I'm now into the first trip in my "new" '87 300TD and I'm discovering all the interesting things that can't be learned in a test drive. In this case the vents on the front dash have shut down twice after about an hour of driving in AC required conditions. The first time it was just the center vents and I was able to get them open again by hitting the max fan override button. The second time the whole dash shut down, no defrost air, no side vents, no center vents and no foot air. I tried the max override button -- no luck. I tried turning the temp up to kick the heat on -- no dice either. It finally came back to life after sitting for half an hour at the grocery store.

I searched the forum and found lots of interesting and useful discussions on the climate control, but none seemed to describe this problem. Any ideas?


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-Mike
'87 300TD Turbo

The a/c controls are all vacuum operated elements, so vacuum supply to switch-over valve inside the car is needed.

Probably a loss of vacuum to the servos in the ACC system. If there are cracks in the hoses from the engine compartment, things will be slow or worse. There are some polyethylene and neoprene lines that pass thru the firewall. I would start checking from the engine back, otherwise, it's the ACC control unit itself. Hope this helps. Good Luck..

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Well a few more days of driving and the vents closing unexpectedly problem contutinues to be intermittant. I've had someone suggest that the climate control unit may be the problem.

To my mind vacum seems to be an all or nothing thing like being pregnant. (I may be quite wrong.) The intermittenant nature of this problem may indicate something else.

I also determined that the econ switch doesn't turn off the compressor, i.e. I still get freezing cold air with the econ button pressed.

Is there a sure and simple way to determine that the climate control or the vacum is the problem?

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-Mike
'87 300TD Turbo

Sounds more like the "brain" (ACC Control Unit) is going south. If you get compressor on the econ setting, that's a good sign. Maybe vacuum isn't the problem afterall. The cluster of symptoms you describe at least points in that direction.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Today I was able to perform the some of the simple ACC test that are outlined in the ACC manual. This is what I found:

Defrost works,

Total Vent Cooling works when switching from defrost, otherwise no,

Ventilation blower works,

The vents are regulated by the temperature wheel as expected,

Econ-mode fails to disengage compressor,

Compressor does disengage when I ground the tempreture sensor coolant,

After about an hour on the road the whole system (all vents) closes up and the compressor continues to run. On a long trip it has been known to come back to life after another hour. It also returns to life after sitting for about twenty minutes.

Based on this I plan to replace the button control unit in the console. If anyone things I'm miss guided please let me know.




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-Mike
'87 300TD Turbo