Alternator voltage jumping around

My original alternator failed on my way to Moab in Albuquerque after 230k miles (good timing actually). EXACT same symptoms. It's likely the voltage regulator. You do NOT need to take it out to have it tested. But yes, it is so easy. I did it in the Autozone parking lot at night.

Take it to an any good auto parts store and have them do a charging system test. They will load test the battery and test the alternator and tell you whats going on. For free.

 

UPDATE: was my alternator. swapped and we are at 14+ at idle. Connections were all good. Actually wasn't as dirty inside as I assumed it would be but likely just slowly killed itself from the dirty water getting splashed into it.

 

Is your battery reading 11.9 after sitting with the truck off for a short period? If so, you may want to look into replacing it soon. Should be hanging around in the 12s at a bare minimum. Check your voltage drop under load too. Flip your headlights on with the engine off and see how fast the voltage drops. It is gets into the low 11s or lower really quickly, you might have battery problems on top of your alternator problems.

 

So, how did the brushes look?

 

Might end being both, I have found that Toyota alternators are not fond of water. My 85 alt went south a couple days after I hit a big puddle on the road. So if the battery was even close to marginal, then I would plan on getting one somewhere down the road- preferably before the next fun trip...