacuum pressure stable. The other possibility is that you have a small leak in the dashboard harness... the vents are controlled by low vacuum pressure and a small leak is enough to cause the flip-flopping. On my 91 I had a very small leak on the back of the HVAC head unit that was causing similar problem, fiexed it by pulling the head unit and coating the seals with silicion dielectric grease.
Probably ought to get yourself a basic vacuum tester ($20ish at any parts stores) and trace for leaks. You can use a check valve on the line that goes into the firewall to isolate that segment