glow plug resistor

[2deuce]

One of my trucks has this disconnected. I have searched and found out that bypassing puts more load on one of the batterys and disables or limits slave starting. I also understand how important it is to keep all your glow plugs working or you will see your voltage rise as each one fails, killing plug after plug until they all fail creating a domino effect. Then with the higher voltage at the plugs increasing as each one fails,(up to 24v) it also increases the risk of card failure. What I'm asking is with the resistor bypassed will voltage ever exceed 12v if a plug fails? Do you lose the domino effect and in doing so protect the plugs and card from premature failure? Can someone tell me if this is true, because if it is I will disconnect that resistor from my other trucks.
Thanks

 

[watkinssr]

with the resistor out of the circuit, the voltage will not change as plugs fail. It's the series parallel arangement that causes the voltage change. It also should effect the card either way.

 

[watkinssr]

In a series parallel circuit, voltage is devided across the two loads in series. the higher resistance segment drops the most voltage.

For example. Given a 100 volt source in a circuit, with two 25 ohm resistors in series, each resistor will drop 50 volts. but put increase the resistance of say the second one to 75 ohms, then that load will drop 75 percent of the voltage.

This is why when there is a break in the line, you can read all the voltage across that break...it effectively recieves infinate resistance.

With a parralel circuit, the ristance is decreased the more of them you put in prarralel. Put two 10 ohm resistors in parallel you get 5 ohms across the pair.

The glow plugs are a parralel circuit. 8 of them in parral. As each one goes open, the resistance increases, so the voltage drop across them increases with the load. By the time your down to one resistor almost all voltage is going through it, and when they all are opened up it should read 24 volts

It would be possible, I suppose, to install a volt guage just for the glow plugs. If it starts going up above 12 you need to check the plugs.

 

[2deuce]

Then with the big resistor out of the circuit, voltage can't raise above 12 volts so as a plug fails the resistance in the circuit rises so amps fall because the remaining plugs use less amps and no harm comes to the remaining plugs and the domino effect is lost. What is meant by "it should effect the card".
Thanks

 

[watkinssr]

Then with the big resistor out of the circuit, voltage can't raise above 12 volts so as a plug fails the resistance in the circuit rises so amps fall because the remaining plugs use less amps and no harm comes to the remaining plugs and the domino effect is lost. What is meant by "it should effect the card".
Thanks

Yikes. typo. It shouldn't effect the card is what I meant. The card, as I understand it (and someone correct me if I'm wrong here...I've never had to work on the card) just controls the relay. So it's physically isolated from the glow plug circuit.

 

[2deuce]

Hey partime, do't take what I wrote as fact. This is what I'm getting from it all. I'm hoping to see this verified by others that are more knowledgeable than I.