Drove the car today and noticed my voltage gauge was jumping around. Sometimes it drops below the midpoint during cruising and other times it seems to be working fine. Needle jumps up and down very quickly at times. Any suggestions on where I should look first? Thanks.
Stock voltage gauge acting up.
- Thread starter oldjunk
- Start date
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67Dart273
Well-Known Member
Do you really have a "voltage gauge" (voltmeter) or the factory ammeter?
Very first thing is to "rig" your multimeter to a good solid battery connection and go for a test ride to see what the voltage is REALLY doing.
Otherwise, it could be a number of things, including but not limited to:
The meter itself could be bad
The alternator or at least brushes bad
A bad electrical connection anywhere from the alternator through the bulkhead (twice) at the ammeter if still in use, and to the battery
Other problems in the alternator
Bad regulator, bad connections in the regulator
Under what conditions exactly does this happen, find out FOR CERTAIN are we referring to a voltmeter or ammeter, and monitor the voltage as suggested above with a multimeter
Is it affected by system load, IE worse/ better when battery is charging after a start, or with lights/ heater/ other on, etc?
Very first thing is to "rig" your multimeter to a good solid battery connection and go for a test ride to see what the voltage is REALLY doing.
Otherwise, it could be a number of things, including but not limited to:
The meter itself could be bad
The alternator or at least brushes bad
A bad electrical connection anywhere from the alternator through the bulkhead (twice) at the ammeter if still in use, and to the battery
Other problems in the alternator
Bad regulator, bad connections in the regulator
Under what conditions exactly does this happen, find out FOR CERTAIN are we referring to a voltmeter or ammeter, and monitor the voltage as suggested above with a multimeter
Is it affected by system load, IE worse/ better when battery is charging after a start, or with lights/ heater/ other on, etc?
Sorry, should have clarified. This is the factory meter. Thanks for the tips. Hope I can figure this one out.
67Dart273
Well-Known Member
Post back with what you come up with. By the way, what year/ model we working with?
Probably the very first thing to do is pull the brushes and inspect or replace them
Then, if you have the older 69/ earlier system, unhook the field connector from the alternator and use a clip lead between the alternator field connector and the battery. Start the engine, slowly bring up RPM, and see if the gauge is steady. Play with lights/ heater, etc to add load to the system.
If this "stabilizes" the gauge, then the problem may have been the brushes, try hooking the regulator back up
If the gauge remains unsteady, you probably have bad connections in the charge wire and your no1 suspect is a bad connection int he bulkhead connector
IF you hav ea 70/ later (isolated field) system, in the test above, you must disconnect the file wires (2) ground ONE, and hook the other to the battery as above.
This unsteady charging could ALSO be a major problem in the alternator, IE vibration could have ruined the insulation on the stator winding. Try running the car, with the field hooked up as above, in the dark. Look for a miniature lightning show in the stator windings.
Please read this article on bulkhead connectors and their problems:
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
Probably the very first thing to do is pull the brushes and inspect or replace them
Then, if you have the older 69/ earlier system, unhook the field connector from the alternator and use a clip lead between the alternator field connector and the battery. Start the engine, slowly bring up RPM, and see if the gauge is steady. Play with lights/ heater, etc to add load to the system.
If this "stabilizes" the gauge, then the problem may have been the brushes, try hooking the regulator back up
If the gauge remains unsteady, you probably have bad connections in the charge wire and your no1 suspect is a bad connection int he bulkhead connector
IF you hav ea 70/ later (isolated field) system, in the test above, you must disconnect the file wires (2) ground ONE, and hook the other to the battery as above.
This unsteady charging could ALSO be a major problem in the alternator, IE vibration could have ruined the insulation on the stator winding. Try running the car, with the field hooked up as above, in the dark. Look for a miniature lightning show in the stator windings.
Please read this article on bulkhead connectors and their problems:
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
'72 Duster 340. Thanks again for the help 67Dart.
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