It could be the horn relay which is typically located in the fuse box. It could also possibly be a defective horn switch which can be checked at the proper relay pin location. You will need a service manual for the proper pin location. The wiring could be bad. Or it could just be the horn itself.
Probably the wrong voltage
If it doesn't blow hot it maybe that there no water in the radiator. if it just doesn't blow at all check the fuses under drivers side dash. Heater is usually marked as HTR.
there should be a diagram on the back of the plastic panel you had to remove to look at the fuses.
possible grounded or bare wire
The difference between MDL fuses and ADL fuses are that MDL fuses are a slow blow fuse with a long time lag. ADL fuses on the other hand, are normal blow fuses with a medium time lag.
because there is a short somewhere
Your electric unit can blow fuses during the winter when you are running your heater for several reasons. The main reason would be that you have a faulty ground on your heater.
A short circuit either in your wiring system or electrical panel could cause your fuses to blow. Most likely, it would be caused by a burned out wire which is frayed and touching a piece of metal in your vehicle.
A short to ground causes all fuses to blow. If you have a trailer connecter then start there first.
you might need to refill the freeon
A: FUSES are very good for short circuit protection. On the other hand a short over current may not make the fuse to blow since it requires heat caused by the current to blow. There are fuses that are meant to blow fast and some fuses are designed to blow slow depending on the circuit requirement
The positive wire going to the EGR could be touching ground.