bad alternator or regulator?

[gumby]

My 73.5T charging light is on and I checked the voltage at the battery's and it only shows 12.2 volts even when I raise the rpm's, at the regulator the black wire ( I think the feed ) from the alt reads 1.5 volts also the blue wire (output?) so what does this mean ,

[jmohn]

Not enough information to make a diagnosis yet. All we know is there is insufficient voltage reaching the battery.

Please do a search for information on this, there are a number of good descriptions (better than I could write) of a variety of tests that will narrow down the cause.

One final thought, if you really have only 1.5 volts on the black wire at the connector to the voltage regulator, then I think your problem is in the alternator.

Jerry M
'78 SC

[gumby]

I asked a garage ( friend) today and he said to ground the field side on the voltage regulator (the black wire) and if the alt is good you will here it pull the motor down and it will charge like crazy! so I just did that and....no change

[jmohn]

Originally posted by gumby
I asked a garage ( friend) today and he said to ground the field side on the voltage regulator (the black wire) and if the alt is good you will here it pull the motor down and it will charge like crazy! so I just did that and....no change

I mean no offense, but you are, apparently, not at all familiar with your car's charging system. If your going to work on this yourself you really need to understand how the system works and what the components are. If you don't understand what your doing you could cause more damage or hurt yourself or possibly burn up your car. It also appears your garage friend is more familiar with modern voltage regulators which generally use the ground side to control excitation; your system, however uses the positive side. If you really want to "full field" your alternator, be sure all the lights and radio are turned off then you must connect the black and blue wires at the connector for the voltage regulator (just disconnect the regulator and jumper the black and blue together). Be cautious, keep the rev's under 2000 and don't run it that way too long (2-3 minutes tops). If your alternator is OK you'll see way over 14 volts at the battery (probably more like 15-17). Don't run it that way very long it will "cook" the battery, just run it long enough to test the out-put at the battery. If you do not see over 14 volts at the battery your alternator isn't functioning correctly. You should still do a "search" for alternator problems, there are several good write-ups on testing the components of the charging system. I trust you've already cleaned ALL the terminals, connections and grounds.

Good luck, be careful, know what you're doing,

Jerry M
'78 SC

[gumby]

Jerry ~ Thank you for the info , I tried it this morning and the battery voltage went up to 15.1 and the light on the dash went out so it looks like my voltage regulator is bad . Thanks again

[gumby]

Jerry , I may have “fixed” the voltage regulator ……I took the cover off it and it looked like a relay ( contact points) to me so I burnished the contacts and voila it charges!

[jmohn]

You're quite right, part of it is a form of relay. If there's nothing else wrong with it (and apparently there isn't) cleaning the points is often all that's needed. Those points "make" and "break" constantly to contol the excitation of the alternator so there was (years of) built up corrosion on them. You probably already realize this, but be careful not to change the relative position of the points as they control the rate of charge.

Congratulations,

Jerry M
'78 SC