The thermo relay is a heavy duty switch to prevent the request switch from overloading with excessive current or heat.
THINGS TO LOOK FOR
As the thermo fan operates over years the internal mechanisms may start to wear and cause a resistance in the thermo fan relay causing an overload on to the relay and the fuse. A common sign is a faulty relay. Melted terminals on the relay indicate that the thermo fan may be overloading the system or drawing too much current caused by an internal fan problem.
IS IT EXPENSIVE TO REPAIR?
If it is a standard thermo relay it may cost around $20.00.
TEMPORARY REPAIR AND LONG TERM REPLACEMENT
If all other relays are the same specs, ie they may have 30 or 60 amps, make sure that the thermo fan relay is the same as the other and then just swapping the relay with another just to get you home if you’re stranded.