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  #11  
Old 04-02-2008, 05:05 PM
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Originally Posted by subzali View Post
Who's Cruiser is that behind you? IIRC you sold the CJ right after you got back, and then came over from the darkside not too long after right?
that's zach's cruiser before he butchered it. it was a beautiful rig.
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  #12  
Old 04-02-2008, 05:29 PM
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Originally Posted by Jacket View Post
So last weekend I was troubleshooting my faulty fuel gauge and pulled the instrument cluster out of my 40. The good news is that I found a short in the fuel gauge wiring and I'm pretty sure its fixed. The bad news is that I touched the hot lead on my ammeter gauge to the dash panel for a second or two, and (after a spark shower and some electrical smoke) now I think that gauge is not working. It used to be "lively", and bounce around when the truck was running. Now it just sits there and never moves.

I couldn't see anything obviously damaged, but then again, I don't remember what it looked like before "the incident."
YES it is entirely possible (and not that uncommon) to fry the amp meter in precisely the manner you described. It *may* be repairable, maybe not.

For this reason, I ALWAYS advise people to disconnect the negative terminal of their battery whenever pulling the cluster on a 40.

Yes, I have also made arc welder when pulling the cluster on a 40 (only once, I learned :-). Fortunately the short was on the upstream side and did not damage the instrument.
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  #13  
Old 04-02-2008, 05:32 PM
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Originally Posted by DaveInDenver View Post
What that means is shorting the (+) side of the ammeter to ground just completely bypasses the ammeter and shunt.
If the meter is buggered, then he shorted the (-) downstream side. Shorting the (+) upstream side can not damage the meter. Only the battery side feed wire or battery.
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  #14  
Old 04-02-2008, 05:38 PM
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Most likely you melted wires and the reason your meter isn't working is a bad wire someplace.
If the between the battery and meter were melted (open) then the system gets no power. No lights no phone no motor car, not a single luxury....

The gauge is buggered. The surge overloaded and opened the windings in the meter. Which is a true amp meter, not a voltmeter. While the diagram shows a shunt which is correct, mechanical gauges are always amp gauges. Current flows through them, the windings create a magnetic field which deflects the mechanical mechanism to move the needle. In the case of an amp meter which is designed to measure large currents, most of the current flows through the shunt, and a small, calibrated fraction flows through the windings. But when the current through the shunt and windings, which are in parallel is excessive, the excessive current through the windings opens them.
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  #15  
Old 04-02-2008, 05:56 PM
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Oh, sure, I'd get the little Yoda for being all technical and talking about a D'Arsonval. ;-) I was told there are important details and there are not so important details. Basically waving your hands and saying it's magic apparently is OK sometimes. Who knew?

Don't have a FJ40 wiring diagram, so I just assumed that the hot side wire leading to the gage wasn't very big, but it sounds like it's a feeder for several things and so definitely listen to Jeff. If the negative side of the gage was what was shorted, that would definitely kill the movement.
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  #16  
Old 04-02-2008, 06:03 PM
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Matt,

If you did indeed fry it I might have replacement for you. I'm pretty sure I have a complete cluster but I haven't looked at it since last year. Someone on here was giving it away and Subzali grabbed it for me last just before the Spooky Night run. I had delusions of going back to a stock cluster at the time

No idea of the condition of the cluster though. On a side note, I also have the air can (and possibly an air filter) from an early year 40 as well (no top though) from the same source that I can't use.
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  #17  
Old 04-02-2008, 06:12 PM
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Hm...now that you mention it I might have one too. I'll look, it might be at my parents' house.
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  #18  
Old 04-02-2008, 11:20 PM
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Originally Posted by DaveInDenver View Post
Don't have a FJ40 wiring diagram, so I just assumed that the hot side wire leading to the gage wasn't very big, but it sounds like it's a feeder for several things and so definitely listen to Jeff. If the negative side of the gage was what was shorted, that would definitely kill the movement.
Yeah it's big, I'd guess 8 or 10 gauge or so. Basically all the current that flows into or out of the battery goes through there, except the starter motor.
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  #19  
Old 04-03-2008, 05:46 AM
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Originally Posted by Rzeppa View Post
Yeah it's big, I'd guess 8 or 10 gauge or so. Basically all the current that flows into or out of the battery goes through there, except the starter motor.
When I got up this morning, I did pull out my FJ40 FSM and looked. I made a mistake, I thought there was a shunt external with small wires to drive the gage in the combination meter, but that is not right. The circuit comes straight off the battery, through the fusible link and into the ammeter and back out to the rest of the system. So all stuff above, yeah, that's just how the guts of the combination meter work, not so much good for troublehshooting...

See what happens when you go and try to cram too much into your head, you push other stuff out. I must have been remembering something else on my truck and now that I scratch my chin I think I know what it was. I had an MSD box on my FJ40 and with those you have to use a ballast resistor and that's probably what I was picturing.
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  #20  
Old 04-03-2008, 09:04 AM
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Originally Posted by corsair23 View Post
Matt,

If you did indeed fry it I might have replacement for you. I'm pretty sure I have a complete cluster but I haven't looked at it since last year. Someone on here was giving it away and Subzali grabbed it for me last just before the Spooky Night run. I had delusions of going back to a stock cluster at the time
Quote:
Originally Posted by subzali
Hm...now that you mention it I might have one too. I'll look, it might be at my parents' house.
That'd be great. I would be much obliged.
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