Hello--I had a former Pontiac dealer replace my accumulator.  The ABS and Reg. Brake Warning Lights went out and the car stopped fine.  However, the accumulator motor would run almost constantly (every other brake application).  The dealer told me this was normal--I had three of these cars when they were new and never remember any of them doing that.  I took them at their word and drove the car for about 3,000 miles, when I lost my brakes nearly completely one time and the lights (both ABS and Brake) started to come on intermittently.

So I took it to arguably the best brake guy in town, who said my accumulator was ruined because it had run so often.  So he put a new accumulator on there, the problem of the system running constantly persisted, so he had the ABS unit rebuilt.  Still the accumulator motor runs almost constantly.

Any ideas?

It could be a bad pump motor relay if it just runs constantly.

thanks for the information--will that show up on as a trouble code when the system is hooked up to a diagnostic computer?  I now have had the car at five different brake shops since this all started.  I now have new brakes all around, a new accumulator and a rebuilt pump. . .still the ABS light is on, the car stops poorly (low pedal) and the stop lights work only when the pedal is pushed far.

A failed relay will not come up as a code.

Also wouldn't it run more often if the nitrogen charged ball runs low on pressure?

There are codes that can indicate a failed relay, but if the motor is cycling on and off and not staying stuck one way or the other I'd venture to say you are ok as far as the relay goes.

my old Accumulator would act in a similar way, But I also was getting some codes for it. I have a aftermarket HYDAC accumulator now, and it runs about every 3rd press.