Hahaha damn you...

This is what happened last time I bought a $900 car...and its still happening...

 

I did something similar to the zip-tie fix, but it's easily adjustable within the cab. On the passenger side of the hvac controls, there are two vacuum solenoids. If you take a look at the vac lines, you can see how to bypass both of those solenoids and hook the vac lines into one another using the T-connector. If your system is anything like mine, you'll hear the flaps shut and no more heat! If it starts to get cold, just unhook one of the vac lines and the doors will drop, allowing heat into the cab.

Let me know if that helps!

 

Its a good idea, but doesn't help me much. My flaps are are warped and leak...haha. I ended up taking the vac solenoid off the heater valve and just using the arm manually. Seems to work great!!!

 

This happened to me today. I switched the heater on and it worked then when I wanted it off it would not shut off. There is no vacuum at the firewall nipple that supplies vacuum to the heater valve, so I zip tied it for now.
Would the flap clips being broken cause no vacuum at the heater valve line? The solenoid valve for the heater valve would certainly cut the vacuum. There is no clicking of the solenoid when turning the temp control ****.
What else should be checked while I am under there that could kill the vacuum to the heater valve?

 

Even though this is somewhat of a ghost thread... I came across some interesting information the other day on exactly this.

Apparently there is also some sort of switch/solenoid/valve controlled by the temp **** in the cabin. I believe it is what controls the heat variations between cold and hot. It likely sends a message to the HVAC system to give vacuum to the valve under the hood which opens and actually lets the hot water into the core.

I read something about a circuit going bad that is a crucial part of the **** control in the cabin. So closing off the heater valve under the hood works, but it getting vacuum is cause by something else.

 

aaah, guys - you do know that the usual cause of not being able to shut off the heat is a 50 cent plastic clip on the driver's side linkage to the temperature control servo, that it takes about a minute to replace, and that there are on-line FAQs about it (search for white plastic clip)