Curmudgeon10

Heat issues from the defrost vents but it is not being blown by a fan. Fan distribution of air appears normal in every other mode of the environmental control system. A/C works. Mystified.

Any ideas?

3.2TLc

Welcome Curmudgeon !!!
So.... the blower fan is blowing cold air with AC and working on all other position modes except for the windshield defrost heat ? But, there is good heat elsewhere ?

Have you tried the climate control's self diagnostic feature yet ?

Curmudgeon10

Here's the strange part: HOT air is blowing in all the modes where it should except it isn't actually "blown" out the defrost vents under the windshield. It just dribbles out, clear very tiny parts of the windshield right above the vent. Not knowing any of the specifics of the system in my car, I would guess that some type of diverter valve is not swinging to direct air up the defrost vents, but there is enough leakage around that valve so that a little bit gets through.

I haven't run the diagnostic. I guess I forgot I had one!

3.2TLc

~ Yeah, try running the diagnostic :

Turn key on, push "AUTO" and "OFF" buttons and hold them both in.
If there's a problem, a letter code will appear in the digital "TEMP" display.
If all's normal, nothing comes up ...... you can just release the buttons and turn the key off to end test.

If a letter "L" or "M" is displayed, the Mode Control Motor may be shorted or obstructed.

Curmudgeon10

OK. Tried this, got flashing "88"s. In electronics, usually that's not a good sign.

Curmudgeon10

Anyone know where the Mode Control Motor is located and how hard it is to replace?

TLer trash

It sounds like your blower isn't working. Check the connector at the blower motor for signs of heat damage. It's above the passenger's right foot. If that's ok, the blower resistor (transistor) is a common failure. Search a little bit, and you'll find lots of posts, pictures, part numbers, etc.