M/board needs replacing again - Dell won't do it

The motherboard on my Inspiron laptop gave in just short of a month before the warranty was up. (March '14) It was replaced by Dell technicians. Now, less than a year later, the replaced motherboard has given in and needs replacing. Dell is refusing to replace it as the LAPTOP is out of warranty. They claim that there is only a 3 month warranty on replaced parts. <br> If I had purchased a new motherboard, I would have a full warranty, so why after it has been replaced by certified Dell technicians is it only 3 months?<br> The Laptop cost R10 000 and I have been quoted R6015 ex Vat for the Motherboard.<br> Totally unimpressed and would like Dell to explain themselves.