91 OCC won't send heat to floor or windshield

I'm only getting heat from the dash vents.

I can force cold A/C air to the windshield if I turn the temp down to 60 and press the windshield button, but when I turn it up to 90, the hot air starts coming out of the dash vents. Also, the passenger vents don't seem to blow as much hot air as the driver vents. A/C is working fine. I've disconnected the battery and done the 60 to 90 recalibration, but no luck.

I've got the factory manual, but making sense out of it is too much for me.

When it used to work, I could hear things moving around inside the system indicating the air flow was changing, but no more.

I was thinking about replacing the A/C Heater Blend Door Actuator since they seem cheap enough.

Any ideas?

Many thanks!

Check the vacuum manifold under the cover below the glove box. Your head unit may have an issue as well. I had a head unit that would not send the A/C request signal to the compressor. Replaced it, and everything works.

Thanks Fred. I'll check it out and report back.

Fred, I did check the vacuum manifold under the cover below the glove box. I simply messed around with it and it started working again. I now have full control. Thanks!!!