View Full Version : Electrical Gremlin

04-06-2017, 10:20 PM
After 1.5 years of boat ownership I have finally figured out I have an electrical gremlin, now I just need help fixing it! I posted on here a while back about my temp gauge pegging "hot", ended up replacing circ pump, thermostat, impeller etc. The boat ran just fine all summer and had no issues. After de-winterizing a couple weeks ago and going out for a test run I had the temp gauge peg again. So I found now anytime I turn on the bow nav light the temp gauge pegs to the right "hot", as soon as I turn the switch off the temp gauge normalizes immediately. Here is what I have found out.

1.) It only happens when I push the switch "up" turning on both bow and anchor light. When I push the switch "down" powering only the anchor light everything is fine.
2.) Pushing the nav light switch up to power the bow light is also the only switch that powers on my green gauge backlights.
3.) I pulled the bulb out of the bow light and pushed the switch "up" to on and temp gauge still pegs hot.

This makes me think it is either the gauge backlights or a faulty temp gauge?

Of note when I had the temp gauge peg hot again I immediately went back to dock, boat did not go into any limp mode, when I finally made it back home (boat on trailer) when I got to the house I turned the perko switch to battery 1 and nothing would power on. I had been out on the lake for about 3 hours, running constantly with perks switch only on batt 1 and had the boat off to fill and dump ballast while listening to music with switch on batt 1 as well. At home when I turned the switch to batt 2 I could power accessories like blower, bilge, depth finder etc. As soon as I hooked up my 2amp trickle charger to batt 1 I was able to power up accessories. I just wanted to give as much information as possible that is why i included the last paragraph. (Called Bakes and they told me I should run perko at 1+2 almost always to avoid having voltage issues).

I appreciate any and all help you guys might have for me. It took me so long to get this figured out because we almost never have the boat out at night so we rarely use the nav lights.


04-07-2017, 10:20 AM
It sounds like an issue with the gauge to me. Are you able to do some electrical debug with a DMM, etc.? I'd test the isolation between the illumination and the sensor input. If not, a practical test (and possible short term work-around) would be to simply disconnect the illumination wire. Be sure to secure it so that it doesn't short out anywhere, at least wrap it with some electrical tape.

This doesn't address the dead battery symptom though. That sounds like something else to me. Maybe a loose connector at the battery or switch?

KG's Supra24
04-07-2017, 10:46 AM
My knowledge is limited but low voltage issues can cause a myriad of issues. Is it time for batt 1 to be replaced? I'd consider getting a new battery in there before chasing anything else, if it is aged.

04-07-2017, 12:06 PM
It appears you have feed through that is using your temperature gauge as an electrical path thus the pegged out meter. Does the illumination light have its own dedicated power and ground? If so, it wouldn't be the light but if it is a shared ground then that ground wire needs to be relanded on the ground bus. Another easy check is to remove the hot and ground wire from the meter and put temporary jumpers directly from the fuse panel (+) and the ground bus (-). I don't think it is the leads and sensor to the engine since your light switch configuration is causing a repeatable malfunction of the gauge and all other times the gauge is reading normal.

04-07-2017, 03:01 PM
I'll try the above ideas. Batt one is only 1 year old. Also I forgot to include that I pulled the alternator and both batteries, had them all tested and everything checked out. (I was thinking alternator could have gone out causing batt to die)

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04-07-2017, 03:11 PM
You have electrical current going through your meter that shouldn't be there and it is probably pegging really hard which is not good for your meter.

04-30-2019, 11:57 PM
I appreciate the help and didn’t realize I forgot to update this thread.

Not being super knowledgeable electrically I ended up having the boat at the dealer last spring for a gel coat repair and had them troubleshoot the light/gauge issue. They told me everything “checked out” under the dash but the problem ended up being a bad/incorrect type of bulb in bow red/green light. The dealer replaced bulb and issue was resolved for most of last season. (Temp gauge no longer pegged hot with lights on)

At the end of last season issue happened again. Flip nav light switch up which turns on bow, gauge backlight and tower anchor light and immediately temp gauge pegs hot. Turn the switch off and temp gauge immediately normalizes. Flip switch down and anchor light works without affecting temp gauge.

So, currently I have stock Attwood red/green bow light with 8w festoon bulb. Light still turns on and works. Could the bulb be faulty if it’s still working? Should I try replacing the bow light itself? I check connection to light and switch in dash and don’t see any corrosion.

I would really like to be able to boat safely after sundown without my temp gauge going crazy. Do you think I’m doing harm if I ignore it and use the lights anyway? Currently I won’t boat after sunset out of fear I’ll mess something up.

I really appreciate any and all help and promise to update thread with results.

05-01-2019, 01:26 PM
My best guess is that the gauge light is grounding to the gauge case. Check the bulb socket and wires to make sure it is properly insulated from the metal of the case.

If you donít find anything there then be sure to check the ground wires (black) from both the gauge and the gauge light, as someone mentioned previously.

05-01-2019, 02:24 PM
My best guess is that the gauge light is grounding to the gauge case. Check the bulb socket and wires to make sure it is properly insulated from the metal of the case.

If you donít find anything there then be sure to check the ground wires (black) from both the gauge and the gauge light, as someone mentioned previously.

So I think the gauge bulb may be the culprit. Since I owned the boat the only gauge the didnít light up at night was the temp gauge. Thought it was strange but never really thought more of it.

I finally decided to try and isolate everything on the switch for testing. When I only had both bow and anchor lights powered on they worked and gauge was fine. When I connected power wire for gauge backlights the temp gauge backlight doesnít come on and the gauge pegs hot.

I feel silly that simply replacing a bulb might fix this issue I have been chasing for like 2 years lol.

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05-28-2019, 09:54 PM

Found a burned out gauge backlight bulb was causing my problem!!!

I replaced all of the small gauges with led blue backlights. I need to remove the sub to access the tach and speedometer ďbig gaugesĒ.

Anybody know if you can change perfect pass bulb color? My faria depth gauge came with red and not sure if you can change it.

My wife says she likes the multicolor and I should leave it haha.

Many thanks to all for the help and advice.

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