Does this sound like an alternator?

ryan2022 · May 16, 2016

Hi guys,

I did a bunch of short trips around town today. I have an '05 Ranger with 80k miles or so.

The last three times I started it, it was more and more reluctant to turn over. The final time it just conked out and wouldn't start.

I got it boosted, and drove it almost all the way home and it started losing power. My foot was almost all the way to the floor and I barely made it in the garage.

We boosted it again when my wife got home. The battery was tested a few months ago and was ok. Its a newer battery.

I just popped in a new alternator seeing how I need the truck tomorrow. The damn DC side of my meter is burned out and I bought a new one at the parts store....it didn't work....yep.. one of those days.

RonD · May 16, 2016

Yes it read like alternator was going out.

But it can take fuses with it.

When you turn on the key you should see the Battery Light(Charge indicator) come on.

When you start the engine then it should go off.

If it doesn't come on with the key check Fuses #9(5amp) and #10(10amp) in the cab fuse box(smart junction box)

But you really need a volt meter to test it.
Battery should be 12.3 to 12.8volts, engine off
Battery should be 13.6 to 14.9volts, engine running.

You can turn on the head lights and then start engine, if they get brighter then alternator is putting out more that 12.5 volts(battery voltage)
If they stay the same or get dimmer then alternator is not working.

ryan2022 · May 16, 2016

Awesome, Thanks Ron.

I'll double check this one. I really hope it wasn't just a loose connection. I believe the battery light was coming on, and I know it shut off once the truck was running.

I'll double check the lights. I need to replace my meter asap!

Ryan

RonD · May 16, 2016

Just as an FYI.

The Battery Light is very important, that's the "ON" switch for the alternator.

For an alternator to generate voltage it needs to be "fed" voltage.
Voltage regulator feeds the rotor 5 to 9 volts, the rotors spin from engine power creates 13 to 15volts that goes to the battery/electric system.
And once started the voltage regulator uses the 13-15volts stepped down to 5 to 9volts to feed the rotor, so self sustaining.
BUT(big but)............if voltage regulator doesn't have any voltage to start with then it can't feed the rotor any voltage so spinning the rotor can't produce any voltage, dead alternator.
When you turn on the key the Battery Light circuit sends 12volts to voltage regulator so it can feed the rotor the 5 to 9 volts for start up.

Why not just give voltage regulator power all the time?
Well, it would act like an electric motor then, alternator would try to turn the engine, lol, and you would end up with a dead battery.
So Battery Light is the"ON" and OFF switch.

1 wire alternators use an RPM switch, the voltage regulator only gets power when alternator RPMs get above 500, voltage comes on and alternator starts generating power, when engine is shut off RPMs drop below 500 and power is cut to regulator.

ryan2022 · May 17, 2016

Awesome! Thanks Ron. That's good info.

Does this sound like an alternator?

ryan2022

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RonD

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ryan2022

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