my 90 sc's brake and anti lock light were staying on and the brakes were really hard to push. So i put a brake accumulator on it and it fixed it for a day. Then it started doing it again. I checked the 4 pin plug and didn't get a reading. So should i try the pressure switch it has a new relay already. Also if i don't drive it for a day or so they will work for awhile or until i shut the car off. Any suggestions? Thanks