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My plane is a '73 PA-28-180 with the "typical" Piper rheostat + transistor dimmer design for the instrument panel dimmer circuit.
Instrument lighting dimming function has been intermittent since I purchased the plane. Sometimes, dimmer wheel works as intended--first travel turns on panel lights at lowest illumination; continue turning wheel to increase lighting up to full brightness.
Other times, first travel turns on instrument lighting to full brightness and further turning the wheel has no effect.
I've had the switch/rheostat work correctly for weeks/months at a time, making me think the problem was fixed, only to have the "full bright" problem recur again. This back-and-forth behavior has happened over and over again during the 5 years I've had the plane.
Anyone have any advice for how to resolve this problem? Is it likely to be a rheostat problem or a transistor problem?
I've tried the easy stuff, like spraying liberally with contact cleaner and letting it dry, and I know my shop fiddled with it quite a bit when I had the panel re-done, but I'm not sure exactly what they did. (When they delivered it to me, the dimmer was working, but now it's not again.)
I know some folks have resolved the issue by replacing the Piper dimming circuit with a new, completely separate dimming circuit, but I would prefer not to do that if possible.
Instrument lighting dimming function has been intermittent since I purchased the plane. Sometimes, dimmer wheel works as intended--first travel turns on panel lights at lowest illumination; continue turning wheel to increase lighting up to full brightness.
Other times, first travel turns on instrument lighting to full brightness and further turning the wheel has no effect.
I've had the switch/rheostat work correctly for weeks/months at a time, making me think the problem was fixed, only to have the "full bright" problem recur again. This back-and-forth behavior has happened over and over again during the 5 years I've had the plane.
Anyone have any advice for how to resolve this problem? Is it likely to be a rheostat problem or a transistor problem?
I've tried the easy stuff, like spraying liberally with contact cleaner and letting it dry, and I know my shop fiddled with it quite a bit when I had the panel re-done, but I'm not sure exactly what they did. (When they delivered it to me, the dimmer was working, but now it's not again.)
I know some folks have resolved the issue by replacing the Piper dimming circuit with a new, completely separate dimming circuit, but I would prefer not to do that if possible.
