under dash heater,A/C unit

[Cbumpus9398]

I have several questions pertaining to the under dash unit on my 1972 f100 ranger. 1st, the heat doesn't seem to be very warm. At idle, it's barely warm, when driving, its very warm. Why does it seem it cool off during idle?
2nd, The inside windshield fog up quick and the fan when on defrost isn't very strong. I have to wipe it with a towel. I tried to remove the unit and I'm afraid to. The air inlet appears to be blocked by some type od panel on the inside of the inlet bellow. Could this be the problem? and isn't the compressor supposed to be on in defrost mode? Mine is not on in defrost mode, only on a/c mode. I need general and technical help with this unit. I'm not even sure of how to remove the unit. Help Help - Charlie

[fordman]

2 check for ripped or torn defrost ducts. Crack a window slightly will help fog go away.
Removing the unit is a pretty big thing.
3 your cowl veny may have debris in it. Try to clean it out from bottom. You can also run a garden hose into the cowl vent under wipers to help flush the debris. Taking off the bellows on those pretty much means removing the whole unit.
Here is a link to where kieth took one apart. Sorry this was all i could find. http://www.fordification.com/tech/ACservice.htm
1 see 2 and 3. Hope this helps.

[Cbumpus9398]

Thanks for the reply. I have checked the duct, it is in great shape. I even blew compressed air with the vents open to see if it was blocked. It was not. I began to try to remove the unit and that's when I could feel that in the cowl, inside the inlet bellow is a piece of what feels like cardboard blocking the entire opening. Should that be there? I can't figure why at idle I don't have warm air. It almost sounds like a circulation issue. Thanks for any help. Charlie

[fordman]

No there shouldnt be any cardboard in there

[fordman]

Heres the page i was thinking about. http://www.fordification.com/myprojects/my67_p55.htm

[Cbumpus9398]

Thank You for that site - that's a lot of help.
So, if I remove that paper???? blockage just inside the bellow at the air inlet cowl, will it allow excess air flow into the truck through the vent, maybe when the system is off? Is that the same as the fresh air option instead of the recirculation option? Will it increase the defrost flow?
Also, isn't the compressor to run in the defrost mode? I hate to keep asking questions, I just don't know much about this part of my truck. Charlie

[fordman]

The doors if proerly sealed. (Which the foam is probably worn after this many years). Will keep air from blowing through. Yes i would remove the paper or whatever it is.

[Cbumpus9398]

Ok. I'll remove it. Thanks
Do you think it'll help improve the defrost air flow?
Also, what's your thoughts on the a/c compressor running during defrost mode?
There is some type of switch (I think it's the clutch switch in the diagram you sent earlier) behind the glove box with 2 wires coming from it that are unplugged. The wires that apparently should be plugged into those wires are plugged into each other. I unplugged them from themselves and plugged in the switch. It appeared to make no difference. What does that switch do? Charlie

[fordman]

Yes on the defrost. I dont know if our trucks compressors ran for defrost. When in doubt. I undo previous owners rigging and put it back original. Then rediagnosis.

[Cbumpus9398]

That sounds great. I will plug those wires back up but do you know what that clutch switch does? There's an arm on the cable and when the temp cable is moved, the arm presses a button on the switch. Do you know about this?

[fordman]

Check thos picture
It has some switches labeled. Im not sure when they would be labeled to turn on a system. http://www.fordification.com/tech/image ... tut_09.JPG

[fordman]

Heres the wiring diagram for it. I guess it depends on how the switches are made to work. http://www.fordification.com/tech/wirin ... g_69ac.jpg

[fireguywtc]

The factory AC should never run unless it is put in "AC" mode on the slide panel. The AC on these vehicles wasn't meant to run in any other position. As for the lack of heat, I think it may be the nature of the factory AC/heat units. I completely rebuilt the unit in my 70 including a new heater core and it never got very warm. It would take the chill out of the air but not much better. Defrost wasn't real great either. It did seem to work a bit better if I let it idle for a while.

The only theory I had for the heat is that I had deleted the fresh air intake so it only recirculated air from inside the cab. My original rubber boot connection was broke and I couldn't find a replacement. My AC worked great because it was designed to draw air from the inside. But I theorized that the heater core was designed to have outside air flowing over it and the fan may not have been strong enough to draw air over the heater core efficiently.

[fordman]

My factory a/c heated fine. The exhaust and engine heat couldnt be cooled very well though.

[Cbumpus9398]

I took the bellow off today to find someone made a duct tape paper that covered the fresh air intake. I removed it. Will I regret that? It did seem to increase the air flow just a little to the defrost. I still do not have warm air while idling. I even changed the thermostat to 195 degree. I did not drive it today because of snow and ice roads today. I'm just not knowing what to do. Thanks for all y'all's help. Charlie