[mmmeat]

Where exactly do I start looking for the problem with my old AC system? I'm getting a big blast of air coming out of the heater plenum when I blow the AC (cold or hot) on, with nothing coming out of the AC vents.

Just in case it matters, the AC compressor is running, but I have no idea if there is any "charge" of coolant in the sytem. The heater blower works really well. The AC has it's own blower though, does it not?

I was told there is a vacuum module/switch that controls this function to switch it away from the heater vent system. If so, where is this?

I hope I'm not asking too dumb a Q..I'm pretty ignorant on AC

Thanks!

 

[Don Rush]

Coolant leaks from your heater core create a very corrosive environment inside you plenum. Often the inner doors that direct air flow are rusted in place. Take out your glove box and try moving the arms manually that protrude from the box.

 

[Harvey]

Only one blower or at least only one motor. I have not opened up the heater box yet but I can imagine there are two blowers. Sounds like it is just not switching from one to the other. If you can move the flappers by hand then I recon it would be a vacuum issue. The can in the right wheel well is for this right? Doesn't that one have a valve with it?

 

[mmmeat]

Only one blower or at least only one motor. I have not opened up the heater box yet but I can imagine there are two blowers. Sounds like it is just not switching from one to the other. If you can move the flappers by hand then I recon it would be a vacuum issue. The can in the right wheel well is for this right? Doesn't that one have a valve with it?

OK, I'm remembering now..yes, that vacuum canister on the passenger fender well is for the AC doors. I'll have oto check it and see if it holds vacuum. I know I have a serious vacuum leak somewhere, as the headlights are not dropping down once I have the motor off, nor can they come back up. The vacuum tank for the headlights is also tested strong and everything else has been replaced. Perhaps this is all related..




Thanks,

 

[Don Rush]

Listen close the second you turn the key off and you should be able to hear the "hiss" and pinpoint the area of the leak.

 

[Mercury6768]

Brian, I had a similar problem regarding AC vent flow and the fix was a very easy one in my case: the small vacuum line that comes out of the AC vacuum reservoir passes through the cowl into the interior. There is (or at least in my case there is) a vacuum line connector that was loose right where the line passes through the sheetmetal, preventing the proper AC door vacuum motor from getting a signal. I connected that back up and all was well. (Take the glove compartment door out to acccess it.) It does sound like you have a more serious vacuum leak, though, if the headlamp doors are not functioning. I hope this helps.

 

[doctordesoto]

the factory manual has the vac hose diagram and a chart that tells what doors are when you move the knobs with the system on--only one blower motor---i got self adhesive foam in different thickness to rebuild the heat/ac box from mcmaster-carr---make sure all the flp doors are flat and seal well before butting it up--the aftermarket plenum seal kit was not of good qualityhave you ac evap cleaned and pres checked or buy a new one---a good heatercore is a must
doctordesoto