12 volt electrical problem........FIXED

[vegasfoodguy]

My Motorhome 1s 1999 Monaco Diplomat, 66,000 miles, 275 cummins.
Volt meter works sometimes, Alt/Charge light goes out when engine started. While driving today, sign said turn on lights for X number of miles.
Temperature gauge runs abour in the middle, When I turn lights on temperature goes to 220, about 3/4 over, turn lights off, immediately
drops to normal.
While dry camping not enough 12 volt to light refer, I start the generator, charge battery a little, refer lights perfect.
Any Ideas?
Thanks.

Terry.

[vegasfoodguy]

Thanks, For the help, Your advice was right on, Loose battery ground drove 200 miles, runs perfect.

Terry

[wa8yxm]

Two or three possible issues.

First the strange action of the temp gauge.. Hook up a volt meter and you will see the voltage drop when you turn on the lights.. The TEMP gauge is a "Fail Safe" Gauge. that means if it looses power, or if the wire to the sensor breaks, it goes to FULL SCALE (Thus alerting you to a problem).. The fuel gauge, You might have noticed, doing the opposite (Going down) as that's it's "Safe" fail mode.

A poor connection can cause a high voltage loss so what was 12 can become 10, or 8 or 6 or less

A slipping alternator drive belt can cause the alternator to spin just fast enough to turn the idiot light off, but not provide power for the headlights, this is epically true if it has "V" belts instead of the more modern serpentine belt.

And a failed alternator.. Likewise may not deliver the amps needed.

[rgatijnet1]

Terry,
It sounds like you have some bad electrical connections from corroded wires/connections. These are usually ground connections, but can also be on the 12 volt positive side. The bad connection can sometimes be behind the dash where the dash meters are connected to ground which is causing them to be erratic.