Squealing belt / charging issue

1984 M1008.

When I bought the truck, the driver's side alternator belt squealed and was being eaten. I replaced it and it stopped - for a month or two. The truck has always started like a champ. Never sluggish at all. All electrical components work as should.

Suddenly, I get a sluggish - almost not start. Truck ran fine for a few hours, then, barely enough to turn it over. I jumped it, and everything seemed to be just fine. When I have enough electrical things on (heater blower, headlights, etc.) the driver's side alternator belt squeals. Truck needs jumped every time basically. Batteries are from January 2018.

One of my Gen lights (I forget which) never comes on. If I understand correctly - is there a chance that I have a poor connection near the gen light that is interrupting the other alternator from charging the rear battery?

If I have half a grasp on it, that would explain the sudden dead battery for starting, never seeing the gen light, and possibly causing the other alternator to work harder and squealing the belt.

Or, perhaps I am way off base and sound like a wacko. I dunno - but help.

I am getting a block heater to eliminate as much glow plug use as possible (I have a button to manually activate the glow plugs btw, not sure of what exact setup I have).

Lastly, I am going to start replacing every bulb that I can with LED ones (I do understand that the Gen lights must stay incandescent so as not to interrupt the circuit)... a list of all the factory bulbs would be helpful (I'm not sure how many lights are under the dash, if there are any in the 4wd shifter, etc..)

I did search the site, but get conflicting understanding of some of this.

No gen light means no power from that alternator...

Check your voltage at each battery running

Figure out what gen light is not coming on...

The -20 manual for the CUCV has a great 74 page electrical troubleshooting section. The very first thing it says for any electrical issue is to load test your batteries and make sure they are charged. Please do that first because everything else is dependent on them being good.

You wrote that a new belt made it all good for a few months. What kind of belt did you put on? I ask because my trucks eat belts like a dog gulping down a treat. Except for Gates belts. The NAPA version of Gates works as well. I have found all the other brands just don't last. It might be as simple as a new belt again. But, load test the batteries and get them charged before you do anything else.

The -20 manual for the CUCV has a great 74 page electrical troubleshooting section. The very first thing it says for any electrical issue is to load test your batteries and make sure they are charged.

I agree. And you can read it all day. No where in that entire book does it at to bypass the resistors on the firewall. When you do that you pull all the voltage/amperage from the glow plug use out of the front battery during cold start and thus the drivers side alternator is forced to resupply the voltage/amperage back. I don't care to argue about it. But the fact remains I have been running them stock all these years and have had minimum issues. I changed a few glow plugs. Nothing that strikes me as unusual for an old Diesel truck. But I still sell/trade people here and other places for the resistors. I have never had any just go bad for me and if I have a bad glow plug I change it. I use 13G AC Delco that are made in Italy now. Just saying. The manual is hard to follow if you delete sections and ignore the specific details of diagnosis. Have a Happy Thanksgiving. Stay warm. I hear tell it is supposed to get very cold for the weekend. Maybe. I have work to do in my shop this weekend same as always.

I don't doubt what you say about the plug system. I have zero knowledge of the system as is or altered. I just know that it was altered when I bought the truck.

I don't know what the advantages or disadvantages are to either side of the argument or how to restore it to factory setup. Perhaps another project.

Gen 2 light never comes on. Gen 1 is on when switch is turned. Gen 2 bulb and socket checked for continuity and are good.

Is this a stock 24 volt setup?

If so, both gen lights need to come on or else the generator will not get excited and will not output. No reason to load test a battery that is not being charged.

If you can take a few pics... of the batteries, alternators, and air filter housing firewall area.

As far as I know it is all stock. The only thing I did was reconnect the slave port, as the wiring was missing. I'll try to get some pictures up.

If you are sure it is stock... I would start with the gen light... ya it won't have really too too much to do with the belt issue on gen 1 but... its a major issue you have 1 battery not charging or charging intermittently...

Here is an update:

The front battery tested at 14v. The rear at 9v. A buddy works at a parts store and checked them with a tool. He hooked it back up to the rear battery while the truck was running and it indicated a bad voltage regulator. Also, both alternator belts are a tad loose. So, I'm replacing the passenger's side alternator and tightening both belts. We'll see. Best case - that fixes it. Worst case, I replaced a 34 year old alternator before it did go bad.

Though, continuing to learn - will the alternator in this link work? If I understand correctly, the alternator needs to have an isolated ground? https://www.oreillyauto.com/detail/...984/chevrolet/k30-pickup-4wd?q=r111666b&pos=0

If it's a stock charging system, the passenger side alternator has to be isolated ground or the smoke will get out. I doubt you can buy one of those in an auto parts store.

KI4FKW said:

Though, continuing to learn - will the alternator in this link work? If I understand correctly, the alternator needs to have an isolated ground? https://www.oreillyauto.com/detail/...984/chevrolet/k30-pickup-4wd?q=r111666b&pos=0

Click to expand...

No.

The stock alternator is based on a 27SI. The alternator in your link says 17SI and negative polarity.

I sell the rebuild kits for your alternator. It's easy to do. Whatever you do, don't give away your original alternator as a core. You will have a hard time finding another.

The links in my signature will tell you about rebuilding the alternator.

Ok. Thank you. I'll check in to it. I haven't gotten rid of my core yet.

Tow4 said:

I sell the rebuild kits for your alternator. It's easy to do. Whatever you do, don't give away your original alternator as a core. You will have a hard time finding another.

The links in my signature will tell you about rebuilding the alternator.

Click to expand...

Listen to da man! It took me about 45 minutes to do this rebuild the first time, and I had never been inside an alternator before in my life. If you can change out a battery and follow simple instructions, you can do this.

PM sent, Tow4.

Remove all the connectors from the diamond shaped "junction" Its on the drivers side firewall next to the glow plug relay, pay attention to how you take them off, clean all the connections and the stud itself. Unhook the batteries before you do this....I chased a GEN 2 issue for days, cleaned those connectors and the GEN 2 light came on and charging resumed as designed. It's free and worth a shot.

BTW the Gen2 dash light is not the same as the others, don't remember the correct bulb, its an easy search. Good luck man.

Very good advice, 90Jimmy. Cleaning connectors, especially grounds, should be the first step with these old birds. Make 'em shiny, and give them a coating of dielectric grease. A lot of problems can be solved that way.

And then there's that nasty connection to the fuse block through the firewall. That's a good place to have lots of problems that are cured by a bit of simple maintenance.

I go to my local re builder he has them in stock on the shelf... however I just get mine rebuilt (when I aint in a rush) sure you can do some stuff yourself but you can't test everything...

If I ever rebuild the like 8 cores I have ya I may shotgun it myself... but when I need 1 or 2... I just give them to him... YMMV.

Hey I have a stupid question. Are both alternators identical? I understand that the passenger side unit must be isolated ground, and I get that, but can they be interchanged? Are they both 27Si?

And one other thing - my passenger side unit has a condenser on the back, but my drivers side does not. Is this correct?

Thanks.