24v Humvee GP conversion?

[rockspider]

Sorry to bring up again a thread about Glow Plugs , but even after reading all I found here about GP's and related items, I still have a question.


From what I understood reading here, correct me if wrong:
The Military at that time choose to have the CUCV (I have a M1008 ) must be able to jump start Nato style at 24v.
For the GP this was done using normal 12v GP and controller, and just adding that big resistor (ballast) to drop the voltage from 24 to 12.
This worked for the Military, but poses the well known snowball-effect when one plug burns, the voltage goes up, and quickly one by one all the glow plugs die.

Here I see many just bypass the ballast resistor and wire the relay to the 1st battery for 12v, and this works fine at eliminating snowball-effect, at the price of not being anymore able to jumpstart it on 24v.
Going this way the suggested GP are the AC60G, keeping the resistor in place the correct GP are Wellman 070.

But this setup takes all the GP load on one battery only, and that can takes its toll on that battery inthe long run, leading to premature failure.


With the production of the Humvee, the entire engine GP system has been converted to full 24v. So now there are available real 24v GP, that were not available at time of CUCV production.
To my poor electrical knowledge, convert the GP system to work on full 24v by eliminating the ballast and using Humvee GP should be the best thing to do, as far as better efficency at a higher voltage, less current flow on wires and relay, no destructive snowball-effect, and maintaining the ability to jumpstart at 24v.
This "should" work with the stock controller, if as I understood the controller works at 12v and just the relay hot wires see the 24v.
I say "should" because I have not tried yet and have not seen any answer about this here.


So the big question is: if it looks so simple and straightforward, why nobody has done it before? Am I missing something??

Thanks in advance

Alessandro
from Italy

 

[Ruppster]

Here I see many just bypass the ballast resistor and wire the relay to the 1st battery for 12v, and this works fine at eliminating snowball-effect, at the price of not being anymore able to jumpstart it on 24v.
Going this way the suggested GP are the AC60G, keeping the resistor in place the correct GP are Wellman 070.

But this setup takes all the GP load on one battery only, and that can takes its toll on that battery inthe long run, leading to premature failure.

Actually, the last sentence is not completely correct. The power consumed by the glow plugs is a function of both voltage and current. I can't remeber how much current the glow plugs actually take but lets say for the purpose of this discussion its 15 amps. Because the ballast resistor is in series with the glow plugs the same amount of current being used by the glow plugs is going through the ballast resistor. Due to this current flow through the ballast reistor the voltage drop across the ballast resistor is about 12 volts. In the process each battery is providing 15 amps and 12 volts. So if you wire the glow plugs to work off the main battery by bypassing the ballast resistor the single battery will still be providing the same amount of current. So no extra load would be placed on the battery in a 12 volt conversion of the glow plug sytem.

With the production of the Humvee, the entire engine GP system has been converted to full 24v. So now there are available real 24v GP, that were not available at time of CUCV production.
To my poor electrical knowledge, convert the GP system to work on full 24v by eliminating the ballast and using Humvee GP should be the best thing to do, as far as better efficency at a higher voltage, less current flow on wires and relay, no destructive snowball-effect, and maintaining the ability to jumpstart at 24v.
This "should" work with the stock controller, if as I understood the controller works at 12v and just the relay hot wires see the 24v.
I say "should" because I have not tried yet and have not seen any answer about this here.


So the big question is: if it looks so simple and straightforward, why nobody has done it before? Am I missing something??

Thanks in advance,

Alessandro
from Italy

You are correct that it is pretty straight forward and I am thinking about doing this myself. The only issue that I have read about in regards to doing this is the connector on the end of the glow plug is different. But it can be done. As far as why or why not a few things come to my mind.

Pro's:
1.) As you mentioned it removes the ballast resistor from the system and that is one less thing to fail.
2.) As you also mentioned you keep the ability to get a jump start from another 24 volt truck.

Now for the con's:
1.) How many people that own a CUCV vehicle have a fleet of 24 volt trucks that can't be converted to 12 volts? While some CUCV owners in this group have 24 volt 6x6 trucks a lot of CUCV owners don't have anything more then 12 volt civilian vehicles in their collection.
2.) If you don't need the 24 volt feature it's a lot easier to just switch to 12 volts (this lets you get rid of the extra alternator too) at the same time. This way if you have a problem any tow truck can give you a jump.
3.) Cost. If you have to replace a glow plug how much more do the 24 volt Humvee glow plugs cost compaired to stock 12 volt glow plugs?
4.) Availability. 12 volt glow plugs are carried by just about every parts place out there. If you need a 24 volt Humvee glow plugs odds are it will have to be ordered and you will have to wait for it to come it. Not a problem if you have another vehicle to use while your CUCV sits in the garage waiting for the part to come in.

So I would have to assume that for most CUCV owners out there that it just isn't worth the effort. The main reasons I am thinking about doing it is for 2 reasons:

1.) I live in Alaska and in the winter the engine turns over easier with the 24 volt starter so I don't want to convert to 12 volts.
2.) I plan on buying a couple of 6x6's in the future and it would be handy to have the 24 volt system in case I have to use the 6x6 to jump start my M1009.

Ruppster
1962 Dodge C700
1970 Dodge CT800
1985 M1009 Blazer

 

[Ruppster]

Just found out I was wrong about one thing. It looks like bypassing the ballast resistor could possibly damage the glow plug controller by causing 24 volts to feed back to the glow plug controller.

http://www.steelsoldiers.com/showthread.php?t=7809&highlight=ballast+resistor&page=2

Ruppster

 

[mangus580]

This "should" work with the stock controller, if as I understood the controller works at 12v and just the relay hot wires see the 24v.
I say "should" because I have not tried yet and have not seen any answer about this here.

You will FRY the stock controller in no time doing this. The controller has a voltage sense wire that monitors the drop in voltage over time, helping to determine when to turn off the glow plugs. This circuit can NOT handle 24v, and is what usually fails the controllers (after the glow plugs die off).

Your idea has merit... It would work great if you went to a manual setup.


Honestly, a PROPERLY maintained stock glow plug system works great. Ideally, you could very easily set up something to assist in monitoring the health of the system.

If a volt meter were put on the output of the glow plug relay, you could monitor your voltage over time. If you see it start to climb up over time (like instead of 11v... you see 13v) you know you have a couple plugs failing and its time to replace them.


I think the biggest snowball effect occurs with either OLD plugs... or incorrect ones. When I replaced them in mine about a year ago, I had 3 bad. I am pretty sure those 3 were bad for some time. But the plugs I pulled out were the 070, which are much more tolerable to this problem.

I have had my truck start just fine at 5 °F by just waiting for the wait light to go out. I know my system is up to snuff, and i run synthetic oil.


I think the bigger problem with the CUCV glow plug system, is there is no clear description of how it works, making it so people dont understand it. I intend to write something up for the FAQ article here soon, on the theory of operation.

Hope this helps...

 

[rockspider]

Thanks for teh answers and for the link to that old discussion, I happened to not find that one on my search.

I understand your point, if 24v arrives to the card orange wire just for a moment before the voltage drops due to the resistor, the card "can" survive, if it gets full 24v all the time, it will dbe dead in no time.

Still think there should be a better way to deal all this GP thingy instead of the ballast resistor.
Maybe using a potentiometer between 24v relay and ground, so to cut in half the voltage to send down that orange wire??


If not possible, I'll go the 12v relay route then, for more safety.
I want to keep the 24v to run a 24v winch, much better efficency.
Jump starting 24v is not so imperative to me, there's nothing 24v around here!

 

[PsycoBob]

I'm not near a CUCV atm- where on the glowplug system does the orange wire come from before it goes to the controller?

You can also use a voltage divider to convince the controller that the plugs are 12v. 2 120ohm resistors in series, one side to ground, one to the glowplug side of the orange wire, connect the controller side to the junction between the resistors. 0.1A thru the resistors so you'd need each resistor to dissipate 1.5w while the plugs are on.

 

[Westech]

here is a STOCK system with new glow plugs. It starts better then my 04 Duramax.



Click here to watch vid.. open with windows player. 6.2deth 006.avi