AC works, but vent selector doesnt!

[jam sandwich]

I tried searching for any threads regarding this, but my 89 just had the a/c compressor/drier replaced and the system charged up. It blows cold air, but only out of the windshield defrost vents! I also think its stuck on outside air too.
I'm trying to figure out what I need to replace.
It seems like maybe the selector switch itself could be bad? It's my understanding that this is vacuum controlled, but I havent been able to find any vacuum diagrams I could look at.
Thanks in advance!

 

[hesutton]

Likely vaccum related, but I don't have a diagram either. If the issue is behind the dash panel, that can be a real pain to fix. I really hate pulling the dash outta any vehicle.

Heath

 

[jam sandwich]

I agree, yanking the dash is not my favorite task. I think some vacuum lines are most definetely cracked and old.. I just need to find out more..

 

[smolkin]

I know at least on my truck a weak point in the vac system is right where the lines go into the blower box in the engine compartment...the lines make a sharp turn and if yours are plastic like mine were and not rubber, they may have cracked from the recent jostling they got. I replaced mine with actual rubber vac line as far down as I could get without tearing apart the blower box.

Unless they changed it on bricknoses, the vac servo for the fresh air door is right there also. Also check the linkage on it, sometimes mine comes loose.

 

[jam sandwich]

Yeah those crummy vac lines in there look like ****. I have plenty of vac hose laying around that I can use. I know I have a vacuum leak somewhere, as my brakebooster acts quite strange (too much pedal travel)

 

[Cincinnati Guy]

Either a vacuum leak or a bad actuator in the valve under the dash. The piece is easy to get off take it off and blow into it and see if it opens and closes, if not its bad. If it does work you got a vacuum leak somewhere.

 

[FordGuy100]

Mine does the same thing. Always starts on the defrost. I find that I have to let it idle for about ten seconds (I figure to build up vacuum in that particular line), turn the fan speed to low, it will switch over to the vents. Sometimes I have to speed the fan up, and slow it down, serveral times before it will go. Also if I brake heavy it will switch to pushing AC out the defrost. Has to be vacuum related. Its been doing that to me for a loooooong time though

 

[jam sandwich]

Mine does the same thing. Always starts on the defrost. I find that I have to let it idle for about ten seconds (I figure to build up vacuum in that particular line), turn the fan speed to low, it will switch over to the vents. Sometimes I have to speed the fan up, and slow it down, serveral times before it will go. Also if I brake heavy it will switch to pushing AC out the defrost. Has to be vacuum related. Its been doing that to me for a loooooong time though

Sounds like your a/c has a mind of its own

I'll check out all the vacuum lines and replace them accordingly then. What are the chances the vacuum actuator in the engine bay is bad?

Thanks!

 

[Cincinnati Guy]

The valve im talking about is over towards the passenger side, inside the cab just right under the dash, just look up underneath and you will see it.

 

[Agnem]

Based on the service history you just gave, they would have exposed the vacuum lines that run from the vac pump to the manifold, and brake booster, to rough handling. I'll make my usual comment.....

You mean you don't have a vacuum gauge as part of your normal aftermarket gauge set on your dash?

 

[jam sandwich]

Based on the service history you just gave, they would have exposed the vacuum lines that run from the vac pump to the manifold, and brake booster, to rough handling. I'll make my usual comment.....

You mean you don't have a vacuum gauge as part of your normal aftermarket gauge set on your dash?

This a good idea... I'll put it on my list along with an egt gauge too
Im gonna do some tracking and replacing of vacuum lines when i get home from work!