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Gauges flickering

T

tbrodes

Regular Contributor
Have a 454 with a flickering gauge issue... Just had new alternators installed, new switches, cables, batteries. Starboard gauges work perfectly....port...not so much. The gauges are fine at lower rpms, but as I get up to cruise rpm (3400) the start to flicker. The voltage gauge drops to 11.5, and the temp gauge and oil pressure peg forward. The tach does not move....here's the thing, if I hit te emergency start switch the gauges go back to normal fr a few minutes.

Any tips guys? Clearly it's a grounding issue....is the selenoid causing the issue?
 
Sounds like a bad diode in the alternator. If so, you'd better get it fixed ASAP or electronic devices will start dying.

Jeff
 
New alternators - God, I'd hope they were subjected to a performance check before they went into the box...I'd look for a significant voltage drop across one of your "new" connections...could be a loose or dirty connection or even a bad wire-terminal joint...
 
hit the batterys with engine off....13.2 volts....with the alt running they are getting to 13.8-14.1 (cheapy voltage meter). makes me think its not the alt? But i should have in hindsight tested the alt lug (was in a suit didnt want to crawl outboard of the engine). Hmmm. ok thanks guys.
 
Sounds like the alternators are fine...check the engine to panel 8 pin connection to see if it is clean and tight...?
 
thats my take away. I plan on checking the 8 pin connector tomorrow night. i havent really looked at thge gauges and how they are wired. is there a ground gauge block under the dash? Its just bizzare. Everything on the boat works, no power flickering, engine just humms along (been in the engine room at power to double check temps...they sound like sewing machines at 3300).

I really feel like this is a ground issue....

BUT it was a great call checking the alt, but it doesnt seem to be it. and all the wiring is perfect from the alt switches and batts.
 
I would suspect the main harness feed asthe issue "disappears" when you connect the EMER switch....of course, this is driven by my WAG that your EMER switch adds another battery in parallel to the main battery. the voltmeter dropping could be either a positive or a negative side issue. if the main connector is good, look to see how the gauges get their supply voltage...very common to find their wiring to be very small and done suboptimally...
 
my game plan is to disconnect connector, check it out....if from there take the volt meter to the gauges and stidy the wiring.
 
Be sure you don't run the engine without the alternator being connected to a battery (in your experimenting). That blows the diodes.


Jeff
 
well i disconnected the big 8 pin connector, had some junk it in....cleaned it out with electric cleaner then diaelctric greased the plug, took in on and off a few times....no gauge flicker! ran the boat 70 miles at cruise yesterday...not one issue even at high speed cruise 3400 on the way home 35 miles at 24 knots. You guys are awesome, I guess that might have been the issue, atleast for now...!
 
Glad that one is done...you may wanna look around and see if you can find a short piece of 1.5" ID (?) shrink tube to put over the 8 pin connector - keept the crud out, the dielectric grease in, and ensures the connector wont separate from vibration...get it mail order or at the local marine electronics shop...
 
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