voltage too high

[Fastfunco]

M925 A2 - everything brand new- military did a frame off - new cab - motor 8.3 turbo- trans - everything-
start up and volt gauge spikes

checked at batteries and im getting 37 volts
batteries brand new as well

Im pretty sure its voltage regulator- but figured I would ask?

while driving home- every once in a while lights were getting really bright - then in a few minutes- back to normal

It might be something incompatible after the restoration was finished- I found that the oil pressure gauge is for a different temp sender--

Any Ideas on the voltage problem????

 

[rmgill]

It would have to be the voltage output from the alternator. Don't run it with that much voltage. It'll kill your batteries. Check the TM's for diagnosing the alternator.

 

[av8or]

Check all of the grounding points for resistance.

 

[wilfreeman]

my deuce does the same thing sometimes. I found that if I turn the main power switch off, them back on once or twice, the gauge will go back to green (charging correctly). Something to try anyway. Mine might be the switch, but I've been getting ready for the GA rally - no time to work on the deuce. I'll pick up a new switch at the rally and give that a try.

 

[Suprman]

In the m939 trucks, I believe cycling the power switch cycles relay(s) in the protective control box if this cures the issue at least temporarily then that's one place I would check.

 

[Fastfunco]

yes-- mine does the same thing-- but not consistently!! it will go back to charging 28 volts if i cycle the Battery
Switch- but not every time- intermittently

i have tried to open the 1020 page TSB on this truck 3 times now-- all it does is freeze my computer--
any other suggestions???

 

[Fastfunco]

In the m939 trucks, I believe cycling the power switch cycles relay(s) in the protective control box if this cures the issue at least temporarily then that's one place I would check.

where is this box located on my M925 A2

 

[HASSON1911]

If it's constant 37 volts, don't run her anymore! But if its for 30sec on start up its considered normal. The brighter heads lights could be as simple as the truck taking more of a load, or just kicking in to charge the batteries

 

[rrrr]

Have you used a multimeter to verify the voltage ? Does this happen when the truck starts and does it show normal before starting ? Have you tried adjusting the voltage output of the alternater ? Did you tap on the gauge to see if its sticking ?

I had the same issue with my 932. I verified the voltage with a meter. I tried to adjust mine but it wouldn't. I ended up replacing the unit. Be advised that 37v will fry your abs ecu. Be very careful.

Good luck.

 

[gem1410]

My m925a2 did the same thing--volt meter in the red--my volt meter reads 35volts---cleaned battery terminals--load tested each battery and all ok--ckecked all connections to the alt and grounds---charging still reads 35 volts----will try changing alt--will let you know what happens

 

[VULCANGUNNER]

Well??

 

[gem1410]

Changed the alternator--at 26 volts now when running