Explorer swap charging system question

[76Bronko]

Hello all.

My setup: Explorer swap 5.0, 4r70W, NP205, EFI Guy harness, using EGR, O2 sensors and downstream sensors. 4G Explorer alternator.

Having a charging issue, and I'm a little stumped. New: battery, alternator, and serpentine belt. Battery takes a charge and holds a charge, but the (new) alternator is only putting out 12 Volts (old alternator also only put out 12v) . The Bronco won't start immediately after you shut it off, because after running for awhile, the battery voltage has dropped slightly below 12V.

I'm thinking that the ECM isn't telling the alternator to charge, all research is telling me the alternator is a smart charging alternator, where the ECM and alternator communicate with each other. I think the ECM is either falsely thinking its in an overvoltage situation or that it's putting the alternator in a low voltage charge mode.... Does anyone have any experience on how this works?

Thanks,
Mel

 

[73azbronco]

so about 12v or exactly 12.0 volts? should easily be pumping out 14ish volts.

 

[bronco italiano]

What brand alternator

 

[ntsqd]

I would give the grounding a very thorough looking over.

 

[Broncobowsher]

Did you wire in the switched ignition wire to tell the alternator to turn on. It isn't a 1-wire. There is a big charge wire. Then 2 more little wires that need to be hooked up. One is voltage sense that should go to the battery, but everyone just loops it to the charge post. Then there is the one connected to the ignition. When the key is in run, it wakes up the alternator and tells it to start charging. It has to be switched or it will run the battery down trying to field the rotor on a stationary alternator.

 

[73azbronco]

That last part also keeps alt from draining batt when off

 

[EFI Guy]

The PCM does not control charging. The green/red excite wire does. Do you have power on the green/red with the ignition on?

 

[76Bronko]

Did you wire in the switched ignition wire to tell the alternator to turn on. It isn't a 1-wire. There is a big charge wire. Then 2 more little wires that need to be hooked up. One is voltage sense that should go to the battery, but everyone just loops it to the charge post. Then there is the one connected to the ignition. When the key is in run, it wakes up the alternator and tells it to start charging. It has to be switched or it will run the battery down trying to field the rotor on a stationary alternator.

I didn't do anything to the harness that EFI Guy reworked, as far as the alternator goes. I just plugged in the three prong connector (but only two wires) from the harness to the alternator, and wired the alternator output wire to the +B battery side of the solenoid. There was a wire in the reworked harness marked 'alternator warning light ground. other side of bulb is hot in run' that is
green and red, but I haven't hooked that up. That was the only wire that mentioned the alternator in the reworked harness.


Thank you for the reply.
Mel

 

[76Bronko]

The PCM does not control charging. The green/red excite wire does. Do you have power on the green/red with the ignition on?

I will check that and report back. Regarding the alternator, all I have done to the reworked harness is plug in the three prong/two wire connector to the alternator and wire the alternator output to the solenoid. I do see the harness wire labeled 'alternator warning light ground. other side of bulb is hot in run' that is green and red, but I havent wired that in yet because I wadnt sure how to wire it up correctly. I have only connected three wires from the reworked harness into the broncos stock harness. The one accessory wire, the run in start wire, and the wire to the inertia switch. Is that technically all that has to be wired in for the Bronco to run well/correctly?

Thank you for your response.
Mel

 

[ntsqd]

snip.......
There was a wire in the reworked harness marked 'alternator warning light ground. other side of bulb is hot in run' that is
green and red, but I haven't hooked that up. That was the only wire that mentioned the alternator in the reworked harness.

Pretty sure this is your problem. That wire is the alternator exciter wire in all of my prior experience.

 

[76Bronko]

Pretty sure this is your problem. That wire is the alternator exciter wire in all of my prior experience.

Okay. I will hook that up today. Kind of confused how to hook it up...Is this correct? Take the end of the wire from the reworked harness and run that to one side of the dash bulbs in the instrument cluster....and then run the other connection to the dash bulb to ground? Then how would voltage flow through the bulb to the exciter wire? I thought since it was marked alternator warning light, that that was all it was...How would you wire it up?

Thank you for the response

Mel

 

[73azbronco]

look here

https://classicbroncos.com/forums/threads/4g-alternator-wiring.301664/

 

[76Bronko]

I mostly understand how the terminating wires go at the alternator. It's where the wires go on the source end, upstream, that I'm confused on....

Checked my coltages and with the ignition on to hot/Run, I have no voltage at the green with red wire, and I have 12 volts at the white with yellow wire. What that means, I'm clueless

Thanks again for the reply and for the help

Mel

 

[76Bronko]

The PCM does not control charging. The green/red excite wire does. Do you have power on the green/red with the ignition on?

I do not have any voltage at the green w red wire with the ignition on. But I do have battery voltage at the yellow w white wire with the ignition on. I will hang out and wait to hear back. Thank you

 

[76Bronko]

The PCM does not control charging. The green/red excite wire does. Do you have power on the green/red with the ignition on?

The PCM does not control charging. The green/red excite wire does. Do you have power on the green/red with the ignition on?

 

[76Bronko]

I do not have any voltage at the green w red wire with the ignition on. But I do have battery voltage at the yellow w white wire with the ignition on. I will hang out and wait to hear back. Thank you

 

[EPB72]

The yellow white wire is the sense wire if measured at alt connector will have battery voltage all the time ,, not sure where the reworked harness is getting power on Lt green / red wire ,,, Here’s a pic of a oe application 2001 explorer …

 

[ntsqd]

Isn't the Bronco's original Alt exciter wire also red with green? If so, then there should be another of those wires hanging loose where the original voltage regulator lived. Jumpering the two together should wake up the alternator and put the system voltage, as measured at the battery, at 13.6 to 14.4 VDC.

 

[76Bronko]

What brand alternator

OEM alternator at first, now have a remanufactured alternator from Auto Zone. Both doing the same thing.

I'm waiting to hear back from EFI Guy about a wiring question.

Thank you for the reply

Mel

 

[bronco italiano]

Your in as capable hands as they get with EFIguy!!!