Re: glowplugs..12v or 24?

From: jim gilmore (jgilmore@ptd.net)
Date: Sat Dec 15 2001 - 16:31:43 PST


Ted H. Has taken me to task on my posting about the CUCV Glow plug
swelling.......

I wrote:
> > Your plugs are probably swelling because the resistors (PN # 14076847)
> >on the firewall are bad. This allows 24 volts to go to the 12 volt plugs.
>Ted wrote,

>........How do the resistors go bad..........

     I do not know how they go bad, just that they do. We have had quite a
few with bad resistors and swollen glow plugs.

>
>
> >The CUCV uses 12v plugs and the HUMVEE uses 24 volt ones.
>
>This is not so. Both are rated the same 11 Volts / 75 Watts of heat.
>Just different ends.

      Well, a 11 volt plug would be for the CUCV 12 volt system right? I
would then think you must be referring to the 24 volt part of my statement.

    I would quote PS Magazine # 428 (July, 1988) ..."glow plugs for the
CUCV and HUMMWV are not interchangeable" . It states that glow plugs for
the CUCV are 12 volt (FSN # 2920-01-151-3627) and glow plugs for the HUMMWV
are 24 volt (FSN # 2929-01-188-3863)

>In the HMMV application, they do away with the dropping resistor
>BUT warn you that if the controller keeps the plugs on for more then
>9 seconds, POP goes the plugs. They run 24 Volts straight to the plugs.

     Now a 11 volt / 75 watt glow plug running on twice the voltage makes
me wonder just what happens to the wattage output. This is why I deferred
to someone who knows electricity better than I ....Aussie Rob.

    I asked him ". If a glow plug for a diesel motor (CUCV)
is rated at 11 volts and produces 75 watts of heat, how many watts of heat
will it produce at 24 volts?"

   To this he replied;
"...... (snipped quite a bit).........I wouldn't do it, but if you must
apply 24 volts (POOF)
The wattage would be as follows....
     (more snipping)..............Therefore, Power of the glow plug at
24volts would be;
Power, in watts is P = E x I
P = 24 x 14.81
P = 355 watts.
I hope this helps
But I would not do it for fear of a big POOF'd glo plug........"

     Now, If Rob's calculations are correct, it would seem that using 24
volts on a 11 volt plug would result in a very short life for the plug and
an extremely high heat (wattage) output.

     So, if the 24 volt HUMMWV uses the same 11 volt glow plug as the 12
volt CUCV (with only the ends being different) , then why does the
CUCV drop 24 volts down to 12 volts to the glow plugs? (The engines are
basically the same 6.2 GM diesel)

        Perhaps someone can show us just what the difference is since the
Army says the glow plugs ARE two different voltages.......

Jim

   NOTE NEW ADDRESS----NOTE NEW ADDRESS---NOTE NEW ADDRESS------AS OF
JANUARY 4, 2001---------

Jim Gilmore
13 Broadway 3rd floor
Jim Thorpe, PA. 18229

570-325-5216 phone



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