How To Solve The Suction Line Not Sweating Issue!

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There are two main lines that come out from the AC outdoor unit. One is a suction pipe, and one is a discharge pipe. It is normal for the suction pipe to sweat or even from a bit of icing when operational. 

But what to do when the suction line is not sweating?

There are multiple reasons which can cause a suction not to sweat. The clogged indoor filter is a core reason. To solve it, wash it properly with clean water. Also, if the insulation over the pipe’s broken then you should re-insulate it. And for a heavily dusted cooling coil, just clean it properly.

So, that was just a glimpse. Below I have given details for each reason and also followed up with adequate solutions. 

So, let’s get into it!

Should the Suction line Sweat?

Sweating for a machine part doesn’t seem normal. But for an HVAC system, sweating for the suction line is necessary. 

The suction line will sweat when it is below the outdoor ambient temperature. If the ac suction line is cold, that is a good thing. 

Many measure the right temperature of the suction line to be similar to a cold beer can. But this measurement isn’t accurate for obvious reasons. 

Since not everyone likes the same level of coldness of their beer. Or probably the person who said it was really drunk at that time.

So, what should the suction line temperature be?

The suction line should be near 35 or 65 °F. On the other hand, the discharge line should be above 150 to 220 degrees of Fahrenheit. You need to keep an eye on if both ac lines get hot. 

If you are asking, should the small ac line be cold? It should be, the small line is the suction line. 

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Source: Mr. Right

On the other end of the spectrum, in the discharge line, there should be no icing. 

But the suction line can sweat, and low ice formation is just fine. So, what to do if your suction isn’t sweating? Let’s get down to this. 

Why Isn’t Your Suction Line Sweating?

There are many probable reasons why your suction line may not be sweating.

So, below we have given all the reasons with their necessary solutions. 

Reason 1: The Indoor Filter isn’t Clean to Pass Air through

In an air-conditioner, there are 2 main units, one is outdoor and another one is indoor. And there are filters in the indoor unit. The filters accumulate dust so that it won’t pass into the room to our breathing system. 

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Source: Home Stratosphere

This blockade will also prevent the air from passing smoothly. This airflow shortage can cause various AC problems, leading to overheating and system shutdown. 

Also, having the AC vent near a ceiling fan will result in more dust formation in the filter. So keep the positioning of the ceiling fan in mind while installing the AC.


If you notice that your ac line is not cold, you may need to clean it. So how do you fix clogged-up AC filters?

Firstly, you need to bring the filter out from the indoor unit. Take the latches off, and on the top, you will find the filters. Pull on the filters from the bottom, and it will come out. Afterward, wash the filters with water. 

Make sure to dry the filters properly. Otherwise, any water droplet can freeze up and cause ventilation problems. 

Also, it’s important to change the air filter now and then. And you might even ask how often should I replace my filter?

The rule of thumb is to inspect your air filter every 1–3 months and replace it even if there is just a small amount of dirt on the top. Replace the filter until it becomes significantly blocked to avoid costly repairs.

Be like this guy and check up on your AC air filter when the weather is also dusty.

Filtrete AC Furnace Air Filter and Simply by MervFilters Air Filter are quite good air filters. However, while buying a replacement air filter, ensure it’s compatible with your ac.

Reason 2: The Insulation Over the Pipe is Broken

Usually, there are white foams over the exposed pipes from the outdoor unit. While it does give some protection to the pipes, it keeps them in ideal temp as well. 

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Source: Armacell

The suction line and the discharge line both need to be at the optimal temperature. Nor too warm, nor too cold. The perfect balance of the temp is the key. So, how to fix this issue?


In this case, the fix is really easy. All you need is new isolation over the pipes. Usually, with a brand new AC, the pipes are covered. But if your ones are broken, you can just replace them. You don’t want to see that the suction line is warm liquid line is cold. 

Also, if your air ducts are broken, you can try out any between ul 723 or ul 181 tapes. These are industry-grade foil duct tapes. They will keep the air cold while it passes through the duct. 

If you are looking for insulating tubes, check the table below. Both of these isolating pipes are really durable and can protect the pipes as well. 

Duck Brand Insulating Foam Pipe CoversBuy Now!
Yotache Open Cell Air Conditioning Weatherstrip Insulation FoamBuy Now!

Both of these isolating pipes can protect your suction pipes and discharge pipes. 

Reason 3: Cooling Coil is Heavily Dusted

The most important part of an AC is the cooling coil. If the cooling coil is cooling properly, the room air will not cool. Also, the cooling coil depends on a lot of other parts, such as the condenser and the compressor.

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Source: Day and Night Air

But, if the cooling coil itself is dusted, it will not pass air freely. If there is no proper ventilation, you may witness both ac lines are warm. So, how do you fix clogged-up dust in the cooling coil? 


If your cooling coil is clogged with dust, you can clean the cooling coil quite easily. 

First, open the outdoor unit and check on the coils. Use a blower or pressure washer to clean the coils. This way, the dust will wash away, and the coils will be clean. 

How to Prevent Suction Line from not Sweating

Prevention is better than fixing a problem later on. This way the problem will not occur in the beginning. The norm here is that the suction line needs to be sweating. The line is sweating means the pipe is colder than the outdoor temperature. 

This means the AC is functioning properly. Also, if the blower speed is too low, the pipe might form ice on top. Keep the maintenance in the head when you are using the AC after a long winter. Also, clean the AC’s blower fan for better ventilation. 


Should the Air-Conditioning Pipe be Hot?

The AC pipe should not be hot. But that doesn’t mean there should be icing on the pipes. The discharge pipe can be hot (around 150 to 220 degrees Fahrenheit). But the suction pipe stays cool all the time. 

How to Refill the Compressor Gas?

Firstly make sure that all the valves of the AC are closed. Then take the yellow hose and see if the pressure is 60 to 70 PSI. Afterward, unscrew the bolt from the suction pipe and insert the gas pipe. This way the gas will be filled in the AC. 

What is a Hard Start Kit?

A hard start kit is a capacitor that starts the AC and Relay device. The hard start kit is designed to give your air-conditioner’s compressor an electrical boost. So, the AC gets an electrical boost when it starts. 


So, that is everything you need to know about, suction line not sweating.

Always remember to work safely and turn the AC off when you are handling live wires. 

Good luck fixing your AC!

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