What was found
WHILE TAXING HYDRAULIC LIGHT ILLUMINATED, PER QRH, NO HELP. CREW STOPPED AIRCRAFT ON TAXI WAY AND REQUESTED TOW, SINCE MAIN PUMP WAS LOW, COULDN'T GET BRAKES. MAINTENANCE REPLACED RELAY 7ML. ALL WORK DONE IAW SAAB 340 MM, SEC CHECKS GOOD, OPS CHECK GOOD.