Greetings everyone. I'm sorry if this is one of those questions that gets asked every other day or so, but I did do a search and didn't find anything. Anyway, I was driving and my radio turned off, the fuel gauge was reading less than it should have been, and then the car died. I turned the key and nothing happened. So, I replaced the alternator and had the battery checked. The battery checked out okay, was charged, and when I turned the key after connecting everything, it started; but only ran for about five minutes. When I try it again I get nothing, but it starts and runs for a little while when I jump it. Every time the radio cuts off first. When I turn the key, with the dead battery, the speedo needle jumps. Any suggestions? I have a feeling I need to do some testing, but don't really know where to begin. Thanks.

If the car stops when it is running then the problem is not the battery. I would check first to see if the batery is being charged. Easily done with a voltmeter (VOM) on the battery, or many parts places will do it for free (Autozone, etc). As you said , you replaced the alternator, so we assume the briushes are new and OK. Most likely is the wiring harness. It shorts together or to ground and there goes your power. That small red white wire is critical as it initiates charging. I think it comes from the dash "charging) light. Check the bulb there and then check the wiring from there to the alternator, it runs under the front of the engine. Many have rewired so it goes along the firewall to right fender to alt.
Best to get a volt ohm meter and wiring diagram for diagnosis.
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744 & 745 16v 4+OD, 245 SE auto, 242Ti 4+OD, 245DL auto parts car

Heading south on route 24 in ma the other day with some extra time I saw a bone yard and decided to check it out. Meandering through some wooded streets I stopped for some directions at a repair shop. Turns out it was a Volvo mechanic, a little grumpy, but knowledgable. Described the same situation you have, as I was planning on an alternator change, and he said 9 out 10 times it is the wire harness. Patched them up and problem solved. Good luck

Your system isn't charging or the batt isn't holding its charge.

With key in accessory position II, are dash lights on? If not check wires (red to back of alt, blk ground wire from case to alt mounting bracket).

If yes, then after startup, do dash lights go off. If not then check regulator brushes.
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1980 245 Canadian B21A with SU carb and M46 trans in Brampton, Ont.

Check the wires at the back of the alternator, and the condition of the entire engine wire harness.

Your brushes may be worn to the point of replacement. Take a look in the 700/900 FAQ from the "Features" pull down menu on this page, and poke around in the charging system section of that FAQ for symptoms that match yours. The FAQ was written with the 700 & 900 series cars in mind, but many of the tips can be applied to 240's as well.

These brushes are inside the alternator, right? I replaced the alternator. There are some differences between the old and new one, however. The new one did not have the small box that connects with a blade-type connection, so I transfered it. Also, the new one does not have a screw that is longer than the rest which the ground wire was connected to. Where should I connect the ground wire? It is connected now, but I'm not sure if it is a good place. Also, the small red wire has seen better days. There is also 2 small wires in the same casing as the large red wire that are pretty torn up. I'm pretty sure I hooked everything up as it was.