Hello, welcome to Just Answer/Pearl. My name is Mike, I willdo my very best to assist you with your question today.
The replacement unit was it new or second hand?
Also the first unit,did the sound just stop one day without warning?
The replacement unit out of ambulance never used the sound went gradually went on and off going round corners all powered up happens on cd or radio the new unit does work when stationary now but crackly.
THe unit installed was the same style as old one just plugged straight back into old wiring by mechanic