Voltage reducer for Glow plug?

[unimog_jason]

Transit,

If you were asking me to post a picture here's what I'm talking about. Sorry for the crude drawing, don't have time for artwork these days.

[Transit]

I see, one terminal is a stud and the other is a collar. Now we need to know the current and voltage drop for one plug, that will lead us to the wire gauge and dropping resister.

[Michelxb]

I see, one terminal is a stud and the other is a collar. Now we need to know the current and voltage drop for one plug, that will lead us to the wire gauge and dropping resister.

It is what I am looking for and so far no information...
Champion #155

[Soundguy]

I just refreshed my electricity knowledge and in fact, we must add resistance when in series. So voltage is reduce bye each glow plug and the resistor of the "indicator" in the dash panel.

It seems that all I have to do is to put a switch in the circuit of the indicator and the 4 glow plugs that are in series and it will be fine. I am looking for explanation on Internet that will describe the plug Champion 155 but nothing for now.
On the glow plug we can see: Champion/ch28/0.9v/068//

series resistance is addative.. however.. if they have 1 terminal.. you have a bunch of parallel plugs it would look like.. thus you would need one series resistor which then feeds all the parallel plugs

soundguy

[Soundguy]

The way you have to wire a Bosch loop plug is a little tricky if you don't have the proper info close at hand.

These plugs do not ground through the body, there are two terminal at the top of the plug. There is a ceramic insulator that keeps the two terminal isolated, if you missing those insulators that's the first problem you need to correct.

http://img.eautopartscatalog.com/liv...1638701BOS.JPG

If your books don't explain how to wire up the plugs I can likely get a diagram from one of my Mercedes engine manuals that will give you enough info to get the job done.

Tracking down a voltage dropping coil might be hard. I know it can be sourced from Mercedes, but I'm sure you could convert the system to parallel plugs for about the same amount of money and you'll get an automatic controller too. Google part # W0133-1606011 to see it.

If you want to go cheap you could just buy 4 plugs, part # 0 250 201 044 and use the old switch and completely eliminate the need for the dropping coil. That's all I've ever done on my engines and it works great.

Jason

if there really is 2 terminals at the top then that answers alot of questions. had this been posted up front it would have been much easier to figure out.

soundguy

[RWolf]

OK let's keep it simple. To find current us a multimeter set to ohm's and read the resistance. The plug says it's a 0.9V. So ohm's law says I(current)= V(voltage)/R(resistance). Current though a series circuit is constant. To find the resistor needed would be 12V - 3.6V(4 plugs) = 8.4V and plug it into ohm's law again this time finding resistance for the resistor (R=E/I). The last thing is to find the power in watts that the resistor will need to handle. This is just another variation of ohm's law (P=E*I). To solve this would be P=8.4V*I(current found earlier). Size the resistor the next size larger to be safe. Now to keep it simple for the indicator. 12V to switch, switch to 12V light and resistor, light to ground and resistor to plugs.

Hope that helps.

[Transit]

Sorry to bust your bobble Rwolf, you have the correct idea; however, you missed some important points.

You are measuring the resistance of a COLD plug and trying to use that value to calculate the current when the plug is HOT. The resistance of a hot plug would be many times greater then when cold. Try the same calculations with a light bulb. A 100-watt bulb at 120 volts will have a resistance of 144 Ohms when on.

[Soundguy]

I agree.. for an incandescent element.. hot resistance will be drastically different than cold resistance.

soundguy

[RWolf]

You are correct and no bubble bursted. I didn't take the heat issue into account because I didn't have the specs for the glow plugs and also had forgotten about that aspect. But it will get you in the ball park and you could always up the resistance value to the next larger value to reduce the current. Either way the OP wouldn't be blowing plugs immediately.

[Soundguy]

I think an inline lamp is where I would start looking .. they make good current limiters that stabilize pretty quickly.

soundguy