Ammeter fj 40 (1 Viewer)

[Warpig 5thMEB]

1976 fj 40 ammeter quite working. Both post on the back of the ammeter are hot full battery voltage, I disconnected the one closest to the steering column wiring diagram says its the ground. both sides of the gauge is still hot? without a wire to it. I'm guesing the ammeter is bad and I need to hook a ground to that post? or is a ammeter different from a voltmeter?

 

[pb4ugo]

Be sure your batt is disconnected whrn pulling rthe gauge cluster. Accidentally ground either terminal can smoke the harness. Do not add a ground. One wire goes to batt. The other goes to alt and fuse box. I doubt its bad. The meter measure flow, charge/discharge. I think the + side is batt. Do you have 12 volts on each terminal?

 

[Warpig 5thMEB]

yes 12 volts both terminals I disconect the ground side still 12 volts there with out a wire

 

[pb4ugo]

yes 12 volts both terminals I disconect the ground side still 12 volts there with out a wire

As it should. Basically, Tthe gauge is marked with a plus and minus so that it is installed in the correct orientation. The amp gauge is part of the batts/alt charge wire. The minus side does not go to ground. Why do you think the gauge is bad?

 

[Warpig 5thMEB]

well it show a hair of discharge when you fire it up but it not working not moving after you fire it up altenator charging but I did put a new chevy 5.3 in it trying to get the gauges to work. well sht I f something up where does it melt the harness under the dash? quick look didnt see anything? the original fuse block is dead fuses old and new look ok won start no power f

 

[Warpig 5thMEB]

I hooked the old alternator wires back up to the new altnator white blue strip and white green strip i cant rember 3rd one gauge still not working I disconected it shut it off took a break capped off wires everthing seemed ok ? came back and nothing will look later f

 

[Warpig 5thMEB]

new fuse block has power? main fuse that normally blows when I do something stupid at battery hot? f chasing wires later

 

[pb4ugo]

Are you using a gm alt? If so, it has an internal regulator. The FJ40 runs a external regulator and will not be used. I run a 1st gen sbc. I personally run a heavy gauge wire from large alt terminal to batt. One of the small wires goes to + all the time. It's usually routed to the large alt terminal. The 3rd wire goes to an idiot light. The white/Bluestripe wire is not used. The white wire at the batt supplies power to the fuse box with a fusible link. I use the batt as my terminal block. The above wiring basically by passes the amp gauge. I disconnect the wires from the gauge and connect the 2 wires together. Checkout madelectricsls website to confirm how you want it wired. There's a lot of good wiring tutorials/tech there.

 

[ukboneman]

Posted this on a thread a couple of weeks ago: "Both sides of the ammeter are positive. Current from the alternator, via the blue and white wire, pass through the ammeter and goes to the battery via the white wire through the fusible link. The ammeter uses the electromagnetic field generated by the current to measure amperage. Sparks will fly if either is connected to negative. Both sides of the ammeter should measure positive with the engine running. If current generated by the alternator is greater than the amperage used by various devices including the engine, then it is positive. If the electrical drain on the system is greater than that being supplied by the alternator, then amperage is negative. the negative from the battery and the alternator goes through the frame."

 

[ukboneman]

So, unplug the three wire plug from the back of the alternator, clean off the terminals and plug it back in. See if it works. Also, check your voltage at the battery with the engine running. It should be 13+ while the battery is charging. These gauges do go bad.

 

[pb4ugo]

So, unplug the three wire plug from the back of the alternator, clean off the terminals and plug it back in. See if it works. Also, check your voltage at the battery with the engine running. It should be 13+ while the battery is charging. These gauges do go bad.

He's most likely not using the fj40's stock alt.

 

[Warpig 5thMEB]

No the alternator isn’t stock it was charging at about low 14 volts before I smoked it will look for melted wires probably in week my next day off. it did sound really good. another exhaust manifold on order yuck. I took the entire motor out of a 2002 Chevy Tahoe 5.3 Vortec gen III I think. The passenger side on a block hugger exhaust worked well but tight that goes down in the middle. driver side I’m going to try a speedway motors LS swap exhaust manifold that comes out the back it has under 3 inches of pipe sticking out from the head it ?? Should give me enough clearance from the stock steering gear box??? if the measurements are right crossing my fingers it’s been a interesting build so far

 

[Warpig 5thMEB]

Flowtech 11730FLT LS Swap Exhaust Manifolds, Natural Cast Finish Part #: 72211730FLTQty: 1 @ $ 225.95 each supposed to fit under 3 inches for the tight drivers side​

$ 225.95​

 

[ukboneman]

probably fried the ammeter also

 

[pb4ugo]

The ammeter wiring and charging system is old and antiquated and is likely fine for the 40's stk wiring and alt. I personally would eliminate the ammeter when using a higher amp output and internally regulated alt like GM's. Again look on mad electrical's websight for wiring ideas. They also talk about the use and history of an ammeter wiring too. If you smoked the harness the white with blue stripe and the white wire probably would not have any insulation left on it in spots. The surrounding wires in the bundle could be compromised from the melting.

 

[Warpig 5thMEB]

Thank you will look

 

[Warpig 5thMEB]

Well the hot side of the ammeter is still hot still no power to tge old fuze block didn’t see anything melted the ground side of the ammeter is cold and disconnected I didn’t check it for juice before I disconnected it I thought it was a ground I bet it was supposed to be hot ?? It’s white blue strip I think might be green stripe didn’t see any burn marks and it didn’t smell? Maybe I disconnected the ignition main plug ? From the instrument cluster or start chasing melted wires under tge dash ?

 

[Warpig 5thMEB]

I’m using a empty 6 pack so it doesn’t touch anything n melt more tgen disconnect battery again

 

[pb4ugo]

With the white blue wire disconnected from the ammeter the fuse box won't have power.

 

[Warpig 5thMEB]

Ok thank you