1993 Grand marquis Heater control issue
 

Hi, New to the forum.... and I need some advice.
We bought this car new.... and have had few issues with it over the years but still love the car and want to keep it around for a while longer.
This happened last spring and now that it's cooling down I noticed it again.
The problem is the temperature control selector... We've had in on cold (in the far left position) all summer... this morning it was cold out so I moved it to the far right (HOT) .... after the car warmed up I tried to adjust the temp back down some but the temp stayed on HOT.... even if it's as far left as it will go.... AND the A/C is on.
So, could this be a vacuum issue?.... or maybe an actuator that's failed?
I'm just looking for a starting point and any advice would be greatly appreciated.
Thanks,
Don

I would suspect the actuator that moves the blend door.

Maybe the vacuum isn't powerful enough to pull it back towards the cold side when it expands from the heat.

The first thing I would try is let it cool down and after starting the car, immediately change the temeperature controller back to cold. If that works, just get to the blend door and lube it up.