Need charging system help.

kpsanborn · Post by **kpsanborn** » Wed Jun 04, 2008 3:35 pm

I do not believe my charging system is working. My year old batteries are not holding a charge. When the M38 is running the ammeter shows no charge, but will show a discharge when the lights are turned on, throttling up makes no change. I have had the generator to a repair shop and it tests out OK. I hooked up another regulator (yes I grounded it) with no different results. I found my main ground point a little rusty and cleaned that all up. Anyone with any suggestions? The weather is nice, and I would like to be using the Jeep!

Post by **Ryan_Miller** » Wed Jun 04, 2008 6:58 pm

Did you polarize the generator?

Wes knows a lot about the electrical systems, he should be around to offer advice in the next day or two.

kpsanborn · Post by **kpsanborn** » Wed Jun 04, 2008 7:52 pm

I have attempted to polarize it, but may not be doing it just right. Someone who absolutely knows the technique would be great help.

Post by **Ryan_Miller** » Wed Jun 04, 2008 8:15 pm

If I understood Wes correctly take the gen to reg cable off at the regulator, then insert a wire in the B hole and lightly touch the terminal of the starter that the battery cables connect to.

Wait for Wes to correct me on this in case I am wrong!

Cacti_Ken · Post by **Cacti_Ken** » Wed Jun 04, 2008 8:39 pm

I copied these instructions from Wes awhile back and saved them.
Ken

Polarizing 24 Volt Generator / Regulator

On 24 volt M38 / M38A1 / M170 / M606

"Disconnect the Gen-Reg Cable at the generator end, note where the alignment lug is (where the slot on the plug of the cable lines up) on the top of the elbow on the Generator. There are three terminals in there, you want the "B" terminal, it is the lower left when looking in to the elbow, and is actually marked. Take a Jumper from the "B" terminal on the generator and just only one time just quickly brush the hot terminal on the starter."

Post by **wesk** » Wed Jun 04, 2008 11:19 pm

Those directions are correct. The end of the cable at the regulator allows you to use a shorter jumper wire. No matter if you use the cable end closest to the regulator or the top connector on the generator you must use the "B" pin that connects to the generator field.

Also you should invest in a digital VOM (Volt-Ohm Meter) and monitor your voltage not your amps. With engine at idle you'll read about 24 to 25 volts. At 1200 RPM you should start reading 25 volts or higher. At 2500 to 3000 RPM you should read about 28.5 volts.

kpsanborn · Post by **kpsanborn** » Thu Jun 05, 2008 11:52 am

I did the polarization process as directed. I do not have a digital meter, so used my needle meter. Here's what I got: Jeep not running: 22.5 volts, idling: 22.5 volts, high RPM: 22.5 volts.
I disconnected the output cable of the generator and measured voltage output by putting my negative lead in the B terminal then positive lead in the A and C respectively. Should this show me voltage readings? I was seeing 1.5 volts from each of those readings. I tried to check amps, but blew the internal fuse in my meter.
_________________

Post by **wesk** » Thu Jun 05, 2008 10:37 pm

It's now time to sort out which unit is bad.

Disconnect the generator to regulator cable at the generator.

Connect the positive lead of your meter to either A or C pin on the generator. Connect the negative lead to the generator case.

Connect a jumper wire to the B pin. Start the engine. Now while observing your meter touch the other end of the jumper wire to the hot terminal on the starter switch. Only do this for a few seconds with the engine speed at about 2000 RPM then quickly remove the jumper wire from the hot starter switch terminal.

If you got an elevated voltage reading above 26 volts then the generator is ok and the regulator needs work. If you still get nothing over system battery voltage (22 to 24) then the generator needs work.

I would suggest that at this point you remove both the generator and the regulator and take them to an automotive electrical repair facility for proper bench checking and repair.

kpsanborn · Post by **kpsanborn** » Thu Jun 26, 2008 6:38 am

After checking the truck out with my friend we decided that even though the belts were adjusted as described in the operations manual, they probably were not tight enough. One reason we thought this was because when doing the generator output test, the belts would start to squeal. As the adjustment was at its' maximum I picked up a couple of new belts, and after putting them on, showed charging on the ammeter. Two weeks of troubleshooting, for a simple problem.

Post by **wesk** » Thu Jun 26, 2008 12:06 pm

We are all guilty at one time or another of "Not seeing the forest for the trees". We often get swept up in a posters problem and ASSUME he has already checked all the basics. We often ASSUME he has posted here because he already ran the trouble shooting chart in the manual and it didn't solve his problem. We often ASSUME the poster has a mechanical skill level higher then he actually may have.

And we all know the many descriptions of the word "ASSUME".

dweeb · Post by **dweeb** » Wed Jul 23, 2008 9:28 am

Does anyone know how a 24 volt voltage regulator mounts in ? I have a project m38 that is in a pile of parts. Also is there a way to use 12 volt gauges on a 24 volt system Pictures would help
Thanks

Post by **Ryan_Miller** » Wed Jul 23, 2008 10:00 pm

The reg mounts on the passenger side frame rail in front of the tub, under the air cleaner and right behind the front battery box.

On the welded frame bracket is bolted on a splash sheild, then the regulator grounding brackets (cad/silver color) then the regulator.

Photo is courtesy of Ben Daugherty.

Post by **wesk** » Wed Jul 23, 2008 10:05 pm

If you absolutely cannot not afford to put the correct elctric 24 volt gages in the dash and you want to use 12 volt gages you are creating more work than you want. I assume you are keeping the jeep 24 volt since you are asking how the regulator mounts. If I were in your shoes I would install standard civilian mechanical gages. Makes no difference what system voltage you have since they don't use the vehicle's DC voltage to operate. The water temp gage will come with a capillary tube and block fitting permanently attached and the oil pressure gage will come with a tubing kit and adapter fittings for the block. The gas gage is the only real problem since the only options are original 24 volt electric or civvy 12/6 volt electric. If you already have the 24 volt tank sender unit then you should shop for a used 24 volt gage. You can install a matched civvy set (gage & sender) but you will have to feed it power separately from only one of the batteries. The 24 volt late M series volt meters will fit right in and are reasonably priced. Or you can leave the 24 volt amp meter since your vehicle system is still 24 volts.

The voltage regulator is mounted on four rubber insulators with ground/bonding straps which are mounted to two long flat brackets which are mounted to the top of a flat steel splash plate which is mounted on top of two "L" brackets that are welded to the right frame rail just forward of the firewall.

Here you see the regulator bolted to it's four flexible rubber mounts and its two flat metal strips with bonding straps at each of the four mounts.

Here you see the front of the complete mounting.

Here you see the "L" brackets just behind the battery tray.

Here you can see the tray.

Need charging system help.

Need charging system help.

problem solved