Can You Replace AC Capacitor With Different Ratings?

AC capacitors can go bad due to their regular usage over time. Like other electrical systems, air conditioners rely on a good capacitor. 

Unfortunately, they can break down if your AC is working under load. But it’s not always a good idea to replace them. 

Can you replace AC capacitors with different ratings? 

Yes, you can replace AC capacitors with different ratings. But you’ll have to consider the 20% tolerance range. For example, a 35/5 capacitor can’t be replaced with a 45/5 capacitor. It’s because the maximum tolerance for a 35/5 capacitor is 42 uF. You should also prioritize picking a higher value. 

Anyways, that was just the brief answer to the discussion. Of course, this answer wasn’t enough to cover the whole topic. That’s why we’ve further elaborated on the capacitors and whether it’s replaceable or not further. 

Let’s get into it!

Should AC Capacitors Be Replaced with Different Ratings? 

It’s safer and keeps you out of trouble. Every manufacturer picks a certain capacitor rating for a reason. They understand what’s best for their products and it should be left that way.

But remember to pick a higher rating and stay within the 20% tolerance range. 

Also, remember to be careful when replacing an AC capacitor. If you think it’s too difficult, don’t hesitate to call experts. 

Functions of AC Capacitors: Everything You Need to Know

Before talking about AC capacitors in detail, let’s look at the basics. In case you’re new, you’ll benefit greatly by knowing the fundamentals.

For instance, you can’t choose which motor to pick for your furnace without proper knowledge. Likewise, to be able to choose an AC capacitor, you’ll have to understand them.

Usually, when the capacitors go bad, people need replacements.

That’s when people start to wonder what capacitors are compatible and what isn’t. It can get confusing pretty easily so we’ll start from the basics. 

Like most people, you may wonder what does an AC capacitor do? 

AC capacitors are used to provide a spike of electricity to power up the motors. Simply put, it’s like ignition in an engine. AC capacitors bring the AC motors to full speed. After your AC reaches its full motor speed, the capacitor stops itself. They don’t have any usage until you start it again. 

In easy words, it’s like when you use a key to boost the car engine. Except, for AC, you turn on the switch, and the capacitor jolts up the system. 

That is why AC capacitor connections are so important in air conditioning. 

It’s also true for the smaller capacitors. A smaller than required capacitor will fail to electrify the air conditioner. In that case, the motor may get damaged trying to start up without enough electricity. 

As you can see, both bigger and smaller capacitors can cause serious harm. That’s why replacing AC capacitors should be treated with utmost carefulness. 

Replacing an AC Capacitor of Different Rating: Is It Possible? 

You’ll have to replace fan motors if your AC is making noise after power outages. That’s when you’ll need to get the motors with the same rating. Likewise, when replacing AC capacitors ratings matters the most. 

Instead of discussing it one by one, we’ve decided to simplify it even further. That’s why we’ve made you a small table-

From the table, you can see the tolerance range of the capacitors. We’ve picked the higher rating only because it’s safer. 

Technically you can pick a 20% lower value, but it’s not advised. We’ve explained a little already but we’ll elaborate more on that later. 

Simply keep going till the end and you’ll be making a decision in no time. 

Replacing a 40/5 Capacitor With 45/5 Capacitor

When calculating capacitance you’ll have to consider the tolerance value. We’re going to use the same tolerance value for all the problems. 

Tolerance indicates the ability of an electronic component to deviate from its original value. For example, let’s take a 1 kΩ resistor with 20% tolerance. It means the resistor can tolerate 800 Ω to 1.2 kΩ. 

In this case, the tolerance of the said resistor is 20%.

The capacitor’s tolerance is quite similar to the aforementioned example. But it’s always 10% to 20% and you cannot cross this threshold. You also should never install a capacitor with a lower rating. 

Are you still wondering, can I replace a 40/5 capacitor with a 45/5? 

The short answer is yes. The tolerance of the AC capacitor is around 10% to 20%. Considering 20%, the tolerance range of a 40 uF capacitor is 32 to 48 uF. But it’s not advised to replace a capacitor with one that has a lower rating. Since 45/5 uF is a higher rating, it’s safe to use as a replacement. 

Also, remember to match the voltage rating. If the voltage rating mismatch, it can be a disaster for your AC parts. 

Solution: Get a matching capacitor or replace it with a 45/5 uF capacitor. I’ve heard rave reviews about MAXRUN 40+5 MFD uf Capacitor, so you can try that out. Or Genteq 45/5 uf capacitor is also a great option.

Replacing a 45/5 uF Capacitor with a 50/5 uF Capacitor

We’ve already explained the tolerance math in the previous segment. The same rules apply to the 45/5 uF capacitor as well. From now on, we’ll keep the segments short. 

The tolerance range of a 45/5 capacitor is 36 uF to 54 uF. Since picking a lower-sized capacitor means less electricity, we don’t advise them.

For a 45/5 capacitor, you can safely replace it with a 50/5 capacitor. Again, the voltage has to match so please keep an eye on that. 

A 370v capacitor’s replacement can’t be a 440v capacitor. Also, don’t forget that a 45/5 capacitor is the best replacement for itself. Another tip is to always keep an eye on the technician who’ll do the job. 

Otherwise you might have to end up with a wood piece in your AC like this fella.

If you can manage that, prioritize it over a 50/5 capacitor. 

Solution: 45/5 capacitor or a 50/5 capacitor. You can trust MAXRUN or Genteq while replacing the capacitors. 

With MAXRUN 45+5 MFD uf 370 or 440 Volt you can even stop thinking about matching the voltage. As it will support both 370V or 440V. 

Replacing a 35/5 uF Capacitor With a 40/5 uF Capacitor

The tolerance range of a 35/5 capacitor is between 28 uF and 42 uF. That’s why picking a capacitor greater than the 20% value is dangerous. It can potentially fry your AC components. 

You cannot use 45/5 uF capacitors as replacements for a 35/5 capacitor. It’s oversized for the 35/5 capacitor. 

Since the range is 28-42 uF, you can pick a 40/5 capacitor instead. However, picking the 35/5 capacitor with the same voltage is the best option. 

Solution: Go for a 35/5 uF or 40/5 uF capacitor of the same voltage. 

To save you some time, we’ve handpicked some compatible capacitors- 

Simply choose any of the options mentioned above and you’re all good. 

Replacing a 40/5 uF Capacitor With a 35/5 uF Capacitor

Replacing a 40/5 uF capacitor with a 35/5 uF capacitor is technically possible. After all, the tolerance rate of the 40/5 capacitor is 32 to 48 uF. 

But picking a weaker capacitor is really bad. Because it may not be enough to charge your electric components. 

Using a lower-rated capacitor means it’ll draw less energy. This will decrease the efficiency of the device. In the long run, the AC components can get damaged.

The correct replacement for a 40/5 uF capacitor is the 40/5 uF capacitor itself. But you can still pick a 45/5 uF capacitor if you want to. 

Solution: Pick a 40/5 uF capacitor or 45/5 uF capacitor. 

Frequently Asked Questions (FAQs)

What happens if you put the wrong capacitor in an AC unit?

Putting a wrong capacitor can cause permanent damage to your AC unit. It can either supply more electricity which will kill your component. Or it can provide less electricity which will result in inefficiency. Sometimes, AC motors can harm themselves by trying to get charged with low electricity. 

Can I replace a 440v capacitor with a 370v capacitor?

Yes, you can replace a 440v capacitor with a 370v capacitor. But it’s not possible the other way around. The voltage rating shown in a circuit is the maximum amount. Installing a lower voltage capacitor will decrease the performance. But installing a higher voltage capacitor may ruin the circuit. 

Can I replace a certain value capacitor with the same value but higher voltage?

Technically, you can replace a certain value capacitor with one having a higher voltage. But it’s very risky. Because there’s one factor called ESR that you need to consider. The ESR or equivalent series resistance has to match in order to replace it. That’s why it’s best never to do it.  

Take Away

That was everything we could gather on can you replace AC capacitor with different ratings. We hope that this discussion has shed some light on you and cleared some confusion. 

It’s better to spend some extra money on capacitors than to pay for AC parts. 

Finally, have a nice day!

Tim David

HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.