Can I Bypass AC Compressor With Shorter Belt?

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If you've decided to use the AC of your car, you might want to know if it's possible to bypass the AC’s compressor by installing a shorter serpentine belt. You’ve come to the right place, for we have researched this question, and we have the answer for you.

Yes, in most cases you can bypass the compressor in your car by installing a shorter serpentine belt.

Let’s talk more about this method to disable the AC of your car in the succeeding sections. Learn the correct way to bypass the compressor and how to get the correct serpentine belt length below.

Read on!

Close up of an HVAC unit motor belt drive. - Can I Bypass AC Compressor With Shorter Belt?

What is a serpentine belt?

Older model cars have several belts that connect to the engine. Each belt powers one engine accessory, like the compressor for the AC or the alternator.

Multiple belts inside the engine compartment mean that they must be thinner, or they will consume a lot of space. However, thinner belts result in less efficiency because you cannot apply as much tension on a thinner belt, since too much tension can more easily break one.

Close-up image of a supercharged automobile engine

Moreover, a thinner belt has less surface area that comes into contact with the pulleys of the accessories, which means that there is a higher likelihood of slipping. Slipping shortens the lifespan of the belt because it will rub against the side of a pulley or the walls of the engine.

Thinner belts become looser quicker over time, and this leads to diminishing performance. The need for less tension on the thinner belts also makes it problematic to have high-torque accessories on the car.

Serpentine belts eventually replaced thin, multiple belts inside the engine bay, and over time, engine designs no longer use multiple belts.

Serpentine belts use advances in rubber technology that are not possible with thinner belts. They are wider and have grooves that increase the surface contact area to improve grip and stability.

Their width allows engineers to implement a tensioning mechanism or a tensioner in newer engine designs. Tensioners push on the serpentine belt to increase its tension and improve grip and torque on the pulleys. A serpentine belt isn't at risk of breaking with greater tension because it is wider, granting it a higher breaking point than traditional thinner belts.

How does a serpentine belt work?

Serpentine belt engine mechanism

A serpentine belt passes through the pulleys of various sizes that power the accessories of your car. The serpentine belt draws rotational energy from the crank pulley and transfers it to the accessories that need that energy.

The serpentine belt normally has grooves on one side and a smoother opposite side.

The side with grooves provides power to accessories that need higher torque, while the smoother side powers accessories that need less torque. The serpentine belt also passes through idler pulleys.

Idler pulleys are responsible for redirecting the serpentine belt so that the appropriate side will pass through a pulley. It is also responsible for creating the ideal angle for the connection between the belt and the pulley.

Can I bypass the AC compressor with a shorter belt?

In most cases, yes.

However, if bypassing the compressor pulley still redirects the serpentine belt into the path of the compressor’s pulley, then you will not be able to completely bypass the compressor pulley unless you uninstall the compressor.

Moreover, the path of the serpentine belt going to a pulley must retain a specific angle so that it can maintain the level of tension and friction that it makes with a pulley. If bypassing the compressor causes the serpentine belt to lose too much angle from its connection to a pulley, then that connection with a pulley could have less torque and less stability. This can be a problem if the accessory that the pulley powers require high torque.

And if you uninstall the compressor, you need to decide whether you’d really like to completely get rid of the AC functionality of your car or not. Removing the compressor will render your AC system completely useless.

However, getting rid of your AC compressor provides you with additional space inside the engine bay that you can use. A ProCharger can take the place of the compressor—it will also draw power from the serpentine belt—and provide your engine with a boost of power.

If you don’t plan to install a ProCharger and the compressor’s pulley is in the path of the serpentine belt, then you could uninstall the compressor and replace it with an idler pulley. This replacement will ensure that the serpentine belt will maintain the same operating angle with the accessories that it powers. You will still need a smaller serpentine belt unless the idler pulley is of the same size as the pulley of the compressor.

How to determine the length of the serpentine belt that you need?

Hand hold crack car power steering hydraulic pump belt and the new one

When you bypass the compressor, you will need to replace the belt too. Since you’re using the belt for the same system, all you need to change is the length. You can bring the old belt with you to your auto store and tell them you need a belt of the same type but with a different length.

And we have the steps to help you get the new length of the serpentine belt that you need in the sections below.

Alternatively, you can give them the PK number of the belt.

What is a PK number of a serpentine belt?

The PK number is a global standard for indicating the size of the belt. Since this is a global standard, there are metric measurements in the PK number, so take note of whether you’re looking at a metric measurement or not.

You’d know that you’re looking at the PK number because it has “PK” within the first three to four characters. It is also printed close to or next to the manufacturer’s part number.

There are three sets of information on the PK number. The first information is before “PK,” and the third is after it.

The first set of characters of the PK number indicates the number of ribs on the belt. If you see 7 or 10 on the first set of characters, then that is the number of ribs that the belt has.

The next set of characters is “PK.” “P” means that it uses a metric designation, while “K” means that it is a belt for automotive use.

The last set of information is the length of the belt in millimeters. Thus, if you have 1204 after “PK,” then you have a serpentine belt with a length of 1204 millimeters.

Determining The Length Of Serpentine Belt That You Need

  1. Park your car on level ground.
  2. Place the transmission into Park (P) and enable the parking brake.
  3. Make sure that the car’s engine is cool before you start measuring. You’d be touching parts of the engine. A hot engine can burn you.
  4. Use painter’s tape to fasten one end of a cotton string or twine on one of the pulleys. Cotton has a very little stretch which is important.
  5. Run the string through the pulleys on your engine that the serpentine belt will pass through. Your string must move through the same ridge. If you start at the first or second ridge, all the pulleys that it will pass through should be on the first or second ridge.
  6. Use a breaker bar to loosen the tensioner. Most tensioners have a “min/max” marking that tells you the minimum and maximum length of belt that you need. When you mark the length of the string, you should set the tensioner to “min” to give the belt room to expand.
    • Belts naturally expand as it wears. Once the tensioner gets to the “max” position, then you need to replace the belt.
  1. Measure the total length of the string in millimeters. This is the effective length of the belt.
    • To get the outside length, add 14 to the total length.
    • Most serpentine belt manufacturers have a 3-millimeter tolerance. This means that if the exact length is not available, you can get one that is +/- 3 millimeters of your target length.
  1. Count the number of ribs that you need on the serpentine belt.
  2. Put the two pieces of information together, and you have your PK number.

Dayco 6PK2135 Serpentine Belt is available on Amazon through this link.

ScotchBlue Original Painter’s Tape is available on Amazon through this link.

NEIKO Drive Extension Breaker Bar is available on Amazon through this link.

Alternative Way To Disable The Compressor

Fridge compressor condenser, close-up. Refrigerator backside including corroded copper pipes, electrical wiring and dust and pet hair. Concept for maintaining and repair appliances. Selective focus

There might be a situation where you cannot immediately remove the compressor, but you want to disable it right away to maximize the power that you’re getting from the engine. Removing the compressor involves the removal of the rest of your AC system, and this can take time to complete.

Another way to disable the compressor—if you don’t plan to uninstall it yet—is to disconnect the power harness that goes to the compressor clutch.

This will prevent the compressor clutch from responding to the AC switch. Anyone can turn the AC switch on, but the compressor clutch will not engage the compressor pulley and draw power from the engine.


Bypassing the AC compressor can be done in two ways. However, it can involve slightly more work if you do not want to affect the performance of the other accessories in your car.

If you enjoyed reading this article, you might find the articles below equally enjoyable to read:

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