Obsolete qlow plugs for generators

[hurst01]

I have been thinking about a way to utilize other glow plugs in the MEP 002 and MEP 003 Gensets. As most of you know, the glow plugs for the 002 and 003 obsolete. They are sometimes available for outrageous prices. The Glow Plugs for the Onan civilian version (CH41) are also obsolete. The CH41 is identical to the CH42 that is required by the MEP002, 003 except that it works off 11 Volts instead of 24 Volts like the CH42. I thought I had run across a large quantity of CH42 glow plugs but when they arrived I found them to be CH41 11 Volt.
I am considering ways to still utilize the CH41s in the 002 and 003 Gensets. The best way I can come up with is to use a 24V-11V voltage reducer. This would have to be installed between the manifold heater and the glow plugs. After doing some research I found that I can make a voltage reducer by using (2) 100 Kilo Ohm resisters hooked in parallel. This would cut the 24 Volt supply to the glow plug to 12 Volts. Now, the problem is to find the resisters that will stand up to the amps required to operate the glow plugs.
Does anyone know what the amp draw is for the glow plugs? Obviously, the 11 Volt glow plug would draw a different amperage than the 24 Volt, but I can't say for sure.
I have found a voltage reducer for 24-12 volts on ebay for about $25 delivered, but the cost of the reducer added to the price of glow plugs would make them pretty expensive. Using the resisters would be the cheapest way but then again, I don't know what the amperage would be. The reducers I found on ebay are also advertised to be vibration resistant which would help on the Gensets.
I have seen the CH42 glow plugs advertised for as high as $97 each plus shipping. My guess is that they know they are obsolete and are price gouging. I have heard of others ordering CH42 glow plugs but not if they had received them or not.

 

[Isaac-1]

Why waste all that desired heat, instead fit a 12V grid heater of the appropriate amperage wired inline with the 12V glow plugs inside the intake

 

[hurst01]

OK, but the 12 volt glow plug will get just as hot as the 24 volt so long as the voltage is controlled to keep it from burning out. There is no glow plug in the manifold, at least not like the one on the head. The other is a manifold heater that preheats the air in the intake. I am not familiar with a grid heater, would you please explain? This could get interesting.

 

[Isaac-1]

right 2 12v matching resistors of matching size wired in series will run off 24V and will split the voltage equally so they each see 12V or there about. In this case you would want a 12v heater with a resistance of about equal the total number of glow plugs, because they are all wired in parallel. For visual examples try searching for grid heaters on ebay.

 

[steelypip]

I thought about (and suggested) putting the two 12v glow plugs in series at one point, but the more I think about it, the more I think it's a bad idea: no fault tolerance. With two plugs in series, if either burns out, an MEP-002A now has no working glow plugs. My set, at least, insists on glow plugs being used in cold weather.

That's why you want dropping resistors. Further, you want a dropping resistor for each plug, so that the voltage doesn't change if one plug goes open circuit. This same design solution is used for LED arrays if you want the rest of the LEDs to behave the same if one burns out.

Now it's entirely doable to use the resistor as a heater in the intake tract. Indeed, it seems a fine idea. But it's still a resistor.

The other option is active voltage control to the plug with a DC voltage regulator rated for enough current to get the job done. This is probably pretty easy, too, although I think you might end up with one regulator per plug because of current limitations. Again, this would be a good thing - if a semiconductor regulator fails, the others keep working. Even better would be that the plugs would work just as well at 20V as at 28 - the regulator would step down whatever was available to the desired 11V.

 

[DieselBob]

How about just using a relay to feed 12 volts from one of the batteries to run the 12V glow plugs. Use one of the original 24V glow plug leads as the solenoid lead to control the relay. Easy to setup and no wasted energy in dropping resisters. Just a thought.

 

[Isaac-1]

Of course all this is somewhat moot as the civilian 12V Onan glow plugs are likely to be just as hard to find in the next few years.

 

[61sleepercab]

I do not know what size threaded hole the original glow plugs were made.
I had an idea ...... can you make a bushing adapter with outside thread the original thread size and the inside drilled and threaded for a modern replacement glow plug ?
I know VW and Mercedes diesel glow plugs are pretty small diameter. Good luck Mark

 

[m16ty]

Only problem with using a resistor is the same problem the CUCV has. If one of the glow plugs burn out, the load will lower and the voltage goes up. This in turn burns out the rest of the glow plugs in short order due to over voltage.

Personally, I'd rather wire them in series. When one goes out the mate to it just won't work instead of burning all the rest of the plugs up if ran off of a resistor. Also, to just wire pairs in series would be really easy and wouldn't require buying anything.

 

[Isaac-1]

I don't recall the thread size, but it is english not metric and is basically only used on these Onan built engines

 

[Jimc]

thread is 7/16-20

how can they be wired in series when they ground to the block? i would think it would be easiest to just run 12v to the plugs....although i havent really looked into it but i cant imagine it would be too difficult. there are two good 12v batteries there, just feed from one of them.

 

[BradBMI]

Does anyone have a picture of the Glow Plug or the NSN?

I picked up alot of automotove stuff from GL (10 skids) with everything you can imagine. Maybe there are a few of these glow plugs in there...I found alot of Gen parts etc staring to figure out what goes to what

 

[Jimc]

according to the 003 manual the nsn is 2920-01-048-8867.

 

[Jimc]

here is a pic i pulled off the internet. of course the nsn on the box is different.

 

[BradBMI]

Will take a little while but I will check all the Packing slips and see if you win the Lottery

 

[BradBMI]

I dont know if its the right one but I saw some that look like that.

Will dig and see what i find

 

[m16ty]

how can they be wired in series when they ground to the block? i would think it would be easiest to just run 12v to the plugs....although i havent really looked into it but i cant imagine it would be too difficult. there are two good 12v batteries there, just feed from one of them.

Good point, I guess I didn't think of that as far as the ground goes.

The only problem with pulling off one battery is you will unbalance the batteries and they won't last long. When the batteries are unbalanced, you are either overcharging or undercharging one of the batteries.

 

[Jimc]

hmmm yeah clearly unless champion decides to do a run of ch-42's some more thought will need to be given to the best way to go about a conversion.

 

[hurst01]

right 2 12v matching resistors of matching size wired in series will run off 24V and will split the voltage equally so they each see 12V or there about. In this case you would want a 12v heater with a resistance of about equal the total number of glow plugs, because they are all wired in parallel. For visual examples try searching for grid heaters on ebay.

I was thinking about wiring them in after the manifold heater. The power source comes into the manifold heater and then to one glow plug then jumps from the glow plug to the other, already in series (on MEP002). If one glow plug burns out the other still works without doing any damage to the other. The voltage reducer would tie in between the manifold heater and the first glow plug then jumped to the second glow plug (series) furnishing 12 Volts to all the glow plugs with no drop, but the resistors should be parallel instead of in series. The ground is no problem as the glow plug is grounded. All that is needed is the hot wire as it is already now.

 

[hurst01]

I don't recall the thread size, but it is english not metric and is basically only used on these Onan built engines

The thread size is 7/16-20 if I am not mistaken. I see a lot of people saying they are 10mm but that is not right.