Lighting surge...

[TangoWhiskey]

What would cause all of the internally lit instrument lights to surge brighter for a split second, then go back to their previous lighting level?

Adjusting the rheostat to a different position made no difference on this recent night flight... just, every few minutes they'd get "bright" and then go back to their previous setting within a split second.

The quickness of the changes made it tough to see any indication on the ammeter, but it looked as though it might have jumped at the same time.

Ideas of what to look for? Made me nervous! Is it normal? I don't recall seeing it before. This was on a 1963 P28B 235. Not certain if it has a generator or alternator (friend's plane, practicing approaches).

 

[Stache]

Your voltage regulator needs to be checked by a professional A&P with the proper electrical equipment. Just one A&P’s opinion.



Stache

 

[mikea]

I'd go with the bad ground idea. Besides looking for a bad ground on the lights themselves, look on some other devices nearby. If you lose a ground reference, you open up the circuitry to all kinds of strangeness, where other equipment might think your lights are nicer way to return the juice than the flimsy ground they're supposed to be using. Imagine if the pitot heat drew its amps through the lights. They'd be bright alright if they didn't burn out right away.

Also the panel dimmer rheostats are notorious for wearing out.

 

[wsuffa]

I'd check grounds first along with the battery. If it turns out to be the voltage regulator, look into getting a Zeftronics solid state replacement. I have no association with them, just a lot of good feedback.

 

[schomburg]

You really need to track this one down. If, for example, only the panel lights are affected, it could be a simple defect in the dimmer control. On the other hand, if its a regulator problem, then the radios are seeing the surge as well, which may not be visually evident, but could get costly.

Bottom line: something has failed. Don't let it induce other failures!

 

[Jeff Oslick]

Adjusting the rheostat to a different position made no difference on this recent night flight... just, every few minutes they'd get "bright" and then go back to their previous setting within a split second.

I agree with Dick. My vote is a bad rheostat. It might even be repaired with a few shots of contact cleaner, but could need replacement. I've seen similar behavior in the volume control potentiometers on radios.

Jeff

 

[schomburg]

Another point: Just because it might be a 'simple defect' in the dimmer rheostat, please don't think of that as trivial. Lighting dimmer controls have been known to cause in-flight fires!