Painless Alternator Wiring

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Dec 18, 2007
Normal, IL
Installed a Painless wiring harness and the alternator is not charging the battery. I have wire red wire 715 to alternator output poist and have re-used the original wires to the external regulator. I have not plugged in the white wire 714 which states "to alternator regulator exciter." Should this wire be connected somewhere? :confused:I have a new alternator, regulator, and battery.

Also, how is the amp meter to be wired? If I read the diagrams right, the output wire should connect to one side of the guage and then continue out the other post on the guage to the battery...If I do this, won't I burn up the wires in the guage? The original diagram doesn't show this very well and the old harness was pretty much destroyed. :bang:

Finally, I can't get the fuel guage to work with the new harness. I installed a new sending unit in the tank and this did nothing also. :mad:

PLEASE HELP!!! :idea:
What year cruiser?
What engine and alternator?
What parts of the original wiring do you plan on keeping?

With the OEM wiring on '78 and earlier cruisers, all current in and out of the battery (except for the starter motor) goes through the amp meter. The stock amp meter has an internal shunt and can handle at least 30A continuously and maybe twice that for short periods.

The fuel gauge circuit only needs to get key on power from the fuse block to work. The circuit goes: fuse-meter-sender-ground and the sender is a variable resistor or rheostat. The higher the fuel level, the lower the resistance. There aren't that many things to go wrong. Check for 12V at the both ends of the meter and if you have power, try grounding the sender side of the meter momentarily (less than a second) and see if the gauge deflects right.
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WRT the ammeter, it requires a shunt. This is called the "fuse link". A wire from each side of the fuse link is attached to the meter and reads the voltage across the "fuse link", which is a calibrated piece of wire from the factory ..

On older FJ40's, the battery + feeds the "fuse link" and then to the +side of the ammeter. The neg (-) side goes to the input of the ignition switch (WL).

REF: FSM 98154.

Don't know about the rest ;

It is a 1973 FJ40 built in September 1972. The only original wires I reused were between the altrnator and voltage regulator.
My guess is that the "alternator regulator exciter" wire goes to the IG ignition terminal at the voltage regulator. This is where the original black wire with yellow stripe connected and it should be hot only with the key in the on position. The orignal wires will go to the same connections on the alternator.

The wire from the alternator B+ lug connects to the - side of the amp meter.

The fuel gauge also needs a key on power supply wire, but it does not have to have it's own fuse because the guages don't draw that much power.
I've been looking for this

Pin_Head,,,I've been looking for this explanation for quite some time I might actually understand it - and I just purchased a real cool multimeter for all my re-wiring projects,,,,now I just have to read the multimeter directions, figure out the FJ40 wiring diagrams, and spend a few days stuck under the dash,,,to sort out some nasty wiring
Pin Head, Thanks for the information. However, this brings out more questions. This will make 6 wires for the 4 wire ignition switch. Do I still need them all? Which wire Painless to which original wire?
I don't really follow what you mean.

There are only 4 wires at the OEM Toyota switch. The common power feed from the amp meter AM, the Acc accessory position for the radio, the key on IGN which feeds the switched side of the fuse block bus bar, and the Start position, which goes to the starter solenoid. Which wires from the Painless kit go to the ignition switch?
I'll have to look tonight. I remember 5 wires in the Painless wiring harness I currently have attached to the ignition, now plus the wire recommended above. I have 2 painless wires going into 1 wire in the OEM ignition switch. This additional wire (alternator exciter) will make 6. Tonight I'll get more information concerning the other 5 wries while I still have my gage cluster out.
It is hard to imagine that you would need any extra wires connected directly to the switch. In the OEM wire, the IGN side of the switch powers the ignitor and coil in addition to the key on side of the fuse block. Besides the starter motor solenoid, everything else goes through the fuse block, because everything else is fused. Connecting anything else to the switch that is not fused is a bad idea.
Here is what I have...Connected to:
Black and Red wire is #734 (Ignition switch B+) and #733 (Ignition switch ignition)
Black and Yellow is #731 (Ignition switch - Coil Ignition)
Black and White is #719 (Ignition switch - Starter)
Blue and Red is #732 (Ignition switch - Accessories)

I have the "Alternator B+" Painless wire going to the + Post on the Alternator, but I currently have the "Alternator Exciter" going no where. Does this help? I don't have her on the road yet, but as stated before, the amp guage does not work and the new alternator is not charging the battery...Please Help!

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