hotrod swinger said

Contrary to popular belief, the ballast resistor is rarely the problem, nor is the voltage regulator. It’s probably a connection problem, possibly more than one connection.

What voltage did you measure between key switched feed at ballast resistor and battery positive? As mentioned above, more than 0.3 V is a significant drop in the ignition circuit that requires investigation.

If you measure a 1.5 V drop, this may give you a charging voltage of ~16 V because the voltage regulator will think the system is running 1.5 V lower than it actually is.

If your measurement is higher than 0.3 V follow the path Del (67dart273) outlined above and measure each connection in your ignition circuit.

The drops add up and are cumulative. For example, you may have 0.3 V at the bulkhead, 0.5 V in the ignition switch connector, and 0.4 V in the ignition switch itself, for a total of 1.2 V.

I worked through this same issue earlier this year with Del’s assistance and it turned out to be a cumulative problem, most significant drops were the ignition switch connector and the ignition switch. It’s important to do the measurements.

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67Dart273 said

No it means that you happened to measure that voltage when the breaker points are open. There is no current flowing through the ballast, so the voltage is the same. If you "bump" the engine so the points are closed, you should read "same as battery" at the "key" end and much lower at the "coil" end, say, 5-10V or so. But that is not what you need to check to test for drop. Please re-read the specific instructions in my post. What you are trying to do here, is to determine the drop from battery PLUS post to the "key" supply terminal of the ballast. The reason for that, is that nearby in the harness, that "ignition run" supply wire--coming from the ignition switch --- branches off and feeds several items, depending on the year/ model of the car............

Feeds ballast and to coil
Feeds VR IGN terminal
Feeds the blue wire going to alternator field
Feeds electric choke if used
Feeds idle solenoid if used
On some models (later) feeds a smog doo-dad or two

All these items draw power and the current loads and stresses the terminals, connectors, and switch(s) in series with the path from the battery to the VR. You are trying to determine if this is so, how bad it is, and after that, you will need to backtrack that path and find the culprit

READ this article from MAD about the cause of bulkhead connector problems. If you don't do this bypass, the article makes some good points as to the cause, etc. ALSO THIS SIMPLIFIED diagram shows you most of the path I am talking about:

What is not shown here is "the rest of the path"..... From the wire labeled "to igntion switch" that goes to the switch CONNECTOR, through the SWITCH, back out the switch connector on the IGNTION RUN wire, back out through the BULKHEAD connector, and to the ballast, and branch of to the VR, etc.

Each one of those points with a terminal/ switch/ connector is a drop "suspect."

You must measure voltage ACCURATELY. Don't just look for "some voltage" measure it to tenths or hundredths. Check both sides of the key switch connector on the power coming TO the key and to the ignition run LEAVING the key. Leave everything connected, key in "run" when doing this so that you have CURRENT flowing. CURRENT is what causes drop through "poor" connections.

If the power going TO the key switch is less than battery, you have a drop through the red/ black ammeter circuit TO the key.

IF that reading to the ignition switch infeed are OK, and the "run" line going back out are OK, then it has to be in the bulkhead connector in the "ignition run" wire. This is not difficult, it's just like a road map. Where is it muddy? What road? Where on that road? Is it "muddy" between the turn off and your mail box? Etc.

Catalog

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