62' Cessna 210B instrument lighting rheostat.

[Lowe Approach]

Howdy all.

The instrument lighting rheostat on my old 210 seems to not be working.
I believe the left rheostat is for overhead map lights and the right one is for instrument (gauge) back lights. Correct me if I'm wrong here.

Does anyone have a wiring diagram for this? I've looked for the S1880-4 rheostat but the only one I found is super expensive. I'd hate to replace it if the problem is elsewhere.

Also what about throwing in led or strip lighting rather than these old incandescent lights, any down side or concerns I should consider?

Thanks

Josh

 

[Dan Thomas]

One rheostat usually controlled the radio lights (internal lights) and the other controlled the panel lighting, which was the overhead lights with the red filters on them. Internal backlighting on instruments was rare back then.

I couldn't find a free .pdf of the early 200 series service manual, but the 100 series for that same era has this in it, and Cessna didn't normally invent different systems for common circuits:



Magnified view of that equipment table:



Two different rheostat part numbers, probably because the radio lights would have a smaller draw and would require a higher resistance.

Some modern radios have internal lights controlled by a phototransistor built into the front of the radio. It varies the light level according to the ambient light. The radio rheostat will do nothing.

 

[Lowe Approach]

Thanks for that info Dan.
That may be my problem right there. Some MX170c radios went in with internal dimmers. I guess I thought that one of those rheostats controlled backlights on the CDIs but maybe not. I’ll have a closer look at that wiring diagram. Thanks a bunch.

 

[Dan Thomas]

Thanks for that info Dan.
That may be my problem right there. Some MX170c radios went in with internal dimmers. I guess I thought that one of those rheostats controlled backlights on the CDIs but maybe not. I’ll have a closer look at that wiring diagram. Thanks a bunch.

Crawl under the panel and look at the backs of the CDIs for light sockets. Might find sockets on the engine instruments, too.

 

[camorton]

I believe your '62 210 has the same basic panel setup as my '62 182. Yes, one dimmer is for the overhead (dome) light, the other is for the panel. This would include any instruments with internal lighting (CDIs) or radios that supported it. The OEM instruments of the time did not have internal lighting. Most had radium dials at best. Some added post-lights later. The rheostats are made by Ohmite. They are available from many sources for <$100 - just get the resistance (Ohms), wattage and shaft diameter needed. If you prefer to order one through Cessna for 5x the price, that is your option. As other's have mentioned, the resistance value needed with vary somewhat as you add/remove load. That's just one of the downsides of the design. There are (transistorized) aftermarket products to solve this issue. Most modern avionics have automatic dimming built-in anyway.

C.