Archived Lost voltage gauge

[apat]

Just got on the road for a 200 mile trip for work and the "check gauges" light came on. A quick scan showed that the voltage gauge was on 8. Being close to home, I turned around and headed that way. What can I check to see if I've lost the alternator or gauge? Any help is greatly appreciated.

 

[GAmes]

Disconnect the grid heater relays (either small wire) and see if the problem goes away. If it does, one or both is bad. Foster trucks sells good replacements. If that doesn't fix it, you need a multimeter. Check the battery voltage, it should be about 12. Start up the engine and the voltage should increase to about 14. If it doesn't, the alternater isn't charging. Check the main 50 amp fuse in the PDC for continuity. If it is good, look for voltage between the two small terminals of the alternator, engine off, key off. IIRC there should be 5-7 volts. If you have that, remove the alternator and take it to one of the parts stores that does free checks. If it tests bad, and you can leave the truck parked awhile, do not buy one of their rebuilds. Foster truck sells the correct parts for a lot less, or take it to a local shop for rebuild.

 

[DavidC]

One of the first thing to check is a load test on Batteries. A shorted/bad cell will drag the charging system down. Next would be the main fuse in the PDC. It is 140 amp. Serpentine belt good ?. Battery connections ?.

Dave