Maxum Tachometer and Gas Gauge Not Working. Help!

[addysdady]

Hi all,

I just acquired a new to me 1999 Maxum 1800 XR. We love the boat and it's a huge upgrade from our old 16' Bayliner. Everything is in good condition and works properly with the exception of the tachometer and gas gauge. I took out the old volt meter and there seems to be power going to both gauges. The gas gauge seems to move every so slightly when I turn the ignition. I am hoping that someone can point me in the right direction as to where to start trouble shooting. Your help and guidance is appreciated.

Thank you!

 

[Scott Danforth]

tach needs a pulsed ground signal on the grey wire (one pulse per cylinder firing per revolution). put your ohm meter on frequency and read the grey wire to +12 volts

the gas gauge works with a variable resistance to ground sender, where 240 ohms is 0 scale and 33 ohms is full scale. the sender is nothing more than a variable resistor to ground. the signal wire is pink.

for testing purposes, use an ohm meter and read the resistance to ground on the pink wire

 

[alldodge]

Gas gauge test

Get a jumper wire, and a voltmeter.
Check for good ground on the gauge
Turn power ON and see if there is 12V on the purple wire.

If 12V is found, jump the pink wire on the gauge to ground, the gauge should peg full, if it does not replace the gauge
If it does peg full, go to the tank sender and ground the pink wire at the sender, the gauge should peg full, if it does replace the sender
If it does not peg full, check ground on the tank