Flickering running lights

[yimstiz]

I have an odd problem on a new-to-me '94 Mariah Z 225 Davanti. The running lights worked fine while the boat was sitting on the trailer in the driveway but on my first sunset cruise with my wife over the weekend, that changed. The running lights turned on fine like they did in the driveway but after about 2 minutes or so, they began to flicker. The anchor light, the running lights and the dashboard lights all flicker. I found that when I turned them off and then back on again, they stayed on perfectly for another 2 minutes until the flickering problem started again. So lights on, all okay for 2 minutes, then flicker. Switch off, then back on, same thing. It seems only to happen underway. When I'm stopped, no problem.

Simultaneously to the noise is a slight buzzing sound coming from the dash. As the lights flicker, the buzzing sound increases when the lights dim/go off and stops when the lights come on.

What could be causing this? Any suggestions on method of troubleshooting? For what it's worth, this is the only electrical problem, everything else works just fine.

Thanks!

 

[tpenfield]

I would check for loose connections at the starter motor (assuming I/O engine) the alternator and the battery. Also if the is a wiring harness connector on the engine somewhere, I would check that to tightness and any corrosion.

Flickering would indicate a fluctuating voltage, or the lights have a disco mode to them

 

[sam am I]

Buzzing and flickering lights are an effect, the voltage regulator is the cause (bad regulator or it's ground reference is flaky)................Just a guess tho w/o being there but with the repeatability of that "2 minute'ish" time from no load to load while running, sounds to be a thermal cycle of a failed/failing voltage regulator. Do you have a voltage gauge or meter to monitor as this is occurring?

The voltage bouncing around might be moving too fast for a meter/gauge to reflect but, worth a shot to check. Perhaps an analog voltage needle would be fast enough, you'd see it jumping around of course in sync with the flickering........Check all grounds first but, my money is on it's most likely the reg is heating up under a load condition and going into a thermal cycling of off -> on -> off -> on and when you shut off the electrical loads, it cools but goes right back at it when re-loaded

 

[Bondo]

Simultaneously to the noise is a slight buzzing sound coming from the dash. As the lights flicker, the buzzing sound increases when the lights dim/go off and stops when the lights come on.

What could be causing this? Any suggestions on method of troubleshooting?

Ayuh,.... Welcome Aboard,.... Go for a cruise,... turn the lights on,.... When the buzzin' starts,....

Look under the dash, find the piece that's Buzzin', 'n See what it is,....

Whatever "It" is,... "It" appears to be where the light switch power originates from, 'n "It" has a problem,....

Could be as simple as a loose connection, ot bad ground,....

 

[HT32BSX115]

Simultaneously to the noise is a slight buzzing sound coming from the dash. As the lights flicker, the buzzing sound increases when the lights dim/go off and stops when the lights come on.

What could be causing this? Any suggestions on method of troubleshooting? For what it's worth, this is the only electrical problem, everything else works just fine.

Thanks!

Howdy,



"Buzzing" in a DC circuit can sometimes be a switch passing current through burned contacts. Burned contacts can be caused by drawing a LOT more current through switch contacts than they're rated.

If there's a little AC in the DC (AKA alternator whine) there can be an audible sound there that follows engine speed. (But I would have a hard time believing you could hear it with the engine running!!)

Try FIRST replacing the switch that controls the lights. Your switches are more than 20 years old. It's not a bad idea to replace switches that control high current accessories.

Another way to "fix the future" and reduce your current draw (which is good anyway) would be to switch to LED lighting.

If you replace your switch, it will force you to check connections (which can do the same thing as contacts........burn and buzz......)

 

[sam am I]

Thinking if it weren't an active running device failing (voltage reg or its' ground ref flaking when driven by the stator due to corrosion, loose bolts etc), the flickering typically and really should still be occurring if it were the proposed passive component causing issue/s........ "burning contacts", "buzzing switches" etc "just sitting on the trailer with lights on" as well but, it doesn't appear to be as OP reports.

No real current draw diff between running and sitting, only a small difference in current through the loads and switches when the potential difference is raised from 12'ish V on trailer to 14'ish V running all at the same given constant loads.

OP states no issues/flickering/buzzing when battery is fully loaded (all switches on w same'ish current through each running same lights etc) in "driveway" and "when I'm stopped, no problem".

Don't think I'd be blindly shot gun replacing switch/s and loads that were fine with the engine off but, oddly are suddenly bad or loads somehow became too much when engine was on?

Doesn't make sense, to me anyway. Suppose vibration could be a factor when running/bouncing, there is a good chance of a loose connector as Bondo suggested.........The sync'd buzzing in that case has me a bit perplexed though, hmmmm, relay maybe. They (the contacts) can buzz quite nicely if their coil supply voltage is too low to make the contacts properly.......

All just a theory however.........

 

[mike_i]

The buzzing noise your'e hearing is most likely a loose or bad connection arcing, not a good thing.

 

[yimstiz]

Wow, so many awesome responses. Thanks to all for taking the time to help. I will go through them one by one this weekend to see what fixes it. The challenge will be to know what fixes the issue without taking it back out on the water. Unless of course, I discover something that is the obvious source of the problem. I will post again what I do and what I find out. Thanks again everyone!