Kinda new to this forum stuff. But I bought a 68 firebird with a 400 in it. I knew there was a charging issue because when i opened the trunk i found 3 alternators in there. So it looked as if they tried to convert to an internal regulator alternator but were still running it thru the external alternator. So to make a long story short i replaced the alternator with a new one along with a new external voltage regulator, and even a new capacitor. After doing as much research on the charging system i could find I'm assuming the gen idiot light in the dash must be working in order for the charging system to make a complete circuit. Well this light wasn't coming on. I took the instrument cluster out and found that the wire, brown w/a white strip, coming from the circuit board was missing about 6 inches of wire. Also connected to this wire is a large brown wire. The smaller wire is like a bell wire. Tried soldering a piece into place, thought i had a good connection, can not get this idiot light to come on. Can anyone send me in a direction to get my charging problem behind me. Any info would be great.
If you are not worried about exact 1968 OEM you can put in a 1 wire alternator like I did. Solved the problem I was having. You can even leave the external regulator in place ( if the look is important to you ) just run a wire to the battery, hook it to the alternator & problem solved.
I ran into a broken pin IN the wiring harness when I was trying to figure out a fuel gauge issue. You can pop it out to make sure the connection is good going into the harness as well. You may need a new banana clip (not sure what they are actually called..).
1957 Thunderbird 289 1967 Firebird Base 461 1968 C-20 327
Yes, unless there is a resistor wired parallel to the light. The alternator is turned off and on via the circuit the warning light is in. I don't think the 68s had a resistor wired parallel to the light.
Power is supplied to the car's electrical system via the horn relay. There is a fusible link at the horn relay and a red wire from the fusible link to the firewall junction block and on to the cabin area and ignition switch. Power from the alternator travels to the main junction splice. From the splice it goes to the battery by way of the junction block on the rad support and from the splice to the horn relay. The voltage sensing, terminal three, of the regulator is also connected to the main junction splice through an orange fusible link.
When the ignition switch is turned on power travels to the generator light in the dash instrument panel circuit board and on to the number four terminal of the regulator through a brown wire, that power turns the alternator on. The voltage sensing terminal three, senses voltage at the main splice and increases or decreases output voltage of the alternator to keep voltage at the splice at approximately 14 volts. When voltage at the ignition switch is higher than that at the alternator the light will illuminate, such as when the switch is turned on and the engine is not running. When the engine is running and the voltage is the same at the regulator as it is at the switch the light will go out. The light will also illuminate if the charging voltage is higher than the voltage at the switch. If the generator light in the dash is burned out or the gen light wiring circuit from the switch to the regulator is broken, the regulator will not turn on the alternator and you will have no charging output.
You did not say if you are getting a charge, just that the light does not come on. When you start the car do you get 14 volts at the alternator? Try taking the connector off the regulator, turn the key on and check for voltage at number four terminal. If you have no voltage at number four terminal you will have to trace the circuit all the way back to the ignition switch to find where the break in the circuit is. A good place to start with that would be the brown wire at the circuit board. Did you check the gen light bulb to see if it was burned out?
I've found a wiring schematic for 67-73 Firebird model years. It shows the two wiring circuits in parallel. But it is not 68 specific. A pink wire from the switch start/run terminal through a fuse to the gen light. A brown wire from the gen light to the voltage regulator. A brown wire from the switch run terminal to a brown white wire that is connected to the brown wire from the gen light.
It would make sense to have two wires powering up the regulator, there would still be power generation if the gen light burned out. Cars with a gauge package would only have the resistor wire, cars with an idiot light would have the resistor wire and the gen light wire.
The regulator start wire has to have the resistance of a warning lamp, or a resistor, in line to prevent engine run on after the switch is turned off due to the ignition system and the alternator turn on circuits both coming from the common start/run terminals of the ignition switch. After the alternator is turned on and power is being generated 14 volts are present at the number four terminal of the regulator and thus 14 volts at the alternator side of the gen light. There should also be 14 volts coming from the ignition switch to the gen light. When both sides of the light have the same voltage the light will go out. If voltage travels unresisted, by a lamp or an inline resistor, back to the ignition switch, that voltage would be travelling to the ignition when the key was turned off and cause the engine to run on after the key was switched off.
After looking at the 68 schematic on "the First Gen Site" I see there is a brown wire from the ignition switch to the "B" terminal of the inner firewall juction block and also a brown wire from the gen light of the dash circuit board to the "B" terminal of the inner firewall junction block. A brown wire goes from the "B" terminal of the engine side of the firewall juction block to the number four terminal of the voltage regulator.
Your first move would be to remove the terminals from the regulator and see if you have voltage at the number four when the key is turned on. If yes you should be generating, if no trace the wire to the terminal block looking for breaks. Test the "b" terminal on the cabin side of the firewall junction block and see if you get voltage when the key is on. If yes the problem is in the junction block or the wire from the block to the regulator. If no you will have to trace the wires back to the switch and the circuit board.
It seems the wiring has been tampered with at the circuit board since you stated there is some wiring missing there, that would be the likely spot if you have no voltage at the junction block. There may be other wires tampered with as well, trace them through the circuits and you should be able to rectify the problems.
Sometimes people install ignition boxes in there cars and hack up the generator wiring in order to stop engine run on problems that can occur when these boxes are installed without putting diodes in the generator power up wires.
Soory for being so long winded, maybe too much coffee this morning.
Thanks for all the info. Getting ready to tear into it again. But yes I'm having a charging problem. Off my ignition switch is a thick solid brown wire that runs to my fuse box and off the same plug is a single wire, brown w/a white strip, that runs to the firewall blocks. And off of the firewall block it runs back up to the instrument cluster for the gen idiot light. The single strand wire coming off the ignition switch is like a telephone style wire.
Ok. So I pulled out my meter and checked the fusible link power wire going to voltage reg. 12.34 volts. Good there. Checked brown wire going to number 4 on volt reg, 11.83. I'm assuming that is fine. So I would also have to assume the circuit to the idiot light is the problem because it does not come on with the key in the on position leading to the conclusion the circuit is not being completed. A lot of assumptions going on there but does that make sense?
That looks like a handy flow/diagnostic chart Jimc posted.
Yes, that makes sense. 12+ volts at the fusible link is the battery voltage from the main splice in the harness. The other wires from that splice go to the battery, the alternator and the horn relay. The 11+ volts at the number 4 terminal is from the switch to turn on the regulator. It's less than battery voltage as the juice travels through all the wires and junctions with all kinds of resistance before it gets back to the regulator and loses some voltage. That wire should go to zero volts with the key off. If the number 4 terminal is switching off and on with the ignition switch you should be generating whether the gen light works or not. If you are not generating then you have another problem besides the light.
The thicker brown wire that goes to the fuse box is to power on accessories that work only with the key in the run/accessory position, such as the radio or the heater fan.
The wire that runs from the switch to the junction block is the wire that feeds power to the number four terminal at the regulator. The wire that goes from that same terminal at the junction block and runs up to the instrument panel will be the one for the gen light. That wire should be illuminating your gen light when the switch is on and the engine is not running. Do all the other lights and gauges in your instrument cluster work?
I don't know for sure, but, the thin single strand brown- brown/white wire from the key switch may be a resistance wire.
There is also another wire that comes off the ignition switch and runs to the instrument panel. It's a pink wire that tees to the fuse box which supplies fused power to the flasher, the back up light switch and I believe fused power to the idle solinoid. From the tee it runs to the junction block to power the ignition and from the block up to the instrument panel to supply power for the oil pressure light, park brake light, gen light, gas gauge, and temp light. If all the other warning lights are working and the gen light not, the brown wire from the junction block must have a break or the gen light lamp is burned out. Or maybe the circuit board is broken