Alternator not charging.

I have a 1944 GMC 270 Straight 6. One of the previous owners converted it to 12 volts and installed a standard delco alternator. The battery wasn't charging and the Autozone guy said it was putting out less than 25% of what it should so I replaced it a couple of weeks ago. I also have a brand new battery.

When I turn on the engine, the volt meter jumps but it stays slightly less than zero. Here is the altenator as it is wired now:



The heavy wire goes to the volt meter on the dash. The yellow wire is hanging free under the dash. Where should the yellow wire be hooked up? Why isn't the battery charging?

Neil

 

hard to see in your picture , is that yellow wire going to the #1 terminal on the alternator? if so , that wire is supposed to excite it....if the other end is just hanging under the dash it will never charge

 

red wire goes to number two, thats all you need to make it charge.

 

Put the heavy wire and red wire to the pos side of the battery and the other to your gauge.

That belt and pulley looks like something off of a riding mower???

 

heres my pictures, number two to bat. terminal, in the second pic you can see
how the #2 connector tends to get corroded over time so make sure its making a
connection.

 

Go for a smaller pulley on the alt while you are at it.

 

This is a better shot.



From what I am reading here, I should connect the yellow wire to the master power switch? I don't have a traditional ignition, just a power on and a foot starter pedal.

Neil

 

Are you sure your alternator is any good ? It looks pretty rough for only a couple of weeks old...John

 

I believe he said he replaced the battery a couple of weeks ago.

For the uninformed the wide belt is pretty standard on older engines.

Here's another diagram (jacked from a Landrover site) that may be easier to follow. The diode that suggested would go in place of the light.


The 2 wire can stay where it is on yours. It looks like you just need to hook up the exciter wire and it should work.

I put 100K on my truck with the setup just like 440Roadrunner has shown it without problems but did blow one diode so a spare is a good thing. they are very inexpensive anyhow.

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without the yellow #1 wire conected you will have to give your engine a little rev up to get your alternator to start charging, 1500 should be good and then let it go back to an idle. you do not need the #1 wire hooked up to make your alternator charge.

 

I got a dash light and a diode just to be safe. The dash light is only a LED so it won't draw a lot of current. As I understand it, a Diode is only a one way gate and only draws about 0.6v power itself. I guess that is enough to initiate the charging.

Neil

 

A simple diode needs .6V to function correctly. In the field circuit, it only drops the field voltage by .6v. meaning you should have 11.4 volts at the field when starting up. If you use the led, the drop will be 1.6 to 2.0V, but will still function as a diode to block voltage from feeding back to ignition.

 

You have to "bump" power to the other terminal just once and you won't have to do it again unless you disconnect the battery again.

 

The use of the diode is so that when you turn off the running engine, the alternator doesn't backfeed the ignition system and keep the car running. I've done this on MANY conversions. Doesn't have naything to do with the voltage feed to the alternator.

 

Why do you think your engine was made in 1944?

 

This is going to piss most of you fellas off but I never run an exciter wire. I run a hot to the battery and if I'm wireing up a new system I also make sure that I run a wire to the battery post on my ignition switch. Never have a problem.

 

You said: The heavy wire goes to the volt meter on the dash. ****** If you have the heavy wire connected to a VOLTmeter, there is no power going anywhere. The other side of a voltmeter should be grounded. You want an ammeter in that line. The other side of the ammeter goes to the battery one way or another.

 

440, u r correct, the LED cannot withstand much more than 20-30milliamps, so a regular diode or resistor or lamp will work. You could wire the LED around the resistor or lamp, (diode drop too small for LED) provided you current limit the LED to 20 milliamps or so with a resistor in series with LED, about 200 ohms or so.

I figured the field is at least 1-2amps (57 bulb is 270ma and lights quite bright), that is why your common variety LED will not work. However there are some LED'S that will take up to 2 amps, but sadly they are expensive and surface mount types.