Let us set the stage: it’s a hundred degrees outside and you’re sitting back enjoying the day. Suddenly, your AC stops working due to an AC unit fuse problem. Why does this always happen in the summer, when you need your air conditioning the most?
The simple answer is that high temperatures are kryptonite for all electrical components, including air conditioner fuses. You might as well accept that this is a problem you, unfortunately, can’t avoid.
The best thing you can do is to prepare yourself for this moment by learning how to troubleshoot most AC unit fuse problems and what to do when trouble comes.
What’s the deal with fuses?
In short, air conditioner fuses protect your unit from more serious types of damage. Your fuse will blow to protect the condenser if more amperage than your AC unit can handle tries to pass through.
Do note that your AC is rated for a certain amperage. The fuse is made to handle just the exact amount of amperage that your air conditioner is rated for.
So it’s important to use the fuse that matches your unit’s rating. Too big of a fuse, it can let through more amperage than your AC can handle and you’ll end up with a fried unit. On the other hand, the fuse will blow more often if it’s too small.
What kind of fuse should you use?
Let’s say you’ve got an emergency with your AC, and you need to replace the AC unit fuse as quickly as possible but you’ve only got a smaller one at hand. In that case, you can use it, but just remember that it’s not a permanent solution.
In most cases, AC systems use TR-type fuses. You’ll find both the size and type of fuse written on the fuse itself. If the writing is not there, you can find out the exact amp rating on your ACs rating plate.
Can’t find any ratings? You can just put in a 20 amp (the lowest rating for AC units) HVAC fuse. That will buy you enough time to figure out the correct rating.
If by chance the fuse blows right away, abort the mission. It means that the fuse is either rated higher or there is a more serious problem like a short in the wiring.
If that’s the case, shut down the breaker, turn off the thermostat, and wait for a professional to arrive. While you wait, we can only suggest a hand fan to keep the heat at bay.
How to check if an AC unit fuse has blown?
If you notice that you can no longer operate your AC unit, chances are you’ve got a blown AC unit fuse. Still, you need to check if it’s just the fuse or a more serious problem.
We recommend you use a voltmeter to make this entire process quicker (voltmeters also look pretty cool which is a plus).
A quick word of warning: use extreme caution when doing any of the following steps in troubleshooting your AC system. If you’re uncomfortable working with electricity, maybe it’s best that you call a professional.
Now that’s out of the way, here’s how to check if a fuse is blown:
1. Locate and open your disconnect. The disconnect is the gray box mounted next to the outdoor unit. Find it and open the cover.
2. Open the cover that protects the wiring. There’s another cover in the disconnect, once you open it, you’ll be able to see the wiring.
3. Find the wires. There are two wires carrying 110 volts each that you need to locate: incoming (labeled as line) and outgoing (labeled as load).
4. Set the voltmeter and connect the leads. Set your meter to the voltage setting. The display should read 0 volts. Next, take your voltmeter’s leads and connect them to the screws (lugs) of your disconnect. You need to connect the red lead to the black line wire and the black lead to the white line wire.
5. Check the reading. If your voltmeter displays any number between 220 and 240, that’s good news as it means there’s power coming from the disconnect into your air conditioner fuses. If there’s no reading there might be an issue with the breaker panel and you’ll need to call a professional.
6. Test the load. If the previous test went well, just repeat everything on the load side of the fuses. Once again, the sign that everything is working well is a reading between 220 and 240. If there is a voltage reading on the line side but not the load side, bingo! You’ve got a blown fuse.
‘’But what if I don’t have a voltmeter’’, you ask?
We get it – not everyone carries a voltmeter in their pocket at all times, and that’s ok. You can still troubleshoot your AC unit fuse issues without it. Go down to your favorite Target or store of choice, buy a few dollars’ worth of fuses, and install them to check if they’re the problem.
Replacing your air conditioner fuses
Onto the main course: replacing those suckers. First, you’ll have to remove the old fuses (duh!). Here’s how:
1. There are two types of disconnects: ones that house the fuses in the same place as the wiring and ones that house the fuses in the handle. If you have the latter type, you’ll need to pull out the T handle to access the fuses.
2. Next, pull out the handle to stop the power. We recommend shutting down the breaker to your air conditioner because there will still be power flowing to the disconnect and one can never be too safe when toying with electricity.
3. If the fuses are in the handle itself, you can start removing them, if not use the pair of pliers with insulated handles (we can’t stress this enough).
4. Put every AC unit fuse back into its place, and turn everything back on. Voila! You’re a true handyman now because you replaced your first set of fuses.
What to do if your AC still keeps blowing fuses?
So you’ve done everything right and you’re still running into issues? Chances are the issue lies somewhere else. This usually points to a more serious problem and if you don’t treat it, you’ll have an ex-air conditioner on your hands.
The cause could be any of these:
1. Faulty capacitor: this component helps regulate the current so if it malfunctions, it causes your unit to blow fuses.
2. Loose components: electrical components can become detached or wobbly in high temperatures.
3. Circuit malfunction: if your breakers keep tripping and fuses keep blowing there might be too much amperage in the power line. The issue could be anything from your power supply to your fuse box.
4. Dirty filters: high temperatures can exacerbate the problem of dirty filters twofold. Your unit will work harder at a higher temperature and as a result, fuses might go boom.
Keeping it cool
Whatever the final result, you can’t deny that playing around with air conditioner fuses wasn’t fun. At the very least, learned a crucial skill that will help you as an HVAC owner (especially during the summer).
Best case scenario, it all went well and it was just an issue of a random fuse. But if it’s not the fuse that caused all the headache, we strongly recommend you call a professional instead of playing around with electricity any further.
Contact Aztil AC if you need to restore your air conditioner to life at an affordable price. We’re available around the clock in Palm Beach, FL and we can find out what’s exactly wrong with your trusty old HVAC.