Battery gauge jumping

[Mick65]

Happy new year guys. A new problem with my truck just started. It's now jumping between 12-14 volts at idle. When it jumps I can see my interior lights and headlights dim. I also feel a slight twitch through the steering column. What would cause this? Thanks!

[R_W]

Sounds like something could be loose. Check the battery ground, make sure it is not corroded at the connection point to the engine. Check fire wall connections.

[tincan1966]

Assuming the truck is original( still has external regulator) it's possible the regulator may be getting a bit weak.

With the truck idling, turn on the headlights and the heater fan. The gauge should drop to 12 but stay steady. If it does, then run it like that for a few minutes, then shut the lights and heater off- see if the gauge stays steady. If it still fluctuates, I would guess the regulator is getting worn and not compensating for the load.

This happens a lot in vehicles that are not driven a lot, especially in situations where more alternator output is needed. simply put, these trucks, when original, have very little draw on the charging system, so at idle, there isn't much need for a lot of alternator output. With modern updates, like HEI, stereos, etc, which draw higher amperage demands, the alternator is almost always charging, even at low RPM.

[TJ's Chevy]

As Tincan put it.....I had the same issue with mine....At idle with all accessories off the gauge would bounce....when I would turn my headlights and fan on it would drop to just before complete discharge. Course I assumed my regulator was shot so I got another one....Cheap Re-pops are $17...weather they work or not I have no clue. lol. To fix the issue I converted to a single wire alternator. 100 amps. Runs much better, and alternator isn't struggling to Push a charge.

[luvbowties]

"Twitch in steering column": is horn unplugged and its relay intermittently engaging--like an intermittent short in horn mechanism inside column? Is that 'twitch' something you feel like static electricity? Horn 'spring-washer' in column can give you such a charge if touching it as it makes-and-breaks.
Sam

[Mick65]

Originally Posted by luvbowties

"Twitch in steering column": is horn unplugged and its relay intermittently engaging--like an intermittent short in horn mechanism inside column? Is that 'twitch' something you feel like static electricity? Horn 'spring-washer' in column can give you such a charge if touching it as it makes-and-breaks.
Sam

I'm not sure as my horn in my cheapo GT steering wheel doesnt work. Instead I have one mounted.

[luvbowties]

Originally Posted by Mick65

I'm not sure as my horn in my cheapo GT steering wheel doesnt work. Instead I have one mounted.

Yours on st. column not working may just be a hint that it is setting off the relay intermittently.
Sam

[Mick65]

Originally Posted by tincan1966

Assuming the truck is original( still has external regulator) it's possible the regulator may be getting a bit weak.

With the truck idling, turn on the headlights and the heater fan. The gauge should drop to 12 but stay steady. If it does, then run it like that for a few minutes, then shut the lights and heater off- see if the gauge stays steady. If it still fluctuates, I would guess the regulator is getting worn and not compensating for the load.

This happens a lot in vehicles that are not driven a lot, especially in situations where more alternator output is needed. simply put, these trucks, when original, have very little draw on the charging system, so at idle, there isn't much need for a lot of alternator output. With modern updates, like HEI, stereos, etc, which draw higher amperage demands, the alternator is almost always charging, even at low RPM.

Sorry, I should have been more descriptive in my original post. I do have an internal regulator, HEI, and an electric fan.