Correct me if I'm wrong, but wouldn't it be the amps that drop, not the volts?

The vehicle is a 1976 vintage. See the first post.

Also see post #3 where the series plugs are confirmed with some certainty.

Why don't you try the older style and confirm that you don't burn the plug out in the process?

perhaps tomorrow. i think i have a brand new one.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

The amperage across the glow plug is a function of the voltage drop and the resistance. The voltage drop across five plugs in series is 1/5 of the total applied voltage. The voltage drop across five plugs in parallel is the full applied voltage on each plug.

The resistance of the plug varies with temperature. So, at the instant of the applied voltage, the amperage is at the highest level. With some time, the plug heats up and the resistance climbs. The amperage drops proportionally. The voltage drop remains the same.

some basic formulas to ponder:

ELECTRICAL ENGINEERING FORMULAS

DIRECT CURRENT(DC)

I = current(amps.), V = voltage(volts), R = resistance(ohms), P = power(watts)



*
CURRENT:
I = V/R or I = P/V



*
VOLTAGE:

V= P/I or V = IR


*
POWER:

I2R or VI


*
RESISTANCE:

R = V/I

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i read your formulas correctly.....

when i test the glow plug tomorrow...

i will die right?

just kidding/

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

You will if you touch the tip in the testing process..........

My car started to staret a little more roughly and with a little smoke comincidentally the glow plug indicator in the dash stopped lighting up. Low and behold 4 bad plugs. I took them all out yesterday and will be replacing them. Those little buggers require some patience when removing them. I think I would still be at it if I didn't have a 12mm Gearwrench.....Do glow plugs generally fail togteher or rapidly after one another? Just wondering.....If I get to sneak to the gargae today I intend to continue to troubleshoot my non-functioning rear windows....My rapidly blinking directional turned out to be a bulb issue. I cleaned up and greased (dielectric grease) the front directional connections and went to test it. it was interesting (Ok so it was interesting tonight - so I have no life ) when I tested the function it rapidly blinked for a few seconds then slowed down and stabalized at the normal rate. It was as if it has a memory to clear....chin scratcher for me...Perhaps the capacitor or relay still had some pent up charge???

__________________
Rob M
Norwich, VT USA
1980 240D Euro delivery 4 speed manual silver/blue
~160K miles

all put in at the same time, i should think they would normally fail around the same time....so it is good to go ahead and change them all, if you have the $.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

to test the glow plug now.

wish me luck.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

from the emergency room.

it is unbelievable the power that an exploding glow plug can generate!

just kidding.

i couldnt get it to even glow. i would have sworn i tested the old style plugs that way before. oh well... old timers disease, i guess.

tom w

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Well, I'm thoroughly confused. I would have thought that applying 12V to a plug rated at 2.4V would turn it into the surface of the sun in short order?????

Could the plug have been burnt out prior to the test?

http://mb.braingears.com/114_115_Disk1/program/Engine/615/15-510.pdf

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