LMTV M1078 Tachometer

Suprman · Jul 8, 2016

That being said I do have universal tachs that will work with the lmtv. They are 12/24 volt Datcon 4000rpm ones with hour meter. They can be adapted to most vehicles and are mil surplus.

Keith Knight · Jul 8, 2016

Well I've wasted half a day looking and learning about a Tachometer for my M1078A1 with the CAT 3126B engine. While researching info on installing a cruise control for it, I found the pin out locations on the engine ECM (electronic control module) that it shows a Tachometer output at pins #38 (+) and #39 (-) for the tachometer signal.
I'm finding that a tachometer for this application is impossible?
Any wisdom would be appreciated.

Thanks

Suprman · Jul 8, 2016

The alternator ac output on the regulator can be used to drive a tach. The datcon universal tachs I have may work off the ecm signal.

InMemoryofRex · Aug 11, 2016

I think Justin Wehring (user name Wehring) installed a tach on his LMTV.

Lmtv772 · Aug 13, 2016

PM me and I'll tell you what tach to use and how to connect it.

coachgeo · Aug 14, 2016

coachgeo said:
Continue from above

Pin one's wires #3020 at connector...
Pin two's wires ... ....

Got to go. More later, keep getting sidetracked with other projects

My apologies for not yet having finished tracing all the wires in the schematic. With pin one and two somewhat figured out then the signal for the tach must be either pin three or four.

The tach is 12v from what have read in here.

Lmtv772 · Aug 15, 2016

The Tach is NOT 12V.
There is no advanced degree required, it's right in the TM.
m1078_TM 9-2320-365-20-1.pdf
Whoever needs to know the pin out can look there, or PM me
The correct Datcon tachometer with 3000rpm is available at amazon for ~$100 (Pm for part #)

coachgeo · Aug 15, 2016

Lmtv772 said:
The Tach is NOT 12V.
There is no advanced degree required, it's right in the TM.
m1078_TM 9-2320-365-20-1.pdf
Whoever needs to know the pin out can look there, or PM me
The correct Datcon tachometer with 3000rpm is available at amazon for ~$100 (Pm for part #)

LMTV772 is correct in that it is all in the TM

below Post were the first start at breaking that info out. from both the TM and another document (linked to in first of below post). first and second link below is most relevant. 3rd is more detailed and didn't get chance to finish it yet as mentioned above.

http://www.steelsoldiers.com/showth...8-Tachometer&p=1859540&viewfull=1#post1859540

http://www.steelsoldiers.com/showth...8-Tachometer&p=1860095&viewfull=1#post1860095

http://www.steelsoldiers.com/showth...8-Tachometer&p=1860108&viewfull=1#post1860108

As to 12v or 24v..... he knows more than I do on that. Guess if one has doubts than can stick a voltmeter to the pins.

Look forward to someone sharing the part# for everyone

Awesomeness · Aug 19, 2017

After reading this whole thread, I'm still not completely clear, is the P901 connector in the dash (by default, without having the winch panel or any extra wiring harnesses that are added in trucks with winch panels)?

TNriverjet · Aug 23, 2017

So LMTV772 (the dude with all the info) is banned? I'd probably buy and install one if we could get a straight answer on the wiring in the dash. Is it there for non-winch equipped rigs?

Suprman · Aug 23, 2017

There is a small harness that plugs into the dash harness and provides the connectors for the upper box switches and tach. It's in the parts tm. All trucks have a pickup the trans control uses it. You can drive a universal tach off the alternator regulator ac terminal.

Reworked LMTV · Sep 16, 2017

Suprman said:
There is a small harness that plugs into the dash harness and provides the connectors for the upper box switches and tach. It's in the parts tm. All trucks have a pickup the trans control uses it. You can drive a universal tach off the alternator regulator ac terminal.

Can I assume this is the terminal on the regulator on top of the alternator? I see that there is some sort of rectifier in the middle of the truck too.

Thanks!

Suprman · Sep 16, 2017

Regulator box on alternator/ Front red terminal is 24v regulation. It divides to do 12v regulation. White terminal on back of regulator is ac output. This can be used to drive a tach.

Awesomeness · Sep 16, 2017

Suprman said:
There is a small harness that plugs into the dash harness and provides the connectors for the upper box switches and tach. It's in the parts tm. All trucks have a pickup the trans control uses it. You can drive a universal tach off the alternator regulator ac terminal.

I haven't had a chance yet, but I want to look through the wiring diagrams and see if there is one for that winch panel harness. I'd like to make a tach harness that performs the same function, but just for the tach without the winch controls. So basically it would plug into whatever connector inside the dash, and provide leads (or a connector, since I have a real LMTV tach) for the tach. Project #62,911 on the list, haha.

Reworked LMTV · Sep 16, 2017

My regulator is a n3030. I note that some of the other posts with regard to tapping the regulator for a signal, used a different regulator. It only has two posts and one military style connector on the front. Do I still use the the white post?

Awesomeness · Jun 28, 2019

Awesomeness said:
I haven't had a chance yet, but I want to look through the wiring diagrams and see if there is one for that winch panel harness. I'd like to make a tach harness that performs the same function, but just for the tach without the winch controls. So basically it would plug into whatever connector inside the dash, and provide leads (or a connector, since I have a real LMTV tach) for the tach. Project #62,911 on the list, haha.

I did finally do this by the way. The plug in the truck's wiring harness is located in a spot right in front of the heater, only accessible by taking all the bolts out of the heater and sliding it forward enough to reach down to the plug.

Ronmar · Jun 28, 2019

I believe the second terminal on the regulator is a sample of the field current being sent to the field winding. It is used to measure how hard the alternator is working and runs to the STE connector... On a 3116 you can sample a tach signal behind the heater or at the small freq divider box next to the STE connector. Sean Filner just documented how to do this in a utube vid this week...

Awesomeness · Jun 28, 2019

Ronmar said:
I believe the second terminal on the regulator is a sample of the field current being sent to the field winding. It is used to measure how hard the alternator is working and runs to the STE connector... On a 3116 you can sample a tach signal behind the heater or at the small freq divider box next to the STE connector. Sean Filner just documented how to do this in a utube vid this week...

There are two models of alternator. The older one, with the N3030 voltage regulator, has the second terminal as a field sense, which isn't going to help drive a tach. The newer alternators have that terminal as an AC line, which will.

Ronmar · Jun 28, 2019

Yea, don't know about the newer models. The only A1 schematic I have which is labeled vehicle S/N 18550 thru 99999 have that second line running to the polarity protection box. I suspect the load control box uses that signal to control the disconnect relays.

STI2NR · Jun 29, 2019

The problem with forums is lots of talk and no action. My goal is to help change that. Here you go!!! BTW I changed the dip switch settings to 134 because of this post... https://www.youtube.com/watch?v=bKs4hFPw7To

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