Charging system

[Shooter308]

Had a no start yesterday. Appears to be a charging issue to me. Reading through the TMs for testing the alternator. Has me checking for 28v on the alternator output . Which I'm only show 24.7v. certainly low. But following the TM it says if I don't see the 28v on the output i should replace cable 2(alternator output cable). Am I reading this wrong? Seems to me that the alternator output voltage is the concern and not that cable. I did also try adjusting the voltage and doesn't seem to help. I think I have a alternator issue.
TM 9-2320-209-20-2-1 pg: 25-47 and 25-48

 

[HDN]

Had a no start yesterday. Appears to be a charging issue to me. Reading through the TMs for testing the alternator. Has me checking for 28v on the alternator output . Which I'm only show 24.7v. certainly low. But following the TM it says if I don't see the 28v on the output i should replace cable 2(alternator output cable). Am I reading this wrong? Seems to me that the alternator output voltage is the concern and not that cable. I did also try adjusting the voltage and doesn't seem to help. I think I have a alternator issue.
TM 9-2320-209-20-2-1 pg: 25-47 and 25-48

24.7V is just the two batteries - I don't think you're charging at all. I suspect either alternator or voltage regulator, especially if you're not getting a response from the voltage regulator adjustment screw. Before pulling the alternator check for proper belt tension. If that's good, check the wires next per the snips I posted below. If those are also good, you should probably pull the alternator and get it tested at an automotive electrical shop that services alternators and starters. They may be able to isolate the problem to either the alternator or the voltage regulator. It's possible to replace just the voltage regulator, which would be less expensive than replacing the whole alternator!

Here are a couple snips from a 1980 M44 series manual that I have:

 

[Shooter308]

As it turns out, when I had the truck outfitted, the needed alternator did not get put on. So it's on its way here. Just gotta put it on and should be back in business.

 

[HDN]

As it turns out, when I had the truck outfitted, the needed alternator did not get put on. So it's on its way here. Just gotta put it on and should be back in business.

What does it have now? Are you getting a NOS unit or a modern civvy one?

 

[Shooter308]

What does it have now? Are you getting a NOS unit or a modern civvy one?

Wish I knew more. It'll be 80 amp, and should bolt right up.

 

[HDN]

I suggest keeping the dead one and getting it repaired. It never hurts to keep a spare!

 

[ToddJK]

A quick easy test to see if the alternator works at all, once the truck is running, unhook the batteries. If the voltage meter crashes, no juice period from the alternator. I would say by looking at the gauge itself, the needle will be in the mid yellow to low yellow range on good batteries if the truck is running and alternator is not working, but not every gauge and alternator are the same. First suggestion works for all. My old alternator went out, not once but twice. First time was bad brushes,second time the voltage regulator went out. Just before the voltage regulator took a , it over charged a lot and fried one of my military batteries.

 

[Shooter308]

Testing seemed to go pretty good. I had a good suspicion it was the alternator. I am still wondering why the TM said change the output wire if the output voltage was low? That part didn't make sense to me, unless I just didn't read it properly.

 

[ToddJK]

Testing seemed to go pretty good. I had a good suspicion it was the alternator. I am still wondering why the TM said change the output wire if the output voltage was low? That part didn't make sense to me, unless I just didn't read it properly.

My guess is because it's an easy fix and the last link between a faulty part and the alternator.

 

[Shooter308]

New alternator is in. Looks to be charging. Went for a ride to get the batteries recharged.