Does it look like this?  (this one came from an 82 ASI camper)

http://www.californiavan.com/84asi_interior/84ASI_interior-Pages/Image14.html

These units were in ASI campers and many other American converted RV's.

They are quite nice, they charge both batteries when you have shore
power and convert 110v to 12v for all your 12v devices.  Much more
versatile than the power setup of a standard westy.

The unit I had was flaky....I found the manufacturer via google.
They are still in business.   They repaired the circuit board in my
unit for only $22

I'm sure they can supply you with manuals and/or test your unit if necessary.

http://www.progressivedyn.com

>i was parting out an 81 westy by my house the other day. Along with
>many needed parts for an upcoming project I am working on, I got a
>Behr in dash AC and a large box that was mounted under the rear seat
>next to the water tank. It has printed on it: Charge Sentinel Power
>Converter, Progressive Dynamics,  25 Amps Output, includes battery
>charger. I found some info. in the archives on the Behr, it will
>work quite nicely with the turbo diesel westy I am building. But I
>could not find anything on the power convertor! It looks like it
>might be a cool piece, if anyone has any info. on it they could
>share I would appreciate it....Rex
>Rex Merriweather
>www.stunttrumpet.com