Questions and Answers

Chevy Astro A/C Vacuum Question Q. Hello Vincent, I spoke with you briefly on the phone via Keen. My problem lies with the air conditioning and venting in my 1993 Chevy Astro van. When the vent or air conditioning is blowing, it will change so the air blows out the defroster and/or floor vents. This seems to occur when a load is put upon the engine, like going up a slight incline or even when accelerating from a stand still.

Eventually, the air will be redirected to the vents after the load subsides. But if the load fluctuates, then the air never fully gets redirected and it creates a situation where not much air gets circulated because its trying to transition the direction all the time.

I read a posting of a similar situation and the response you gave. Focus was towards a part in the vacuum system, I think it might be referred to as a vacuum accumulator or vacuum storage canister. Described as, "...a round black plastic softball sized thing".

I have tested the end that connects onto this part from the intake manifold, and there is vacuum. There is a "T" junction at the top of the ball-shaped canister, and the line on the other side of the "T" junction also has vacuum. This hose then goes into a wire/hose bundle under the windshield wipers and I think probably to the back of the instrument control switch on the dashboard.

This makes me wonder if the control switch could possibly be malfunctioning, but then I think probably not simply because air does come through the vents, just not all the time like it should. What I've researched to this point is that a source vacuum hose comes into the instrument control switch, then individual vacuum lines (color coded) branch off from the switch to actuator valves which in turn direct air flow (defroster, dash vents, floor vents, etc.). Could one of these individual vacuum lines be the cause?

Could the actuator valves be bad? Could a directional door be sticking such that there's not enough vacuum to hold it place?

Thanks for any further ideas or information you can provide.
Cory
Kent, WA

A. I see you've done your homework! Great! Although it could be a problem inside the van, It's most likely under the hood. Think about it. Do you know how hot it gets under there? The environment under the hood makes all those hoses rot in time.

They may have vacuum when running but you need to unplug each end of hose from their ports and plug one end while applying vacuum to the other and see if it holds. The same with the storage ball. I would just buy a roll of vacuum tubing and run new hoses under the hood. Unless there was dash work done, like a radio, I would be looking real close at the lines under the "bonnet".