Help needed with CUCV charging system to reverse 12 volt conversion

[vegavairbob]

Purchasing a rust-free M1009 but unfortunately it was converted to a 12 volt system (I hope it was done with the one-wire method)
One non original alternator is currently used on the drivers side. Current owner bought the truck converted and it starts and runs fine.
One original HD alternator comes with the truck which leads me to believe one alternator had failed as current owner only has one of the original alternators that wasn't hooked up.
Both batteries are still in it. Not sure how they are hooked up. I believe one battery is not.

Please help with diagnosing what was done (or what would have to be done to convert to 12 volt starting/charging) and how to put it back to 12/24 (besides getting another HD 100 watt alternator (and installing both HD alternators.).

Thanks in advance.

Also the glow plug light is out and a manual toogle switch is used. Id like to hook that up correctly as well with a working glow plug light.
In all cases would the 24 volt starter have to be removed to convert it to 12 volt starting? meaning do I need a 24 volt starter in addition to replacing one of the missing HD 100 watt alternators?

 

[Sezzo]

The two batteries are connected parallel (12V) and not in series (24V). The 24V starter is replaced with a 12V starter. You just need one 12V alternator for this hacked up wiring. The 12V from the batteries go to the wiring block and from there to the glow plug relay. The resistor on the firewall is probably disconnected or removed completely. I think with this hacked up wiring there is no use for a glow plug card. That's why you have a manual glow plug button to ground the glow plugs for glowing. You can connect the manual button to the wait light but for most hackers this is too much work so they just don't do it. Safe this CUCV and convert it back to the stock 12/24V hybrid system - it will thank you for that.

 

[Barrman]

The most popular 12 volt conversion is called the Roscommon conversion. They were a company in Michigan that did conversions. You should be able to find those instructions online.

The Technical Manuals for the CUCV trucks can be found under the TM tab at the top of this page. The one ending with -20 has the wiring diagrams in an appendix at the back. Between the Roscommon and the -20 you should be able to figure out what has been done and what you will need to do.

Another option might be buying a CUCV under hood engine harness. You still need to source a pair of good 27SI alternators and a 24 volt starter to complete the conversion back.

 

[vanaisa]

Rosscommon:

 

[dstang97]

Too bad you are not closer. I have all the parts you would need to fix it. Was your wiring hacked up?

 

[vegavairbob]

'll consider your parts and would pay shipping.

 

[ehuppert]

Guess I'll add some fuel to the fire..... If the charging system is charging, truck is starting etc., i personally would focus on other services like brakes, suspension, fluids, tires etc.

If you're restoring the truck to original from a "purist" position that's one thing. If you need 24 volt for some reason, okay, then I get it. As for me, my Cucv was converted to 12 volt, along with a gas motor....

The CUCV series trucks don't really require a lot of amperage to run. The 24 volt system (Believe the 27si originals were 100 amp each) was for military add-ons (shelters, radios. etc) and has always been a little problematic at best. The wiring in your pics doesn't look horrendous …

My opinion, if charging and starting system works, focus on mechanicals...…

Later on you can examine the present conversion (Comparing with Roscommon pdf) to see how mucked up it is or isn't.

Just my 2 sense!

Eric

 

[vegavairbob]

Thanks for your comment. Blazer has new brakes and the transmission was rebuilt. It runs fine. It doesn't start quickly. My p/u started quicker with twice the voltage. After I change the harmonic damper I just bought (snagged a GM Genuine old stock unit) I will have a 24 volt starter, and two HD 100 alternators installed. (need one). I like the idea of 24 volts going to the starter in the winter. The main thing that is different on CUCVs I want on mine. I bought this one because its fairly close to home and there will be no bodywork or paint work needed other than the bumpers, grill/guard and mirrors to 383 green (which I can do myself with spray cans) and the price was pretty good. I do need help with the wiring changes. I have a PDF of 24-volt to 12 volt but its confusing.

 

[vegavairbob]

Rosscommon:

I have that download . The wiring changes confused the shit of me, Parden my expression. I certainly can't reverse them. But thanks. I appreciate it.

 

[vegavairbob]

Too bad you are not closer. I have all the parts you would need to fix it. Was your wiring hacked up?

I need a 24volt starter, HD 100 watt alternator for the driver side. Maybe a glow plug card? . everything is avail. new or old stock online but I'll consider your parts and would pay shipping. I'll have the Blazer in a week but I won't know how the wiring was altered. I did replace a positive cable to the firewall on my previous one. I read the 24 volt to 12 volt conversion pdf. (wish there was one to reverse it). The wiring changes is confusing. I did install and prime a fuel filter on my last one by the book with no trouble so I can do work on it with instructions I can understand. Barrman suggested a new engine harness. Is it easier with a new harness? I would think that's more work. Or do I need one regardless?

 

[Lothar]

Looks like you might need a second battery tray. Can't quite see.

 

[vegavairbob]

Looks like you might need a second battery tray. Can't quite see.

It might still be there though because there was no reason to remove it.