FWIW, I always ran a direct 12 volts to my plugs (civilian.)
CK5
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Cucv won't start
- Thread starter Richcz28
- Start date
Civilian trucks don't have a huge resistor bank, because they're already 12v. I have no clue why the Military opted to do it the other way. The front battery in a CUCV is 12v and runs everything else without using any resistor banks.
The whole CUCV specific charging system just mystified me. Seems like they could have done the whole setup better using more common parts...but wtf do I know?
My plan was to eventually ditch the entire setup and install a civilian 12v setup with dual batts and a 100 or so amp alternator.
My plan was to eventually ditch the entire setup and install a civilian 12v setup with dual batts and a 100 or so amp alternator.
The 24v system IS confusing. My cucv is 12v with dual batteries. I don't buy into the crap you hear on steelsoldiers "24v systems are better, don't change it." Better if you want to spend twice as much money for obsolete NOS parts to keep it working right for the same results.
I think U.S. Military vehicles are 24v, because everyone else in the world uses 24v for Military vehicles. Don't know why, maybe for radio systems.
You're doing it wrong.
And, I'm surprised no one caught this........ Fordum.
When you hook up one end of a test light to a powered input and the other end to a ground, the bulb is going light no matter what is going on inside of the part in question. All you're doing is hooking the light up to the power source. May as well be hooking it to the positive battery terminal.
What you could do, unplug the power source to the GP, hook one end of the light up to the power wire and the other to the spade on the GP. If it lights, the GP has continuity. No light, no continuity, bad GP.
The betterer way to test would be with the previously mentioned ohm meter.
The way I read it, the test light would not light unless it was self-powered. I just assumed it was.
But right afterwards I saw the post where he was not getting current through 7 out of 8 plugs, and I just ignored the other.
He said:
That would work with a selfpowered test light. Note, he said put one of the test light's leads onto the spade connector and the other end on the threads.
This would put the GP across the test light, and the power lead for the GP would not be in the circuit.........From what I read.
As for 24 volt systems in general, they are better than 12. Just like 12 was better than 6 when that changeover occurred.
I will admit that a mixed system of 12 and 24 is not optimal, but a straight 24 has several advantages.
Smaller, stronger starter motors, smaller wires, less current all the way around.
Its why the new cars will be 43.5 volts. (Actually 36 volts plus charging voltage of 2.5 volts per battery)
But right afterwards I saw the post where he was not getting current through 7 out of 8 plugs, and I just ignored the other.
He said:
That would work with a selfpowered test light. Note, he said put one of the test light's leads onto the spade connector and the other end on the threads.
This would put the GP across the test light, and the power lead for the GP would not be in the circuit.........From what I read.
As for 24 volt systems in general, they are better than 12. Just like 12 was better than 6 when that changeover occurred.
I will admit that a mixed system of 12 and 24 is not optimal, but a straight 24 has several advantages.
Smaller, stronger starter motors, smaller wires, less current all the way around.
Its why the new cars will be 43.5 volts. (Actually 36 volts plus charging voltage of 2.5 volts per battery)
With all the stories you tell of your vast experiences in life..... you, of all people, should know..... never assume. 
You are certainly correct about a self powered test light. Not a common item in the home mechanics tool box though. Not too mention knowing how and when to use one.
The amp testing thing threw me off. Could 7 of 8 GPs go bad in one sitting? What are the chances?
You are certainly correct about a self powered test light. Not a common item in the home mechanics tool box though. Not too mention knowing how and when to use one.
The amp testing thing threw me off. Could 7 of 8 GPs go bad in one sitting? What are the chances?
Fordum's assumption about my post was right... 
That's why I clarified it in my second post on the topic.
That's why I clarified it in my second post on the topic. After I posted, something dinged, and I went back and looked. Sure enough there was where you had corrected it.
But, life intervened and I couldn't get back here right away.
Now, first of all, I should post this in a separate thread, but it looks like most of the cucv guys are here, so......
If you have not found this place yet, check it out. Nice diagrams and explanations about these trucks.
http://www.cucvelectric.com/index.html
In looking at the schematic, I discovered something very interesting about the GP system.
It sucks.
The GPs are in parallel.
And the load resistor is in series with them! One load resistor!!
Which means, that their parallel resistance must equal the load resistor. That is the only way that the load resistor will drop half the voltage.
That is fine as long as all the GPs are good.
But, if one burns out, then the remaining ones get more voltage. The more that burns out, the more voltage the rest get.
I would have used indivual resistors. Then one burning out would not effect the rest.
That outfit I linked to sells a replacement controller board. Their explanation of how a controller board works shows it should prevent damage to the GPs if some burn out.
Its actually a pulse width modulator like the fan controller Galdemsuga was having trouble with.
It measures the voltage getting to the GPs, and turns the relay on and off to keep them from burning up.
So, in answer to the question of how likely it is all but one GP has burned out, it depends.
If he is using a manual switch, or if the relay board is not doing its job, then its likely. Plus, we don't know the history of the truck. It might have always been hard to start.
Now, with the sudden cold snap, combined with the batteries probably being low from sitting, its possible that a bunch of them had been bad, but it was still able to crank.
But too many things conspired to stop it this time.
But, life intervened and I couldn't get back here right away.
Now, first of all, I should post this in a separate thread, but it looks like most of the cucv guys are here, so......
If you have not found this place yet, check it out. Nice diagrams and explanations about these trucks.
http://www.cucvelectric.com/index.html
In looking at the schematic, I discovered something very interesting about the GP system.
It sucks.
The GPs are in parallel.
And the load resistor is in series with them! One load resistor!!
Which means, that their parallel resistance must equal the load resistor. That is the only way that the load resistor will drop half the voltage.
That is fine as long as all the GPs are good.
But, if one burns out, then the remaining ones get more voltage. The more that burns out, the more voltage the rest get.
I would have used indivual resistors. Then one burning out would not effect the rest.
That outfit I linked to sells a replacement controller board. Their explanation of how a controller board works shows it should prevent damage to the GPs if some burn out.
Its actually a pulse width modulator like the fan controller Galdemsuga was having trouble with.
It measures the voltage getting to the GPs, and turns the relay on and off to keep them from burning up.
So, in answer to the question of how likely it is all but one GP has burned out, it depends.
If he is using a manual switch, or if the relay board is not doing its job, then its likely. Plus, we don't know the history of the truck. It might have always been hard to start.
Now, with the sudden cold snap, combined with the batteries probably being low from sitting, its possible that a bunch of them had been bad, but it was still able to crank.
But too many things conspired to stop it this time.
Doc Feel Good
1/2 ton status
When I checked my GPs, I just pulled em an used an old battery. They should get hot very fast.
I replaced all my GPs with Wellman 070s (I think that was the make).
No problems since.. (except the alternator)
(and the rear ring gear)
(and the fuel filter, replaced it with a napa unit)
-Tom
I replaced all my GPs with Wellman 070s (I think that was the make).
No problems since.. (except the alternator)
(and the rear ring gear)
(and the fuel filter, replaced it with a napa unit)
-Tom
check out that link. They sell alts and repair kits I think. Plus they got a good diagram of how the dual alts work.
Never done any business with them, don't have anything they have parts for. But they have some real good info.
Never done any business with them, don't have anything they have parts for. But they have some real good info.
From what I've been reading the only plugs that work with the Cucv are ac 13g because of the small spade connectors so I'm trying to get some through summit because Chevy apparently thinks they don't exist. Unfortunately summit doesn't get them in for two weeks.
For what it's worth, I live just 10 minutes from the Summit warehouse, so if you need a local person knocking on their door.... 
Yeah, kennyw kicked over a hornet's nest when he took them on about it a few years ago. I've publicly stated repeatedly they need to get their noses out of their vendor's asses and the TM manuals written 30 years ago and into the real world of these trucks. I'm not terribly popular over there.
NATO standard is 24v. Most big trucks and equipment run off of at least 24v. It's the way for big stuff...CUCV's are just more military equipment.
Wrong. Wellman 070's are the correct plug. Non swelling and the connectors slip right on. My M1008 came from the Army with them in it and the replacements I put in went exactly back in their place and worked great.
AC13g's are outdated and obsolete.
The Wellman's are available on Ebay and through a few internet merchants. Kind of a specialized part being that they only work for military 6.2L engines. Price wasn't horrible though.
The Wellman's are available on Ebay and through a few internet merchants. Kind of a specialized part being that they only work for military 6.2L engines. Price wasn't horrible though.
I only use distributors I know are reliable and will accept returns and even pay for return shipping of defective products. Ebay is created by the internet and is not real so if you pay for something there is no guarantee. I would feel safer spending my money on lottery tickets and newports. If I am going to spend 100$ it is going to be for the correct parts that were designed specifically for my application.
Any glow plugs for a 6.2 diesel will work 
You just have to switch to standard spade connectors. The CUCV connectors are the odd one out of all other 6.2 diesel trucks. No reason to spend extra cash for 'special' plugs, that aren't special.
You just have to switch to standard spade connectors. The CUCV connectors are the odd one out of all other 6.2 diesel trucks. No reason to spend extra cash for 'special' plugs, that aren't special.
