Ford 8N Charging diagnosis

[yotehunter66]

Went to check my voltage output for my alternator yesterday and my volt meter went crazy as soon as I touched my negative lead to the battery terminal. I'm wondering if a bad diode or voltage regulator would cause that. It is converted to 12 volts.

 

[LD1]

What whas the hot lead connected to?

What alternator? Does it have an internal regulator or external?

Alternators make voltage in AC. Then us the regulator and diodes to get 13-15v DC to charge the battery

 

[yotehunter66]

I didn't even have the positive lead from my meter hooked. When I did I got the same result. My meter was jumping all over and not giving me a steady reading. It's a brand new alternator with built in voltage regulator. I've never had a meter do that before with just the negative lead touching. I didn't measure the battery with the tractor off. I'll do that as soon as I can and report back. Maybe my meter is messed up but I don't think so. Just weird. I also touched the lead to another ground, other than the battery and got the same result.

 

[yotehunter66]

Got home and checked the voltage on the battery and it read 13.3 volts, had it on trickle charge all night. Tractor started right up but as soon as I tried to check voltage with it running my meter went crazy again. Any thoughts?

 

[Soundguy]

Electrical noise from the breaker points ( and Genny brushes if you had one), really messes with cheap consumer grade autorange voms, and units with slow sample rates.

Your ammeter should tell you I current is flowing from the alt into the battery ( charging)

Or

Current flowing from battery to support ignition ( discharge )

 

[yotehunter66]

My ammeter shows a slight discharge when the tractor is running. Should I have the alternator checked? If I remember right I wired the charging wire to the hot post on the starter and the sensing wire to the hot twrminal on the resistor/twrminal block. Their is a diode in the wire.

 

[Soundguy]

Wow. Incorrect on both counts.

1, wiring #1 to a always hot line will drain battery

Didn't here where #2 wired

2, if you wired the alt to the post on the starter its probably dead now, and starter unhappy.

If wired to hot side of start relay, then you defeated your net charge/discharge ammeter scheme making it a useless tool.

I recommend you retreat, regroup, then rewire the tractor correctly. Then see if it has a problem and go from there.

 

[yotehunter66]

I'll check it tomorrow. Going off memory and it's not so good anymore.

 

[Soundguy]

Post back after verifying/correcting wiring and charging battery

 

[yotehunter66]

Finally got around to checking the wiring and the only one I had wrong was the charging wire from the alternator. I had it on the hot side of the amp gauge instead of the load side. As soon as I moved it to the right side I was showing about 22 amps. So assume my alternator is charging.