A CL65 PIC RPT ON POSSIBLE RF INTERFERENCE AND THE ACFT'S SUDDEN TURN WHILE FOLLOWING A SPINNING COMPASS. IN CONTACT WITH ZID; IN.

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LEVEL CRUISE AT FL240; FO WAS FLYING. AUTOPLT ON; IN IMC CONDITIONS. FIRST INDICATION WAS CAPT'S FMS AND HDG BEGAN TO SPIN TO THE L; WITH THE SPIN OF THE INST HAVING A HIGH DEG OF SPIN. NEXT; THE AUTOPLT DISCONNECTED WITH THE ACFT IN A L BANK AND TURNING L. WE BROUGHT THE ACFT BACK TO LEVEL FLT AND REALIZED WE HAD NO GOOD HDG INFO. NEXT; ZID CALLED AND INQUIRED AS TO OUR HDG. I RESPONDED THAT WE HAD A PROB WITH OUR HDG INFO. NEXT I BELIEVE I HEARD THE CTLR TURN ANOTHER ACFT AWAY FROM US. WE NEXT RECEIVED AN EFIS COMPASS MONITOR WARNING MESSAGE FOLLOWED BY A RED HDG FLAG. WE RAN THE ABNORMAL CHKLIST PROC FOR AN EFIS COMPRESSOR MONITOR MESSAGE WITH A RED HDG FLAG. WHEN THE CHKLIST PROC HAD BEEN ACCOMPLISHED; THE HDG INFO SEEMED TO BE RETURNING TO NORMAL. AFTER ABOUT ANOTHER 60 SECONDS; WE FELT THE HDG INFO WE WERE RECEIVING WAS GOOD COMPARED TO THE STANDBY COMPASS. I BELIEVE THROUGH THIS WHOLE INCIDENT THE HDG OF OUR ACFT PROBABLY VARIED BY 160 DEGS TO 140 DEGS EITHER SIDE OF OUR INTENDED COURSE. THE INCIDENT LASTED ANYWHERE FROM 3-4 MINS. THE INCIDENT HAPPENED IN THE SECTOR OF ZID JUST E OF THE CTLR OPERATING ON 134.00 FREQ. OTHER THAN AN AHARS FAILURE; I WONDERED IF AN ELECTRONIC DEVICE IN THE CABIN COULD HAVE CONTRIBUTED TO THIS ANOMALY.