Why is one 30 AMP fuse pair blowing on Carrier Tech 2000 SS AC Unit?

Miss wired or shorted low voltage wiring. Have you changed stat? Animal chewed wires at foundation wall or in attic?

without a wiring diagram you will need a assistance.

Split system Air conditioners are very often on two or more separate breakers, with a control voltage (24vac commonly) connecting their operation. the condensor unit and out-door fan generally on a 220 vc 'paired' breaker, possibly a quick disconnect near the unit with fuses inside, or an independant breaker pair, and the evaporator unit with INDOOR fan on a 110 or 220 vac breaker.

switch the fan to 'ON' at the thermostat... this is the midpoint of the system electrically. If the fan comes on check for voltage at the condensor unit. a check to see if the thermostat is the problem... remove the thermostat and connect the red, green and either the white or yellow wires (not both) if you chose white you should have heat...yellow AC...

most split system AC have a small buss fuse on the control circuit board of the indoor unit. looks like a glass tube with metal caps held by metal clips. In 40+ yrs experience I have found it is more likely one or both of the 30 amp buss fuses near the outdoor unit (replace both even if one is still ok) or a 30 amp breaker in the quick disconnect box.
In many systems the control voltage to the thermostat derives from a transformer in the outdoor unit... it could be as simple as a broken wire. Without a full diagnostic, a complete description of the unit ( AC or heat pump, etc) this is all speculation

Are you heating or cooling? When the outdoor unit shuts off how does it come back on. Or are you saying that the outdoor unit is short cycling off and on

When you say the 'condenser' stopped running - I'm 'assuming' you are talking about the outside unit, and I'm also 'assuming' that when you say it stopped running you mean 'nothing' runs on the outside unit - fan motor OR compressor. The fan motor will drown out the compressor running noise which is a 'low rumbling' sound - often not heard by the layman because of the noise the fan motor puts out.
Assuming you are talking about the outside unit and 'nothing' is running either fan motor or compressor then you might be 'in luck.' Because the most likely reason for the outside unit to be totally off will be a 'blown fuse' or a 'tripped breaker.' The good news is that in 'hot weather,' especially the kind of hot weather that has been present this summer (especially in the south) - blowing a fuse or tripping a breaker is not necessarily an expensive repair.
Indeed, it's not uncommon for a AC unit to blow a fuse (or trip a breaker) on occasion, although it must be noted that doing so is also is sign on something seriously wrong with your AC, i.e. a fan motor breaking down electrically or even a Compressor, both being expensive items to replace.
But, as I said, it's not uncommon for a fuse to blow once in awhile.
I would check my fuses (and breaker) and see if this is what has happened.
If you have fuses (usually located outside close to the condenser) and have no way to check them (you check them with a ohm meter looking for continuity) - then just 'replace' them with new ones. Note: always put 'time delay/dual element' fuses back in - even if the ones that are in there now are 'one time' fuses. 'Time delay' fuses do just what they say they will do - (they hold for just a second or two during that initial start up (of the compressor) without blowing).
If a blown fuse/tripped breaker is your problem then "most" of the time the AC will run ok and you will not have any more problems.
However, if after replacing the fuses and turning the AC back on - the fuse(s) blows instantly, or a short period thereafter (say a few minutes or an hour) then you probably have a problem that is causing it - i.e. the fan motor or compressor is going bad.
Note: one thing that you can fix that might be causing the fuse to blow is a dirty condenser. So, check the condenser coil (think of it like a car's radiator). It 'must' be clean to run properly and when it gets 'really dirty and clogged with dirt it will cause high head pressure and can cause the unit to blow fuses and trip breakers.
Good Luck!

Is the furnace fan (indoor fan ) running. If not the problem is with the inside unit. It supplies the control power to operate the entire system and has a control fuse on the circuit board. If it is running but not the outside unit then the problem is outside.

I would think that when you changed the fuses you 'cured' the problem - which was a blown fuse(s) - but now you have the same problem again - a bad fuse(s).

To test this - you could replace the fuses again - but first - I would make sure that the fuses you are using are 'time-delay' fuses. It should say on the fuse itself 'time-delay' or 'dual-delay' or something like that.

If you're using fuses that are not 'time-delay' your problem could be solved as easy as buying some 'time-delay' fuses.

However, -- fuses blowing -- are usually caused by electrical motors - i.e. compressor/fan motors - breaking down 'electrically' - and heating up and causing the amp draw to increase past the point of the fuses, i.e. a 40 amp fuse will blow when the AC starts to exceeds that rating.

One "longshot possibility" - is - if the condenser is 'really dirty' - it will cause the compressor to run hot and possibly cause the fuses to blow. I would make sure 'all power' including the inside thermostat is "off" - and then 'wash out' the condenser (the coil in the outside unit) real good with a water hose.

Of course another possibility is that you have a loose electrical connection(s) somewhere in the AC. If you're inclined to - you can again - make sure all power is off - and poke around in your AC looking for loose wire connections. Just be sure 'all power' is off before you do this.

If you are using 'time-delay' fuses and your condenser is 'clean' and you can't find any 'loose connections' - and you continue to have the same problem (blowing fuses) - I would suggest calling a Service Tech.

Note: never replace a fuse with a bigger fuse, i.e. if the fuses in your unit are 40 amp - 'do not' put in 50 amps.

It is possible that the fuse(s) you are using are not the 'right size' but that would have to be determined by a Service Tech and actually - is not a strong possibility, although certaintly possible.

hope this helps

Hi!!

This means that the condenser fan motor (outside unit) failed, this caused to build hi pressure and either activated a safety valve to release the extra pressure or blew a line and R22 Refrigerant escaped from system.

The fix is to replace motor fan and capacitor find the leak and refill system with R22 Refrigerant Gas. It is safe to turn on the Fan Only mode on the Thermostat until a HVAC Tech arrives.
To perform this job parts and labor included will cost: about $300 -.$400. Look on the Yellow Pages for a Tech in your neighborhood.

Good Luck!! Don't forget to Rate this post!!

Breaker has popped either at breaker box or at the safety shut off switch. Fuses are blown or the sending unit has popped.

Hi!!! Does your ac unit work fine?If not check your low voltage problem..You have a low voltage problem check the wire going out to your condensor make sure that they are not touching..Good luck..Check low voltage wires..short in progress..