2 questions!

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Joel Chapman

Joel Chapman

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Both questions are in regard to my 1971 dart swinger 360 w/factory ac.

1) when I switch the panel to defrost it continues to blow out the vents. From what I can tell I don’t have a broken vacuum line and ideas on where to start chasing this rabbit hole?

2) how do I remove the vent box (see pic) from under the dash? I’m trying to get the radio out and it seems to be in my way.

thank you as always for the help!

F29F8CF0-4A4A-4958-BA9E-2374E9DF8FE4.jpeg
 
Never had an AC Dart but I believe those vents to be controlled by cable I could be wrong. It's not uncommon for them to come apart or break at connection point for the pivot point for the door inside the heater box to become jammed or broken . One possibility is to separate the heater box by removing the clips around the exterior of the box and look inside to see what's going on . But thinking back my 71 barracuda did have dash pots controlling AC functions either way I still think something's probably jamming or disconnected
 
Go to MyMopar and download a factory service manual. I don't remember if it's Dodge or Plymouth. Vacuum diagram/ troubleshooting on AC / heater is towards the back

I don't remember anymore I believe there are only two vacuum hoses through the firewall. One goes to the heater/ coolant valve, the other ties in with the vacuum system, and there is the little round reservoir tank as well "in that mix"
 
67Dart273 said:
Go to MyMopar and download a factory service manual. I don't remember if it's Dodge or Plymouth. Vacuum diagram/ troubleshooting on AC / heater is towards the back

I don't remember anymore I believe there are only two vacuum hoses through the firewall. One goes to the heater/ coolant valve, the other ties in with the vacuum system, and there is the little round reservoir tank as well "in that mix"
Click to expand...

Will give those a look! As far as the vacuum lines go I can’t find any that seem to be broken. I’m thinking the slider my be due to the cardboard falling apart and jamming it. No clue on why the defrost isn’t working tho
 
If I remember correctly, that front series of vents is held on by 3(?) nuts, visible from the bottom. When undone the whole assembly will drop out from the heater box leaving room for radio removal.
 
there are 2 screws down near the floor that hold the dash vent assembly up against the main plenum. Then there are studs down through the dash behind the blank spaces between the vents. Deep well socket to get the nuts off those.
 
Been a while since I’ve had one off to remember, but I do remember 1/4 inch drive and deep well sockets being involved. You mentioned the cardboard sliders. I’m thinking your talking about the ones inside the HVAC control unit that the push buttons operate that look like straight sawblades. If so, you’re absolutely on the right track. If you can find the Chrysler Power magazine archives, there’s an article that shows how to disassemble the vacuum operator and repair it. I do know in the later model units the paperboard sawtooth sliders were replaced with what looked like fiberglass, which were far more durable. Years ago when I had my first Duster, I scored one from a 1974 Valiant that had the figerglass, but still had to JB weld the control assembly together.
 
So update! Have everything apart or visible. The cable from the temp control slider to the door seems to be swing the lever to its end position even tho it’s not showing up at the end of the temp on the faceplate.


As far as the controls not switching to defrost. Again I don’t see any broken vacuum lines leading any where. But thanks to the Manuals that you guys referenced I am going to do a vacuum check like it suggests. My guess is the white switch box itself is what’s not working. Also there seems to be a relay/resistor/box or something along those lines that has two blue wires going into it. Is it possible that this is my issue? If so what’s it called so I can try and find a new one?

6F9C01CD-9D45-45E1-966A-0B28C6B5E280.jpeg
 
You can diagnose your white switch box pretty easily. Unplug the master vacuum plug and identify where vacuum comes in when your idling. If you don't have vacuum to the plug, you know you have a leak. I had a Mighty-Vac set with the tubing and fitting kit at the time and was able to connect it to each actuator to operate them. You could do the same thing with a piece of washer tubing with some fittings on it and jump from the engine vacuum port to each actuator across the plug. Here's the replacement unit.
OER 3895790: AC/Heater Control Switch 1960-1974 Mopar A/B/E-Body - JEGS High Performance
 
A common problem with the cables is when the attaching clips become loose and you think that the cable feels like it is working but in reality the whole cable is sliding in the clip. This can happen at either end of the cable where those clips are. The fix- either remove the clip and re-tension it or install a small screw in the clips hole.
 
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