I pulled the regulator off the firewall last night and those two resistors checked out. The other thing I found odd is that both the armature and field wires coming off the generator have continuity to ground. May be normal, but other than the wiring diagram I don't have a lot to go off of.

The amp clamp is an AEMC model 407 FYI

Thanks

 

Thank You Landro!

Yes sir, you're correct, with the Regulator disconnected from the generator you will see continuity while measuring for resistances between the generators Armature or Field terminals to ground. In post #11 you tested the Generator by shorting the field connection to the battery connection at the voltage regulator and while monitoring the battery voltage you saw it increase to 8 volts. So that tells me, and maybe only just me as in I could be wrong, that there is a problem with the Voltage Regulator as you took it's regulation part out of the circuit and you took control of it for testing. But then when reconnecting the Field wire back to the Voltage Regulator, it was back to the battery voltage of 6.3 volts instead of around 7.3 volts. I wish there was another good voltage regulator around you could swap in to test with.

About your DC amp clamp meter. Yes, it is good for DC. It's a Nice, nice unit. Here's the link below and if you download the pdf on page 32 it gives directions on how to set it up for DC current measurements.
But you probably already know that.

https://www.aemc.com/userfiles/files...ers/407_EN.pdf

Good Luck and let us know how you came out on this.
One other thought:
Is it just the light the picture was taken in? These contacts look burnt. If they are that will keep you from getting current to your field windings.



These look burnt. Maybe high resistance here.

 

Quick follow up. Ran the truck last night and checked the voltage at the three terminals on the regulator around 1500-2000rpm. Battery terminal was battery voltage as expected. Field was 2.2 volts, and the armature was 4.1 volts. The referenced points look burnt from the lighting, but they're all brand new looking.

Thanks

 

What are the results of the these two service manual tests in Part 3, Chapter I, Section 1.a:

Generator Output Test on the vehicle?
Open Circuit Test of the Field on the vehicle?

 

Thank you for the follow up! Showing 4.1 volts on your armature and the resulting 2.2 volts at your field terminal tells me your cut out relay, (the one on the right above the BAT terminal) is not closing so it's not connecting the battery to the generator. If it was closed you would see over 6 volts at your armature terminal and somewhere around 4 volts on your field I believe. Why won't it close? Maybe 2 reasons. 1. The generator could be weak and its not generating enough current to pull the cut out relay in. Or #2, The generator is good but
the cut out relay contact return spring has too much tension and the available current can not over come the spring tension to pull the contacts in.

In the post above Brian made some good suggestions about going to the manual and doing a generator output test, and an open field test. Both of these are great indicators of its health and if the generator passes then that will point further towards a voltage regulator issue which I think will bring you to looking into the cut out relay spring tension adjustment.

I wanted to mention too, if you do these tests, on the generator output, it may have you short the Arm and Field terminals together and connect that to the ARM connection of your voltage regulator. IF it fails, and you dont see 35 ish amps at your amp clamp, move the wire connection from the voltage regulator ARM terminal to the Batt terminal and test again. If you now have a good current reading from your generator, you know the voltage regulator is not working properly and maybe its a cut out relay adjustment.
And whenever you have the cover off the voltage regulator, it won't work properly. The cover needs to be on after any adjustment to really see if its right. Has to do with the internal magnetic fields that are developed inside the voltage regulator. Its a lot of take cover off, make adjustment, cover on, rev motor, take a reading, cover off, make an adjustment, cover on, rev motor, take a reading, etc...

Thanks!

 

A simple way to bench test the cut-out relay:

Remove the regulator from the vehicle. Connect a variable DC power supply to the regulator with the positive output to the metal frame of the regulator. Connect the negative power supply lead to the ARM terminal on the regulator. Connect a volt meter to the metal frame of the regulator and the BAT terminal. Slowly increase the voltage on the variable power supply. When you get somewhere between 6.0 and 6.6 volts on the power supply, you should hear the voltage regulator click once and see the separate volt meter match the power supply output. The moment the clock happens and the separate volt meter registers, that voltage should be between 6.0 and 6.6 VDC. Outside of that trange and the cut-out on the regulator needs to be adjusted accordingly.

 

Jumping the gen output to field terminal got it charging at 8+ volts and 35ish amps so that really only leaves the regulator which is new or the wiring which seems to be correct.

Thanks

 

I think I have a DC power supply laying around, I'll give this a try to isolate the regulator.

Thanks

 

Hooked up the DC power supply as you described and was able to get the cutoff relay points to close at around 6.2ish volts. When everything is back on the truck the point are definitely remaining open. I even manually tried to close them and the voltage didnt increase.

 

Glad to see that the cut-out relay tests ok appropriately.

When it is back on the truck, what voltage do you have between the regulator frame and the ARM terminal?

 

Around 4.4

 

4.4 Volts is not enough to trigger the cut-off.

Taking a stab in the dark here - can you overlay a jumper better the generator and regulator Field terminals and see if that makes a difference?

Then move that overlay to go between the generator and regulator ARM terminals and see if that makes a difference?

Then again with both overlays?

 

Great tests!

If adding those jumpers don't give you good results let's double check your voltage regulator ground at the cab. I would just run a test jumper (test clip lead even) between the voltage regulator base and your + battery ground terminal. If that helps, then you'll know you need to add a ground between where your battery ground cable connects to the engine block or frame and your cab or better yet your Volts Reg base. You would think the ground wire you have right now that grounds the regulator base to the generator would take care of that, but maybe there is a bad connector at either end or an open in wire itself or maybe poor electrically connecting generator mounting bolts but you were showing 8 volts at near 35 amps full fielding your generator so I would doubt it's that.
If its not a bad ARM or Field wire, then the Generator ground to the regulator, or the regulator ground to the battery are about the only two things left I think.

 

As for the ground, I believe the factory wiring harness has a dedicated ground to ground between the generator and regulator. I guess we can add that to the overlays to test as well...

 

I overlaid a jumper from the field to field, arm to arm and ground to ground and didn't see any change. There is a dedicated ground wire going to the regulator but I also made sure there is bare metal on the firewall to ground to. The generator output is still only 4.4 volts at charging rpm right at the generator arm terminal.

Thanks