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Discussion Starter · #1 ·
I am installing the 3G system in my 67 XR7 and it does not seem to be charging. I have a new 130 amp alternator and it is wired exactly like the diagram in the forums show except I have not put in the 560 ohm resistor yet. Would this be enough to prevent it from charging. I'm getting about 12.3 volts across the terminals off, a little less running, and even less under load. I have the green wire connected to the 904 wire from the ignition switch. I have the choke wire connected to the black/white wire on the alternator harness. The yellow wire from the harness is connected to the bat side of the solenoid. With the key off I get the same voltage at the alternator as the battery which seems to indicate that the mega fuse is still good. With the engine running there is no increase at the alternator. Does this mean the alternator is not sensing a need to excite. I've scoured the posts and no one seems to have the same issue I'm having. I need help.
 

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So- no change with the new alt huh? I think the guys who tested your old one were not correct then.....a quick peek at a wire diagram for the 3g conversion sounds like you have it correct Gary..? I don't suppose you had them test that one before you drug it home huh? Just for piece of mind it wouldn't hurt to verify it for sure. If it tests bad again I'd question thier method....but who knows? Could be bad luck on parts - sounds to me like were missing something though.....

Did the stock one work right? Just making sure the harness your tying into was know good. If so - I
d go through and ohm it out and look for opens anywhere you made a connection. wiggle it while tesing at joints/crimps to look for anomolies
 

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Discussion Starter · #3 ·
OK, I put in a new mega fuse, new battery ground wire, and new #4 wire from alt to fuse to solenoid. Not sure which solved the problem but now getting 14.38 amps at idle. My question now is this too high. I have ordered the headlight relay for halogen lights but have not installed it yet. New volt meter looks pegged at 15 volts but I'm assuming this is the 14.38 I'm getting at the battery. Time now to tidy all the electrical wires and move on to the interior. Thanks for all the input from this and my other threads relating to my tail light and charging issues. This site is a real help.
 

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Bad grounds fix 90% of the electrical gremlins.....I don't think you have any problems Gary as long as your regulator is working good you should be OK. Check voltage at points down stream of your VR to be sure it's around 12V
 

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If the battery is low and you have any large draws (headlights, upgraded stereo, etc) running the alt will "sense" this and produce more voltage until the battery is back up where it needs to be. Typically the newer high amp internally regulated alternators produce 13.3V at the charge post at idle. At least all of mine do. Bad69 is right on, check the voltage further out in your harness, dome lamp, tail lights, etc. are easy enough to get to.
 

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Discussion Starter · #6 ·
My voltage regulator is connected to my radio wire and reading about the same as at the battery. Don't I want this to read the same to determine if my system is charging? I just plugged in my new headlight relay for the halogen bulbs is there anything else I need to do to protect the existing wires from the high output alternator?
 

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Your wiring can handle way more voltage than what your currently putting out. What you need to worry about is amperage. Simply put, amperage is the amount of current flow drawn (or consumed) by an electrical item. The whole idea behind installing a relay in your headlight system is to keep the large amounts of current consumed by today's halogen headlights out of your headlight switch, which was designed for the smaller draw of incandescent bulbs. The relay is activated by a very small current across its coil which throws a heavy duty, high amperage switch inside the relay closing the circuit between your larger gauge source wiring and the headlight, eliminating the huge draw of the headlights running through your 40 year old headlight switch.

My system on the Panther contains numerous relays for the Taurus 2 speed electric fan, EEC-IV injection computer, Oxygen sensors, Ignition, Fuel Pump, Headlights, Electric lids, Starter, Theft deterrent, Etc. All of these being controlled by low amperage control circuits. I am running a 130Amp 3g alt as well. It CAN produce 130 Amps if needed, my Taurus fan has a huge draw when it fires up from a dead stop, my relays and wiring were sized to handle the load.

I would and do run a 150 Amp circuit breaker between my alt and battery.

The simplest way to tell if you are charging it to take a reading at your battery with the car off (~12V), then start the car and let it idle. If the voltage reading is higher (~13V to 14V), you are charging. It is possible to overcharge, which simply means that the voltage regulator is not sensing the cars needs so it does not stop charging. The green sensing wire from your regulator needs to be hooked to a keyed (hot while running, dead when off) source to function properly.

Good luck
Bill

Edit: I see you have a Maxi-fuse, what amp rating?
 

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No - if the regulator is doing it's job (ie "regulating") it should do it's best to keep the voltage consistent and not overcharge. You can easily test this simply by disconnecting the neg post off the battery while the car is running...if it's working right, the alt will carry the load because the regulator is providing the voltage to operate the car. If it dies - then you have either a bad alt or a bad regulator (or a connection related to those). You should be able to measure that voltage with the battery disco'd and still see 12.5 - 13.5 Volts if that's the case. (You could drive the car without a battery actually). It's advisable not to re-connect the neg battery post back on the car while it's running because there is a very outside chance that you could stress the internals of the alt or any electronic ignition components you may have. I have never experienced that - but you will see plenty of warnings out there about it. Any time you want to run a high amp/current draw circuits on older cars that have smaller load-designed wiring you really need to run them off of relays. Relays give you the ability to operate those types of things by adding a path over higher amp wires that is just triggered by the existing wiring. An example would be the the horn circuit........you run the horn off a relay --- just take the feed from the horn button and apply direct battery voltage to the horn via the relay. It will go from an anemic honk to a wallering ocean vessel on the high seas because it actaully gets the full 12V rather that the 8V through the stock 14 ga wire and crappy connections/ground etc. Same thing applies on the lighting circuit....if you go to a higher draw lamps, you need to run them off a relay since the stock wiring would not handle the load.
 

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Discussion Starter · #9 ·
I am using a 175 mega fuse. With the engine off I'm getting 12.3 volts at the battery. With the engine running at idle I'm getting about 14.3 volts. Everything is working so I'm hoping all my electrical issues are behind me and I can start putting the rest of the car back together. The green wire is connected to the 904 wire and is switched. The battery is pretty old maybe replacing it will help. Thanks everyone for all the help.
 

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That is Great News!
 

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Well, I figured this thread was as good as any to post in, of all the threads I've read on here about this topic, before I start a new one! Hopefully I can get some insight!

I have a 68 Standard with 302 2v all stock except the Pertronix ignition. Did the 3G upgrade with a 1995 mustang 3.8L V6 Alt and it was charging at 15.09 volts at idle. The alt has the stock harness that goes with it, along with the 6 gauge power lead with the fuse-able link in it. Everything is hooked up correctly according to the schematics that's been posted around. Yellow wire to B+ on solenoid, white wire plugs back into the alt, and the green/red wire to the 904 wire from the old regulator harness.
Battery charged up to 13.8 volts when I shut off engine after running for about 5 min. I didn't wanna cook the battery so I re-read all the posts about this upgrade.

With that said, I have since replaced all grounds and power leads with 4 gauge wire and a 175 amp mega fuse. Alternator to block, firewall to block, chassis to block, battery to block, Alt power to solenoid, and Battery to solenoid, have all been cleaned, tightened, and ohm out at .001/.002.
I had the alternator tested at two different places and it came in 14.2/15.4/16.8 on the print out. Passed both times.
I also thought that maybe the field was high, due to sensing that the battery was low due to the fact that I've started the 68 multiple times between rebuilding the P/S pump and this upgrade without actually driving it and giving the battery a full charge, so I charged up the battery with my wall charger. It pulled 8 amps and slowly dropped to 1, and it sat at 13.4 volts.

After all that, alt now reads 15.04 volts when running. Disconnect the 904 wire and the voltage drops to the battery voltage (currently 13.1v), plug it back in, and back to 15.04 volts it goes.

Is this correct? Acceptable? Will it cook my battery? (Also, my ammeter doesn't light up at all after the change) (turn indicator light doesn't blink inside, but they didn't really before either)

Any insight would be appreciated!! Thx!
 

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Well, I figured this thread was as good as any to post in, of all the threads I've read on here about this topic, before I start a new one! Hopefully I can get some insight!

I have a 68 Standard with 302 2v all stock except the Pertronix ignition. Did the 3G upgrade with a 1995 mustang 3.8L V6 Alt and it was charging at 15.09 volts at idle. The alt has the stock harness that goes with it, along with the 6 gauge power lead with the fuse-able link in it. Everything is hooked up correctly according to the schematics that's been posted around. Yellow wire to B+ on solenoid, white wire plugs back into the alt, and the green/red wire to the 904 wire from the old regulator harness.
Battery charged up to 13.8 volts when I shut off engine after running for about 5 min. I didn't wanna cook the battery so I re-read all the posts about this upgrade.

With that said, I have since replaced all grounds and power leads with 4 gauge wire and a 175 amp mega fuse. Alternator to block, firewall to block, chassis to block, battery to block, Alt power to solenoid, and Battery to solenoid, have all been cleaned, tightened, and ohm out at .001/.002.
I had the alternator tested at two different places and it came in 14.2/15.4/16.8 on the print out. Passed both times.
I also thought that maybe the field was high, due to sensing that the battery was low due to the fact that I've started the 68 multiple times between rebuilding the P/S pump and this upgrade without actually driving it and giving the battery a full charge, so I charged up the battery with my wall charger. It pulled 8 amps and slowly dropped to 1, and it sat at 13.4 volts.

After all that, alt now reads 15.04 volts when running. Disconnect the 904 wire and the voltage drops to the battery voltage (currently 13.1v), plug it back in, and back to 15.04 volts it goes.

Is this correct? Acceptable? Will it cook my battery? (Also, my ammeter doesn't light up at all after the change) (turn indicator light doesn't blink inside, but they didn't really before either)

Any insight would be appreciated!! Thx!
I don't see anything that sounds to bad there - at 15V your within a good range as long as the current (amps) is safe for the wiring you have. A good quick test is just to feel around on the wires and be sure nothing is getting dangerously hot. A better test would be to have a amp meter in place (which is always advisable) and see what the current draw is when you have all your gadgets and headlights on......
 

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Thanks! I drove it around today. My go to guy at a local shop said the same thing. Said drive it for 30-45 minutes and feel the battery for heat or bulging. I temp gunned the battery case, and used my hand, several times while out an about. Came in about 100 degrees tho it didn't feel like it was that hot. Caps didn't pop off so that's good!
Odd thing is it didn't help my turn indicators at all, just stay lit when turning. Looks like a solid state upgrade may be in order!
 

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that could be quite a few things including the switch itself though...... further investigating required. I'd start by checking the easy stuff - the bulb sockets are good contacts and the grounds are clean/good......etc
 

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Well, the lights blinked before, kinda......not at idle.
I have a new turn signal switch in the column, switched to LED bulbs and sockets are clean. When I reinstalled the dash harness (I rebuilt it, it was all F'd up by the P/O) I don't think I payed much attention to the ground as I may should have, seeing that I was eager to get it in. I'll get in there and clean it up. Only thing I haven't rebuilt or replaced is the headlight switch. I dont have dash lights. Head lights work, but no power to the dash from the switch.
 

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Do us a favor and start yourself a thread on what you have done, and give us lots of details. I think We are straying away from Gary's post.
 
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