No interior fan on heater or vent, but A/C, bi-level, and defrost OK

[82DMC12]

When I turn my mode switch to heater or vent, I have no fans at all. However Max AC, AC, Bi Level, and Defrost work normally with all four speeds (thankfully AC is ok!). I assume this has something to do with the mode switch and/or wires going to it, but is there something else I should be looking at before I pull my center console out for the 50th time?

Andy

[Mark D]

The mode switch seems like the best place to start from the way you describe the issue. Aside from the vacuum seal related issues (that can be addressed with the rebuild kit) mode switch electrical issues also seem to be common. If you've had the console removed as many times as you said it could be something as simple as a loose connector or it could be melted contacts inside the switch itself.

http://dmctalk.org/showthread.php?8091-AC-Mode-Switch

Based on how you describe the issue it seems like there aren't any issues with the fan itself which would be an even more labor intense job to have to remove and replace. So at least you've got that going for you :)

[82DMC12]

The mode switch seems like the best place to start from the way you describe the issue. Aside from the vacuum seal related issues (that can be addressed with the rebuild kit) mode switch electrical issues also seem to be common. If you've had the console removed as many times as you said it could be something as simple as a loose connector or it could be melted contacts inside the switch itself.

http://dmctalk.org/showthread.php?8091-AC-Mode-Switch

Based on how you describe the issue it seems like there aren't any issues with the fan itself which would be an even more labor intense job to have to remove and replace. So at least you've got that going for you :)

Well maybe not 50 times but over the course of nearly 20 years of ownership it's been out a few times. Sounds like a good job for a rainy Sunday morning. There used to be a photo diagram that shows where each wire goes on the mode switch - anyone know where that diagram is found? Maybe I have a couple wires reversed.

[Mark D]

Yeah pulling the console out is not a fun job so I can see how it might feel 50 times ;-)

Here's a link to the electrical diagrams, the fan speed switch and mode switch are shown in the very first diagram for the A/C controls

http://dmctalk.org/showthread.php?40-All-Wiring-Schematics

[82DMC12]

Hmm, well this wiring diagram doesn't suggest there could be a loose wire causing my problem. The mode switch gets power from green/white, and passes the power to the low pressure switch and compressor as well as to the fan switch. If I had a loose wire the fan switch wouldn't work at all. I'm guessing the mode switch is messed up inside or getting burned.

[Ron]

You might be able to clean this guy up with an ink pen eraser or fine sandpaper.
Be very careful taking it apart -- Some parts can be can be very brittle!
60389

[82DMC12]

You might be able to clean this guy up with an ink pen eraser or fine sandpaper.
Be very careful taking it apart -- Some parts can be can be very brittle!
60389

Thanks Ron, do you know if there is a guide to taking the switch apart? I know there's a circlip retaining ring thing.

[Ron]

Thanks Ron, do you know if there is a guide to taking the switch apart? I know there's a circlip retaining ring thing.I thought there was a How To Guide in the Resource section here, but didn't see it.

Check this out for 'fun with the clip'- https://www.youtube.com/watch?v=358qaLbb-Sc

[David T]

Before taking the switch apart I would check that you have the wires connected to the switch correctly. If you do take the mode switch apart you should probably rebuild the vacuum section while you have it apart.