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Charging system problems

The_Epsicle

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Charging system problems (RESOLVED!)

I drive a 1994 Ford Ranger 4.0, auto 4x4, auto tranny. I was recently doing some A/C work that failed catastrophically and now my battery light is on, I had to engage the clutch for the A/C with a jumper wire and I ended up having a high pressure line explode and spray refrigerant everywhere.

I tested between the red alternator wire and the positive side of the battery with the negative disconnected and I was reading 0.2 OHMs, when the engine is running the alternator reads as putting out 10 - 11 volts and it does not increase or decrease depending on engine speeds. with the engine off I read 12 volts at the battery. There is a yellow wire on a connector for the alternator that has no connection to the negative terminal of the battery at all and I think it might be grounded out somewhere along the wire or there's a fuse, I had no issues with the charging system prior to yesterday. I replaced the alternator today to no avail, it was still reading 10 volts with the engine running. Help please I need this truck to run by the weekend. :sad:.

UPDATE: The alternator is good, the ignition switch is good, the battery is good, no fuses are blown, the fusible link is good, the car starts and runs fine for several miles, the light is still on I sent it to a mechanic to have someone double check my work and everything came back the same. I am making 12.6 volts with the car on, I am currently focusing on the instrument cluster and so far have not found any issues with it. I will be checking all the pigtails and wiring again when I get the chance, when I test the wiring again I will break the harness apart and visually inspect every wire contained inside and if I find any issue I will replace the entire wire.

RESOLVED: This is an instance that shows I shouldn't doubt my instincts, the green/red striped wire was grounded out between the alternator and the instrument cluster, I ran a jumper wire between the two connectors and the light went off, checked the voltage and I was getting 14.2 :headbang:. Special thank you to RonD for all the help he gave, he knows his stuff.

EDIT: I took it for a brief ride around town today and noticed that the engine sounds a lot stronger than it did before, my erratic idle seems to be mostly gone and many of the rough stumbles I've had on take off have disappeared as well. I think that wire was putting a drain on the system for awhile and only recently triggered the charge light.

UPDATE (8/12/2016): I took off the wiring harness today and discovered a mouse had chewed the wire.
 
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You probably blew a fuse when doing your jumpering.
 
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black_demon69

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I drive a 1994 Ford Ranger 4.0, auto 4x4, auto tranny. I was recently doing some A/C work that failed catastrophically and now my battery light is on, I had to engage the clutch for the A/C with a jumper wire and I ended up having a high pressure line explode and spray refrigerant everywhere.

I tested between the red alternator wire and the positive side of the battery with the negative disconnected and I was reading 0.2 OHMs, when the engine is running the alternator reads as putting out 10 - 11 volts and it does not increase or decrease depending on engine speeds. with the engine off I read 12 volts at the battery. There is a yellow wire on a connector for the alternator that has no connection to the negative terminal of the battery at all and I think it might be grounded out somewhere along the wire or there's a fuse, I had no issues with the charging system prior to yesterday. I replaced the alternator today to no avail, it was still reading 10 volts with the engine running. Help please I need this truck to run by the weekend. :sad:.
next time if you must jump the wires on the connector to the compressor cycle switch located on the accumulator it is much safer. A/C will have to be on in the climate controls inside the truck.

as far as alt is concerned you might have blown the voltage regulator on the alt
 

RonD

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No Ground wire on an alternator.
People add them some times but there will not be a "factory ground"
Alternator is grounded by being bolted to the engine.

First, hook up battery cables if they are off, then test alternator wiring with volt meter.

B+ terminal, with stud and nut, on the back of the alternator, should have 12volts(battery voltage), key on or off.
If not then follow it's Black/orange stripe wire back to Starter Relay on inner fender, it will change into a Gray wire, that gray wire is a Fusible link(like a slow blow fuse), and it will be broken, replace it.

There is a 3 wire connector on the alternator, unplug this connector.
Yellow/white stripe wire should have 12volts, key on or off, if not then there is a 15amp fuse in the engine fuse box for that wire, it is blown, #20 I think

Light Green/red stripe wire is the ON/OFF switch for the alternator, it comes from battery light in dash, it should have 12volts only when key is on.

White wire is a jumper from connector to Stator in alternator, make sure wire ends are not fray, i.e. "holding on by the thread" that goes for all 3 wires on this connector.


If every thing tests OK hook wires back up and then start the engine.
Battery voltage should now be above 14volts.
If it is under 12.2volts then alternator is bad.

That 14+ volts should drop down to 13.6volts in a few minutes, that means voltage regulator in the alternator is working.
Lights on, Fan blower on high, at any RPM, battery voltage with engine running should be 13.6volts, after initial recharge(14+ volts)
 
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The_Epsicle

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Isn't the voltage regulator part of the alternator itself, if so shouldn't replacing the alternator have fixed it? I checked every fuse in the power distribution box and couldn't find any that were blown, I heard there is an inline fuse for the alternator but I don't know where it is. I'll clarify, I jumped 12 volts from the battery to the A/C relay in the fuse box to engage the clutch on the A/C.

EDIT: I'm really sorry I only skimmed those replies, I should read more clearly. If I did that I probably wouldn't have this problem right now. Thanks guys.
 
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RonD

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"I heard there is an inline fuse for the alternator but I don't know where it is."

'94 4.0l probably still has the Fusible Link, that is the Gray wire mentioned my post above.
Fusible links were attached to the starter relay(solenoid), on the same post as the positive battery cable

A Fusible Link is an inline fuse in the form of a short wire that will melt and separate without starting a fire, like any fuse does, but fusible links can absorb temporary high amp spikes without blowing, which is why they were used.
Fusible links are color coded, Gray is the color Ford used for it's 12gauge fusible link.
Wire from alternator would be 8gauge, fusible link wires are 4 gauges higher(smaller) than the main wire, so the 12guage wire will get hot a separate before larger 8gauge would

1994 Rangers had 95 amp alternators
 
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The_Epsicle

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UPDATE: The fusible link is fine, my power distribution box doesn't have a fuse in slot 20 and it doesn't look like it ever did. I can't find a diagram for my power distribution box online and somewhere along the lines the owners manual got thrown away. I re-checked all the fuses in both the fuse box and the power distribution box and didn't find a single blown fuse. I'm recharging the battery right now so I can't do all the tests that RonD laid out but I will when I'm done, I'm a little concerned because the light was still on with the brand new alternator from NAPA.
 

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The way the Battery light works is to use the alternator as the Ground for the bulb.

A light bulb glows when power is "passing" thru it, so it needs 2 different voltages, in this case 12volts(battery) and 0volts(ground, battery), if you hook up 12volts to both contacts of a light bulb it won't light up, because no power is passing thru it, current needs to flow for bulb to glow.

Battery-------Key switch-------------Battery Light------------------Alternator---ground.

When you turn the key on the bulb gets 12volts on one contact, and if the alternator is not generating power then it is a "ground" so other contact is 0volts and power flows thru the bulb, Battery light is on.

When you start engine and alternator is working then both contacts on the bulb are now 12volts(13.5volts) , so bulb goes off, no power is flowing thru it.

A bulb is just a thin wire that glows when it heats up from power flowing thru it, so its wire at the alternator should show 12volts when key is on, this 12volts comes thru the bulb from ignition switch.

Battery light flickering or "glowing" at idle means alternator voltage is dropping below battery voltage, if battery is 12.5volts and alternator is only generating 11.5volts at idle then bulb will come on since alternator side is lower voltage so current is flowing thru bulb.
If alternator voltage increases with RPMs then light goes off
 
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The_Epsicle

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UPDATE: I did all the tests and they were all fine but for some reason I'm still not making enough voltage. I'm at a loss for what this is so I'm going to take it to a mechanic I trust to check the system over.
 

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Bad alternator.

Wiring is the wiring, if it checks out then alternator is bad, regulator(in alternator) can be blown just from hooking up the battery after install, they are just small "chips" now, magic smoke can come out of them at any time.
And we all know electronics don't work after you let the magic smoke out. :)
 

The_Epsicle

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Bad alternator.

Wiring is the wiring, if it checks out then alternator is bad, regulator(in alternator) can be blown just from hooking up the battery after install, they are just small "chips" now, magic smoke can come out of them at any time.
And we all know electronics don't work after you let the magic smoke out. :)
I'm not fully convinced of that unless I have two alternators that have failed in exactly the same way and if they both have failed in the same way then I am concerned that I have a fault in the system that I'm not seeing that will just kill any alternator I put in there. I'm not skilled in finding electrical gremlins, for $20 I'm going to have my mechanic double check my charging system and make sure I didn't miss anything. If it's the alternator well then I just spent $20 for a little piece of mind to know nothing else is wrong.
 

The_Epsicle

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Light Green/red stripe wire is the ON/OFF switch for the alternator, it comes from battery light in dash, it should have 12volts only when key is on.
I found out I cannot get in to see the mechanic until Friday when I need to leave to travel 300 miles. I tested all the wires again and the green/red wire had no power running to it at any point (key on or off, and engine running) if I understood you correctly that means my alternator isn't engaging and therefore will not charge anything. So now I know what's wrong(more or less) :yahoo:.

With that in mind you say it comes from the battery light on the dash, could the wire just be grounding out before it reaches the alternator or making a short circuit with another wire in the harness? Does anyone know how this wire is routed throughout the vehicle so I can check it?

Thank you RonD for helping me get this far :icon_thumby:

EDIT: The Red/Green wire has continuity to the positive cable on the battery but when I try to ground it, key on or off, I do not read any voltage.
 
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RonD

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Wiring diagram here: http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_1.JPG
Just looked at a '94 diagram and it is the same.


Should be Green/red stripe wire, and yes that is the ON/OFF switch for an alternator.
When you turn the key on the battery light should come on, if you disconnect the 3 wire connector on the alternator the battery light should go off, that is it's ground, if it doesn't go off then yes that wire is grounded somewhere.
If light goes off then you should have 12volts at that wire in the connector.

Because an alternator is in essence an electric motor used in reverse, if it is left "on" when engine is off it would drain the battery, trying to turn, this is what that wire is for, it turns alternator off.
Because this is an important circuit you will see a 510 ohm resistor by-passing light bulb, it is there in case bulb should burn out, resistor would pass enough voltage for alternator to turn on.


One wire alternators use an RPM ON/OFF switch, they turn on when XXX RPMs is reached, and turn off when RPMs drop below XXX, alternator RPMs of course not engine RPMs.
 
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The_Epsicle

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Thanks RonD, I'm going to look at replacing that wire tomorrow, I discovered my power steering pump(which will be replaced as soon as Harbor Freight sends me my pulley puller that was supposed to be here 2 weeks ago:annoyed:) is leaking ATF onto that section of the wiring harness. I'm going to clean that section up and inspect/replace any damaged wires there, my money is on my problem being in that section. Again thank you so much for your help, you're awesome :icon_thumby:
 

The_Epsicle

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No dice, the way I'm going I am going to end up breaking something important and it will never run again. I know when to quit so I'm going to take it to the mechanic tomorrow. Unfortunately this means I'll be driving a PT cruiser to Minnesota but at least it has air conditioning... :annoyed:
 

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