Alt was not charging on my 1490 and auto parts store test showed "bad diode". Bought a new lifetime alt that tested good at store but on tractor still not charging. 12.3v at battery and post on alt. Not sure where to look next. Any help or advice is appreciated.

Thanks.

I would have the alternator checked. Hal

Did you try raising the rpms a bunch and then check?

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Is the indicator light in the dash good? When I do a Delco conversion I use it to excite the alternator.

Big wire at bolt on terminal to the big lug on the solenoid.

One spade goes to the big bolt terminal on alternator, the other back to the "on" position on the key switch by way of the idiot light. I forget which at the moment, and it is raining too hard to go outside.

Took off a Delco 3 wire that tested bad and installed new "good" Delco 3 wire but it still won't charge. Ugh.

Thanks.

You can check the diodes with an ohm-meter. With the wires disconnected from the alternator, set the ohm-meter to ohms and touch one probe to the large terminal and the other to the alternator case. Then reverse the wires. There should be current flowing only one way. If there is continuity both ways, the diodes are bad. I have run onto this problem recently myself at a local auto parts store, so when they tried to replace it with another one with the same problem I caught it at the counter with my Ohm-meter. Burns me down that the rebuilders are not replacing the bad rectifiers. School Kids for evening help, or what? Hook the battery to the big terminal. This battery wire goes directly through the Ammeter to the Alternator. Then a small 12v wire from the switch should go to the alternator to excite the field coils and then it should work. ---Derrol in Texas---

not enough info. What did you install? take off? Surely you didn't install a new Lucas? Delco? 1 wire or 3 wire?

not enough info. What did you install? take off? Surely you didn't install a new Lucas? Delco? 1 wire or 3 wire?