Wow this has been a pain,
So one day about a month ago our little 240 that could suddenly couldn't. It just wouldn't start. Thankfully it just wouldn't start about a block away from a mechanics shop, so I got my roommate to help me push her there (I forgot to take it out of drive, so it wasn't such an easy push). The mechanic said that the starter was dead, so a painful $400 later we got a new starter ($300 more and we got a new exhaust system too, ouch). The day later guess what happened, the car wouldn't start. We got it towed to the same mechanic, seething. They told us it was just a dead battery, they charged it up, and we were good to go. 3 days later it dies again, this time we check it out, get it started again, and lo and behold the alternator is out. hmm. I think to myself I'm gonna do it my self. So I do. And it runs fine for a week or so. Then it dies while we're driving out of town. Hmm. Could it be the fuel filter since it was kind of chugging before it died and when we tried to restart it would turn over, just didn't want to start. Ok, so I got a new fuel filter, and just because I could, I put in new spark plugs, a new positive cable from the battery, and a new air filter (just to cover all the bases). And it runs fine for another week. And then, kaput. The battery is dead, again. So the alternator isn't kicking in, but only sometimes. It's like a dice roll everytime I turn the key. I can try to start the car 4 or 5 times, only hearing the solenoid click. And then all of a sudden it fires up. I bought one of those portable jump starter (battery in a box with jaws) just as a backup plan. When the key is in the on position, the battery light doesn't come on, like it used to. And everytime I turn off the car, my aftermarket cd player loses all the preset stations. I know this is a lengthy post, but anyone got an idea?
Tyler

"When the key is in the on position, the battery light doesn't come on, like it used to."
That's your clue. It should be on in position II, engine not running (and goes off engine running).

Check the thin red wire to the alt and make sure it's attached. And also, the thicker short stiff blue wire that grounds the alt. case to the engine block. With those two in place the alt. light should be on in the II position, engine not running.

To see if the red wire is okay (through the harness to the gray plug), ground it to the engine block with the key in position II (engine not running). If the alt light goes on then the wire's okay.
--
1980 245 Canadian B21A with SU carb and M46 trans

Keep that hot-shot jumper ready. the alternator is going on strike.

The alternator must have outside excitation to start charging. After it gets going, it self-excites.

The outside excitation comes from the warning lights on the dash, especially the BATT light. When the key is in Position II, before starting, all the warning lights should be on. This allows checking for burnt out bulbs.

The lights for Batt, parking brake, brake failure, and bulb failure find their ground through a thin red wire that ends up connected to the back side of the alternator.

When the alternator is not spinning, that connection is to ground. A small voltage comes through those bulbs, just enough to excite the rotor field. When the alternator starts spinning, the ground is lost so the lights go out.

If that thin red wire has problems, the alternator does, too. (1) If it gets grounded some other place, the warning lights stay on all the time, and the alternator won't start charging. Battery goes dead.

(2) If the red wire is open, grounds nowhere, the warning lights never come on, and the alternator won't start charging. Battery goes dead.

You say that the warning lights don't come on, so I would believe that (2) is your situation.

That wire, and others, get to the alternator via a harness that runs under the front of the engine. A hostile environment, subject to insulation failure.

that wire, and others, are part of the four that come from the gray connector on the firewall. They are also included in the harness that has known insulation failure 1982/3 to 1988.

Look a the wires from that gray connector. Missing insulation? DO NOT TOUCH.

There is an easy fix, requires running a replacement wire. Check the archives as there are plenty of posts covering that fix.

Good Luck, and don't buy a battery or an alternator until you KNOW they are bad.

bob

:>)

One of my fears is leaving the light on in the trunk or if you have one under the hood, but that would be to simple. Check the tension on your belts and from what I read, change out the bushings associated with the altenator. On occasion my charging light comes on while driving and a simple roll of a fuse corrects that, but that would be to simple. Re do your positive cable and any other cable you can get your hands on.