[encantotom]

Mine was vacuum plumbed wrong so I took a hand vacuum pump and used it to trace the functions of the control and the lines going g out if it to get them correct that rubber plug on t h e back can easily leak

Use an ohm meter to trace the unit and 12v like Richard said for the wires keep in mind you will likely have sone things that don't get used on the control panel

Tom

[TGDianics]

I am in the process of sussing it out. I will publish the results when done.

I'm mystified as to the vacuum source. I assume there is a vacuum pump somewhere? Any ideas?

Tim

[Richard]

Yep. Look under the coach in front of the driver tire. Ford vac pump made by hella and look for
A black round vac reservoir

[folivier]

On my '93 the vacuum was produced by a venturi device rather than a pump. So with the engine running up front under the coach you should hear a hissing sound from it.

[Fulltiming]

These are lousy photos, not enough light but here is the face and the rear of my heater control. Not much help since there are so many wires the same color.

[TGDianics]

On my '93 the vacuum was produced by a venturi device rather than a pump.  So with the engine running up front under the coach you should hear a hissing sound from it.

Vac pump or SNAKE?

[encantotom]

yea, mine started leaking on my 90 so i replaced it with a ford f350 vacuum pump

tom

[Richard]

I don't know if this will help or hurt.

http://www.evanstempcon.com/guides_scs.php

In the past I have found a LOT of useful information on their site.

[TGDianics]

Thank You

[Quirkrjiii]

Richard,
Thank you. I think that will help.

Dick Quirk