So, I'm new here, but I've been peeking in for a while trying to diagnose a problem that my 93 940 wagon was having. Thought I'd share the result as a way of "giving back."
The car stalled one night as my wife drove home from work. She had taken an exit off the freeway and it stalled. The stalling involves all dash lights coming on, tach drops to zero, followed by a pretty quick restart and seemingly problem free ride home. I should mention that this wagon is an automatic, so I was not able to simply drop into neutral to start. Had to pull completely over, stop, put trans in Park, and then start.
Well, the stalling became more and more frequent, especially at stop lights, turns, any time when the accelerator was not depressed... but occasionally when accelerating, as well. I had no voltage meter, still don't, and I don't have confidence in my ability to use one, but I think the time has come.
Anyway, I finally brought the car to Scandia Volvo, near Fremont, CA, where they hooked me up quickly. $370 later, but same day service. They were very helpful, too. Explained how they diagnosed the problem, etc. Basically, they had a hunch and used a "good" Power Stage Amplifier to swap out mine and let the thing idle for half an hour. When it did so without stalling, they had their man, so to speak.
The power stage amplifier is located (on this model) next to the air filter. It is mounted on the driver's side fender wall, behind the driver's headlight.
(it is also called the ignition amplifier)
As a matter of fact, there are 4 available on ebay right now. They say "Buy now" for $10.99, which seems like a heckuva deal. I wish I wasn't so broke, I would grab a couple for myself for future testing/replacement. This is the link to the ebay sale:http://cgi.ebay.com/ebaymotors/Volvo-Saab-240-940-Bosch-Power-Stage-Ignition-Amplifier_W0QQitemZ390144013580QQcmdZViewItemQQimsxZ20100116?IMSfp=TL1001162310007r18720
So, I hope this helps somebody. I'll probably be back eventually with some ridiculously ignorant questions, so I felt it best I throw my 2 cents in first.