try my method, for my aircon cooling coil, I go back TCM and ask them pin point the fault, after the fault had been ascertain, ask them how much it will cost to repair, then go outside workshop and ask them quote and compare, most properly you will get a cheaper quote.
You can try Autoaid at toh guan road east, call bro rick at 94873722 for info.
disclaimer: I am under NPMP so TCM might had waive off any charges for checking my latio during my cooling coil check.