1998 Mercury Sable - no heat. Temperature gauge goes up to about 1/3 (never to 1/2 which it always used to) and then floats slowly between 1/3 and 1/4. I have changed the thermostat, temperature control module & sensor. One mechanic said there was a screw in crooked in the heater case that was causing the blend door not to open and close properly. He supposedly put some kinda of plastic glue on the case and changed the blend door. I had some heat when I left his shop but later that day had none. He now will not return my phone calls after I paid him $350. If I switch from cold to hot, the air gets a little warmer and I can hear a pop like the door is switching over.
Another mechanic said the coolant fans are kicking on when they shouldn't be. Right after starting car if I turn heater to the vents and floor the coolant fan kicks on before the car warms up. He said they should only kick on when on defrost if on the heat side. It's very cold right now so we took the fuse out of the coolant fans so they wouldn't kick on but still no heat.
The heater hoses are hot coming from the heater core and the core was changed just two years ago.
I noticed the other day that my gas guage was also floating between 3/4 & 1/2. Could all of this be due to some electrical problem?
I sometimes smell antifreeze but there has been some spilled on the overflow tank. I don't have white smoke coming from the tail pipe. I had the oil changed and they said it looked okay. I was concerned about a head gasket problem. The second mechanic started the vehicle without the overflow cap on (my suggestion to check for bubbles) and it did push coolant out the top (I thought maybe this was because it had been filled completely to the top). This mechanic didn't act like it shouldn't so I'm not sure either way.
I've now spent $500 and still have no heat. Please help!
Based on your description, it sounds like the engine isn't getting hot enough to heat the vehicle. Try this. Start the engine, let it warm up with the heater on high. Feel both heater core hoses. Both should be hot. If they are, recheck the blend door. If only one is hot, flush the heater core.