HVAC issues

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MopaR&D

MopaR&D

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Hi everyone, I have a 1970 Duster 318 in which I just got the vent controls working. When I got the car the controls didn't work, and there was a simple on/off switch hotwired to the fan that didn't work either. I found a replacement control box on eBay, and I hooked it up so it will mostly work. I now have heat, and I manually changed the vents so I always have heat blowing out the top vents. Now, I have three problems. One, the heat isn't very strong and in cold weather the inside of the car never seems to heat up. Would this be because I have no headliner, old weatherstripping, and no driver's side door panel? How can I make it hotter? My second problem is with the A/C. I don't know the last time it was used, and I want to know if I should rebuild the compressor before I hook up the wiring or just recharge it and go. My third problem is with the control box; the old box that was in the dash when I got the car was a white box that had two selector "levers", one for the mode (heat, A/C, etc.) and one for the temperature control. Then on the side it has a vertical selector lever for the fan speed. I want to know how exactly the vacuum lines should be hooked up, and if there is a way to get the bezel for it and screw it in correctly to the dash.
 
whew, where to start.
1st the heat as I have just fixed my heat issues. The heat inside the car will definitely not be as warm with bare metal above your head and cold air blowing in all over the place. but you can get it working to it's fullest potential.
1. check the hose to the heater core for a valve. The valve may be partially open or be restricting flow.
2. you said you manually set the a/c doors for heat, check to see if the outside vent is open. (that heater core isn't going to get very hot with 20* air blowing past it) and set it to pull air from inside the car not the vent.
3. pull the heater hoses to the heater core and blow it out (make sure it's not clogged up)
4. *optional* if you have a food thermometer, check the temp at the radiator and then the temp at the hoses at the heater core. should be almost identical. you can also check to see that your thermostat is functioning properly. Mine opens at 180 almost on the nose for my slant 6.

sidebar - most people like to fix a hot running car by changing to a colder thermostat or by removing it altogether (not recommended)


ok on to the next topic.
If the compressor is in question, rebuild it, unless you want to pay to have the system retro-fitted, vacuumed, and charged only to have to pay to have it redone when the compressor locks up and spits the belt.. if the system was working before and just lost pressure, take it to a shop and have them test for leaks. (take it to one of those "free A/C test" places and have them tell you where the leak is.)

As for the vacuum diagrams... find a factory service manual or a junk yard to go looking. but someone around here is sure to have pictures or diagrams. All of the screws for the bezel are on the back, real fun to take out. but again find a local junk yard and look for a 73-76 a-body it will most likely still have the bezel unless someone was really determined to get it.

oh and welcome to FABO! :salut:
 
player1up said:
As for the vacuum diagrams... find a factory service manual or a junk yard to go looking. but someone around here is sure to have pictures or diagrams. All of the screws for the bezel are on the back, real fun to take out. but again find a local junk yard and look for a 73-76 a-body it will most likely still have the bezel unless someone was really determined to get it.

oh and welcome to FABO! :salut:
Click to expand...

I have a FSM, but in it it shows how the vacuum hoses are supposed to hook up to the button-type '70 control box, not the later lever-type one.
 
I'll give you a bump. This is one of those things that should be in the tech archive.
 
I went out and looked at the vent doors today. It turns out that the outside air door is directly linked to the heater core bypass door. In other words, the only possible way for air to flow through the heater core is by having the door to the outside air open and the bypass door under the heater core closed. I was trying to think of a way to close off the cowl so that I could open the fresh-air door on the right side so the fan would suck in air from the inside instead of down from the outside through the cowl. If you get what I mean...
 
yep, I think. the temp selector moves only the blend door and the top selector operates the a/c compressor and output/input locations. for example.
top selector on "vent" setting is outside vent open, compressor off, output main.
so if the top selector was set to "max a/c" and the temp selector was set to heat should give you compressor off, outside vent closed, output main. right? now I haven't made it to the cooling side of my issues (bad compressor pressure switch) so my compressor wont turn on.
The only setting that closes the outside vent is "MAX A/C"
 
Yeah, but my issue is how when the outside air door is closed, the recirculation vent is open and that is after the heater core. The recirculated air will bypass the heater core if I put it on MAX A/C.
 
unless the differences between 70 an 73 are that huge you should be able to put the top selector on MAX and the temp selector on heat. That's the way mine works.

take a peek at ebay item 120205095713
has some good pictures of the a/c heater box.
 
Nope, mine is different. It is similar, but has the optional fresh-air vent doors that you can open and close on each side to let outside air blow in when driving. It's actually quite odd that I have that option along with A/C, but who knows. I'll try running it on MAX A/C the next time I drive it and see if there's a difference. BTW the temp control cable is a little messed up so I have to pull and push the cable myself.
 
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