Chassis heat problems

[Don Bradner]

Revisting this one: As far as I can tell, the pump and sporlan valve are
functioning correctly (can see the pump, and took the valve apart, at which
point I can observe that the pump is pumping). The slide switch that controls
heat is attached to a circuit board that is a timer circuit. Output is either
+12V, or nothing, and the further to the right you move it the longer the
on-cycle lasts. There is no full-on condition. The cycling I heard appears to be
normal, and what I thought was a breaker is a relay, #12 in the front nose
panel.

I was alerted me to the presence of another valve, located under the top front
step. It is difficult to reach, and I investigated it using a camera. I can put
a hand on it, and there is no obvious vibration or sound when the relay kicks
the other valve and the pump cycles. The valve does not exactly match what was
described, but it is certainly in the water line to the front heater core. There
may not be any decent way to test it except by pulling it out, not a fun job.

Picture of the valve at http://www.arcatapet.net/image/heatvalve.jpg

On 3/2/2008 at 5:06 PM Don Bradner wrote:

>Until a few days ago, my chassis heat was working fine, now it is dead.
>
>The chassis heat on this coach is a lot simpler than has been described
>for many others. No summer/winter valves, no always-on Sporlans, no
>Webasto or Primus.
>
>The water system consists of a single Sporlan valve and a pump, both
>actuated by a slide switch in the cockpit (below the backup monitor
>controls). The valve should open and the pump turn on whenever the switch
>is in the Warm position and the ignition key is on.
>
>When this is done (engine off in order to hear things), there is a
>discernible click at the Sporlan, and the pump starts. After a few
>seconds, a circuit breaker can be heard to pop, and it goes off. Maybe ten
>seconds later the breaker resets and things run for a few seconds more.
>
>Question: Could this be a stuck Sporlan (pump blowing breaker because of
>back pressure)? I've looked through the various documents available and
>don't see a good way to test a Sporlan valve.
>
>Don Bradner
>90 PT40 "Blue Thunder"
>Posting today by satellite from Pea Soup Andersen's, Santa Nella, CA
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