LMTV dash Voltmeter is bad

[tennmogger]

My dash voltmeter in the LMTV dropped from 'correct' to 'not correct' on a trip. Turning off the truck indicates the 'not correct' reading is same as powered off. The voltmeter is dead.

Just as a sanity check, the voltage was checked at alternator output, and is good. Tested at 24 v terminal in the Power Distribution panel shows correct voltage.

A DVM probe into the meter's disconnect plug, truck side, showed correct voltage'.

Took the voltmeter out and tested it on the bench. Yup, inputting 28 vdc to black and red terminals does nothing, and no resistance between those terminals either. The lamp in the meter works just fine.

Looks like the meter movement has opened up. Has anyone done a bench test on a voltmeter? If that worked, please let me know.

Any spares around? On second thought though, this is a good time to install a more accurate meter, and to add a 12v circuit voltmeter.

This is what I am ordering:

https://powerwerx.com/panel-dual-volt-meter-red

I'll have to make a couple of adapter plates to mount the smaller meter. A photo will be added when it's done.

 

[Suprman]

Thats pretty neat. I have gone thru alot of voltmeters in various trucks.

 

[simp5782]

My dash voltmeter in the LMTV dropped from 'correct' to 'not correct' on a trip. Turning off the truck indicates the 'not correct' reading is same as powered off. The voltmeter is dead.

Just as a sanity check, the voltage was checked at alternator output, and is good. Tested at 24 v terminal in the Power Distribution panel shows correct voltage.

A DVM probe into the meter's disconnect plug, truck side, showed correct voltage'.

Took the voltmeter out and tested it on the bench. Yup, inputting 28 vdc to black and red terminals does nothing, and no resistance between those terminals either. The lamp in the meter works just fine.

Looks like the meter movement has opened up. Has anyone done a bench test on a voltmeter? If that worked, please let me know.

Any spares around? On second thought though, this is a good time to install a more accurate meter, and to add a 12v circuit voltmeter.

This is what I am ordering:

https://powerwerx.com/panel-dual-volt-meter-red

I'll have to make a couple of adapter plates to mount the smaller meter. A photo will be added when it's done.

I run the single output of one of those digitals. It works well and is only a .2 or so volt off generally. It has given me 2yrs of trouble free use.

 

[FloridaAKM]

My voltmeter is wonky also as it indicates in the green till the engine warms up, them drops into the yellow zone. The voltage @ the slave port shows 26.8 volts during this same time frame. If the lighting control is switched to service, powering up the headlights & associated markers, the voltage goes in the lower green area. While driving the truck, the voltmeter indicates the same voltage. It is probably time to change out the voltmeter with a known good one or the one that tennmogger referenced.

GO AWAY DORIAN!

 

[Ronmar]

I am going to go with a single digital 0-30V and a switch to go between 12 and 24.
FloridaAKM I would say you have an alternator/regulator problem or a connection issue. 26.8V is not a good running voltage(should be 14.5/29V). 26.8 divided by 2 is 13.4V which is barely above a 24/7 float voltage for a 12V battery(the gensets I maintain run 13.2 24/7). You would have to run a whole lot of hours to charge your batteries. Low state of charge is probably the biggest battery killer out there...

 

[FloridaAKM]

I cheat by making sure the batteries are fully charged by connecting a Genius charger thru the slave port & letting it stay there till there is nothing but a solid green or slowly pulsing green light. This keeps the batteries hot & not sitting with a low charge that will eventually kill them. This is done monthly, or when I finish running it to make sure I don't kill the batteries. I will checkout the regulator/alternator to make sure they are performing up to par. Thanks for the info!

 

[coachgeo]

I cheat by making sure the batteries are fully charged by connecting a Genius charger thru the slave port...

you got a thread on how you wired this up and what genius charger you used for this?

 

[FloridaAKM]

No thread, just bought a Genius 7200 charger & plug a bolt into the positive center of the slave port & connect the positive lead to the bolt. The negative lead goes to the ground bolt on the side of the slave port & plug in the charger. Set the charger for standard or AGM batteries & let it do the rest of the work. I could buy a low amp plug & use it, but the other two deuces have a different two pin port on the slave port, so a smaller bolts work there too. I am too close to retirement to continue spending lots of money on stuff that is not utilized that often.