The link below is a one-page PDF (Adobe Acrobat) that shows what I did to replace my intake heater relays with stronger units. It's been two years with no hint of problems.
Replacing the Dodge OEM Heater Relays3/17/10 - After all these years, the relays are still working like new.
2/02/15 - Five years more and the relays still work like new.