All but 3 vents blow cold air w/ AC on


Asked by Aug 14, 2009 at 11:18 AM about the 1999 Pontiac Montana 4 Dr STD Passenger Van Extended

Question type: Maintenance & Repair

I have a '99 Pontiac Montana w/ 100K miles. Within the last week, the 3 left dash vents (driver's side left of steering wheel and the center and left of the 3 center cluster vents do not blow cold air when air conditioning is only blows ambient temperature air from outside or heat if turned up). ALL other vents (remaining 2 vents in dash, passenger side and rear roof vents) blow cold air when AC is on.

I noticed this after taking the van through an automatic car wash that blew water up to wash the undercarriage when driving it in. Could a vacuum line have come loose or something like that?? If not, could it be one of the vent doors has stuck that controls the 3 vents in question?

Any thoughts/suggestions? Thanks in advance.

4 Answers


I have the same problem with my '99 also. I checked the filters in the back of the glove box and they we in bad shape. All the vents got colder after I removed them but still the 3 left dash vents were not. There has to be a vacuum motor somewhere or the hvac control unit must be bad. If I find anything else out, I will post it here.

3 of 3 people found this helpful.

Thanks for the post and reply. That's interesting about the left 3 vents not working after taking the filters out. I agree...probably a vacuum motor or a diaphragm that either went south or a hose or two got disconnected. On a different car I used to have, that was a problem I encountered...the center vent diaphragm busted and I had to replace it. If you find out anymore, please post. Thanks again!

3 of 3 people found this helpful.

my 98 Venture was doing the same,, but when I added more refrigerant to the system,, we have COLD air from ALL the vents

2 of 2 people found this helpful.

We tried the same with ours, but it didn't do the trick. Turned out the compressor was bad. With my other car however, adding refrigerant did the trick. Definitely worth the $$ to try adding the R134 to see if the system needs a recharge first. Much easier and cost effective remedy to try before ripping out the compressor. Glad yours worked out with the additional R134.

1 of 1 people found this helpful.

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