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Old 08-10-2015
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Join Date: Apr 2014
Location: Uxbridge, ma
Posts: 2
Regualtor / Alternator / no idea


I have been resurrecting a Ranger 2003 XLT 4.0L (4WD)

I need to ask a question on a possible regulator issue.

Okay, a little background.
Starter, battery, belt, alternator/regulator all 1 year old. Alternator is 3 days old. Regulator is on back of alternator.

I was working on a air bag warning light issue. While I was working on this I was playing the radio. Truck previously started in the morning.

After about an hour or so, with doors open and resolving the air bag issue; the truck wouldn't start. A clicking noise was heard.

Seems to be a repeat problem lately. I naturally took my volt meter and measured the voltage. About 12.5. I took my jump battery and got it started.

I had replaced the alternator on 7-27. I drove to Auto Zone (where I bought it). They tested the battery and said it could use a charge. They tested alternator and it was good. The voltage regulator was not.

So I explained that I just purchased it off them and he said "it happens".
Got a new one, it was bench tested before I went home.

Replaced alternator again, made sure battery charged to about 13.0 before starting. All is well.

I head back to Auto Zone, they bench test the previous's okay.
They test my truck and it says regulator bad.

Truck starts consistently in the morning, but it appears to be some sort of drain.
I'm assuming, maybe a coincidence when I had all doors open and radio on. I don 't know.

Any suggestions on where to start?

When I purchased the truck, the original alternator was frozen and we finally got it started.
Order of replacement was:
Starter, then a belt, then a battery and now the alternator/regulator.

Could it be I might have damaged something else?

I should also say that I've cleaned the terminals/connectors as well. At least around battery and alternator

Thank you Al
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Old 08-10-2015
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Join Date: Jan 2014
Location: Vancouver, BC
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I would do a quick test.
key off
test battery voltage, should be 12.3-12.8volts, new battery 12.8v, 5 year old battery 12.3v

Now if possible have volt meter hooked up to battery where you can see it and start the engine, volts should stay above 9.8volts.
If voltage drops more then could be a bad cable or starter motor going out, drawing too many amps.

After engine is started you should see 14+ volts at battery, but under 15volts
This is the "recharge voltage" the voltage regulator uses just after battery drain from starting.
This voltage should drop to 13.6volts after a few minutes.
Generally the voltage regulator will run a "maintenance charge" of about 1.1v above battery voltage, this will keep battery charged but not "cook it", above 14v long term will shorten battery life.

Once voltage is at 13.6v turn on head lights, voltage should drop and then come back up to 13.6v
Turn heater fan to high, same drop then back up.
Turn on everything you can thing of, lol, doors open, cargo light on, voltage should stay at 13.6v.
This drop and return is the voltage regulator working like it should.

If things don't come out as above then test the voltage at alternator.
Key off
Voltage meter black probe on battery negative, or good ground
Red probe on B+ terminal, large terminal on back of alternator, should read battery voltage here, i.e. 12.5v
Pull off 3 wire connector on alternator
Yellow wire with white stripe, red probe, should be battery voltage, if not Fusible link is bad

turn key on
Light Green red stripe wire to red probe should now have battery voltage, turn key off, voltage should be 0 now, this is the ON/OFF switch for alternator(battery light on dash), just FYI, if this is left ON then battery will drain.
The main reason there is a "accessories" selection on the key switch is so the alternator is not ON, and draining the battery.

New rangers have a "battery saver" relay, once the key is off and all the doors closed, the battery saver relay will start a 20-40min count down, once timer gets to 0 the battery saver relay will cut power to minimum, so if a dome light or glove box light was left on by mistake it should good off, it also cuts power to GEM module.

battery saver relay makes it hard to test for voltage drains, because you need to wait 20-40min. before you can see what the true amp draw is.

Last edited by RonD; 08-10-2015 at 01:03 PM.
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Old 08-10-2015
Join Date: Jun 2005
Location: Havertown,PA
Posts: 467
Was your airbag warning have continuous chiming?. I had an Escort that had a air bag error and chimes would chime even with car off. It drained battery.
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Old 08-11-2015
Thread Starter
Join Date: Apr 2014
Location: Uxbridge, ma
Posts: 2
No chime

Thanks for the heads up on the chime.

I replaced all of dashboard lights a few days ago and that exposed a blinking air bag light.

It was code 27. Which says the diode in the passenger airbag module was bad. So I could either replace the entire module for $80 or replace the led diode for $3. I headed off to Radio Shack and got it done.

Great video on YouTube for this.
This is how I came across this battery not charging due to working on the problem.

I checked the battery yesterday it's down to 11.2 volts. Starts up constantly.

I'm trying to find another battery so I can rule it out.
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Old 08-11-2015
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I would check volt meter on another battery, 11.2v is a very dead battery car battery
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