Although i have been fixing my 140 and 240 for more than twenty years, i had'nt known about this wonderful Volvo chat site until Thanksgiving. I've been seeing some questions on Brickboard about 240 electrical problems (surprise!), and i just thought i'd mention a few things i have discovered.
My 1984 245 had trouble starting until i tried to squeeze the plug into the socket of the computer in the engine ($#%&!). So i then emory-papered the aluminum (?) pins on the computer receptacle and brillo-ed the insides of the plated brass connector holes on the cable plug. I applied a dab of Volvo anti-oxidation conducting paste (brown goo) to the mating surfaces and plugged them together, and it lasted for at least another five years.
Another time with my 1984 245 i found that when i turned on the turn signal the engine would stop. It turned out that the turn signal shared the same fuse with one of the fuel pump relays, and the contacts for that fuse were dirty...and one contact at the relay was very oxidized. So i cleaned all the contacts, applied the brown goo to the relay contact, and it worked fine. It turned out that when the turn signal drew current through the fuse also being used by the relay, a voltage drop occurred across the dirty end of the fuse and the relay quit because of lack of sufficient voltage.
Recently, before the 1984 245 was retired, it would start and stop sporatically, and i could hear the buzzing of the fuel pump relay under the rug on the passenger side. It turned out that the smaller of the two red wires at the positive terminal of the battery was not getting enough of the 12 volts because of an oxidized connection where it was screwed to the main cable at the battery. Another job for the emory paper.
Thanks for all the insight i've been picking up from you contributors.