temp gauge and heater

ford crown vic, 1999, 125k miles, no engine work has been done,did flush cooling system in spring of 2013 and put in a 50/50 mix of coolant and distilled water (from a jug). No problems for the summer of 2013, have been using heater with no problems until around Tuesday of this week.
Car runs fine, no leaks, coolant checks out good. BUT now..
My temperature gauge hardly moves (up) and the heater blows warm air only.
If I am driving the gauge will not move, if the car sits running for awhile it will move up some and the heat will get warmer inside of the car.
My guess maybe a stuck thermostat? Anyone ever had a problem like this?
Thanks to any and all help.

ford crown vic, 1999, 125k miles, no engine work has been done,did flush cooling system in spring of 2013 and put in a 50/50 mix of coolant and distilled water (from a jug). No problems for the summer of 2013, have been using heater with no problems until around Tuesday of this week.
Car runs fine, no leaks, coolant checks out good. BUT now..
My temperature gauge hardly moves (up) and the heater blows warm air only.
If I am driving the gauge will not move, if the car sits running for awhile it will move up some and the heat will get warmer inside of the car.
My guess maybe a stuck thermostat? Anyone ever had a problem like this?
Thanks to any and all help.


Sounds like you are on to something with the thermostat. I'd replace the stat and see what happens.
Especially if it has not been done recently.

It's a stuck thermostat. Buy a new t-stat for your year of car (I believe a 192 or 194 degree) and install. Shouldn't take more than 15 minutes.

Do NOT over tighten the bolts on the t-stat housing. The polymer intake manifold coolant crossover can crack and then you'll have to replace the whole thing.

IIRC, they should be tightened to the same torque as the spark plugs.

((((UPDATE))))

Yeah, It was the thermostat. Put a new one in yesterday, tested it real good today and had no problems.
Thanks to all who helped.