Okay, this past weekend was spent (with a lot of help from you all) troubleshooting my charging system. Ultimately I had a bad alternator (which had been replaced a couple weeks earlier). The place I got it from swapped it out free of charge, and everything was going perfectly. 12.x volts when car was off, 14.x volts when running. That was Sunday afternoon. Drove the car to work for the last three days (100 miles a day) on the way home today, the radio cut out and the water temp guage and fuel gauge went down to nil (the initial symptom I noticed when the problem started a month ago). Sure enough, as I dragged into the driveway and pulled out the volt meter, 9.x when running and not running. Belts on alternator are tight and lined up well (thanks to three new bushings).

I am at my whits end, not even sure what to check now.

Questions at this point:

1. What could fry an alternator
2. could anything having to do with the radio be the cause - I had a radio installed in the car about a week before these problems started.
3. Where do I go from here. We have a great Volvo mechanic here, I don't want to do it, but I need a car that will run.

As always, thank you a million times for the help! I have had more fun owning this car since finding this forum than I could have imagined.
--
'82 242, 98 XC (aka money pit)

Where are you getting your alternators from? I went through a bout with Advance Auto and went through 3 bad units before finally getting one that worked. This of course was after hours of troubleshooting wiring that was fine because I kept dismissing the alternator being bad because it was "new". Anyway, after the 2nd bad one I made them test it out of the box at the store so I didn't have to keep going back forth. The third 1 tested ok lasted exactly 1 week, and quit, the current one, has been in all winter and knock wood, its still working, but man what a PITA!!! Good Luck to you...
Chuck Jaxel, I now have 6 Volvos!!!!
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Chuck Jaxel, Pine Hill NJ, Near Philly...

You may want to check the quality of your ground wire. If it is warm to the touch when the engine is running, your ground may not be very good. A thicker ground wire may help or even running the ground back to the battery negative side. THe wiring is gone to crap by now if it is original and from the '80s.

I was just like you a few months back.

I did the following and haven't had a problem since.

1) Replace positive wire from alternator to battery.
2) Replace the ground wire from alternator to frame.
3) Replace the alternator wire in the wiring harness (red one).

And the most ghetto fix....smacking the dashboard.

Sometimes the ALT light doesnt light up when I turn the key to II.
A hard smack on the dash and it lights right up. A wire is probably lose, but i dont have the time nor the energy to hunt that wire down behind the gauge cluster.

Good luck with your car.

This is an 82? Has the wiring been checked? The wires to the alternator
may be exposed and shorting in the black jacket under the block.
Are the connections good to the alternator? Good ground? Good red cable?
The last thing I would suspect is the alternator.
I drove around with a spare charged battery until I had my charging
system tuned up properly. Most of the work was soldering on good wire
and chopping out unjacketed stuff. Use dielectric silicone on the
connections once they are cleaned up. The metal continuity is critical
to success. The 240 does not lose alternators like GMs. Its wiring
fails, especially on the early 80s ones.
--
Stef -- 1981 245 B21A SU M46 chrome roofrack 321000km my volvo pages

When you go to start the car, have you been playing close attention to what happens when the key first hits the ON or RUN position, before you ever crank the starter?

In this key position, with the engine not running, a number of your instrument panel bulbs (including the charging/battery indicator) should be illuminated. The mechanism for this, is that 12 volts should flow from the instrument panel, through these bulbs, then through a wire to the field windings of the alternator (I believe my terminology is correct here; I know the concept is). This is referred to as the "excitation" current for the alternator, which kick starts it into generating voltage. Once it starts generating voltage, it supplies its own excitation current. Without an excitation current from some source, the alternator would never start generating voltage. I've seen stated here that at a certain rpm, the alternator "self-excites", and provides its own excitation current, and hence starts generating voltage, but I don't know whether or not this is indeed true.

Do you know if your instrument panel lights have been illuminating in the ON/RUN postition before cranking, every time you start the car? While you continue troubleshooting, you should ensure this is the case.

--
David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto

A common theme to this alternater-related problem seems to be the old wiring. It makes sense that bad wiring would cause the charging circuit to not be complete. But, would bad wiring actually cause the alternator to burn out? I am asking because I currently have the exact same problem on my 82 240. I bought one alternator from Auto Zone and it lasted about 1 week. I bought another one from Advanced, but I am affraid to put it on until I can figure out if I actually have a wiring problem that is causing the alternator to burn out. Any additional information on this would be very helpful.

Also, Should I be getting 12 volts at D+ with the car not running, but in the on position?

Thanks

Gerald

I had the same problem which was also accopanied by a friendly shock when i turned off the engine and touched the door jam....ouch. Make sure your alternator is well grounded.

Nathan,

At the risk of boring you, here is a "canned response" that I hope will relate to your problems—or raise some relevant comments from others.

P.S. David Armstrong's tip relates to B, down at the bottom...

=============================>>>
The Battery's main job is to supply power to the starter. Period.

Once the engine is running, the Alternator supplies power for Everything Else — plus a little extra to keep the Battery charged. (The Battery is just along for the ride at this point.)

In simple numbers, the Battery is capable of supplying a nominal 12 Volts. The Alternator can put out about 14 Volts. (Anything over 12 Volts is what keeps the Battery charged.) A meter on the Battery terminals shows Battery voltage with engine off, and Alternator voltage when running. If it drops below 13.0V when running, you're reading Battery again.

If the Alternator output falls below 12 Volts, the Battery starts taking up the slack (not its main job) and "running down". The fewer the electrical demands, the longer the running down will take. I once went about 40 daytime summer miles after leaving a wire off the (V8) Alternator.

Voltmeter readings can be misleading, however. For example, six flashlight batteries connected end-to-end will read 12 Volts on a meter. But they would hardly power your headlights, let alone turn the starter motor. They wouldn't have the "Capacity".

Alternators sometimes lack Capacity too. They may show 14+ Volts with the engine idling, but less and less as lights, fan, etc. are switched on. The usual suspects in this case are:

1 - The Voltage Regulator/Brush unit attached on the back of the Alternator
2 - Worn/grooved commutator (in the Alternator, where the brushes ride)
3 - Worn/Glazed/Loose/Slipping drive belts
4 - Poor connection(s), Alternator-to-Starter-to-Battery + terminal
5 - Poor "Ground" wire connection (between Alternator body and mounting bracket)

If the Alternator output never rises above the Battery's 12 volts, it could be due to:

A - More severe versions of any of the items listed above

B - Failure to "pre-exite" the Alternator's charging circuits (Key On current flow from the Battery Light (and 3 others) on the Instrument Panel via the thin red wire to D+ on the back of the Alternator.

C - An internal failure within the Alternator itself (least likely)
=================================]
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.