If you buy an ACDelco unit (and possibly aftermarkets) there will be a seal on the underside to seal. Again, if it makes you feel better, seal it in some additional way. If your resistor had no seal under it you could run a bead of RTV or the like(on the underside) and it should seal it! Jerry

 

Thanks Jerry. I bought the Delco unit and it did have the spongy material that seals around the resistor. I may run a bead of rtv just to be safe.