Just bought a 1998 lmtv

[Deftonez]

Hello everyone first time posting and newbie to the site. A couple weeks ago I won an auction for a 1998 m1078 up at fort Hood Texas and I am currently driving it from fort Hood to Sacramento, CA. Currently having 2 issues:
1. Truck is running kind of hot today it has been spiking to 230 then very slowly going back down.
2. Main problem is the truck doesn't seem to be charging. Currently it is at 22 volts and last night when i was driving and pulled into the hotel I couldn't start the truck unless I did the starter relay trick. Also when we mess with the exciter relay by pressing the contact it drops by 1/2 a voltage same if we pull the relay out. There is also 22 volts on 4/5 contacts except the bottom leg.

So my question is, is it the voltage regulator, or the generator, or some other people I haven't read about? We are currently in New Mexico making our way to Phoenix hopefully to stop for the night by midnight.

 

[Rmtaunton]

Hopefully Andy will see this he is a guru on these things and good luck and have fun on your adventure


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[Coffey1]

Check the relay make sure it's the correct one.
Pull it out and see if it has five or 4 blade contacts and correct voltage relay

 

[Deftonez]

Check the relay make sure it's the correct one.
Pull it out and see if it has five or 4 blade contacts and correct voltage relay

Yeah I did check and it is a 24v 5 prong and I did switch it out with a couple of the other 5 prong 24v relays

 

[Suprman]

Excite wires go bad. Remove both regulator wires tape both off. Run new wire from fuel solenoid positive to front regulator terminal only. Do not connect anything to back regulator terminal.

 

[Deftonez]

Thanks for that info... I will have to pull up the TM when we stop for the night and try it out

 

[Coffey1]

There's also fuse links on alternator that look like washers they might be faulty.

 

[Coffey1]

There's also fuse links on alternator that look like washers they might be faulty.

 

[DigDirt]

Excite wires go bad. Remove both regulator wires tape both off. Run new wire from fuel solenoid positive to front regulator terminal only. Do not connect anything to back regulator terminal.

What gauge wire do you recommend when rerouting excitation wire from fuel solenoid to regulator?

 

[Suprman]

Dosnt need to be thick. Its basically just a signal. I usually use a piece of old harness from one of my parts trucks.

 

[Reworked LMTV]

Have you or anyone done this fix? Sounds like the replacement nut is special?

View attachment 693409There's also fuse links on alternator that look like washers they might be faulty.

 

[Suprman]

I have never seen a truck with the fuse links at the alternator. You would be able to verify outputs at the two alt terminals with a multimeter and then go from there. Without 24v at the regulator excite terminal the alt will just spin but not make power.

 

[Reworked LMTV]

You may have a blown head gasket.

 

[SausageGuy]

The spiking to 230 then going down slowly sounds more like a thermostat or water pump issue.

 

[Floridianson]

If I remember my gage was reading around 230* and cycling. Checked system with IR gun and gage was wrong and truck runs great.