HELP!!! Charging System Trouble

[rockjock]

thats what i thought but wanted to double check to be sure at this point.

 

[PanamaExpat]

Did you get a chance to check it all out? Wondering if you discovered anything.

 

[RonD]

There should be two fuses in the engine compartment fuse box, a 40amp and 15amp per this drawing:
http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_charging_1991_1.JPG

Also make sure the short jumper wire on the back of the alternator is not loose or "hanging on by a thread"

Also with engine off and key on the larger wire on the back of the alternator should read the same voltage as the battery, 12.4v in your case, if not then that wire is not connected to the battery so can't charge the system.

 

[rockjock]

i just got home from church so headed out to the shop now.

RonD i dont have a jumper wire on the back of the alt. but ill check for the voltage with the KOEO.

 

[rockjock]

12.31 AT BATTERY WHILE RUNNING - 12.31 AT ALT

12.78 AT BATTERY WHILE ENGINE OFF - AT ALT 12.78

CHECKED RESISTANCE OF LARGE LEAD TO ALT FROM SOLENOID O.OO OHMS

IVE PULLED THE + BATTERY LEAD WHILE MOTOR RUNNING AND THE MOTOR DIES????

Everything is pointing to the Alt but it had been tested many times with different testers and its shows as passed each time.

 

[RonD]

Just FYI, don't pull a battery cable while engine is running, you can fry electrical parts doing that.

The voltage with engine off and on tells you the alternator is pulling power from the battery instead of charging the battery.
So yes, engine spark(coil) is running off the battery so when battery is disconnected engine dies.

From your first post you have a 1994 explorer alternator with wiring harness.

You have to have the extra wires hooked up to the alternator or you will get no voltage out of the alternator, they run the voltage regulator.
There should be 3 wires besides the larger wire hooked up to the alternator, one of those is a short jumper wire.
"S", "A" and "I" are the wire labels.
"S" is a short jumper wire
"A" runs to power box or solenoid
"I" runs to the charge gauge or idiot light in the dash board, then to ignition and other systems.

 

[rockjock]

Just FYI, don't pull a battery cable while engine is running, you can fry electrical parts doing that.

The voltage with engine off and on tells you the alternator is pulling power from the battery instead of charging the battery.
So yes, engine spark(coil) is running off the battery so when battery is disconnected engine dies.

From your first post you have a 1994 explorer alternator with wiring harness.

You have to have the extra wires hooked up to the alternator or you will get no voltage out of the alternator, they run the voltage regulator.
There should be 3 wires besides the larger wire hooked up to the alternator, one of those is a short jumper wire.
"S", "A" and "I" are the wire labels.
"S" is a short jumper wire
"A" runs to power box or solenoid
"I" runs to the charge gauge or idiot light in the dash board, then to ignition and other systems.

Ok here where im at now i found the all the leads

KOEO tested before connection to the alt (not hooked to the alt)
"A" has battery voltage
"I" has zero volts
"S" is at zero volts

SAME WITH ENGINE RUNNING

 

[rockjock]

should I have the ALT retested????


THe "S" lead is not hooked to anything could this be an issue???

 

[RonD]

"I" won't have voltage unless the alternator is outputting voltage
"S" is the jumper wire to control alternator voltage so needs to be connected back to another alternator connection.
There should be a 4th(5th counting B+) connector, with a spade connection that the "S" wire plugs into.


This diagram might be easier to understand:
You should have the 2G setup
http://www.grandmarq.net/vb/showthread.php?29841-Alternator-wiring-diagrams-1G-2G-and-3G

The white/black wire, "S" to "S" jumper, is what seems to be missing that is what allows the alternator to output voltage.

 

[kimcrwbr1]

You should be getting battery voltage or a little less than battery voltage at the I wire on the alternator with the key on run. that is the wire that tells the alternator how much voltage to produce.

 

[rockjock]

"i" won't have voltage unless the alternator is outputting voltage
"s" is the jumper wire to control alternator voltage so needs to be connected back to another alternator connection.
There should be a 4th(5th counting b+) connector, with a spade connection that the "s" wire plugs into.


This diagram might be easier to understand:
You should have the 2g setup
http://www.grandmarq.net/vb/showthread.php?29841-alternator-wiring-diagrams-1g-2g-and-3g

the white/black wire, "s" to "s" jumper, is what seems to be missing that is what allows the alternator to output voltage.

zero voltage at "s" and "i"
CHECKED FOR RESISTANCE AND BOTH ARE O.O OHMS

 

[kimcrwbr1]

Hook a jumper wire to any key on hot to the I wire on the alternator it should show charge when the engine is running. You should get around 2.5 volts above battery voltage at around 1500 rpms.

 

[kimcrwbr1]

It should be the red/ltgreen stripe wire used for your coil pos circuit.

 

[rockjock]

i found a hot with key on wire that is unused. i have 14.5 at the battery and back of ALT now is it safe to leave it hooked up permanently???

 

[kimcrwbr1]

I believe so is the amp guage working also. Do a load test turn the lights on high and heater on high and chech the battery voltage around 2000 rpms you want no less than .5 above battery voltage. If the battery is 12.8 volts with the key off you want nos less than 13.3 volts with the lights and heater on high.