How many amps is it drawing as compared to how many it is rated for? If the amps are withing range, it is probably OK. My guess is that it is drawing higher than rated amps and they owe you a replacement.
The ones I have installed have not been polarity sensitive. Drove me nuts the first time trying to figure out which way was right.
She took my address and my name
Put my credit to shame
Sunspot Baby, sure had a real good time