Do we have any electrical system guru’s on here?

[767Jockey]

I've been told that I can eliminate the red light and just put a 560 ohm resisitor in the line that goes to the ignition switch. If that's true and that'll work, that's fine with me. I have a functioning voltmeter and no use at all for the red light as a warning. Will the 560 ohm resistor in the line to the ignition switch without the red light being hooked up work as a way to excite the alternator into action?

[patrickt]

Originally Posted by 767Jockey

Will the 560 ohm resistor ... work as a way to excite the alternator into action?

It all depends on what you're wearing at the time.

[fastpace]

Originally Posted by 767Jockey

I've been told that I can eliminate the red light and just put a 560 ohm resisitor in the line that goes to the ignition switch. If that's true and that'll work, that's fine with me. I have a functioning voltmeter and no use at all for the red light as a warning. Will the 560 ohm resistor in the line to the ignition switch without the red light being hooked up work as a way to excite the alternator into action?

Yes you should follow the wiring information you posted under "Cars with 5 gauge cluster" then. So the Lt Grn/Reg wire off the "I" ignition terminal should go through a 560 ohm resistor to a switched power source that is powered at both the start and run positions of the ignition.

[patrickt]

Originally Posted by fastpace

...that is powered at both the start and run positions of the ignition.

Most charging lamp feeds to the VR come off the ACC circuit of the ignition switch and not the START or IGNITION circuits of the switch. The reason is that you don't want the feed to the lamp back-feeding to the starter solenoid. If you do that, you'll know very quickly. The easy way to tell on your particular Cobra and wiring system is to just pull your coil wire so the engine won't start, turn the ignition ON and the charging lamp comes on, now crank the engine and see if the charging lamp goes out. If it does, then the feed to it is coming from the ACC circuit(s) of the ignition switch which gets cut out when cranking. Another way to check is to just pull the wire off the starter solenoid and try and start the car. Of course it won't crank, but watch your charging lamp and if it goes out then you know it's fed from the ACC pole of the switch which is getting cut out. Now, every ignition switch in the world doesn't cut the ACC circuit out while cranking, but you get the idea.

[Chicagowil]

The circuit must be completed to get the Alt Reg "excited". It is possible to have an Alternator that has a failing diode that will give a "false" voltage as if it is charging but it is supplying a "ripple" DC voltage charge instead of a full rectified charge. That can also damage your other electrical devices (such as a fuel pump). They are not designed to run on voltage with an "AC" component.

The original generators required a mechanic to "flash" the field to get the right polarity for the generator to charge correctly. Many a generator was installed and replaced because "shade tree mechanics" did not understand this concept.

The alternators with an internal voltage regulator need to sense the charging needs to establish its charge effect. Thus the connection after star- not the "ACC" feed.

Thom

[767Jockey]

Now I'm all confused - not hard to do when it comes to electrical.

1- If I take out the light from the circuit and install JUST a 560 ohm resistor in the line that runs from the alternator to the ignition switch, will it work?

2- Does it matter if that line runs to the IGN or ACC terminal on the iginition switch?? If so which terminal should I run it to?

[spdbrake]

Originally Posted by 767Jockey

Now I'm all confused - not hard to do when it comes to electrical.

1- If I take out the light from the circuit and install JUST a 560 ohm resistor in the line that runs from the alternator to the ignition switch, will it work?

2- Does it matter if that line runs to the IGN or ACC terminal on the iginition switch?? If so which terminal should I run it to?

1- yes
2- to the ign terminal

[767Jockey]

ARRRRGHHHHHH - This thing is driving me NUTS!!

I installed a 560 ohm resistor in the line that goes from the alternator to the IGN terminal on the ignition switch. I start the car and it does the exact same darned thing. It gives me 13+ volts, and within a couple of minutes it drops off line down to no charge at all. Both the voltmeter in the car and checking at the battery with a VOM confirm this, it's about 11.9 - 12.3 volts after a while.

-I have checked all the wiring. It is correct.

-I have checked all the wiring connections. They're all soldered, heat shrink wrapped and solid.

-I have checked all the grounds - battery to frame, engine to frame. They're all clean metal to clean metal and tight.

-I have checked the alternator on three different auto parts store alternator testing machines. All test good.

What the heck am I missing here? Could it be the alternator is faulty? Maybe it works initially then drops off line as it heats up or something? Other than throwing another $140 alternator on it how could I test that? Any ideas out there what ths could be? I'm pulling my hair out in frustration now.