89 300ce ABS

My local independent mechanic installed new pads and front rotors but the ABS is acting up. He says half the time he doesn't have to fool w/ the ABS. Now, the ABS activates intermittently especially upon first braking after startup. He says the sensors sometimes get fouled after new pads and need to be cleaned up which he did after I returned the car. He says the dealers don't even try to clean they just put in new. Still problems.