Truck REFUSES to charge after 6.0L GP harness install?

[crash-harris]

I'm very close to calling it on all fronts mechanical. Thought about just plowing into a bridge support on the way home this afternoon with everything that has been going on here (BAD vehicle screwjoo).

Sorry in advance for the long read...

Since the MOMENT I started the truck after installing the new 6.0L GP harnesses, it has been refusing to charge correctly. I have a 130A 3G, Duralast reman with a 1/0 cable running from the alternator to a 200A resettable breaker, then another 1/0 cable to the fender mounted starter relay. All battery cables, both positive and grounds are also 1/0. All the eyelets on the positive cables up to the fender mounted relay have 5/16" holes in them (couldn't find any smaller for the alternator output or breaker), and are soldered on and adhesive hearshrinked. I followed the harness wiring from the diagram in the tech section (same as when I did the swap on my 300 almost a decade ago). The charge sense wire was previously connected to the battery terminal, but I moved it to the output side of the breaker. All harness connections for the alternator are soldered and heatshrinked (had them crimped before all this, soldered them to eliminate possible cause of my no-charge problem). Oh, and the battery light on the dash hasn't burnt out. I also have a digital voltmeter in the cab that is connected directly to the driver's side battery terminals.

Some of you may remember that a few years ago I had a fusible link burn up due to some grounds missing. There's now a 8ga cable running from the back of the intake to the wiper motor, a braided ground strap from the core support to the frame rail where the driver's side battery is grounded, a factory strap from the cab to frame and two parts store 1/0 cables running from the factory block ground location on the passenger side routed to the battery ground locations on either frame rail (driver's side of the block was missing the bolt, couldn't find another or the thread pitch without buying other tools).


I cut the weatherpack connectors off the new harnesses and crimped 2 wires each into 5/16" ring terminals (so 4 total) and installed them in place of the existing harness that was just bits of 10ga wire hand-wrapped and tapped together (didn't know that before replacement). After finishing up, I started the truck to move it back to its parking spot and was only running on battery voltage. I removed the breaker from the equation and connected both cables on either side of it to the same post with no change. I thought that the 3G alternator or regulator had suddenly decided to die after almost a year (or less?), so I replaced that. New reman alternator had an actual Motorcraft regulator on it. Truck seemed to charge better (14V at idle) until the next time it left the driveway. It wouldn't charge over 14V. I fought with this for a bit until I heard belt squeal, tightened the belt and all seemed normal. So I got new belts (also Duralast, same as the old) and put them on right after it stopped charging again with no change. At that moment, I revved the engine up to about 3K and it started charging. Research indicates that the alternator/regulator aren't self-exciting, but will kick on when reaching threshold speed to excite. Still not sure why 2 alternators suddenly decided to no longer self-excite.

Today when we left the house to pickup our Hyundai from the stealership service center, it seemed week (13.9-14V at any engine speed). After getting the car, the truck just refused to charge, no matter what. I took the breaker out of the equation again with no change. I started at the stealership at 12.4V and was at 12.1V when I got home (cracked the window a few inches then rolled back up later and radio was on with volume off).

I don't understand what's going on here, or why this is suddenly an issue rearing its head after swapping to 6.0L GP harnesses. I've made sure I didn't touch anything else on the GP controller (but I do remember removing the large nut and one smaller one from it and reinstalling them). I even pulled the engine harness connector apart again to make sure that wasn't causing problems and it's still packed with dielectric grease from when I did the Molasses Carnage Corrections. Am I missing something, or do I need an exorcist?

 

[crash-harris]

One more note, when the digital voltmeter is reading only battery power, the factory dash gauge reaffirms this with the needle on the 12V tick.

 

[laserjock]

Do the glow plugs cycle correctly? Is the alternator case grounded well?

I would start the truck and warm it up. Once it’s warm, shut it off and start disconnecting things until you get to the bare essentials. Pull the extra wires off the starter relay. Disconnect the GP controller and anything that is not absolutely required for it to run. I might even go as far as jumping the IP from the battery. Start by adding your charging circuit back. If it charges then, start adding things back until you find what’s causing the issues.

That’s the best I can tell you.

 

[crash-harris]

The plugs cycle correctly. I've been planning on getting another short cable to connect the 3G case to the filter head bracket just to be sure. I only have the fusible links and the two 1/0 cables at the starter relay, but I do have all the accessories connected at the driver's battery terminals. I'll have to try disconnecting the GP controller while running.

What in the controller would cause such a thing though? Still going to try it.

 

[DrCharles]

The only way the controller could be your problem is if the glow plugs were stuck on. They draw more than even a 3G alt is capable of putting out.

I think it's more likely that either you have a bad connection that's getting worse, or your alt itself is defective (bad brushes, regulator, or diodes). Can you take it off and have it tested?

 

[crash-harris]

I just put this one on. Previous one was doing the same thing.

Come to think about it, could the controller be sticking on?

During the very cold days, when the engine has been stone cold (first start of the day), I swear I haven't been hearing the GP afterglow cycle. Other times I've heard it, but I just figured that on those cold days the afterglow cycle has just ran longer.

If this ends up being the cause, what is the recommended replacement? I've only seen DieselRX ones as a complete assembly. Not sure if I can just get a continuous duty winch relay or something to replace just the relay.

 

[franklin2]

On the charging problem, the 3G and most stock alternators are not self-exciting. That is what the voltage from the dash light is for on the green/red wire. I would put a meter or testlight on this wire going to the alternator, with the key off it should be dead. Turn the key on but do not start the truck, this wire should have voltage. This is what brings the alternator online to charge. By revving the engine you are relying on any residual magnetism in the alternator to start it charging. Sometimes it's enough, sometimes it's not enough to start charging.

I am not sure I would put the sense wire beyond a circuit breaker. Normally it would work ok, but if the circuit breaker ever tripped, then the voltage output of the alternator will go wild, it will lose it's reference voltage to control the output of the alternator. May never happen, but it could theoretically.

 

[laserjock]

I doubt it’s the GP staying on. That would pull the voltage way lower and would have burnt the plugs up by now most likely.

My best guess is the exciter wire or case ground. Technically the exciter wire should go to the hot post on the pass side battery; however, if you run heavy enough cable, it shouldn’t matter at what point you tap into the hot circuit. My exciter wire is right on the output post.

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I used this pigtail. Just connect the green/red wire to key on power. Yellow wire with ring terminal goes on the output post.

 

[crash-harris]

I did originally have the yellow wire connected to the passenger side battery. I've seen where people had suggested putting it at the fender mounted relay, but I don't have enough stud left with all the fusible links and two 1/0 cable lugs to relocate it there. I though about just going back to print it on the output studs like I did with the gas truck. I'll just about try anything at this point.

Going to try today or tomorrow to do a few of these things and ground the 3G case from the back if I find a cable in my spare parts.

 

[Macrobb]

Yellow wire should be hooked as close to the battery as possible as it senses voltage drop. Putting it on the alternator output hurts if you get any voltage drop from there to the batteries(which will happen more when there is more current flowing(more amps).

Make sure your red/green wire is getting power at key-on. If it's still not putting out power, something is wrong with the regulator module on the alternator.

 

[franklin2]

I doubt it’s the GP staying on. That would pull the voltage way lower and would have burnt the plugs up by now most likely.

My best guess is the exciter wire or case ground. Technically the exciter wire should go to the hot post on the pass side battery; however, if you run heavy enough cable, it shouldn’t matter at what point you tap into the hot circuit. My exciter wire is right on the output post.

You must be registered for see images attach

I used this pigtail. Just connect the green/red wire to key on power. Yellow wire with ring terminal goes on the output post.

What we are calling the "exciter wire" is the wire that is hooked to the dash light and then the ignition switch and brings the alternator online to charge(green/red). The "sense" wire is the yellow, and it can be run directly to the battery output on the alternator. It can do a better job tapped in somewhere remote in the harness near to the batteries, but it will work ok on the back of the alternator.

 

[laserjock]

Just to clarify, any key on hot will work.

 

[crash-harris]

I'm really curious to see if I'm getting power to the exciter wire. Might be an intermittent thing that would cause me to have to trace all through the truck. Pulling out my red Haynes manual now to locate where it connects on the other end.

...And it looks like it indeed goes to the charge indicator in the instrument panel via the original external regulator. Obviously that bit has been cut out for the 3G swap and it would now be running straight to the charge indicator. Either going to be able to test some things in about an hour or tomorrow.

Side note, how much you wanna bet this is a result of some crap a PO did at some point in this trucks life?

 

[crash-harris]

Does anyone have a small white wire on the left side of the GP relay? I wanted to disconnect the controller as to not draw power when testing for 12V at the alternator exciter wire (pulled the harness to probe it). Took the yellow power wires of f and got rapid clicking with ignition on, so I said screw it and just reconnected it. When I did, I noticed that small, white wire wasn't tight. I couldn't move it up and down in the stud, but I could slip it around. Tightened it, got 12V at the alt harness for exciter wire, started truck and voltage stabilized ar 14.4V at idle. My digital voltmeter in the cab is .2V low (verified by testing 12V aux outlets connected to the same positive wiring). Good to know, but not a big deal. Output lug was reading 14.4V as well as both batteries, all aux connections at the underhood fuse panel I made and at the aux outlets in the cab.

Could that slightly loose wire on the GP controller relay really have been my issue?

 

[laserjock]

I kinda doubt it. The white wire on the GP controller is the ground. The GP controller turns on with key on power. If the glow plugs are not connected, you get rapid clicking.