Hardware Test 4MOT/4/40000003: HDD-1326
I run Apple Hardware Test and got this Error: 4MOT/4/40000003: HDD-1326.
What should it be?
iMac, OS X Mavericks (10.9.2)
That indicates that the cooling fan that services the hard drive has failed or is failing. Depending on your iMac variant, this is either a difficult DIY repair or one that you can't do at all at home. Suggest you have Apple look at it to confirm AHT's diagnosis and to offer a repair cost.