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[Derrickl112]

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[Doug Roberts]

I am trying to get an alternator replacement for my M1078 . I have the part # N 1506-1 , 1995 Stewart Stevenson . Have you fixed yours? Any suggestions on where I can go ?

 

[dporter110]

I replaced the Voltage Regulator on one of mine and that fixed the problem. They are brushless alternators so I believe the internals are pretty much bullet proof. I paid $50 for a NOS N3030 regulator.

 

[Mike2124]

Hi, new to the forum, and a new M1079 owner. I believe I have a bad voltage regulator as well. Where did you purchase yours? I searched for the NOS N3030 but could not find.
Thanks
Mike

 

[mkcoen]

I bought one last week on a popular online auction site. Unfortunately it was more than twice what the other poster paid. Of course that was 2 years ago and more trucks out now mean more people looking for these mean higher prices.

 

[Suprman]

AC lead is an output ignore it. No 24 volts at regulator input is bad wiring. Go from outside terminal (+) on fuel solenoid to red connection on regulator see if it makes voltage then. 12 volt regulation is derived from the regulator dividing the 24 volt reg lead.

 

[scottmandu]

There are parts in the alternator that can go bad and need replacement, however they aren't terribly expensive. Also there are two different regulators.

 

[Suprman]

I find the majority of the first gen trucks out there have wiring issues to the regulator. Without 24v to the regulator the alternator will not excite and make any voltage. Run a test wire from the 24v post left side of the breaker panel to the 24v regulator positive and see if your voltage comes up. If the alt hasn't make power in a while it make whine and grumble for a second or two. It's an easy test. These alternators are more reliable than the m939 60a versions.

 

[Mike2124]

Thanks for the info. As soon as I get the time I'll get back under the cab and start messing around. I have been having trouble finding parts. Google gave me nothing for the voltage regulator except for a top dollar government sales co. Looks like the common auction site have parts intermittently but not right now.

 

[mkcoen]

Turns out the regulator I bought for mine is for a 2nd gen alt and I have the original alt so if yours is a newer one I might be able to help you out. Now I have to source an old style.

 

[Mike2124]

Do you know what is 1st gen? I have a 1996 M1079. I have had almost zero time to tinker with it since I got it so was just looking for the quick and obvious fix (swap regulator). If that didnt work at least I have a spare to use or sell.

I will hopefully get to the truck this afternoon (cant keep at home, so its at the VFW), and get the cab up. I'll get back with the gen and regulator #s and let you know if I could use yours.

Will also try to check some connections to the reg, but electrical is not my strong suite. That, coupled with lack of time, make it hard to get this thing fixed. All I know is that the voltmeter is pegged (whether power on or off) and the batteries are not taking a charge. All else seems fine.

Thanks

 

[mkcoen]

Do you know what is 1st gen? I have a 1996 M1079. I have had almost zero time to tinker with it since I got it so was just looking for the quick and obvious fix (swap regulator). If that didnt work at least I have a spare to use or sell.

If yours is the original alternator it's a 1st generation. My M1078 is a 1998 and it is 1st gen. If that's the case my regulator won't work on yours either. Pull the plug going into the regulator and see how many prongs it takes. Looks like the older style is a 5 prong connection and the newer style is a 6 prong.

The older style regulator is a N3030 and I haven't had any luck locating one.

 

[Mike2124]

If yours is the original alternator it's a 1st generation. My M1078 is a 1998 and it is 1st gen. If that's the case my regulator won't work on yours either. Pull the plug going into the regulator and see how many prongs it takes. Looks like the older style is a 5 prong connection and the newer style is a 6 prong.

The older style regulator is a N3030 and I haven't had any luck locating one.

Turns out that the 24V connection to the alternatior was completely disconnected! There were signs of where it had grounded out in places after it came loose, you can see the burn marks in the photo. I am lucky nothing fried or caught fire. Thank you suprman for suggestion to look for loose wires first - that certainly was the case.

Mccoen, the alternatior is new-ish, date code on it is 2012. The regulator is an N3207. I have yet to hook up the cables, it got dark and I didnt have the bolt. Working on that tonight so I will see if it all works. I may need your regulator if mine got fried, or perhaps I'll take yours anyway as a backup if the price is right and its the right part #.

Thanks for the help guys

Mike

 

[coachgeo]

Turns out that the 24V connection to the alternatior was completely disconnected! ...

772 mentioned below earlier. Not sure it relates here cause your wire looks pulled out, not disconnected

.... Seems like the Army mechanics liked to take stuff apart, but not put it back together on this truck!

That's how they usually do it and I am thankful for it. It shows the next person handling the truck what was done before and what was taken off. You are supposed to do your PMCS anyway, so you'd find all the lose ends

 

[Mike2124]

I think mine just came loose. Supposedly it was working (I bought it from a guy who bought it at auction). My guess is it wasnt fully secured when the new alternator was installed, sometime after 2012. Not sure if locknuts should be there, but this one had none.

 

[Mike2124]

Well, I connected the 24 post at the alternator, which also included a small wire that got the voltage regulator functioning. It is now blinking alternating green lights back and forth. I am not sure if they should be solid green or alternating. But the volt gage still pegs high when the power is turned on, and remains high when turned off. Does anyone know what the lights on the regulator should be showing? My next steps are to check the alternator output at the batteries, to see if I am now getting a charge, and then check to see if the voltage gauge is faulty.
.

 

[Suprman]

Alternating green is normal. Use a multimeter to check the voltage maybe the dash gage is wrong. If you do have significant over voltage you will damage your trans ecu and other things.

 

[scottmandu]

If yours is the original alternator it's a 1st generation. My M1078 is a 1998 and it is 1st gen. If that's the case my regulator won't work on yours either. Pull the plug going into the regulator and see how many prongs it takes. Looks like the older style is a 5 prong connection and the newer style is a 6 prong.

The older style regulator is a N3030 and I haven't had any luck locating one.

I've got a N3030 regulator.

 

[mkcoen]

I've got a N3030 regulator.

PM sent

 

[Mike2124]

Everything checked out fine with the voltmeter at the batteries and the alternator/regulator. So I think my system is good, just a bad voltage gauge that probably fried when the cable grounded out.

So - any idea where to get a gauge? Its a Medallion # 12378797, preliminary searches aren't bringing anything up.

Thanks
Mike