Charging system woes

[MarcusOReallyus]

Yeah, it's one step at a time.


Hey, just for grins, I looked up a few terminal blocks for you. If you can find an exact match, great, but you can use something that's functionally equivalent, too. For example:

If you want to get fancy, you could use something like the JB4-375-RC on this page. This would allow for future additions.

Or, you could go with a Chevy part that is nearly the same.

Or this.

Or the cheap route.

Or back to fancy. This is a nice setup. If'n t'were me, I'd do that in red, since it's a hot point.


Anyway, you have lots of options.

By the way:

The 24v resistor bank is completely gone, and there is a lead coming from the jumper battery cable that supplies 12v to the glow plug relay.

Is that lead fused in any way? Fuse, fusible link, or breaker, you really need one of them. The GPs draw 100 amps when operating (measured by member antennaclimber a while back), and you really need to have that circuit protected.

You can take a look at how I did it. It's overkill, but I like overkill.

 

[tim292stro]

I may have fixed the charging issue...

Yay!

...Drivers side alt is producing 12.5 - 13 volts. Pass side producing 27-28 volts. Battery front reads 12.8, back battery reads 13v. Across both is 28 and some change...

If you give it some time during run it should "earn" its way to 28.8 - remember that the field coil in the alternator gets its power from the same battery, as the battery gets charged the power (Volts * Amps = Watts [power]) increases and the alternator can make more power at the output.

...However, Gen 1 light stays on. The brake light indicator and low coolant light stay on as well.

Try the test lamp at the Gen1 alt, if it goes out while the engine is running (may take up to 15 seconds after the lamp is connected), and you see the 12V battery starting to charge (climbing from 13.5 up), the alternator is probably fine. Have you checked your fusible links yet? Some people think they are just wires, but they re designed to blow like a fuse - they are just harder to tell when they've blown.

Glad to hear you're making progress!

 

[frontiersman]

To do this test, while engine is running, I clamp the negative lead to a ground, and hold test light on positive output on alternator? In theory, if alt puts our beyond what the test light is (12v), it should go out?

 

[frontiersman]

Also, should I have the voltmeter hooked up as well? No on the fusible links....haven't been educated enough to move on to those lol.

 

[tim292stro]

To do this test, while engine is running, I clamp the negative lead to a ground, and hold test light on positive output on alternator? In theory, if alt puts our beyond what the test light is (12v), it should go out?

Connect from the output (+) to the idiot light lug - going from positive-output to ground is really just testing that the battery is there .

Also, should I have the voltmeter hooked up as well? No on the fusible links....haven't been educated enough to move on to those lol.

You can do the voltmeter across the ground to positive-output (still need the battery hooked up), this will tell you if your alternator is putting out a charging voltage. You need to look at your fusible links as well, take a moment to learn about them, they are kind of like a floodgate in your electrical system - if they blow they represent a "dam" in your electrical system preventing the flow of power, and when in good repair they allow electrical power to flow.

If you think about it the charging system is fairly easy to diagnose, there are only a few areas where the failures can happen:

1. The alternator
   • Could be brushess if not brushless (cheap)
   • Could be the regulator (internal or external - fairly cheap)
   • Could be the rectifier array (fairly cheap)
2. The idiot lamp
3. The wiring
   • Includes the fuses and fusible links, as they are there to protect the wires
4. The control (ignition switch or relays)

This is why I advocate with electrical problems that you should check your major components for function first, you'll never know if you are wasting your time on the other stuff if you don't know if the alternator is good. Same thing for the idiot lamp, and control. If you know your alternator works, your idiot light is good, and the control is doing what it's supposed to, that only leaves the wiring to troubleshoot.

 

[frontiersman]

Ok, another dumb question. Which lug is idiot light?

 

[tim292stro]

There should be a two wire plug with a brown wire coming out the top of the alternator - the brown wire is the idiot light. Keep in mind that to get the alternator to start charging, you might need to rev the engine a bit (sometimes idle doesn't cut it).

 

[Warthog]

There is a good tutorial in the CUCV Helpful Threads sticky for fusible links. It also lists all of the fusible links on the truck.

Listen to tim292, he is a very smart cookie when it comes to electrical work.

 

[frontiersman]

Gen 1 is going bad. Did the above test on idiot light with engine revved, test light never went out. Max output is 12.5-13v. Since this is the driver side alt, does it have to be isolated ground? If not is there a good substitute I can get? If is has to isolated ground, can someone recommend a place I can ship to so it can be rebuilt (nowhere around here that rebuilds starters or alternators). Thanks.

 

[tim292stro]

Did you do that with the two wire connector fully pulled out? I admit I should have been more clear and if I wasn't it's my fault - the other wire in that two wire connector is also required for operation. It should be pulled to the same voltage as the output of the alternator.

There is a fusible link from that terminal to the 12V block that has been removed from the firewall in you earlier pictures - there is a larger fusible link from the Output terminal to the same block on the fire wall. For a short manual test, you can get away with jumping that second terminal (I believe from memory it's a red wire) to the output terminal. Test this first before throwing in the towel on the alternator.

The test light from output to the idiot light terminal tells me that the output fusible link is probably good (or at least less likely to be your cause).

A rebuild kit for these alternators is pretty cheap (found one kit for $25) - and anyone with basic mechanical skills and hand tools can install it - all the instructions are in the TM (here's another link) you've downloaded and read by now... right? It is true, the low-side (GND-12V) alternator does not need to be isolate, but if you keep it that way, should you kill the high-side (12V-24V) alternator you'd have a "spare" isolated alternator to swap over if you can only find a non-isolated alt in whatever local store you're near.

 

[tim292stro]

For your convenience, I've taken the TM diagram I posted in post#5, and erased everything but the stuff we care about for this problem.



You'll note there are 4 wires coming out of the alternator, a black Ground to the chassis, a thick red Positive 12V from the output terminal, and two wires in the two-pin plug - the brown goes the idiot light, the thin red is the power for the regulator itself.

 

[Warthog]

Frontiersman please forgive us as we have forgotten to ask some basic questions. Sometimes we take it for granted.

1. What are your mechanical skills?
2. Do you have the basic understanding of electrical principles?
3. Can you read a wiring diagram?
4. Have you downloaded the technical manuals?
5. Have you read the first few pages of Section 2 of the TM 9-2320-289-20 or the TM 9-2320-289-34 manual? This explains how to read the wiring diagrams.

 

[frontiersman]

Warthog, I have owned and restored 2 1943 jeeps (one an MB and the other a GPW). I am a Registered Nurse, very little electrical knowledge. I finally got all the TM'S downloaded last night, as my service here is slow. You guys have been patient with me, I know, and thanks for that. Luckily there is a member who lives nearby (rlltide97) who brought his yruck back to life like I am doing. He is going to help me get the butchered wiring straightened out (thank goodness). With your guys help, I have brought this truck from being a wasp heaven to where it is now. It is soooo close to being right lol. Again, thank you to everyone for all the help.

 

[frontiersman]

rlltide12, sorry lol

 

[frontiersman]

Last update. Gen 1 was bad. I replaced it with part number 01-0136 from O'Reilly's. It has a lifetime warranty and is a 100 amp. I had to swap pulleys, and use the original spacers to get the belt lined up. It's working like a well oiled sewing machine, no idiot light, putting out correct voltage, etc. Thank you to everyone for the immense help and patience. On a parting note, if anyone has a spare 12v junction block, I would like to buy it and pay shipping. Want to keep it as stock as I can.

 

[Warthog]

Did you keep the old unit or trade it in as a core?

 

[frontiersman]

No, I kept the old one. It's an original isolated ground unit. When funds permit I am going to have a reliable shop rebuild it for a spare.

 

[MarcusOReallyus]

Rebuilding one is brain dead easy. On Warthogs recommendation, I got a kit from ASP Wholesale, and did it myself. Both of them. First one took about 45 minutes, because I was taking it very slowly. 2nd one was about 20 minutes, IIRC.

It's a good winter evening project.

BTW, the kit I got came with the wrong capacitor. It was square. Now their webpage is calling out a "Heavy duty 1.5Mfd Barrel type Capacitor". That sounds right, and the picture looks right, but call to be sure.

While I was at it, I picked up a hardware kit, too. I did use a few pieces from it. Could have gotten by without it, though.

 

[tim292stro]

I'm glad you're in good shape now. Thanks for closing the loop on this, so often on forums help is extended to someone, but no one ever tells us what happened....

Again, congrats on the fairly cheap fix to the factory wiring!!