For starters, A/C units blow fuses when the system is shorted or overloaded. Start by having a well recommended professional come out and look at it(standard Operating Procedure). Fuses can be blown by a variety of things, Gollnick however is correct, the system is designed to not blow fuses.
You can look yourself, by examining both the inside(furnace/airhandler) and the outside(condensing/heat pump unit) for loose, shorted, or unprotected wires. Sometimes an animal may chew through the electrical wiring causing the wires to be exposed. This could cause an occasional short, which could blow the fuse. Make sure before you examine the wires you shut the breakers and thermostat OFF(remove/shut off disconnect to outside unit, and unplug/switch off furnace as well), you don't want to be touching hot wires.
A compressor going out could be the cause of this. A couple of questions:
Does the system not cool very well when it does run?
Can you tell of it is the condesing unit fan motor of the compressor making the noise?
Somethings that can put a load on the system, blocked vents, stopped up furnace/air handler filter, blocked up Evaporator coil, and blocked up condenser coil. Make sure your vents are open(one or two closed, won't make a big difference), make sure your filter has been changed, and wash the outside condensing unit out with a water hose.
To wash the unit, turn it off and turn your water hose onto a medium-high setting, then gently wash in an up and down motion while moving slowly sideways. DO NOT just spray the water hose on the unit in a sideways fashion it WILL close the thin aluminum condenser coil fins up, causing more of a load.
After you've done these things, replace the fuse again and try it, if you find loose/exposed wires have a professional replace/fix them. I would advise against attempting to fix them yourself.
Finally, if the compressor is/has gone out, it will cost more to replace the compressor than the unit, if it is 14 years old. Parts for old units are not cost effective to replace. At minimum chances are a new unit is more efficient than you old one, typically units 14-15 years old are 8 to 10 seer units, minimum SEER efficieny these days is 10 seer. Normally, with our customers we recommend a maximum of 12 seer units, as in Texas we dont realize the efficieny of a 13+ seer system. However, in Ohio you may see beneficial gains by going as high as 13 or 14 seer system. If you do decide to buy a new high efficieny system, beyond perhaps 14 seer you will end up spending more than you will save. Another thing to note, this will be the last year you will be able to purchase a 10 or 12 SEER A/C system, effective Jan. 1 2006, the government has mandated a minimum of 13 seer standard efficieny rating for A/C systems. Keep this in mind, because 10 and 12 seer systems cost about 30% less than 13+ seer systems.
In case you're wondering about the credentials of this post, I work my father in a family owner/operated HVAC company in Texas, I've spent the last 5 years working for my dad, and he has 45 years experience here in Texas. Where the A/C and the guy selling beer are the two most loved men.
By the way, with all costs added in a new condensing unit can(would here) run you between $1300 and $2200 dollars. Depending on size, SEER efficiency, labor difficulties, etc.
-Rob
