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alternator light

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paul74

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My 74 B was parked for a week-longest its been quite for months-because I was out of town. Home now. Had to run errands, well, go for a ride if I must be honest. Every time I turned the car back on the red light shown brightly for 30-40 seconds before going out. This is new, it has always gone out immediately after starting. Is a problem looming-Am I needing to do some preventative maintenance?
Thanks
Paul
 
Ditto on David's comment but add...

Assuming that the light is REALLY going all the way out...Check by doing you thing in a darkened garage and looking carefully at the light. If it still glows and possibly brightens a little as the revs increase you have a failed diode in the rectifier pack. If any of the diodes in the rectifier pack were dead or going out to lunch the condition would not heal itself.

If you are sure that the light is going fully out here are two suggestions. If the symptom continues for a few days pull the brush pack and either clean it or replace the brushes if they are really short, especially the outside one. The other is of course to insure that the belt is tight and not slipping. Belts with the "teeth" inside are best as they run cooler and have better grip at all speeds than the standard ones.

Jack
 
Can you replace diodes yourself?
 
Depends on how comfy you are with electronics and a soldering tool. I've found appropriate diodes at Radio Shack in the past. Some alternators have a proprietary pre-assembled bridge as a one piece component, others are made of four individual diodes.
 
Not on Lucas alternators. The diodes are built into a "pack" and the pack has to be replaced. It isn't a difficult task though.

Just a thought, before you go to all of this trouble remove and then re-plug the gang connector at the back of the alternator and see if that does anything. Sometimes things look well connected when in reality they have developed either an real open or just have a high resistance. Look too for any signs of melting of the gang plug boss.

Its best to look at everything on the end of the unit while you are there. Pull the alternator, remove the back cover make a drawing of where each lead connects and then have at it. Most alternators us one screw to hold the regulator in place. That is the square metal thingie. Then you take the screws holding the white plastic brush box off and lift that away. While you have it in your hand look into the cavity and at the least clean it out with some high fraction carb cleaner. At worst the outer brush will be worn short and if that is true you can either replace both brushes, swap the two, or just tug on them to get more tension so that they press harder on the slip rings. Next disconnect the leads to the rectifier assembly and take it away. Rudimentary soldering is required. Just don't overheat anything as it will travel down the wire and trash the diode on the other end. Reverse is as usual doing everything backwards.

Jack
 
Thank you guys. Before yesterday's drive the lite did go out at 1000-1500 rpm. I did shade the lite with my hand to make sure it was out after the 30-40 seconds and it did seem to be. I will check the plug and belt before I go on the errands I did not finish yesterday. This alternator is only a year old, from Kragen Auto. Thanks for the replies and help.
Paul
 
update- The light goes all the way out. The belt is tight. The plug looked bad.
I pulled it and the large brown wire has a crack in it with a piece of the insulation actually missing. The 2 smaller wires look ok but all three seem not as tightly connected to the white plug block as they should be. Some of the individual pieces of the larger wire are actually hanging loosely around the inside of the plug block. The Moss catalog shows a three terminal plug but says the wires should be soldered into the connectors. I dont solder, or have not done so yet. Is crimping these wires the wrong way to go?

When I plugged the plug back in the light went out right away as it should.

Paul
 
Time to learn to solder, easy enough. I bet you even have a friend that would do it for you.
 
The trick on soldering things that are going to be used in an automotive environment is to do it as quickly and lightly as possible. Excessive heat in a local area tends to make things brittle and the vibration from the car's operation will sometimes cause almost invisible cracks and therefore "opens" in a circuit that are hard to locate. I usually make my very best effort at crimping a connection using the best tool that I can put my hand on and then do a quick heat up and solder float just to fill up the tiny cavities of the crimp. Then I use that black shrink tube stuff to make a nice looking collar over the crimping. It may take a little to get the hang of it but when you get proficient things look like you actually know what you are doing. LOL

BTW: Not to offend anyone, but using those colored collar crimp on terminals is a dead giveaway to a novice having done the work. You can use them sometimes, but just strip the colored collar off and use what is left as a normal crimp bit.

Jack
 
Allright. I confess. I would have, I mean might have, used a colored crimp on terminal...
Jack, Thanks for the heads up and technique tips. I'll use them.
Paul
 
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