I have an Atomic 4 engine in my 1983 Catalina. Two of the gauges, the fuel and temperature gauges, are not working. The manual doesn't have a wiring diagram and it looks like someone has been working on the wiring. Any suggestions on how I can get these gauges working again?
Mark Matthews responds:
Thanks for the question. Prepare to get out the voltmeter and do some sleuthing, especially if a mad electrician made the rounds before you. Wiring a gauge is essentially no different than wiring a lightbulb, so don't be cowed by the project.
These gauges have a ground and a DC power source, usually activated by turning the key. Track down the wire coming off the ignition and use a voltmeter to determine which one is the ground and which supplies positive current. Take care not to make sparks—the volatile nature of gasoline needs to be taken into account whenever working on gas-powered engines. The problem is likely to reside in one of three places, either in the sender unit, the wiring, or the gauge itself. If the gauge is stuck in one place, this is usually a sign that the gauge is the problem and will have to be replaced.
The sender unit can also go over time, and may need to be replaced. You can test this with the Ohm setting of a voltmeter. Is there one wire or two coming from the sending unit? If there is one wire, the unit is grounded via the engine block. Two wires mean that it’s operating as an insulated circuit. Check to see that these wires are connected where they should be, and not crimped, chaffed, of otherwise compromised. Some gauges are connected in series too, so that when there’s a problem getting power to one, the whole array can shut down.
Check to see that the float mechanism on the tank gauge is not jammed or otherwise obstructed. You can also use volt and Ohm readings to divine whether or not the unit is the problem or if power supply is the issue.
Test for 12 volts off the gauge with the ignition on, using the ground on the sending unit to complete the circuit. If there’s no juice, the ignition is faulty. Take off the sensing line from the back of the gauge. If the gauge is for temperature, it should go to its lowest reading while an oil pressure gauge should shoot up to the highest. If it doesn’t, these are faulty.
Finally, you should know that there are others who have probably sifted through some or prt of the problems you now face. I’d refer you to the Catalina E-mail Discussion list where you can query other owners on this and other topics pertaining to your boat. Good luck.