What would cause the heating module to short out in the electric seats of a 99 Grand Cherokee LTD?

Answer 1

it could be 1 of 2 things.#1-it overheated or #2- the wiring going to it shorted out due to overheating.

I heard that some Jeep models had faulty seat heaters that overheated, dont know if it was a recall item. my seats get red hot, but nothings broke yet.

There is a recall on the heated seat elements from 1999 to 2004 Grand Cherokees. Call your dealership with the VIN (vehicle identification number) and they will be able to tell you if they have been replaced. If not, it should only take them a few hours.