why could anti lock and brake lights come on intermittantly for several weeks then go solid

Have you checked your brake fluid lately?

I have a few months ago. was OK but will have it checked again. Thank you very much for responding....

Doesn't explain why they went off for a week once alternator was replaced though...That's the strange thing....

I don't think so... I will ask... The last 2 times I have taken the car out now though and driven considerable distances like 30 miles, got stuck using the break a lot in a 2 hour traffic jam and for some reason they did not com on at all, and I know no one has put any break fluid in since the last time out with the car 3 times ago when they were coming on.Of that I am certain.... Doesn't seem to make any sense...

When the system is just a little bit low, if you use them often you will pump the system pressure up that will turn out the light. Then if it sits for a while the pressure will drop and light comes back on. My advice would be to have a friend who knows or a pro check it out.

Thank you so much! I did call my local Buick dealer's service dept and even took it to after market parts place who had a computer to check and of course the lights were not on because even though they were on when I got there they said the car had to be off to put on there little computer and because the car was not in gear and lights wouldn't come on they could not read any codes. At that time I called the local Dealer's service dept and they pretty much said would have to wait until lights were solid on that they wouldn't be able to read either unless they were. My main concern was that if whatever drained that initial alternator had something to do with the lights coming on because that's how it all started the first time that it might happen again eventually. The alternator went 2 weeks after the lights stayed solid initially. Which of course could also just have been coincidence I guess... I thank you very much for your time and efforts....Going to take it and have someone check the brake fluid tomorrow... Will let you know...:)

Could you tell me how then went on your Buick a year ago. I'm having the same problems

I'm not an expert but I had an ABS light on a 2000 grand prix, was intermittent for a while and then went solid. couldn't figure out what was going on. It seem to have good brakes, but if I left the car sitting for A few days I might or might not need a jump, when the ABS light went solid I started having solid lower capacity from bat and it WOULD need a jump if not started for a few days. I was changing the CV axles when I found a disconnected wire without a connector. Turned out the wire had broke going to my ABS sensor for one wheel. After getting everything reconnected there was a difference on the braking and ABS light went out no reset no codes or anything and I have at least 5 hours worth of radio play time on that battery and it will kick right over without a jump. My suggestion would be check for shorts or bad connection 'somewhere' in there good luck with that one. I'm just happy my CV axles went out and showed the sensor wire. And I know this post is old and I talk way too much but i included some extra detail in case it might help somebody that has similar problems. Plus My car is fixed so now I can sit around being bored till the next problem comes up. Nah, this might be a good time to put the new speakers in! Good Luck gals and guys!