when i get up to higher rpms my heater kicksto defrost and when it comes back down it kicks back to whatever i had it selected to. any suggestions.

 

Sounds like it's time to replace the check valves in the vacuum lines. Should be one at the brake booster (vacuum brakes), and one along the firewall. I would replace both of them first before digging in any further. The vacuum line for the selector control enters through the firewal near the a/c & heater core lines. Hard black platic line about 3/16" thick. Then changes over to a softer rubber line when it enter the cab.


The check valves are like 2-3 dollars each, usually.

Hope this helps.


Good luck with your ride.