I have a 90 coupe. 128,000 miles on it and overall it is in great shape. I have put 2 alternators, 3 batteries and 1 starter in her in the last 2 years. Unfortunately I am not electrically inclined. I am afraid to take it to the shop, this is one of those things that will probably cost me a zillion dollars for a very cheap part because it takes a shop so long to find. Can any body help. last week she startered fine and ran great. Today nothing. New Interstate battery 1 month ago.

 

Before you do anything else, hopefully with the car in the exact same condition where you are not getting anything when you try to start it, disconnect the battery and check the resistance between the hot and ground leads on the battery. It should be open. Also check the voltage of the battery with it connected and disconnected. If there is no difference, charge the battery, then check it again.
I would look for a ground problem or a short. It could be intermittent, like insulation rubbed off of a wire that is shorting out sometimes. Inspect and clean the connections of all of the big wires that run between the starter, battery, and alternator, ground included. Make sure you have everything turned off and try connecting the ground wire to the battery, preferably in the dark or deep shadow. Look for a spark between the battery terminal and the connector as they get close to touching. You can even kind of tap the connector on the terminal a few times watching for any signs of a spark. That will tell you if you have a short. Unfortunately, it won't tell you where it is. You can always try pulling fuses one at a time to see if you can isolate it to a circuit. If you can't find a short or ground problem, then I would suspect voltage regulation next. If you can get the car started again, check the voltage at the battery while running. It should be around 13-14 volts. You can also check the voltage with a freshly charged battery in the circuit. It should be at least 12 volts. If it is below that with the car off, then you have a short that is dragging down the voltage. If it is too high with the car running then the voltage regulator isn't doing it's job. I believe most cars have the regulator in the alternator now. Since you have changed alternators, this seems unlikely to be the problem. Having made all those changes in such a short time leads me to believe that you have an intermittent short. I had one right where the hot lead goes into the alternator. The insulation had worn away where the wire rested on the edge of the valve cover. However, when that happened, there was no electrical power to the car at all. I am assuming, of course, that you are completely devoid of any electrical in the car at all.
If all or most of this is greek to you, ask some of your friends or car buddies if they might be able to help you out. It doesn't take too long or require much work beyond loosening a few nuts/bolts and maybe having to jack your car up. Usually, a dead battery after one month means you have a pretty good short or the alternator isn't working. What I used to do to check for a dead alternator is get the car running, then disconnect the positive lead from the battery. If the car died, it meant the alternator wasn't working. If it kept running, the battery was bad. If the battery measures 12 volts out of the car (or disconnected), it usually means there's a ground problem.

 

We could use a few more symptoms. I take it that the starter does nothing, not even a click. Do the courtesy lights come on, radio work, headlights work? What is the battery voltage? Since it won't start, you should begin looking at the starter circuit. First remove the battery cables (neg first) and clean the cable lugs, battery terminals, and the bolts and reinstall the cables (neg last). Next try your spare ignition key as the pellet contacts in your everyday key are worn and may not make good connection to the contacts in the ign tumbler which causes VATS to deny cranking. Unplug the clutch safety switch (gear selector switch if automatic) and jump it and try a crank while measuring the voltage on the jumper . If you get 12v on the jumper, then the problem is in the starter, if not, then you likely have VATS problems. Remove the hush panel above the drivers feet and locate the two wires coming from the steering column going to a 2 pin connector. Unplug the connector, insert ign key and measure the resistance across the wires coming from the steering column. It should measure the same as the pellet. If over 13k ohms, you need a new ign tumbler. You can temporarily bypass VATS by connecting a fixed resistor the same value as your pellet across the 2 wires from the wiring harness (goes to VATS module). You can use a 1/4 watt 5% resistor from Radio Shack. If you still have no crank , let us know what happened for more diagnosis tips.

 

More symptoms. A/C window is --- and radio will not come on. Service engine soon light and service ABS are real dim. There is a clicking inn the dash on passengers side. It I pull the LCD 5 amp fuse the clicking stops. What are the changes that the computer is shot?

 

Sounds like too low battery voltage to me. Measure the battery voltage at the battery terminals with a voltmeter. If below 12.0 volts, remove the negative cable and charge the battery up with a battery charger and then connect an ammeter from the negative battery post to the neg batt cable and after the courtesy lights time out, measure the leakage current. It should be less than 50 milliamps.