On Nov 27, 4:39 am, WayneC > wrote:
> Here's some diagrams that might help you understand what's in your car:
> http://www.docrebuild.com/dr-r-web/AC-VAC2.PDF
>
> Look at the diagram at the bottom center of the page and note the
> unlabeled device at the top of the picture... that's a metal diverter valve
> that sits in the engine compartment and has heater hoses connected to it.
> The heater hoses are attached to the nipples shown at the top and right
> coming out of that valve, the small hose shown as white in the diagram is a
> vacuum hose that actuates the diverter valve to send hot water through
> to the
> heater core under the dash when you turn on the heater, or to bypass the
> heater core and send the hot water back to the engine.
>
> note: This particular picture shows a system without a/c, but I believe
> that same
> valve is present on cars that DO have a/c as well, but they just don't
> show it
> on the a/c diagram (upper left on the page), they only show the airflow
> door actuators.
> I don't have a C3, so I can't verify that.
>
> That valve can stick or become disconnected from the vacuum hose, or
> there could
> be a leak in the vacuum system that prevents sufficient vacuum from
> reaching the valve.
> It is a common point of failure. The valve is not particularly expensive
> to replace.
>
> It could be checked by applying vacuum directly to the valve to see if
> the heater
> then works (you should be able to feel that the water hose from the
> diverter
> to the heater is cool before vacuum is applied, then heats up with
> vacuum applied).
> You may need a vacuum pump to test with, or you can "borrow" vacuum from
> another vacuum source on the engine by "Tee"ing into that good vacuum
> source.
> (Simply sucking on the hose orally is not likely to produce sufficient
> vacuum.)
>
> You could also disconnect the two water hoses from the diverter valve
> and clamp
> them to opposite ends of one short section of copper tubing (5/8" I
> believe) to bypass
> the valve for the winter, then reattach them to the diverter valve in
> the spring.
>
> Good luck.

wow...thanks for the detailed answer. I'll check that out tonight
when I get home...