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Rock Sam

Rock Sam 1/21/2019

2016 BMW 535i Luxury 6 Cyl 3.00L

Engine

Symptoms of a Bad or Failing AC Low Pressure Hose and How to Replace a Car Air Conditioning (AC) Low Pressure Hose?

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Symptoms of a Bad or Failing AC Low Pressure Hose:

An AC system is made up of a variety of components that work together so that the AC can produce cold air for the cabin. The AC low pressure hose serves the function of carrying the refrigerant that has passed through the system back into the compressor so that it can continue to be pumped through the system, providing cold air. The low pressure hose is usually made up of both rubber and metal, and has threaded compression fittings that secure it with the rest of the system.

Traces of refrigerant on the hose:

Because AC system is a sealed system, any traces of refrigerant on the hose can be an indicator that it could possibly be leaking. The refrigerant that passes through the low side hose is in gas form; therefore sometimes leaks will not be as obvious as they are with the high pressure side. Low side leaks will present themselves as a greasy film somewhere on the low side hose, often on the fittings. If the system is continuously run with a leak in the low side hose, it will eventually empty the system of refrigerant, and the vehicle will be unable to produce cold air.

Lack of cool air:

Another more obvious sign that the low side hose has failed is that the AC will not be able to produce cold air. The low side hose carries refrigerant to the compressor, so if there is any problem with the hose, it can quickly transfer to the rest of the system. Usually the AC system will start having problems with producing cold air once the hose has completely failed.

Step 1: Remove battery cables from positive and negative terminal. When replacing any mechanical components, it's always recommended to remove power from the battery. Remove the positive and negative cables from the terminal posts and make sure they don't connect to terminals during this repair.

Step 2: Complete procedures for draining refrigerant and pressure from your AC system. Once the battery cables have been removed, the first thing you'll need to do is remove pressure from the AC system.

Step 3: Locate the leaking low pressure hose and replace. When you completed the pressure check in part three of this article, hopefully you marked which low pressure line was broken and needed to be replaced.

Step 4: Remove AC low pressure hose from expansion valve and compressor. The diagram above shows the connections where the low pressure lines are attached to the expansion valve. There are two common connections; the connection from this valve to the evaporator is typically all metal; so it's very rare that this is the source of your leak. The common connection is on the left of this image, where the AC low pressure hose attaches from the expansion valve to the compressor.

Step 5: Check all AC low pressure hose connections: Once you've replaced the old hose with the new low pressure hose, you'll want to double check the connections to the compressor and the expansion valve. In many cases, the service manual will explain how to properly tighten the new connections. Make sure to double check that each fitting is secured as recommended by your manufacture. Failure to complete this step may result in refrigerant leaking.

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