Weird Voltage Fluctuations (4 Viewers)

[joshrabon]

Little backstory, 2000 LC at 310k currently. 3-4 months ago, I started getting a no crank issue. In the process of fixing that, I replaced the battery with a brand new odyssey agm, the original alternator with a reman from Toyota, and the starter with an oem. No issues after putting it all back together.

I currently have one of those diodes in the alt-s spot to boost voltages to make the the agm happy.

This week I’ve noticed weird flux in the voltages. Starting from cold 14.8-15. I think that’s good. But as the truck warms up, the number drops. It usually settles around 14.2. But then it starts bouncing around. Down into the 13’s. Assuming the diode is boosting .4v, that’s putting me down into the 12’s at some point.

I’m going to throw a new serpentine belt on to rule that out, but what else could be causing this? Any help troubleshooting this one?

 

[badlander]

I have the same setup and one time the voltage didn't go down after runnimg for a short time as it usually did. I pulled over and stopped the engine and pulled out the diode/fuse and plugged it back in again and then all worked as normal. Maybe it was a bad contact in the fuse socket, I don't know, but it worked fine after that and has ever since. I suspect that sense wire circuit is very voltage sensitive and dependant on excellent conductivity to work properly.
Maybe it will fix your issue.
Good luck

 

[joshrabon]

This morning I noticed the temp got up to 197 briefly at a light on the way into work. Never happened before. Kind of leading me down this serpentine belt train of thought. How noticeable would belt slippage be?

For reference, normally at 190 +/- 1 or 2. Just had timing belt, water pump, thermostat, and a coolant swap done in January. No issues since.