Questions and Answers

Dodge Caravan HVAC Problems Q. Vincent, I have a 1995 Dodge Caravan Sport 3.3 liter V-6, automatic transmission, A/C, ABS brakes with 130,000 miles. It's a great car and I love and care for it. Fire Engine red and the stock white mag wheels. Anyway, enough of the looks, what about the operation. Over the last few years my bilevel air controls have been acting up.

First under load on the highway at 60+ mph hitting a hill the blower would go from bilevel dash to the defrost. Once the engine kicked down into 4th gear it would slowly return to bilevel or dash.

Presently I cannot get the air to come out the dash vents. The air always defaults to the floor or the defrost if it is chosen. I have traced the vacuum line from the brake master cylinder to the fire wall with no obstructions. Any other good idea?

Thanks,
Peter
Cambridge, MA

A. There is a check valve in the vacuum line between the engine and firewall. This check valve holds the vacuum in the HVAC system when the engine is under heavy load and engine vacuum is low.

I suspect this check valve is bad and allowing vacuum to bleed off when engine vacuum is low. Replacing this check valve should fix the problem.

If it were my vehicle, I would take it a step further. I would go to the local junk yard and get a vacuum bottle out of a wreck. I'd find a nice place to mount it under the hood and I would run a new vacuum line from the engine, to the check valve, the vacuum bottle may already have one on it, to the vacuum bottle and then to the HVAC system.