heater problems

[gabegt90]

I noticed today coming home from school the my heater does not heat unless I turn it all the way up My car has the automatic climete control.When I put heat for hi-lo or vent it does not heat up unless I turn it up all the way. I searched the past fourum of when dave84 heater was not working do you think it may be the vaccum line or do you think getting a new sensor will work what do you guys think

[89GrandMarquis]

Here's what I understand you are saying:

You have the Temperature Control Lever set to maximum temperature, and you aren't getting enough heat in both the Hi-Lo and Mix settings.

One idea: the Temperature Control Lever cable routes over to the In-Car Temperature Sensor. I recall that this cable can be adjusted, so that the two are "in sync" (so that the when the Temperature Control Lever is at max the In-Car Temperature Sensor is also at its max position too). I remember seeing this while laying on the floor, or peaking through the glove box opening (after the door is swung down).

As has been already posted on this site, disconnecting (and plugging) the vacuum line to the servo will drive the Temperature Blend Door to full open (max heat).

Beyond these two ideas, troubleshooting any more becomes more difficult. This system has five servo motors, operating on four doors, two separate fan control speed switches, a function selector switch (electrical), two separate vacuum switches, and an underhood blower lockout switch.

[gadget73]

Pop the vacuum line off the blend door servo behind the glovebox door and see what happens. If you get heat, its almost surely the sensor. They don't seem to be terribly reliable. The one in my car was replaced in 1997 and I had to replace it again in 2005 to get heat. My car was also owned by chain smokers, so I guess about 10 years with that kind of life, or about 15-20 years with non-smokers is all you get.