Chrysler Repair: engine cut off, chrysler new yorker, voltage gauge

Question
At first my car would not start.  I had the battery checked, it was not dead so I replaced it.  Then the motor and the whole car cut off.  My mechanic said it was the alternator.  I replaced it.  It is still doing the same thing.  I was told now that it is the voltage regulator.  I would like to know what it wrong with the car. It is a 1989 Chrysler New Yorker.

Answer
Hi Betty,
It sounds like the mechanic is not really analyzing the problem, unless you happened to notice that the reading of the voltage gauge on your dash is showing a lower than normal reading when the car has been running, which would be a sign of a problem with the voltage regulator. However the "voltage regulator" is part of the engine control computer and so that is a very expensive part to replace. So I would not buy into that approach without further testing. In my '89 LeBaron the gauge usually reads a little under 1/2 scale.
I don't understand what you mean by "doing the same thing": is it that the engine will crank but "not start", or is it that the "motor and the whole car cut off", and by that do you mean there are no lights, not even the emergency flasher? I need to know where things stand right now so as to give you useful ideas of how to test this situation.
One thing you can try which would tell me about what the engine control computer has detected to be wrong, if anything, by reading out the fault codes that may be stored in its memory. For this to work, the battery has to at least have enough voltage to light the "check engine" light
(or it may be labelled "power loss" if you have turbo engine). If it is, then do this-
Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). Then watch the 'check engine' light: it will be "on" for a couple of seconds then begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
Then send a follow-up question and tell me what coded numbers you read out, what is the present "state" of the electrical system (will the engine turn over, are there lights?), and which engine you have so that I can be specific with any advice.
Roland