My MM has a sliding lever to control the temperature. This is not to be confused with the blower control.

When I slide the lever from hot over to cold it gives resistance when pulled toward the cold side and then it pops behind the dash and the lever then moves back to the middle. It will blow hot air all the time.

Can that lever be accessed from under the dash so I do not need to tear the entire dash apart? I am assuming something must be caught in the flapper or it is rusted on one side.

The windshield was leaking for a year when the truck was sitting and we did not realize it. Now the heater control lever will not stay over on the cool side.

options on the problem and easiest fix?

The heater control vavle should be in the driver's footwell on the heater pipes that come thru the firewall. You either have a rusted cable or something's hanging up on the vavle itself.

How much disassembly do I need to do to get to it?

It does slide from half way all the way over to hot but it will not go from half way over to cool. In fact even at half way or all the way over on hot it still feels like the air temp is the same. I think its rusted or blocked also.

Even with the blower in the off position it still blows light heat out.

Why would it not shut off completely when the blower is shut off?

When the blower shuts off is there a flap that should close to completely close the air from coming in? I have never fiddled with any heating lever system

If on the e-way in the off position it blows like its on low speed even though its off completely. My guess is the air is flowing enough at speed to cause the fan to rotate a little and make it feel like its actually on?

Anyway could you briefly explain the easiest way to get to that lever assembly under the dash so I can repair this?

Should be accessible from the driver's footwell. Find the two steel 1/2" lines coming thru the firewall and trace them to the first turn upwards and you should find the water valve there. Disconnect the control wire and see if the lever frees up. If so, try to force the water valve loose. If not, try to readjust the wire.

You get heat/air flow because unless the air source select lever is on recirc, the air pressure from truck movement forces air in. It's always open.

Got it. Thank you. I thought there was just a shutter under there somewhere and not an actual valve. lol.. I heard that clinking noise so I assumed it was a shutter of some kind.

I never thought to put it in recirc mode. I will have to try that. I usually never do because it causes the windows to fog up in every car I have owned.

You breathe out a lot of water vapor, which fogs up the windows. The flow thru ventilation flushes it out...