With out seeing the trimmers it is a little difficult to tell but with process of elimination - you may want to check the blades to see if the bolts on the blades are to tight there should be very little play so the blades move freely, that wold cause it to heat up, or you may have a short in the wiring which could also cause it to heat up. For the wiring you will have to take the handle and housing apart. If you have to take it apart take your time and lay everything out in order that you take it apart so that all you have to do is go in reverse order to put it all back. Any problems or questions feel free to ask and I will gladly help.