Grounding or Line Polarity Fault: 5 Steps to Fix

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Home appliances such as washing machines, dryers, heaters, and furnaces need to stay in a good health. Otherwise, your life can get really hectic. 

But, what if there is a grounding or line polarity fault in your appliances?

To fix reverse polarity, you need a voltmeter. If the meter reads more or less than 115 then there is a problem. Change the lower voltage attached cable on the transformer. For establishing ground, attach the neutral wire to the body device. 

Well, that was a quick glimpse. But to get a better understanding, dive down below. 

How to Detect Grounding Fault?

A ground fault occurs when any loose hot wire touches the furnace. The ground wire sticks with any conductive part of the furnace. So that it can take the electricity running on the body of the furnace. 

So if any hot wire touches the furnace, it can cause grounding faults. Also, this can cause a short circuit in the furnace. Resulting in the breaker turning off. So flip the switch to turn it back on. 

How to Detect Ground Fault


Always be careful around electricity. If you are not feeling confident, always do these tasks through professionals. 

How to Diagnose Reverse Line Polarity?

Before solving any problem, you must recognize what the problem is. Problems with reverse polarity can be fixed. But before that, we need to identify if the problem exists in the first place.

Identifying Reverse Polarity

If you assume the problem is with the polarity, you must run some diagnostics. This way you will be sure if the problem is with polarity or something else. 

To check reverse polarity, you need a voltmeter. You will be reviewing the wires of the built-in transformer. There are 4 wires connected to the transformer. The black and the red wires are live and high voltage wires. 

But the wires which are usually orange and white are the low voltage wires. You will be checking the voltage of these wires. The voltage should be reading around 115 volts. 10% more or less than this amount is not good. 

So the voltage can sit between 104 and 126 volts. If the reading is higher than this, such as 150 or so, there is a problem with polarity. A reverse polarity fault means the wires are connected to the wrong ports. Reverse polarity fault furnace is very common. 

If you are thinking, what does neutral polarity fault mean?

Neutral polarity fault means when the neutral wire is connected to one of the wire ports. It’s supposed to connect to the body of the device. 

Fixing the Grounding or Line Polarity Fault

Grounding and polarity faults can occur at any time. If that ever occurs, you can follow the below steps to fix it-

  • Check the voltage between the ground wire and the black wire. Then check it between the white wire and the ground wire. Finally, check the voltage between the black wire and the white wire. 
  • Try to switch the polarity back to the normal state. Change the wires on the transformer. 
  • This should give you the cumulative 125 voltage.

I hope the above info is going to help you to recover the issue. Now let’s move on to the next part.

How to Fix Reverse Line Polarity?

So, if there is a problem with the polarity, how can you fix it? Well, you will be needing a voltmeter. Otherwise, you cannot measure the voltage running through the wires. A voltmeter is really inexpensive. 

If you are looking for a quality voltmeter to help you fix the issue, we got some great recommendations! Check out these 3 really sturdy voltmeters that can help you get a better read of the voltage: 

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All of these voltmeters will last you a long time. They run on AAA batteries, so it’s easy to find a power source for the multimeters. And they can all last for generations. Who knows, maybe your grandchildren can also give it a go one day! 

Also, you should learn the way of using a voltmeter, it’s actually really easy. Just use both of the prongs of the meter, where you want to check the voltage.

Now that you have your voltmeter ready to go, let’s learn about how you can fix it. Below we have divided the whole process into 5 steps. This way you won’t get a hard time working on the furnace. 

Step 1: Check if the Polarity is Reversed

Before doing anything, you need to be sure if the problem is with the polarity or not. So, check the line polarity on a furnace. We already discussed how to diagnose reverse polarity. 

But to clarify, we’ll go through the process again. Take the back panel off the furnace. Check the wires and find the transformer out. On the transformer, you’ll see 4 wires. Two of them are low voltage and 2 are high voltage. 

Check if the Polarity is Reversed


You need to check the 2 low voltage wires. Attach the prong of the voltmeter to the black wire of the transformer. And take the other prong on the motherboard in the terminal strip. There you’ll find one wire labeled as “R”.

Attach the other prong to the “R” terminal. Now you’ll get the polarity of the furnace. 

Step 2: Check the Voltage of the Wires

The voltage of the wires should be 115 volts. The voltage can be 10% more or less than 115. Which means a minimum of 104 and a maximum of 126. Anything above or below means there is a problem with the polarity. 

Reverse polarity can even cause lower amperage. Drawing Lower amperage in a blower motor is a common issue. but it can be easily fixed. This is how you can check the voltage of the wires. 

Step 3: Power Off the Furnace

So, if the polarity of the furnace is wrong, you need to change it. But to do so, you need to turn the power off. There are huge risks if you work while the power is on. The furnace can get damaged. Also, there is a risk of catching fire in your house. 

Because of that, it is better to turn the power off from the main circuit of the house. 

Step 4: Unplug the Low Voltage Wires

Now you can work on the furnace. Reverse polarity means the polarity of the wires is opposite of where they are connected. So the negative is connected to the positive and the positive is connected to the negative. 

So, you just need to change the places of the wires. There are two sets of wire which is connected to the transformer. One is high voltage and one is low voltage. We are working with the low-voltage ones here. 

The low-voltage wires are usually orange and white. You should be able to just pull on the wires to unplug them. york furnace reversed polarity is a common issue. You may see the same color of wires inside this furnace. 

Step 5: Plug the Wires into Opposite Ports

Now that the wires are unplugged. Just change the wires to the reverse position. For example, if the orange wire sitting on the right, plug it in on the left. And if the while wire sitting on the left, plug it on the right. 

Afterward, turn the power on and check the voltage of the wires. They should be reading around 115 voltage. 

After following these steps, you should be able to fix the reverse polarity issue of your furnace. You can also try using an inline duct fan near the air duct. You can even use a ceiling fan close to an air condition vent for better cooling. 

Does the Furnace need to be Grounded?

The ground or neutral wire is really important for any device. Otherwise, you can get electrocuted when you touch the furnace. The whole house can get electrocuted as well. If the ground wire is loose, you may see l1 neutral polarity fault nordyne. 

Grounding the furnace is really easy. Just take the neutral wire and put it in any part of the furnace. This will let the electricity flow freely to the ground. If the furnace is not grounded, you may need to set 999 on speed dial. 

And that is everything you need to know about grounding reverse polarity. 

Frequently Asked Questions (FAQs)

What Happens When the Polarity is Reversed?

When the polarity is reversed, the flow of the electricity moves in the wrong way. The time the wires are interconnected, it’s called reverse polarity. In that case, the negative wire is connected to the positive, and the positive is connected to the negative. 

Should I Change the High Voltage Wires on the Transformer?

You should never change the high voltage wires. The transformer lowers or highers the voltage depending on the device’s need. If you change the high voltage wires, it can ruin the whole furnace. 

Can Reverse Polarity Ruin the Furnace?

Reverse polarity won’t let your furnace function properly. If the flow of the electricity is wrong, the furnace cannot work properly. Maybe reverse polarity won’t destroy your furnace, but in the long run, there is a risk. 


So, that what everything you need to know about grounding or line polarity fault.

Always be careful while working with electricity. Use rubber gloves and turn the power off. 

Good luck fixing your furnace!

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