Instrument Panel Problem

[Diana]

I have a 1990 130 hp I/O Mercruiser. My problem is some of the gauges work, and others do not. The tach, speedometer, gas, and trim indicator do NOT work.
The volt, oil pressure gauge, as well as lights are working.
Is there 1 commom problem I may be having between the non-working meters?
Thanks!
Diana

 

[bruceb58]

Re: Instrument Panel Problem

Bad power or ground possibly.

 

[Diana]

Re: Instrument Panel Problem

Bruce,

Ok, but being a typical women, where is the ground? Or where do I connect it?

 

[bruceb58]

Re: Instrument Panel Problem

Typically, you will have a fairly large +12V(red) and ground wire(black) wires brought up to a fuse panel from the rear of the boat where the battery is.

The ground wire to the guages will be a smaller guage wire that connects to a bus bar where the large ground attatches to the fuse panel.

To check for ground at the guages, you can put one lead of your voltmeter on the red wire and then measure the grounds at the various guages. Do this with the ignition on so that you don't get fooled by a resistive connection.

Likewise, you would do the opposite for checking power. Put one lead on the large ground wire and measure the voltage at the power input to each guage.

Be aware that there will be more than 2 terminals on these guages. 2 of them will be the power and ground, one will be the back light and one will be the input to the guage from the sending unit or the coil in the case of the tach. Tyically the ground will always be black and the power connection will always be the same color(normally purple) on every guage.

 

[Silvertip]

Re: Instrument Panel Problem

Here's a diagram for a "generic" instrument panel. It doesn't show a trim gauge but the wiring will be similar to a fuel gauge. Some gauges working and some not indicates a bad ground or loss of 12V. Note that these two lines are generally daisy-chained from one gauge to the next. If the gauges that don't work are next to each other, the problem is likely between the last gauge in the string that works and the one that doesn't. Hope this helps. Color codes are generic here as well. May not be and probably are not the same on your panel.