Cooked Optima Yellow Tops

[CaptainChaos]

1990 M998. Was cruising right along and started to smell rotten eggs, pulled over to discover the batteries hissing and discharging steam. Batteries date 9-21. Note: they were not secured by straps or proper mounts by previous owner so my question is flopping around, bad alternator, voltage regulator or what? Where do I start?

 

[98G]

Voltage regulator is my guess.

Time to get out the fluke meter...

 

[CaptainChaos]

That was my initial thought as well. Grabbed a couple of yellow tops, cleaned the battery compartment and all connections thoroughly. I removed the cap on the voltage regulator and got 33 volts upon cranking the engine and the in cab gauge immediately hit the red. I know the regulator is adjustable but my question is what is the range of adjustment as I understand I should be between 28 and 28.5 volts. Any help is greatly appreciated.

 

[Guyfang]

If it worked before, no amount of adjusting is going to help.

 

[CaptainChaos]

Time for a new regulator then.