No Heat

[JohnDur]

1995 XLS w/167K. AC works fine but not matter where I turn the temp control I get no heat. Temp guage is right where it should be. During the late summer I noticed AC was kicking in when the temp control was around 80 deg.

Any thoughts?

Thanks,
John

[TrailDust]

Originally Posted by JohnDur

1995 XLS w/167K. AC works fine but not matter where I turn the temp control I get no heat. Temp guage is right where it should be. During the late summer I noticed AC was kicking in when the temp control was around 80 deg.

Any thoughts?

Thanks,
John

The old adage that sometimes the simplest thing can be the cause of a problem could be the case. Have you checked the fluid level in your radiator? Water/coolant from the engine cooling system is channeled to a smaller radiator typically located along the upper firewall in the engine compartment. If the radiator level drops sufficiently no water will flow into the heating radiator and, you guessed it, no heat. The engine will compensate for the increased heat in the cooling system caused by the decreased amount of cooling fluid and then open the thermostat to allow a higher volume to flow, and when it does so your engine will indicate a normal temperature. Once a critical level is reached, though, the engine will heat up. Check it out...maybe that's it...maybe not....

TrailDust

[JohnDur]

Thanks for the tip. The coolant level looked fine, I topped it off to be sure. Still no heat. Scooted under the dash and found two metal tubes that got hotter as the car got warmer. I assume these are the heater in/out as they sit right behind the radio.

Looks like there is a white plastic swivel type mechanism up there. Any idea what controls that?

Thanks

[new echo owner]

You might need an A/C amplifier or control head.

N.E.O.

[TrailDust]

Originally Posted by JohnDur

Thanks for the tip. The coolant level looked fine, I topped it off to be sure. Still no heat. Scooted under the dash and found two metal tubes that got hotter as the car got warmer. I assume these are the heater in/out as they sit right behind the radio.

Looks like there is a white plastic swivel type mechanism up there. Any idea what controls that?

Thanks

Every car is different. Some have mechanical flow mechanisms and others are electronic. Could be a solenoid switch...dunno. If the two tubes you described are the inflow and outflow lines, then perhaps there's a fan located right at the heater that is not functioning? Anyway, tell us what you find out.

TrailDust

[Dave's]

Look under the hood for the heater hoses. Check the firewall area near where you know the heater is. Look for a valve of some kind and verify it operates when heat is selected. That should make a good starting point.

[new echo owner]

I think he is already past that point since he had check underneath the dash and both pipes to the heater core are hot, so the water control valve is working. But the mix door inside the car is not mixing.

N.E.O.

[swiftjustice]

Read this thread:
98 Avalon XLS Trunk Release Problem and Heater/AC Control Problem

Although its dealing with A/C issues, the fault finding process is the same as the controls for the A/C and heater.
If you are not getting heat, there are only five potential problems:
1. Water control valve in engine compartment inoperable. (lookat it while someone operates heater to verify the arm is opening and closing the valve)
2. Temp control solenoid or actuator motor in dash inoperable (i.e. not sending signal to motor to open valve or motor not opening despite getting a good signal)
3. Missing interior thermostat for Auto heat control
4. Bad auto temp controller
5. Heater core plugged.