One Wire Alternator Trouble
I have a 1990 Bronco XLT with 5.8 EAOD that I am having serious voltage drop problems with. When it is running, if I turn on the blower motor or other high drain item, the volt gauge in the dash drops significantly, the motor slows, lights dim, and if I run it long enough, the "Check Engine" light comes on. When I park it, the battery is low. What stinks is that when I got it, the entire truck and its wiring was filled with mud and corroded, so not sure what's going on.
I've thrown lots of parts and time at chasing an elusive "bad ground/short", and I'm stumped. Here's what I've replaced so far:
Blower Motor
Blower Resistor
Dash Gauge (whole instrument panel)
Dash ground (G201)
Ground in the pillar behind the driver seat
Frame/engine ground underneath the alternator
Body ground from frame to core support
Alternator
Starter
Starter Solenoid
Battery
All the starting/charging wiring
I'm now thinking it has something to do with the "self exciting" one wire, 200 Amp alternator I got from Motor City Reman. It's a large case 3G style alternator, and the wires look exactly like this:
http://www.oldengine.org/unfaq/3ag/3agcon.jpg
I had the "battery" post wired through a fuse into the positive terminal of the battery, and a wire from the battery to the solenoid post. The wire marked "A" in the picture, which I believe is the voltage sensor, was run from the plug directly over to the battery post on the back of the alternator(!). The third wire was cut off inside the plug I received from Motor City Reman.
I think what was happening is when I flipped on the blower, I was putting a drain on the system, but the "self exciting" alternator was "sensing" voltage at the battery terminal of the alternator, which will always be the same no matter what. As the battery drained, the alternator was busy telling itself everything was fine and running at 14.5 volts, so no need to supply extra voltage.
I tried rewiring it through a distribution block as follows:
Alternator Battery Wire > Distribution Block > Battery
Alternator "Sensing" Wire Yellow/White > Starter Solenoid Terminal
Battery > Back to Starter Solenoid Terminal
I left all the stock fusible link wires on the starter solenoid terminal, but moved my car alarm, amplifier, and offroad light wires from the battery terminal to the distribution block.
I still have one wire sticking out of the harness below the starter solenoid, it's green and red, and it ends in what looks like half an inline fuse holder.
Of course, NONE OF THIS MADE ANY DIFFERENCE, in fact, it seems worse.
1. Dash volt gauge now reads WAY higher when running with no load on system. No numbers on gauge, but somewhere in the "L" on "NORMAL," which is two thirds between 8 and 18, so probably around 14.5 volts.
2. Voltmeter still reads 14.5 volts at the alternator post, starter solenoid, and battery terminal when it's running, no matter what load I put on it and no matter what the volt gauge on the dash says.
3. BUT, when I put a load on with the blower, headlights, etc, dash gauge drops to ~12-13 volts, and I can hear the engine slow down and all the lights dim. (It's absolutely not the gauge, already replaced and same thing.) Again, battery, starter solenoid, and distribution block all still read 14.5 volts no matter what dash gauge says.
I'm missing something, but what? Is it that wire sticking out of the harness below the starter solenoid? Do I need to run the sensing wire somewhere other than the starter solenoid? AM I COMPLETELY LOST?
Appreciate any help.
I have a 1990 Bronco XLT with 5.8 EAOD that I am having serious voltage drop problems with. When it is running, if I turn on the blower motor or other high drain item, the volt gauge in the dash drops significantly, the motor slows, lights dim, and if I run it long enough, the "Check Engine" light comes on. When I park it, the battery is low. What stinks is that when I got it, the entire truck and its wiring was filled with mud and corroded, so not sure what's going on.
I've thrown lots of parts and time at chasing an elusive "bad ground/short", and I'm stumped. Here's what I've replaced so far:
Blower Motor
Blower Resistor
Dash Gauge (whole instrument panel)
Dash ground (G201)
Ground in the pillar behind the driver seat
Frame/engine ground underneath the alternator
Body ground from frame to core support
Alternator
Starter
Starter Solenoid
Battery
All the starting/charging wiring
I'm now thinking it has something to do with the "self exciting" one wire, 200 Amp alternator I got from Motor City Reman. It's a large case 3G style alternator, and the wires look exactly like this:
http://www.oldengine.org/unfaq/3ag/3agcon.jpg
I had the "battery" post wired through a fuse into the positive terminal of the battery, and a wire from the battery to the solenoid post. The wire marked "A" in the picture, which I believe is the voltage sensor, was run from the plug directly over to the battery post on the back of the alternator(!). The third wire was cut off inside the plug I received from Motor City Reman.
I think what was happening is when I flipped on the blower, I was putting a drain on the system, but the "self exciting" alternator was "sensing" voltage at the battery terminal of the alternator, which will always be the same no matter what. As the battery drained, the alternator was busy telling itself everything was fine and running at 14.5 volts, so no need to supply extra voltage.
I tried rewiring it through a distribution block as follows:
Alternator Battery Wire > Distribution Block > Battery
Alternator "Sensing" Wire Yellow/White > Starter Solenoid Terminal
Battery > Back to Starter Solenoid Terminal
I left all the stock fusible link wires on the starter solenoid terminal, but moved my car alarm, amplifier, and offroad light wires from the battery terminal to the distribution block.
I still have one wire sticking out of the harness below the starter solenoid, it's green and red, and it ends in what looks like half an inline fuse holder.
Of course, NONE OF THIS MADE ANY DIFFERENCE, in fact, it seems worse.
1. Dash volt gauge now reads WAY higher when running with no load on system. No numbers on gauge, but somewhere in the "L" on "NORMAL," which is two thirds between 8 and 18, so probably around 14.5 volts.
2. Voltmeter still reads 14.5 volts at the alternator post, starter solenoid, and battery terminal when it's running, no matter what load I put on it and no matter what the volt gauge on the dash says.
3. BUT, when I put a load on with the blower, headlights, etc, dash gauge drops to ~12-13 volts, and I can hear the engine slow down and all the lights dim. (It's absolutely not the gauge, already replaced and same thing.) Again, battery, starter solenoid, and distribution block all still read 14.5 volts no matter what dash gauge says.
I'm missing something, but what? Is it that wire sticking out of the harness below the starter solenoid? Do I need to run the sensing wire somewhere other than the starter solenoid? AM I COMPLETELY LOST?
Appreciate any help.
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