no start , i think some how i killed all the glow plugs and the resistor bank

[MarcusOReallyus]

Given the age of these things, I don't have a hard time believing all 4 are bad.

I did the math a while back, so I don't think the TM is wrong, but maybe.... Let's see

The TM says the spec on the GPs is 1-3 ohms. That means the total resistance of the GPs is between .125 and .375 ohms, with .25 being right in the middle. Given that we have 8 of them, the variations are going to pretty much average out, making that .25 ohm number a pretty safe bet.

Since this is a voltage divider circuit with two resistances (the resistor bank is one, and the total resistance of the GPs is the other) which is designed for a 50/50 (12v/12v) split, we know that the resistances must be equal. So, given the tolerances of the GPs, it makes sense that the resistor bank is the same resistance as the middle of the range for the GP bank, which is .25 ohms. Therefore, the TM is correct, as far as I can see.

I'm back to "30 year old electrical equipment has a high failure rate".

Anyway, problem solved for me. I just took it out. I have no need to be jumped by 24v vehicles, which is the only way the resistor bank offers any benefit.


Since apparently you DO need that benefit, I suggest you take apart the resistor banks, clean them up, and measure the resistance of each individual resistor. I think you'll find that either one has failed in each of them, or there's enough corrosion in there that one is effectively out of the circuit.

I'll see if one of my boys wants to disassemble mine while I'm at work today. Then I can measure each of mine individually.

 

[joshuak]

Anybody feel like checking theirs and see what they get?

I'm troubleshooting in the same area. I measured the resistance for the complete bank and got 0.3.

 

[doghead]

http://www.parttarget.com/5905-01-193-7212_5905011937212_5330011937212.html

 

[MarcusOReallyus]

Just for fun, I threw the numbers into Excel to see what I get. I used the lower end of the GP spec (1 ohm) the middle, and the high end (3 ohms). Then I calculated the total resistance for them. I also did a random distribution, which is closer to reality. Here's what I got:




You can see that the random distribution hits pretty close to the middle on this one.

In Excel, if you are using the RAND function, it will automatically throw out a random number each time you hit F9, so you can change a random distribution to see the different results. I did that a bunch of times, and the total resistance ranged from about .16 to .33. That's probably a realistic range, and I doubt if I did it a hundred times it would change much.

That puts the voltage to the GPs anywhere from 8.73 to 12.98.

Interesting. Looks like it's set up to favor the low end of the range, to protect the GPs from over-voltage.

When I change the resistor bank number to .5, the voltage on the GPs range from 5.82 to 9.54.

That's not a huge difference from the range with the resistor in spec. Interesting....

Anybody know how hot a resistor will get when fed less than 10 volts?

 

[MarcusOReallyus]

I'm troubleshooting in the same area. I measured the resistance for the complete bank and got 0.3.

I'd say that's probably close enough that you should look elsewhere for your problem. Unless you have a meter that can call out the decimals to the hundredths of an ohm, you aren't going to get any closer than that.