M920 charging/alternator question

[Karl kostman]

Hey guys my 920 had not run in 2.5 years and when I went to start it the other day it fired up like I drove it yesterday. After starting the engine and letting air build of course I am watching oil pressure and all other pertinent gauges closely I noticed the voltmeter was only reading about 8 volts on the discharge side of the gauge. After the engine had run for about 15 minutes I brought up the RPMs a bit and the gauge came up to maybe 9 volts still on the discharge side of the gauge, I know this isnt right. The truck was charging normally when I parked it in the warehouse a couple years ago can you give me any ideas on whats going on with this alternator? Does an alternator lose charging ability just sitting there not being used? How do I get it fixed?
All ideas appreciated
Karl

 

[simp5782]

Hey guys my 920 had not run in 2.5 years and when I went to start it the other day it fired up like I drove it yesterday. After starting the engine and letting air build of course I am watching oil pressure and all other pertinent gauges closely I noticed the voltmeter was only reading about 8 volts on the discharge side of the gauge. After the engine had run for about 15 minutes I brought up the RPMs a bit and the gauge came up to maybe 9 volts still on the discharge side of the gauge, I know this isnt right. The truck was charging normally when I parked it in the warehouse a couple years ago can you give me any ideas on whats going on with this alternator? Does an alternator lose charging ability just sitting there not being used? How do I get it fixed?
All ideas appreciated
Karl

Check voltage off the back of it. Don't trust the gauge

 

[juanprado]

Check batteries are fully charged and load test individually

 

[Karl kostman]

I will check voltage off the rear of the Alternator and all the batteries are brand new 6TLs but will check voltage and see where it is!