Adding a Trim gauge and now nothings working…

[Bigbassfish]

So originally my boat has 4 gauges, voltage, tach, Speedo, and fuel. I’m in the process of redoing my dash, and tonight I removed the tach as it is no longer needed, and swapped the voltage meter with an analog trim gauge. To do so, I removed the tach, and then taped off the wires leading to it, one blue illumination wire, two black grounds, two purple ignition wires, and a grey sender wire. As for the trim gauge, I simply removed the voltage gauge, and used the black ground and purple ignition from it, plus the trim sender I already had behind the dash. When I turn the key on, none of my gauges work now… I did find if I turn the nav lights on, the fuel gauge shoots way past full, and the trim gauge jumps a little, but still stays in the fully down position. Any ideas what I did wrong?

[Bigbassfish]

I forgot to add that none of my gauges illuminate now either.

[yupitsme]

Missing ground somewhere - probably. The grounds are probably grouped on to one spade terminal and that terminal is disconnected. That's my guess.

[Bigbassfish]

Could it be that the two ground wires I pulled off the tachometer need connected? I can’t wrap my head around why the tach would’ve had two ground wires AND two ignition wires, unless the second set of ground and ignition wires were extra and simply needed to be connected to something. Would I be able to uncap the two black grounds and the two purple ignition wires and connect it all to the new trim gauge? That would leave the trim gauge with 3 ground wires and 3 ignition wires.

[yupitsme]

Yeah... I'd think you need to connect the grounds. These boat mfgs. are not like auto mfgs. no telling what you'll find behind the gauges. One of those "not" connected ground wires could go to another group of ground wires that are causing your problem.

[wmitch2]

I agree, it sounds like you're missing a ground. They are likely "Daisy Chained" and it sounds like you interrupted the chain. Re-connect the grounds and see if that solves your problem.

[Bigbassfish]

So it sounds like a missing ground would account for the fuel gauge showing past full and none of the other gauges coming on, but how does it make sense that the nav light switch has become involved? Key is turned on, nothing happens, but key on and then nav lights on is what makes the fuel and trim gauge jump.

[yupitsme]

Missing ground(s) creates many electrical demons to appear. Without actually tracing down each circuit there is no way to say with certainty why things do what they do. The fuel gauge is a function of resistance. Trim gauge probably is too. Something is probably back feeding the negative(ground) circuit with positive voltage causing what you're seeing. Connect any ground wire you see, that isn't connected, to a ground source. Start there.

[Bigbassfish]

I think I’ve got it mostly figured out, connecting all the purple wires to the new trim gauge, as well as all the black wires, seems to have fixed the gauges and the illumination, but now the beep from turning the key on no longer goes off…

[Bigbassfish]

And if someone could help me make sense of this, according to my multimeter there is continuity between all three purple wires, but when I turn the ignition on, only one of them is hot…how is this possible??

[Bigbassfish]

Also thought to add, multimeter shows 12v to the harness end of the red warning horn connection so not sure why it wouldn’t be working… I tested the horn by jumping the connector to the battery and it still seems to be working as well.

[lpugh]

So originally my boat has 4 gauges, voltage, tach, Speedo, and fuel. I’m in the process of redoing my dash, and tonight I removed the tach as it is no longer needed, and swapped the voltage meter with an analog trim gauge. To do so, I removed the tach, and then taped off the wires leading to it, one blue illumination wire, two black grounds, two purple ignition wires, and a grey sender wire. As for the trim gauge, I simply removed the voltage gauge, and used the black ground and purple ignition from it, plus the trim sender I already had behind the dash. When I turn the key on, none of my gauges work now… I did find if I turn the nav lights on, the fuel gauge shoots way past full, and the trim gauge jumps a little, but still stays in the fully down position. Any ideas what I did wrong?

The blacks must be kept connected together same for two purples, suspect they are not, also you may have tripped circuit breaker doing this work

[Bigbassfish]

I’m an idiot, the alarm wasn’t sounding because the kill switch was flipped. I would’ve sworn I tested it with and without the kill switch and it wasn’t working, seeing voltage at the connector also threw me off but thanks for the help as always!