alternator won't charge

R

robbymeyer

Member
Hi guys,
Jeff just helped me fix up my family's 1972 1210 pickup. Its a 392, automatic 4x4. I have put about 1k miles on it since getting it back. A week ago I replaced the alternator with a remanufactured unit. The pulley had gotten loose on the original one and I am afraid I damaged it driving around like that. The reman alternator fit nicely and I got all the wires and belts on. Now when I start the truck the battery is being constantly discharged. I checked the voltage on the alternator connectors. The main output and pin #2 both have 12 volts. Pin #1 is at 0.3 volts, so I guess the field is not getting any power. To check that the alternator can work I wired a 25 watt 10 ohm resistor between b+ and pin #1 on the alternator. I fired the truck up and it started charging perfectly. I have a few questions. First, is the switch that controls the circuit for alternator pin #1 just the ignition switch? Second, is there a common place that circuit breaks (switch, bulkhead connector, along the flimsy resistor wire)? Last, can I replace the resistive wire with a bigger 16 gauge conductor and just use my power resistor to limit the current into the field?
Thanks,
rob
 
There’s a ton of alternator stuff on here and on madelectrical. I’m sure others will post that know more, but let me try to exercise my knowledge a bit.

There’s a ‘turn on’ wire from the ignition, a ‘ramp up’ wire that tells the regulator to make more juice, and the battery wire. If you’re getting power from the alternator then your turn on wire is fine. If you get the ramp up on current draw and the battery dies you are not getting enough juice to your battery. That would mean upgrades or bypasses. If you don’t get the ramp up from the alternator it sees a constant draw and there’s so much resistance it can’t see a change. There’s a ton of resistance and routing for charging and ramp up. There are a lot of places where it could be so it’s a matter of following and replacing more than likely.

Read up on this. It has a lot of great info.
catalog

As a personal note, I had a lot of issues (low power to accessories, battery constantly draining, funky voltage readings) on mine. I replaced the engine compartment side of the on wire and ramp wire and then bypassed my gauge (not completely) to get more power to my battery. She runs great now. Now my issue is my 10si can’t keep up with heavy winching.
 
robbymeyer said:
hi guys,
Jeff just helped me fix up my family's 1972 1210 pickup. Its a 392, automatic 4x4. I have put about 1k miles on it since getting it back. A week ago I replaced the alternator with a remanufactured unit. The pulley had gotten loose on the original one and I am afraid I damaged it driving around like that. The reman alternator fit nicely and I got all the wires and belts on. Now when I start the truck the battery is being constantly discharged. I checked the voltage on the alternator connectors. The main output and pin #2 both have 12 volts. Pin #1 is at 0.3 volts, so I guess the field is not getting any power. To check that the alternator can work I wired a 25 watt 10 ohm resistor between b+ and pin #1 on the alternator. I fired the truck up and it started charging perfectly. I have a few questions. First, is the switch that controls the circuit for alternator pin #1 just the ignition switch? Second, is there a common place that circuit breaks (switch, bulkhead connector, along the flimsy resistor wire)? Last, can I replace the resistive wire with a bigger 16 gauge conductor and just use my power resistor to limit the current into the field?
Thanks,
rob
Click to expand...

Hi rob,
do you have an external voltage regulator on your IH? If so disregard the following. It is only relevant to the internally regulated 10 and 12si delcos. They were released in 1971.
Terminal 1 (marked on alternator case) is the connection for the charge failure light on the dash. If the regulator senses a failure it grounds your charge lite. Don't connect it to the b+ term directly. Should not be needed to charge.
Terminal 2 (marked on alternator case) is the battery voltage feed back to tell the regulator when the voltage set point (around 14.5v) is reached. This terminal is wired into the +12 volt side of your electrical system. For all intents ands purposes it can be wires directly to the b+ terminal. This is a so called 1 wire conversion along with a 10si alternator and an internal regulator. This is a cheap swap.
 
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can I replace the resistive wire with a bigger 16 gauge conductor and just use my power resistor to limit the current into the field?
Click to expand...

Short answer is no. The alternator is in a "system" with the battery and it's output has to vary with load and battery charge.

Your description sounds like an externally regulated system, same as is on my '71 1210. The regulator is on the driver's side bulkhead just above and to the side of the steering column.

Check the electrical stickies For a thread on the various delco alternators and see where yours fits, or run it by an electrical automotive rebuilder to id it. More than likely the regulator is shot and you can get a brand new electronic version with the proper plug in receptacle for around $20. I got mine at carquest.
 
Thanks for all the replies. To make a long story short I got the alternator charging again. It is a 10si with the 3 wire setup. I had replaced the connector to terminals 1 and 2 over the weekend which did not seem to work at the time. Today I poked everything with a volt meter including both sides of the bulkhead connector. It all looked good so I fired the truck up and it started charging. I'm not sure why it didn't work Sunday night. Now I'm afraid there is an intermittent connection on the field energizing wire, but until I see the battery discharging again I guess I'm fine.
 
When you replaced the terminals did you also replace the wires? When I did mine I replaced the wires back to the bell housing. Those things were in rough shape. I had intermittent charging issues till I replaced that section of wires, the pigtail, and put in the bypass.

You don't want to get stranded. I'd keep jiggling things and troubleshooting. Before I finally got mine fixed I had mine die on the road.
 
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