Chrysler Repair: Chrysler Dash Chronometer: early 80s, dash clock, penta star

Question
Hello Roland,
    I hope you can shed some light on this. I am in Birmingham, UK. My parents have a 1979 Airstream ("silver bullet") motorhome, imported to UK in around 1981. By the door is a small digital clock with green 12 hour display and "Chronometer" printed on it. It is a good little clock. Last year it packed up. Been meaning to take a look at it and only just took it out. It comes apart easily. After some tinkering, having replaced a transistor, inductor and capacitor, it is working well. The puzzle is the correct wiring - this clock has 5 wires!

Recognising the penta star logo moulded in the back and a bit of googling confirms it is the dash clock which was an option on Chryslers for a few years from '79. How it got into the Airstream is a mystery, but installation is quite professional with hole in wall and wiring. Maybe it was available as a spare or came from a smash. Must of been there before it was exported as doubt any clocks like it were ever available in UK.

Want to make sure when I put it back it's wired correctly. Under the clock is a rocker switch which turns off the display. The wires and corresponding circuit board connections are as follows:

1 -> BLUE -> IGN.
2 -> RED -> B+.
3 -> BLACK -> GND.
4 -> ORANGE (with BLACK DOTS) -> E2.
5 -> YELLOW (with BLACK DOTS) -> W1.

1 to 3 are self evident. I have it rigged with 12V across B+ and GND. Feeding IGN then turns display on. The other 2 wires go to the clock microprocessor. Imagine one is a dimmer? Maybe the other a separate battery backup?

As originally installed the B+ and IGN were both connected to the display enable switch while ORANGE was connected to permanent 12V (That arrangement worked). YELLOW not connected. Connecting YELLOW or ORANGE to +12 or ground doesn't seem to do anything.

I could just put it back assuming my connections are right, but if you can advise how Chrysler intended it should go, at least it'll have every chance of telling the time for a few more years - and fill in a big hole in the wall!
Thank you very much in advance.

Best Regards,
Richard.

Answer
Hi Richard,
Yes, I found such a clock in the '83 rear wheel drive circuit diagrams manual. The wires are to provide a dimmable illumination when the headlamps are turned on. I don't know how your headlamp switch is set up but if there is a pin that gets 12v when the headlamp is moved to park or regular run position and furthermore has a variable resistance also tied to that point, the wiper of the that variable resistor is attached to the orange lead and the yellow (with black trace) wire is to be attached to the first pin that I described above. I assume the headlamp switch is wired for variable illumination of the instrument cluster and so you will probably find these pins on the headlamp switch. I suspect that the wire colors may be consistent as Chrysler electrical engineering is that way.
But I don't know whether the overall vehicle is Chrysler-engineered.
Good luck on this vary nice undertaking for the folks.
Roland