1978 F600 instrument cluster white plastic box; number on box: D8TF-10848AA & printed circuit; number on circuit: D8TF-10C956 TIA! any way to bench test the gauges? what is the small metal box attached to the printed circuit?
mr. moderator I apologize if this should have been piggybacked onto a previous post

 

No need to apologize...

The small metal box, I bet, is a "voltage regulator" that is really a lot like a directional blinker. It's a bi-metallic strip that heats up, opens a contact, cools off, and close again, and repeats. What this does is maintain a steady overall voltage to the gauges to make them accurate no matter what the battery voltage is. If this "voltage regulator" is bad, either the gauges will not work, or they will register very high.

Calling NumberDummy

 

Please ask further questions in the LARGE TRUCK forum.

D1AZ-10804-A .. ICVR ~ Instrument Cluster Voltage Regulator (Motorcraft GR-513) / Obsolete ~ Available NOS & from auto parts stores.

1978/91 F600/800 /// Misc: 1971/89 FoMoCo Passenger Cars /// 1971/86 F100/350 // 1971/91 Econoline // 1978/86 Bronco // 1983/85 Ranger // 1984/85 Bronco II
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D8HZ-10K843-H .. Printed Circuit Board / Obsolete

1978/79 F600/800.

NOS PARTS SOURCE in Olathe KS has 1 = 913-220-5746.

MILLER OBSOLETE PARTS in Binghamton NY has 1 = 607-722-5371.
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E2TZ-10848-B (replaced D8HZ-10848-B) .. Instrument Cluster Back / Obsolete

1978/79 F600/800 // 1980/86 B600/700 School Bus.

No Ford dealer or obsolete parts vendor has any.

There are 2 on ebay listed under this Ford part number, applications say Freightliner, but most ebay sellers haven't a single clue what parts fit.