Need help with Niehoff 100A 14/28 Alternator on M1079

[ke5eua]

I picked up a M1079 for a member and got it topped off with fluids. I flat towed it to the house, that was an adventure in itself. Last night I was going over it preparing for the road trip to bring it to it's owner in Louisiana and noticed the battery gauge was in the low yellow. Got out the vmm and verified it wasn't charging.

Now, went through the entire tm, and did the troubleshooting procedures and to verify past step 8 I need a known good regulator. Problem is I don't know if it's the regulator or the alternator. Anyone have a known good regulator I can use, or I can put this one on your truck to verify it's bad or good. I'm in Central Texas and will travel, although I'm sure the wife is tired of being in the car as we've traveled between Temple and College Station all week.

In the pics you will notice my Vaniar equalizer installed, I put it on it while I had the truck slaved to a wrecker so I could balance the batteries.

I would like to get on the road Monday, no later than Tuesday as I also have to make it to Alabama to pick up some trucks.

If there is anyway I can rule out the regulator manually please let me know.

To answer the basics:

Did you read the TM's? Yes, I even went as far to print out the 34 page schematic foldout and trace the wires.
Did you search the site? Yes, came up with one post about a frayed wire. Checked and it's not the case.

Regulator in question.



Current battery situation.



28v side output with engine running.



Individual battery voltages while engine running.

Left (Main +)



Right (Main - [Also 12v side]) This is why I put the equalizer on when I was charging from the wrecker.

 

[NDT]

HMMWV guys, is that regulator the same as later trucks? Looks like it.

 

[ke5eua]

HMMWV guys, is that regulator the same as later trucks? Looks like it.

I'll lift the cab tomorrow morning and snap a pic of the alternator.

 

[NDT]

I think not after all. There is one on ebay in NC, maybe they can next day it to you on Monday early AM. Search FMTV regulator.

 

[ke5eua]

I think not after all. There is one on ebay in NC, maybe they can next day it to you on Monday early AM. Search FMTV regulator.

Saw one out of alabama. Just hate to order a regulator to find out it was the alternator instead.

If I had a schematic of the regulator I could rule it out ahead of time.

 

[ke5eua]

Ok guys, went to C.E. Niehoff's website and they have troubleshooting guides for the regulators, Ya!!!

For this regulator / generator combo this is the guide.

Edit: uploaded wrong guide. Corrected for N3030 regulator

View attachment TG0018A_uid12172009221392.pdf

 

[lindsey97]

Bad batteries possibly? Unhook the batteries from the truck, charge them or load test them, check acid level. Batteries should be 12.6 or above if good. I would charge them overnight and then let them set 24 hours unhooked from anything and see what the voltage comes down to. If it's cold they will drop more, but I doubt it's cold where you are located.

 

[ke5eua]

It was the alternator. Batteries were / are good. Voltage readings were while truck was running so expect them not to be 12.6 due to electronics. The troubleshooting chart that C.E. Niehoff provides has you figure out if it's the alternator or regulator without the need for a known good regulator.

Owner is coming up to tow the truck to Louisiana. The 80 mile trip showed more issues than I would want to deal with for 500 miles.