First repair to my BMW 535D MULF Unit by Revtronic was in November 2017. Prompt service then and happy with everything. Unit broke down again in April 2019 - it's on a 14 year old car. Sent back for extensive bench testing and report. The unit overheats on hot days and is a poor design (BMW take note!). The heat builds up and makes the unit malfunction intermittently due to the circuit board being enclosed in an un-ventilated metal box (!) Initially, Revtronic suggested adding a small fan (like that used in PC's) but instead swapped my MULF unit for a tested / refurbished "new" one - with a full year's guarantee. Reduced charge for the extra work due to previous unit costs. Picked the new unit up. They fitted it, programmed it into my car and tested it all worked. Again, very happy with the professional way Revtronic have dealt with my malfunctioning MULF unit. No hesitation in giving them HIGH RECOMMENDATION for anyone with car electronics problems - MUCH less expensive than "Main Dealer "prices.