1969 Plymouth 440 alternator questions...

I am very much a newbie here so I apologize. My brother picked up a '69 Road Runner with a 440 V8. The battery is new and seems like the alternator is not charging it. Placing a voltmeter on the battery when the engine is off shows 12.6v. However, when you start the car with the lights on the voltmeter shows only 11.0v. I have found a dangling wire attached to a terminal held on by a screw on the bottom of the backside of the alternator that goes nowhere. The blade type terminal on top of the alternator looks like it goes in to the voltage regulator. Now, placing a voltmeter on the screw terminal (the one with the dangling wire) while the engine is running shows 28 to 30v! While the engine is off it shows 6 to 7v. Is this correct voltage output on a 12v system?

Do you think I need a new alternator and where should I reattach that dangling wire?

Thanks in advance. Sorry to be so green.

Reply to
danb_31
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'69 was the last year of the mechanical regulators which in your case seems to either be miswired or defective. The best thing would be to convert it to a solid state one (if it hasn't been done already). The

28V means the alt is good, as that's about right for unregulated output. See
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for parts (amoung others). You might want to pick-up a wiring diagram or complete shop manual if you/he plan to work on it.

-jim

danb_31 wrote:

Reply to
JimV

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Reply to
John Kunkel

If the charging system is STOCK (big question on a '69 Roadrunner with a

440, since '69 Roadrunners mostly came with 383s or Hemis (is this an original 69-1/2 440 six-barrel car? If not, then that isn't the original 440). But I digress....

STOCK wiring for that car calls for only two wires going to the alternator:

1) a heavy wire that runs from the big stud/nut terminal of the alternator, through the firewall, to the ammeter guage

2) a lightweight wire that runs from the voltage regulator to the field terminal of the alternator. (note that if someone swapped on a later alternator with TWO field terminals, one of them should be grounded).

So, I suspect that your main charging wire is disconnected. The voltage regulator is screaming "CHARGE!" at the alternator, and the alternator is trying which is why you see 30 volts at the terminal. But the current can't get back to the battery, which is why the voltage at the battery sags after the car is running.

Others have suggested that electronic regulators are a good way to go, and I agree. But there's no need to re-wire for the later Chrysler electronic regulator. Wells (and others, I'm sure) make electronic bolt-in replacements for the '69 style regulator. I have one on my '69

440-powered Coronet R/T :-)
Reply to
Steve

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