Who would run straight 24V glow plugs if they could?

[mistaken1]

It is my understanding that when the CUCVs were procured 24V glowplugs for the 6.2 were not available. With the advent of the HUMVEE 24V glow plugs for the 6.2 became available.

So removing the resistor on the firewall and running straight 24V to new 24V glow plugs seems like a natural upgrade but then there is the problem with the glow plug controller sensing the higher voltage and short cycling the plugs.

I like the idea of spreading the glow plug and starter load over two batteries.

antennaclimber can modify is replacement glow plug module to operate correctly with 24V glow plugs.

I am curious as to how many people would be interested in converting their CUCVs to straight 24V or am I all alone in this?

I have not researched it yet but thought I would ask if anyone knows if the HUMVEE 24V glow plugs are self limiting like the AC60Gs?

 

[doghead]

I understand the idea of using 24 volts for the glow plugs, to load each battery equally but, your assuming your batteries perform equally if that is your goal. Since they charge separately and do not get used equally(rear battery is unused after starting, that's not really gonna happen.

I have had no issue with resupplying my GP relay with 12v off the 12v stud(simply made a new jumper wire and removed the original wire).

I do not know who makes 24v GP's for the 6.2, other than Wellman(never needed them). After a lot of talking with Chuck Gillis and some experience with Wellman plugs, I have no interest using them. Swelling and early failure for no apparent reason, is what I have experienced with them.

I think your idea is not bad, just one more way of doing it. It might be real difficult to help people diagnose and discuss their issues, if there are even more choices out there.

Sounds totally doable though, with a modification to the voltage sense portion on the controller card.

Keep in mind that the Humvee will be phased out soon enough, then there may not be 24 volt gp's readily available then. (unless they are common or used in other applications) They also have a "bullet" connector, don't they?

 

[thedeliverator]

I'd be interested in running 24V glow plugs if and only if I could run everything else on 24V; headlights, tail lights, wipers, heater blower, etc.

The hybrid system we have is an adaptation to allow what is a mostly 12V civilian vehicle to operate and be started in the middle of a 24V military world. It works decently well. I can see why people convert down to fully 12V. And I have no doubt that there was a significant cost savings building the hybrid system as opposed to building a fully 24V system from the beginning.

'Real soon now', for the last ten years, we've been hearing that vehicle electrical systems will go to a higher voltage to deal with the host of issues and inefficiencies that are inherent with 12V.

 

[hurst01]

It is my understanding that when the CUCVs were procured 24V glowplugs for the 6.2 were not available. With the advent of the HUMVEE 24V glow plugs for the 6.2 became available.

So removing the resistor on the firewall and running straight 24V to new 24V glow plugs seems like a natural upgrade but then there is the problem with the glow plug controller sensing the higher voltage and short cycling the plugs.

I like the idea of spreading the glow plug and starter load over two batteries.

antennaclimber can modify is replacement glow plug module to operate correctly with 24V glow plugs.

I am curious as to how many people would be interested in converting their CUCVs to straight 24V or am I all alone in this?

I have not researched it yet but thought I would ask if anyone knows if the HUMVEE 24V glow plugs are self limiting like the AC60Gs?

Can you tell me what kind of resister you have on the firewall to allow you to use 12V glow plugs? Do you know the value of the resistor? Thanks,

 

[gimpyrobb]

Couldn't you just use an isolated relay? 12v trigger to activate 24v to glow plugs?

 

[cpf240]

Can you tell me what kind of resister you have on the firewall to allow you to use 12V glow plugs? Do you know the value of the resistor? Thanks,

The stock CUCV has a pair of large resistors mounted on the firewall behind the air cleaner to, in combination with the glow plugs, drop the voltage seen by the glow plugs to 12v.

 

[scottladdy]

I've thought about this since posted and would have to say I would not change to 24 volt plugs. I understand the desire to balance the number of discharge/charge cycles across both batteries, but don't believe it is a problem that needs a solution.

I manage my batteries by swapping them periodically as part of routine PM. At least every six months I like to check under the batteries to clean the trays. This also gives me a chance to clean the clamps and posts.

Not all that hard, takes about 30 minutes.

On the other hand, as was previously pointed out, the demand for 12 volt plugs is not likely to drop significantly for quite some time. They are also readily available at a consistent price point. And, there is no re-engineering required (aside from the resistor bypass which I do recommend).

So, I would have to ask the OP if there are other problems that would be resolved by moving to 24 volt plugs aside from the discharge/charge cycle balance on the batteries that, as Eric pointed out, is not truly resolved as the mission of each battery is different in the hybrid electrical system our CUCV's have. I am just not seeing any myself.

 

[hurst01]

The stock CUCV has a pair of large resistors mounted on the firewall behind the air cleaner to, in combination with the glow plugs, drop the voltage seen by the glow plugs to 12v.

If anyone knows, I would like to know what the resistor is and the resistance value of it for another application.

 

[MarcusOReallyus]

Couldn't you just use an isolated relay? 12v trigger to activate 24v to glow plugs?

Yes, you could. I don't see any value in it, but it would not be hard to do.

 

[MarcusOReallyus]

If anyone knows, I would like to know what the resistor is and the resistance value of it for another application.

Hmmm. IIRC, the GPs are supposed to be 1-3 ohms. So, let's take 2 ohms as a normal value. That means the total resistance of the GPs is 2/8, or 1/4 ohm.

Since this is a simple voltage divider, the resistor bank has to be the same value, so, 1/4 ohm.


Now before somebody comes along and tells me it's in the TM, I'll look it up.


Here it is. Page 115 of the -20:

Resistance should be 0.28 ohms.

Close enough!

 

[doghead]

IIRC, I once looked it up by it's NSN and found all of the specs for the resistors.

 

[MarcusOReallyus]

IIRC, I once looked it up by it's NSN and found all of the specs for the resistors.

Right before you bypassed & removed them? Do you remember if there was a spec for how hot they get and how long they can operate at full current? Might be interesting for hurst01's application.

I can't imagine they can take it for prolonged periods.


I should add that there are two resistors in there, in parallel, so each one must be .56 ohms.

 

[doghead]

Actually, I think I recall that there are two for redundancy. Not sure right now.

They are very big and look to be speced to major overkill, for what they do.

Yes, mine is bypassed, but still there and able to be reconnected in less than a minute just in case I find myself in a combat situation with a dead(open celled) front battery and I have a support vehicle with a NATO slave cable.

 

[MarcusOReallyus]

Actually, I think I recall that there are two for redundancy. Not sure right now.

They are in parallel, so if one were to open, the voltage divider equation would change. Instead of being a 50/50 (12v/12v), you'd have a 66/33 arrangement (18v/6v) arrangement. GPs getting 6v is probably not conducive to rapid cold starts.

They are very big and look to be speced to major overkill, for what they do.

No doubt! Typical military specs. Needed, though. In a recent thread, somebody calculated the heat dissipation is on the order of 1500 watts, IIRC.

EDIT: Bleh, my math was off. I was shooting from the hip, and missed. The voltage would be 16/8, not 18/6. With one of the resistors open, the remaining resistor is presenting .58 ohms to the circuit, vs. the .28 for the GPs (and their leads, I'm guessing). This gives the 66/33 ratio (actually, .66666/.33333). 67% of 24 is 16, not 18, leaving 8v for the GPs. My back brain bugged me about this until I actually did the math, and found my error.

 

[Keith_J]

The glow plug ballast resistors are in pairs for heat dissipation, they put off just as much heat as the glow plugs themselves. Redundancy? Not even as failure of one would cause the other to rapidly fail, just like when glow plugs fail.