I have a 1970 factory A/C cab pickup. I have a great heater but no defrost, and it wont blow heat anywhere but out the dash vents. I have checked the cable's and they seem to be working (pulling/ shutting doors). I did a little research on the internet and new models where talking about a vaccum hose coming off the manifold as the culprit. Can any body tell me if this is a possibility of give me some pointer's? It has a 350 with edlebrock manifold if that info is needed. thank you all. PS Happy Thanksgiving to all.
Defrost Fail I don't know the AC equipped models but I do know the FSM is loaded with pictures of how it all works , the various plenum doors and so on . The vacuum diaphram , if so equipped , is easy to test , just suck on it's hose and see if it holds vacuum..... My '69 C/10 is a base model with the usual leaf jammed & broken plenum doors . If the deadheads here (they read but don't offer much help as they're not really old truck lovers) don't chime in , try a plea over on the '47 ~ '54 page , those guys helped me loads with my '76 , they collectively know everything and are not scared of being helpful like most new school Hot Rodders seem to be .
Any Luck Yet ? Sunday I lucked onto a '69 C/20 with the un touched base heater , I took it all apart so now I know how it works and what to look for . In this one , the flapper at the very bottom of the heater distribution plenum in the cab has a flapper that closes off the floor vent & so forces hot air up through the defroster vents . They tend to get full of leaves so the flappers & heat doors don't move correctly .
No I have have not really had time to take a look at it. plus I have no indoor place to work on it and when I have free time it cold and blowing 30 mph. I know the door you talking about moves. I not sure if there is a nother door further in that's not moving. I know I have some lines in the glove box area that are not hook up and I believe I need to trace them out and hook them up and then try everything again. When I get a chance I try that idea you previous posted to make sure the vacuum diaphram is working. I'll be sure to post anything that I find out, to dry to help other's with the issue. Thanks for the tips vwnate1.
yep x2 on that one. the way to tell is to turn on the heat and you will hear leaves and stuff blowing around in the vents. also the two vents down on the kick panel. open them up as you drive down the road and if leaves a nd junk come flying out its a good bet the vents are clogged with leaves too. which means your rockers are filled up too and not draining rain water as the should and are probably rusting from the inside out.
