Climate control problem (switch?) 2000 Astro w/ rear heat/ac

[manyon]

Wondering if the actual control knobs for the climate control have gone bad.

When I turn the 3 knobs on the climate control nothing comes on. I do hear some sort of pressure relief happening as I turn it from off to a/c to fan to heat/defrost. On that knob (far right) there is no clicking when I turn it to each setting. Its just smooth turning it from off all the way to defrost. Would it be possible that just the knob is broken?

About 3 months ago I replaced vacuum hoses. Ive read through everything on this board regarding climate control and can't really find anything related to my problem (nothing working at all. Note even "just defrost mode")

I did notice that the water control valve was rusted out but didnt think that would cause this problem. Any advice would be greatly appreciated. Thanks.

[Herbie]

Wondering if the actual control knobs for the climate control have gone bad.

When I turn the 3 knobs on the climate control nothing comes on. I do hear some sort of pressure relief happening as I turn it from off to a/c to fan to heat/defrost. On that knob (far right) there is no clicking when I turn it to each setting. Its just smooth turning it from off all the way to defrost. Would it be possible that just the knob is broken?

About 3 months ago I replaced vacuum hoses. Ive read through everything on this board regarding climate control and can't really find anything related to my problem (nothing working at all. Note even "just defrost mode")

I did notice that the water control valve was rusted out but didnt think that would cause this problem. Any advice would be greatly appreciated. Thanks.

First thing: The rear heat and rear AC are totally separate systems. Hence separate knobs. It would be dumb, but you could run the rear heater and AC at the same time. As far as I know, each one is "just" a fan switch - they turn on and adjust the respective fan only, they do not control any air mixing, etc.

Ok, that out of the way, there are a few possible failure points. Does turning the fan-speed knob at least make the fan change speed? Or does it not come on at all? If you switch to AC or MAX AC, does the AC clutch energize?

[manyon]

Thanks for the reply Herbie.

To be clear, the rear heat and a/c haven't worked since I bought the van 3 years ago. I think it was disconnected at some point by the po.

Regarding my original post (front heat/ac) I don't hear the a/c engage at all and the fan doesn't come on at all for any of the settings. I checked the fuses and the relays under the hood and they all seemed ok.