My 1997 mercury sable gs is not giving me any heat, just fairly warm,
2 months ago took to mechanic, he changed the thermostat & back flushed it, new anti-fluid.
now getting heat.

However now its back to no heat again, was on the expressway had to tramp the pedal down to pass a truck when the blower motor just shut off, i took my foot off the gas an the blower came back on with only warm heat.
Went back to my mechanic, he cant find the problem, can somebody please help me out here?

 

If both heater hoses are hot when the engine has been run a while that would eliminate the thermostat.
Now you could have possibly one of two problems.
The first is are the blend doors working properly?
The other is , A body control module (GEM , Generic Control Module) controls the heater operation and could be not functioning correctly.

 

Thank you, where could i find the gem, generic control module please?

 

It's located under the dash next to the fuse panel.

 

Thanks much, i'll give it a try

 

Would that cause the blower motor to shut off when the gas pedal is pushed
down hard?

It has shut off when my a/c was on last summer too.