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Ask Dave: New roof fans installed. Why do lights now flicker after 30 minutes?

Dear Dave,
When we picked up our new travel trailer, we had the dealer install new Maxx Air fans with remote controls. Now the lights in the bathroom and bedroom start to flicker after being on for 30 minutes or so. My question is, since both the fans and the lights are 12 volt, is it reasonable to assume that the dealer has wired something incorrectly? They say no, but I don’t know what else could have happened. None of the other lights flicker—only the ones where the new fans were installed. —Richard, 2022 [Cruiser RV] Twilight

Dear Richard,
I’m not sure how your Twilight is wired, as most RV manufacturers will prewire the roof vent openings to install a power vent. It is dedicated, so it should not affect the lights. Most technicians will not tap into the power going to the lights as it would be switched, and you would always have to have the lights on to run the fan. You can verify this by having the lights off and see if the fans work.

A couple of questions. You stated, “When we picked up our new travel trailer.” So, I assume the dealer installed the Maxx Air before you had the chance to use the unit. It could be that the lights flickered before the installation, as the dealer would most likely not have had them on that long in the PDI stage. I would suggest doing a test with the fans off and see if the lights flicker after 30 minutes with no power draw from the fans. If they don’t, then somehow the fans are interfering with the power to the lights.

What type of bulbs are in the lights?

Next question, what type of bulbs are in the lights: halogen or LED? A cheap fixture or bulb can get hot and have an issue. Also, if the fixture is wired wrong, it can create a problem. We changed out old incandescent bulbs in a ’93 Itasca and about half the fixtures were wired backwards! With those bulbs, polarity is not an issue—it just creates resistance and a glow.

The unit comes down the line with a purple and green wire hanging from the ceiling, the person on the line grabs a fixture that has white and black, they hook up the light and it works no matter which way it is wired. Some of the cheaper LED lights may get hot if connected wrong. If they are LED, I might try getting a good LED bulb like the M4LED brand and see if that helps.

Does this happen when connected to 120-volt power or when dry camping? If it is dry camping, it could be a house battery “gremlin.” You might want to put a multimeter on the battery to see what you are getting for voltage drop. You can also test the power coming to the flickering light. Also check the wire connections at the lights and the vent fans to make sure there is a good tight connection.

One final thing. The unit is still in warranty, correct? Whether they did something in the install of the fans or not, the lights are not working correctly and they should fix them under warranty.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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Jesse Crouse
3 months ago

Hold the dealers feet to the fire to find and fix the issue. You paid for the rv to work in all respects and electrical issues can turn serious in a second. If no resolution and was financed at the dealer call the bank and if necessary stop making payments.

Thomas D
3 months ago

Led lamps with dimmer? If so its probably the lamps
Some don’t like dimmers. In a s&b home you want bulbs that say dimmable. May be the same for 12 volt dc lamps. Polarity should not make a difference. They work or not on dc. And yes it could be convertor sending pulsed current. Next time it happens, pull the shore power so the rv is only on battery. Bet the blinking goes away.

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