No output from alternator

[Curious Hound]

Well I've got 2 alternators. The trick worked on the new alternator but I put the original back in and straight wired power to pin 1. It came on for a few seconds then quit. Maybe I fried it. So maybe some resistance is required to not do that. Anybody know?

Did you fry something? I’m not sure. That circuit does expect a certain amount if resistance. There is even a resistor in parallel with the indicator lamp so the circuit will function in the bulb blows.

 

[Conflict]

I put the new alternator back in and wired it through a 7.5 amp fuse and a 470 ohm resistor I had because the elec schematic showed a 442. No good. Tried 150, then 100, then just a bulb. No good. Straight from the fuse to pin 1 and it comes on and stays on and hasn't died yet. Volt reg will tolerate no resistance. So I'll find a key-on power source, send it through a fuse and call it fixed. I guess I'll put a voltmeter on the dash for info. The unanswered question is why can't i duplicate the circuit depicted in the electrical diagram?

 

[Conflict]

I'll take the alternator that I may have damaged down and get it tested.

 

[Curious Hound]

Are you sure you are getting full battery voltage to pin 1 through the normal circuit from the ignition switch? I'm not talking about checking it with a test light. This is a case where you need a volt meyer to give the actual voltage reading.

When you bypass that circuit with a jumper, you say the alternator works. So, that indicates that the normal circuit is faulty - loose or dirty connection somewhere or maybe even shorted to ground somewhere between the unducator light and the alternator.

 

[sgtsandman]

To add to what Curious Hound is saying, you can also have good voltage but with a bad wire, you won't have the amperage needed to support proper function. Proper voltage just shows you have connection, it won't show if the wire will support the current flow needed. If you have the right amperage test light, you can test to see if the wire can support the proper amperage.