What year car are we talking about? It soulds like the alternator is putting out ok, but there is a pulsing load. Is this a car that has a circuit breaker protecting some circuits? If so there could be a short, and the circuit breaker is opening and closing, causing the pulsing. A headlight switch CB can cause this, if there is a short in the headlight wiring, and the switch is on (just an example).

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

While a diode may well be bad, I've seen stator windings in a '74 Coronet in terrible shape with 2 of 3 burned through, 1 diode dead, and still sort-of charging. Those alternators are quite easy to disassemble for inspection because the brushes are so easy to remove from the outside.

It's a 1973 Dart with stock wiring.

Woah!! Here's something else I just noticed; When the key is turned on, but BEFORE engaging the starter, the ammeter shows about a third of the way towards discharge (these old ammeter gauges aren't very clear as to readings but I'd guess about a 16 amp discharge!). Once started the gauge comes back to it's pulsing center. Funny I haven't seen that before but probably wasn't looking for it.

So the HEI swap is powered through a relay, which is on whenever the key is on, which means that the module and coil are getting power whenever the key is on, engine running or not. With ever accessory off, would the coil and module pull that much power? Or maybe I have some kind of short after all (noticed that the horn has stopped working)?
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roor bong pictures

you need a multimeter.
radio shack $20, get you one.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

You can always get a disposable one at Harbor Freight for about $3 on sale.......

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

for novices, i recommend the more expensive ones to save the frustration. we want to make the introduction to multimeters as pleasant as possible because it is one of the most important tools in your toolbox.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

I've got one as mentioned before.
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medical marijuana card

yes, you did I apologise.
does your multimeter have an ammeter function? if it is of fair quality it should have a separate lead port for either a 10A or 20A capacity. an amp clamp would also be valuable at this point.

try unplugging the relay and see if the key-on power draw is still there.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.