(All this in regards to a 1982...)

Blower works (makes more noise as I move it from 0 to 3), AC works (blows nice and chilly), "vent" works (pumps air into the cabin), defroster works (dries the windshield inside in a jiffy), but the dang unit refuses to pump hot air into the cabin -- fan blows nice and hard, but absolutely nothing comes through the cockpit vents.

So, 2 questions:

1. Am I going to have to rip the dash off to get at whatever's not allowing the hot air into the cabin? I've read through the AIM on the AC unit installation process, and it looks that way

2. Does the typical "Shop Manual" cover the AC system?

I'd dearly like to get this fixed, there's nothing quite so mood-killing in the winter as a cold cabin.

Any tips on fixing whatever's jammed in the AC system keeping the hot air away from my toes would also be very welcome.

 

How about tell us what model year you're freezing in.

 

Test the hot water shut off valve under the hood. It could be stuck closed.

 

82! Yeah that'd be useful information...

 

I'm a bit confused about your problem. Can you never get hot air? Or do you get hot air but only from the defrost vents?

 

I'm pretty sure that I remember hot air coming out of the defrost vents, but not coming out of the vents that should point at the driver and passenger, but it might have been unheated air. Definitely cleared the windshield, so I think it was hot air.

 

If you get hot air then the hot water shut-off valve is not stuck closed. Also the blend (heater core bypass) door is not the problem.

The floor outlets are the default flow position. There are two vacuum motors that select the air outlets. One of them switches from the floor to the dash. It operates in normal A/C, max A/C and vent modes. Since you get A/C out of the dash vents it is obviously working. Another vacuum motor switches between floor and defrost.

My factory service manual is vague regarding exactly what the vacuum motor that switches between floor and defrost does but it appears it operates the same diverter as the other motor. For that reason I suspect your problem is with the mode switch.

To verify that you will have to remove the shifter bezel at a bare minimum. (I find it easier and safer to remove the parking brake cover before removing the shifter bezel.) You'll probably need to remove the gauge pack as well.

Once you have access, trace the vacuum hose with the blue stripe at the #3 position on the mode switch to the vacuum motor (I believe you will be able to do this) and disconnect it at the motor. Set the system to "HEAT" and feel for vacuum at that hose. There should NOT be any vacuum. If there IS vacuum then the problem is the switch. If there is not vacuum but air is not coming from the floor then there must be some sort of mechanical problem with the mechanism as I've never heard of a vacuum motor getting stuck in the operating (with vacuum) position.

 

Great input.

Turns out that I misremembered the defroster working; it categorically doesn't.

I'm now certain that I get *no* air out of the top/defrost vents, and I suspect that I'm not getting air out of the floor vents either.

 

So air only comes out the dash vents regardless of mode setting and you can get it either hot or cold. Is this correct?

If here are a few potential trouble spots to check.

1) The vacuum mode switch may be defective.

2) Small vacuum line(s) leading from the mode switch may be cut or severely leaking.

3) The diverting mechanism may be physically jammed or frozen into position.

4) Vacuum motor(s) may be defective.

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The tan striped hose leading from the #4 connector at the mode switch goes to the "A/C valve". It should have vacuum ONLY in "A/C", "MAX A/C" and "VENT" positions. If it has vacuum at "HEAT" or "DEFROST" the switch is defective.

The blue striped hose I mentioned before should have vacuum ONLY at "DEFROST". Vacuum at any other position means the switch is defective.