I've had a couple of people tell me that my 76 Valiant didn't originally come with A/C and that the unit in the car now is a dealer add on because it's a black faced unit (the rest of the interior is tan) that is mounted under the dash. There's no AC vents in the dash itself, just the defroster vents up top. If I turn the heat on it will blow out of the unit under the dash. I don't know if it was plumbed up by the dealer to do that, or if this is how the AC unit looked from the factory. Anybody know what the code is on the fender tags for A/C?

The A-body never got in-dash A/C vents; the factory system was first offered in '65, modified for '73 and modified again for '74, but the A/C outlet was always bolted under the dash. Some of the underdash units were chrome, some were black and some were black with a glued- or screwed-on color trim. The way you describe its operation is a little out of whack. The correct modes are as follows: "Heat" sends air blowing from the floor vents, "A/C" or "Vent" sends air blowing from the underdash unit, and "Defog" sends air blowing out of the dashtop vents onto the windshield. If you're getting air out of the A/C vents when you select "Heat", there's a problem with the vacuum-operated mode doors or the controls.

The dealer add-on A/C units were chunkier and had the A/C controls and A/C blower fan built into the underdash unit itself, independent of the heater-defog box and controls. The factory A/C is controlled by the same mode and temp sliders ('73-up) or pushbutton panel and temp slider ('65-'72) as the heater and defog.

Dan- I must disagree. I once owned a 74 Valiant that had in-dash a/c vents. The oddest thing is that it didn't have the vent doors under the dash. The A/C equipment was all contained within the dash and the vents were as well. Only one I've ever seen like that though.

Interesting custom job, then -- no such factory equipment.

Factory equipment of A/C was under dash, never in dash.

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Mopar Muscle is well defend by Slant Six!

Valiant Duster 1971

[quote="SlantSixDan"]The way you describe its operation is a little out of whack. The correct modes are as follows: "Heat" sends air blowing from the floor vents

Something must be out of whack with the system then, because when I set it on "Heat" it definitely blows out of the AC vents, not out from underneath the dash. I couldn't remember if Chrysler just left the AC option on the heater control panel because it was cheaper than having another panel for non AC cars made. Thanks for the info.

No, non-A/C cars have a different mode slider, with no A/C or Max-A/C position.

I changed the waterpump and hoses today so I decided to just take out all the plumbing under the hood, condenser, and compressor since it was junk anyway. I swear the car gets better acceleration now...the compressor and the brackets supporting it must weight 45 lbs.

I'm having the same problems with my Duster that you are having with your car except my Defroster does not work. The Defroster is controlled by the top damper on the drivers side. I think the heat is controlled by the bottom damper on the drivers side. There is three dampers total.

Dan, need some help with this one. I can get my defroster to work if I manually shut the damper by pulling on the rod at the vacum pod. But as soon as I start the car up it slams shut again blows air back out the defroster vents. Is there an incorrect hose connection at the controls. The bottom damper has vacuum when the switch is set to heat but yet heat stil comes out of the A/C vents. There is a third damper on the drivers side top but I don't know what it controls. Any suggestions

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Yep, sounds like your vacuum hoses aren't hooked up correctly, *OR* your vacuum switch is worn and misrouting vacuum. There's no substitute for the vacuum diagrams in the factory service manual...