If my 70 car front dash defrost isn't working, what steps do I take to troubleshoot? What position should those two flapper doors be in for the HVAC box? Aren't there one or more small vacuum cannisters in the car that have something to do with it? How does one test them with a Mity-Vac? I have vent, heat, and AC function but can't get the air diverted to dash defrost when moving the lever to that position. Thanks for any help!
I will look for my vacuumn diagram and try and post it when I get home today. You can easily use your Mity-Vac to check your vacuumn motors. I would start under the hood and use the Mity-Vac as a source. Pump up to 10" and it should hold the vacuumn. If it does not then start checking for leaks. Next place would be the vacuumn can on the firewall. Bypass and pump again. If it hold now you have a leak in the vacuumn can. In not then you have a leak in the lines, heater control or vacuumn motors. Then it gets to be real fun and will go over more when I get the diagram. I think your diverter for the defroster is the cable but I am not positive on this.
