LMTV Wiring/No Crank

[95 Paul]

Hi All
I'M working on a 2003 C40 LMTV with a Cat & Allison. Everything was working fine until the alternator went bad and burned up some wiring. I can get the truck started if we jump out the relay on the frame for the starter. The check transmission light is on the dash and have no crank signal going to the relay. Also we are getting signal from PTS to the K11 relay but no crank. Any one have a wiring schematic or direction of what to look at next would be helpful. We are think the TCM is bad, just need to know which wire is what.

Thanks

 

[GeneralDisorder]

How did the alternator burn up? That can be the result of batteries being hooked up wrong in the absence of the LBCD (polarity protection device).

Here's the diagrams:

FMTV Schematics A 0 A 1 R : Stewart and Stevenson : Free Download, Borrow, and Streaming : Internet Archive

Family of Medium Tactical Vehicles wiring schematics. A0, A1, A1R WTEC III, A1R Gen IV

archive.org

 

[Ronmar]

Is k26 energizing With ign on? Thats the neutral start relay controlled by the trans. K26 powers K11, K11 when energized sends power to the start switches to allow engine crank using those switches as they feed the aux start relay on the frame… trans trouble may indicate something in the trans or its power feed is wrong and you are not getting the neutral start signal to power K26…

 

[hike]

Perhaps off topic: C40? Learn me up, please—

 

[95 Paul]

GM ALL

Thank you for the information sent so far, unfortunately we had to put this job on the back burner for a bit, LOL. The wiring schematic that was sent, is for an older truck, this one we are working on has different controls and relay panel. The neutral switch/signal appears to be not working . We are looking for wiring diagrams for the transmission control module so we can test what wire does what. Most of the wiring is hard to identify since its all the same color and numbers are worn off. If we jump out the starter, everything works normal.

In addition does anyone have a source for an alternator? Its a Niehoff 12 & 24 volt unit, #19207S0CN12422863.

Thanks

 

[Ronmar]

Save your money and put in a straight 24v alt and use a 24-12 converter to feed the truck 12v loads. pulling the 12 out of the middle of the 24v on the alternator cuts its output by nearly 1/3 at full load, so a straight 24v 100A alt will actually deliver more than the dual volt “100A“ Neihoff… you can also do this for well under half the cost of a new neihoff…