I am now almost finished bringing back a friend's old '86 sedan from the "driveway death" and had run into some very vexxing electrical problems.

It began as battery discharge and very low voltage w/ no voltage light illuminating.

Checked Alt, replaced brushes/regulator. Cleaned where brushes ride in alt.
Hooked alt back up, tensioned belts properly.

Result: Getting more consistent voltage---14.4V or thereabouts from exciter post on alt.
Batt light on faintly, more light at low RPM, less at high RPM--that's expected.
Voltage at the alt. post of fat red wire running to starter however, was ridiculously high--about 25V. I checked and rechecked....same readings (I was looking at right markings on my analog meter.) I'm thinking alt. is toast--but have doubts about that.
Voltage at post on starter where fat red wire from alt. connects to only 12V. Weird....
Voltage between batt. posts is also 12V. OK---maybe batt. is problem...(tested in good '90 245 and battery is fine as readings are a hair under 14V.)

Of course, all who have dealt with these gremlins know that they cause the strangest things to happen in the electrical system....The most irritating: OD on m46 cutting in/out, or not engaging at all even when the "5" light in the cluster is constantly illuminated (BTW--took the time to check the solenoid, all wires to it, checked relay, checked switch, blah, blah...all to find they were all good).

Began to run circuit component tests. Load tests of 14V good on all wires in charging system. Cleaned all contacts.
Replaced + & - batt. term cables (they were horrible anyway).
Checked all grounds and they were good.

Now--I'm two weeks into this stupid project on just the electrical problem and I'm sounding more and more like a sailor when I'm out in the driveway and the neighbors give me strange looks.

I've taken the car out on test runs--some around the block, some for 50 miles and haven't drained the batt, but still suffer from the weird side effects of the problem....

Then, while test driving one day, batt. light suddenly goes off...OD works, horn now sounds at correct volume & tone, stereo doesn't keep shutting off & turning on...etc. (I'm thinking..."help from above?")....but, after about 1/2 hour more driving, batt light back on...same symptoms again....Road Rage hardcore.

Ok--so I take the alt. out and test it at the local autozone. It's just fine...so I have them test it a few more times....still fine. (Wasted more time and cut my forearm and knuckles in the process)

Put Alt back in....now I'm thinking I'm going to have to pull the harness from under the front of the oil pan and inspect....(hurray!)

However--after I get the alt back in and am testing voltage just for kicks, my hand lightly bumps the loop connector of the fat red wire and I see a spark jump INSIDE of the connector housing--the little area that you can see between the insulation and actual connector.

Immediately the car's idle drops/jumps/settles back when this happens. Oooh, look, now my voltage is about 14V at both terminals on the Alt, basically same at batt. & BATT light off on cluster. (Now's where I start swearing, but not at the car, but at myself)

I repeat bumping/jiggleing the wire right at the contact...same results... Great, now I can at least replicate prob/fix.

Turn off car, disconnect fat red wire...It turns out that the connection between where the ring part of the connector and the butt side of the connector are pressed together (BTW--what a dumb idea for terminal connector design instead of one piece)has corroded and there is intermittent separation, causing the spark and all my voltage woes.

I play a bit with the connector and it easily breaks in two....Now, how come this didn't happen the last half dozen times I've handled that wire and when I inspected it?

Replaced connector---All's Copacetic.

So, I guess the moral of the story is....sometimes you have bad luck, good luck, and need to inspect things more closely when it comes to electrical problems on 21y.o. Volvos.

Upside: Learned a whole lot about the entire wiring/circuits in the car because of all the phantom problems!

Downside: Now my buddies who are also into the 240's are asking me to look at their electrical problems. My answer: Look at the Brickboard....educate yourself, try troubleshooting.....then if all fails, I'll look but I'm not promising anything!