The drive seat heated seat doesn't work on just the bottom. the back warms up but not the bottom. when I try to turn it on the light for the bottom doesn't turn on, but the back does. is it more likely the heating element it broke. or the switch? can I just take out the heating element and put 12 volt thru it to test if it warms up? also if the element is shot, would anyone happen to have a part number for it?