m1008 voltage gauge in the yellow on start, is that normal?

[Barrman]

The only time my 1009 has not started was when I was 60 miles away in the family Suburban with my Scouts and Jennifer had to run to town in the 1009. I could hear the glow plugs cycling on the phone and the starter turning and turning and turning and turning. It made me hurt having to listen to the abuse it was taking. I had her turn everything off, get out of the truck, walk to the mail box and back. Then reach in, turn on the key, let the plugs cycle and then hit the starter. Fired up within a second. I don't know what she was doing, but that is how she starts it now. From outside the truck.

Some people just need modified starting procedures.

 

[maxpanic]

Sorry, for some added confusion, just to clarify. The truck will start, the gauge just won't leave the yellow. The gen 1 and 2 lights stay all the way on while it runs. The horn doesn't work nor do the lights, headlights, tail lights or turn signal lights even when I turn on the dash switch to activate the running lights. Turns out the only thing she did different that I do is she turned on the cabin fan in the hopes of cooling herself off in the hot sun. Must have been a funny sight, I avoided doing that cause I didn't want a face full of dust. Anyway, I think something in the cabin fan being on might have disconnected the alternator part of the system from the rest of the system? I checked the isolated ground and it is still isolated from regular ground. What typically goes out when you play with the cabin fan?

 

[maxpanic]

Oh, and whats TM has the best electrical troubleshooting schematic please?

 

[Barrman]

The -20 manual has a huge 70 some odd page electrical troubleshooting section. Does the heater fan still work? The fuse for it also is part of the charging circuits. Check that fuse and the very bottom fuse on the box which is the 24V fuse for the Alt 2 circuit.

follow the -20 and let us know what you find.

 

[carctruck]

The red/yellow/green/red military voltage gauge is really pretty neat. I can't remember which TM has this listed out, but one of them for one of my trucks does. Pretty much, here is what the colors mean.

Low red= below 18 volts

yellow=18-25 volts

green=25.2-30 volts with the little tick in the green at 28.8 volts.

upper red = above 30 volts.

Just turning the key on with good batteries should be in the upper yellow because 25.2 is what two fully charged batteries are supposed to be. This is basically what the yellow/green line shows. The glow plugs pull a lot and will drop the gauge down to mid yellow normally.

I just read your post and wanted to write that I had a similar issue, my gauge has always read in the upper green, in fact it seemed that my batteries were seeing some over voltage at the same time my gen 2 light was flickering, never did anything cause nothing ever went dead. I recently fixed a glow plug issue where the glow plugs were just cycling on and off after start for a while, now my voltmeter reads exactly like you said it should and my gen 2 light has stopped flickering.....neat?

 

[overkill375]

sometimes fixing one thing fixes another, sometimes fixing some thing causes other problems. old MV trucks are tempermental (but fun)

 

[maxpanic]

alright, I am going to change the glow plugs, I will use the AC 60G and grind off the .050 width that is to wide for the clips.

 

[M1008driver]

I will use the AC 60G and grind off the .050 width that is to wide for the clips.

I would take the time to put some insulated connectors on there of the right size. The reason is these systems are old and you will probably get better results with your new 60g's. I did. NAPA has them.

 

[maxpanic]

That's a good point on the glow plug clips. Do you have a NAPA part number you can recommend?

I changed the glow plugs and my situation is still fairly dire on my m1008. I pulled both alternators and I rebuilt the drivers side one after rebuilding the passenger side one a little while back.

My symptoms at this point include the following after re-installing the alternators.
1. gen 1 light stays on.
2. if I turn on the service lights switch the horn honks and stays on until I turn off the service lights switch on the left side of the dash.

Any one have any clues? I will continue the troubleshooting on Tuesday. I am thinking of buying a new alternator at 108 amps from autozone to see if that will make the light go out, maybe I messed up on the rebuild? I doubt it. I got the first one right and the second one should have been easier. couldn't hurt other than the wallet to buy another and put it in and then I would have a spare.

Thanks All!

That is all I know at this point.

 

[Barrman]

The horn problem is more than likely the button on the steering wheel.

Did you test the components inside the alternators? What was wrong?

 

[maxpanic]

I took out the alternators and had them tested at my local rebuild shop. They work fine both with isolated ground. I did have some grounding issues and got some of those fixed. Now I am down to two issues only.

1. The horn is always on if I turn on the service lights switch, even after I removed the horn switch internals on the steering wheel. So I dug into the TM, 9-2320-289-20. On page 2-69 it tells what to do if the horn is always on. Remove the relay, Then it references paragraph 4-22 to tell the location of the relay. It shows the wires coming out of the top of the fuse box and right off of that wiring harness there is the relay. I have something in that location that looks like the relay so I removed it. The horn is still always on. Then I pulled the horn fuse, that worked and prevented the horn from turning on. To me this makes no sense and I am doubting that I have correctly located the relay. Is there anyone that can verify the horn relay location?

2. The gen 2 light never comes on. I switched the light bulb with gen 1, gen 2 still won't come on. again I went into the TM. on page 2-59 it mentions what to do if the generator light won't turn on when the ignition switch is in the on position. It says to trace the circuit. It also references F-11 for the schematic. The schematic shows a diode that seems to be inside the cab and has brown wires coming from it and going to it. Can anyone tell me where this diode is?

Thanks,
Max

 

[Terracoma]

The schematic shows a diode that seems to be inside the cab and has brown wires coming from it and going to it. Can anyone tell me where this diode is?

Photo credit goes to Warthog.

 

[firefox]

You made a comment about both generators being tested with isolated ground.
Only one of the generators is supposed to have the isolated ground. The one that feeds the
rear battery.
Bruce

 

[maxpanic]

I believe they are both isolated ground type alternators with gen 1 taking its isolated ground to chassis ground. Is this incorrect?

 

[maxpanic]

Thanks for re-posting warthogs photo terracoma, that helps a bunch on my item number 2.

 

[doghead]

I believe they are both isolated ground type alternators with gen 1 taking its isolated ground to chassis ground. Is this incorrect?

Correct

 

[firefox]

My understanding has been that the generator is the same, but the isolated
ground kit is added to gen2. This is the way they come from the factory.
I don't see any reason why you couldn't bypass the isolated ground and use an
isolated ground wired generator for gen1. Just more parts.
Bruce

The reason I brought this up is because I don't believe there would be a ground strap there on the original truck, so unless someone before you has added one, you would need to do that, which I assume you have, but someone latter reading this might
be mislead and not check for one.

 

[tankie88]

My horn didn't work once.It was the the connection on the horn it self had oxidized.

 

[maxpanic]

so I located the diode and used the diode tester on my digital multi-meter. it cam back as .523 instead of what I would expect at .7, seems like the diode may be good still though, anyone have thoughts on that?

I would also like to know if anyone can tell me where the gen-2, passenger side alternator relay is?

 

[Warthog]

so I located the diode and used the diode tester on my digital multi-meter. it cam back as .523 instead of what I would expect at .7, seems like the diode may be good still though, anyone have thoughts on that?

I would also like to know if anyone can tell me where the gen-2, passenger side alternator relay is?

Switch your leads and see what the reading is. It should go to infinity (and beyond..... )

The GEN2 relay is under the dash, along with the Voltmeter relay and Starter Relay. All three should be attached to a metal plate just above where the ICE/STE Cannon plug is in the center of the lower dash.

On the horn, there is a diode on the back side of the horn relay that are know to fail. This causes the horn to be on all the time.

The horn relay is above the fusebox.