95 Lasaber altenator output cuts in and out

My 95 Lasabre has been acting funny for a few months. My check engine light has been on for a while and neither autozone or advance auto could get their readers to connect to the computer. After a while my car started to die going down the road. It acted like it was starving for fuel, which, it turns out, it was. It would stall out then start up after an hour or so. Eventually it became so bad that I took it to the nearest service station, Midas, to have them look at it. I told them about the trouble I had reading the computer but they had no problem. They got erratic readings from the crank and cam sensors. Replacing the crank sensor had no effect. They then check for fuel pressure, something i whis they had done first, and found that my fuel pump was bad. After replacing my fuel pump the car worked fine, but they were still getting erratic readings from the above mentioned sensors. And the check engine light is still on. Now, when I'm driving, my battery light will come on and go off. I can actually see the lights go dim and then brighten at night. I replaced the altenator to no effect. Then tonight the car seemed to shut off for a half second about three mins from work. It did this twice, with idiot lights coming on and everything. It then ran fine all the way home(an hours drive), except for the altenator problem. It seems to stop producing power and run on the battery for a few minutes and then come back on. The car has about 140,000 miles on it but otherwise runs really nice(it was my grandmas car :) ). After reading some of the threads here I'm going to spend the weekend checking my grounds, but any advice would greatly apreciated.
Thanks,
Dave

Mine is having a similar problem ('87 LeSabre). I believe it is caused by the circuit for the idiotlight, which is used to energize the alternator. Bypassing this and using a bulb/resistored wire from the alternator's output may be a good way to test if it is this wire or not...

Here is a success story concerning the 140 amp alt and charging system problems. Keep in mind that the positive connections are more subject to corrosion than the ground on the battery. The alternator hot wire goes to the positive connection as well. They have to be absolutely clean to be consistent.

http://www.automotiveforums.com/vbulletin/showthread.php?t=480871

Thanks for the tips. I checked the link you provided and unfortunatly I did get my alt from autozone:::laughs::: Oh well. Still trying to get this problem worked out. Taking time for thanksgiving first.
hope you all enjoy your holiday.

Just Found out I have OBDI with the ODBII connector. I read somewhere that they ran out of connectors during assembly so they just started using the new ones. This is probably why the local parts places couldn't read my trouble codes. Question is, can I still read the codes by jumping it? The computer is trying to tell me something and I'd like to know what it is without paying a shop another $45 to find out. One place told me my computer was bad because they couldn't read it. Is that possible? Does the PCM have anything to do with alt output?

"One place told me my computer was bad because they couldn't read it. Is that possible?"
I thought Midas did read the codes!

“Does the PCM have anything to do with alt output?"
No to the above! Output is controlled by the internal regulator.

Erratic electrical surges (high -low voltage) can cause all kinds of problems with sensors getting and sending erroneous feedback to the PCM. Inconsistent sensor feedback will set codes. Computer controlled cars do not run well with low or high voltage!

If you found someone that can read the codes on yours, you better go back to them. Actually, they used three or four combinations of pin locations in the 1995 OB11 connector. Some shops even with the right equipment may not have the correct cable.

Just Found out I have OBDI with the ODBII connector. I read somewhere that they ran out of connectors during assembly so they just started using the new ones. This is probably why the local parts places couldn't read my trouble codes. Question is, can I still read the codes by jumping it? The computer is trying to tell me something and I'd like to know what it is without paying a shop another $45 to find out. One place told me my computer was bad because they couldn't read it. Is that possible? Does the PCM have anything to do with alt output?

OBD I system with an OBD II connector
You need to make up jumper wires to read codes, you have to jump pins 4 and 5 on the OBD 2 connector. A (A is OBD 1)= pin 4 B(B is OBD 1)= pin 5 and the data stream is M( M is OBD 1) is pin 9. So if you have OBD 1 equipment to read codes and the data stream you can hook up into that OBD 2 type connector. I hope this helps.

Well after playing around with it for a day i broke down and took it to the shop. They were able to read the check engines codes. As far as the altenator he recommended replcing it with an ac delco alt since the one I got from autozone was "basically junk". I've read this before so that's what I'll end up doing. The computer says I have a bad cam sensor, so they're replacing that. That might fix the stalling problem that croped up in the last few days. I'm wonderingif the bad alt damaged my fuel pump, crank and cam sensors? OH yeah, it was muffler man who said I had a bad computer and midas was the one who eventually read it for me. I have it at a local repair shop now so hopefully I'll get better reults. I only went to those chain stores because I was out of town. I live 60 miles from work and got stuck away from home. I'm supposed to have it back monday so I'll post the results when I get it back.
Dave

"I'm wondering if the bad alt damaged my fuel pump, crank and cam sensors."

Read post #6 again. Usually high or low voltage will cause erratic feedback from the sensors (all sensors), but will not damage them. I would think the codes you were getting were the result of the alternator spikes and no output, more than the sensors. If it were me, I would have corrected the alternator problem before throwing sensors at it. Well, at least you will have new sensors now. :biggrin:
:sunglasse

Well, after 5 days and $600 it turns out my wiring harness was bad. The mechanic said it pretty much fell apart in his hands. That was the cause fo my alternator problem and my sensor problems. I noticed that my return hose for the water pump was lose when I replaced my altenator(which I didn't need) and it had been leaking fluid on my harness for some time. I never saw it since it's behind the altenator. It's an expensive lesson but at least I have all the new parts on my car. Everything works great except for my cruise control, which wants to keep accelerating and decelerating. I plan on asking the mechanic about that because it's something I use often. Just wish I hadn't spent all that money treating the symptoms instead of finding the problem.
Dave