Hoses, Valves & Sensors

Somewhere small, which is why a visual inspection rarely finds it. Slow losses of this kind usually come from a joint O ring that has hardened, a hose that has begun to permeate, or a compressor shaft seal that leaks only when the system is at rest. Refrigerant carries oil with it, so look for an oily film with a dust deposit at joints and fittings. A workshop leak test with a detector or ultraviolet dye finds it far more reliably than looking.

It is the boundary between the high and low pressure sides, metering liquid refrigerant into the evaporator through a restriction so that the pressure drops sharply and the liquid flashes to vapour, becoming very cold in the process. A thermostatic valve senses the temperature leaving the evaporator and adjusts flow mechanically. An electronic valve does the same under control unit command. When it sticks, cooling is either weak or the evaporator ices up, both with a correct charge.

Only in specific ways and rarely usefully. Some hose sections can be re ended by a specialist with the correct crimping equipment, which is worthwhile on an unusual or unavailable part. What is not acceptable is any patch, tape or sealant on a line carrying refrigerant at pressure, and sealants added to the circuit contaminate workshop recovery equipment and block components downstream. The formed section listed here arrives with its fittings and its route already correct.

Every time a joint is opened, without exception. The rings compress and take a set, so a reused ring is the single most common reason a repaired system leaks within weeks, and they cost almost nothing. Use rings of the correct material for your refrigerant and lubricate them with the oil specified for the system, which for an electric compressor means the electrically insulating grade rather than conventional compressor oil. Never use general purpose grease.

Because the refrigerant is evaporating too early or too much, which drops the core below freezing so condensate turns to ice and blocks the airflow. A stuck expansion valve is the classic cause, and so is a fault in the temperature sensing that should modulate the system. The symptom is cooling that works well for a while and then fades as airflow disappears, recovering after the system is switched off. Have the pressures and the sensor data read rather than guessing.

O rings and small fittings sit right at the bottom of the range. Expansion valves are modest. Formed hard lines and compressor pipe assemblies cost the most in this category, and to those you must add recovery and recharging, which is a workshop charge that applies whatever the part costs. The live minimum and maximum are shown in the band at the top of this page. Finding the leak precisely before ordering is the main saving available.

The mechanical part is straightforward and the refrigerant handling is not, and in most markets venting refrigerant is prohibited. The system must be recovered before any joint is opened, evacuated afterwards to remove air and moisture, and recharged by weight with the oil accounted for. That requires a machine matched to the refrigerant type. A sensible arrangement is to order the parts and have a workshop with the correct equipment carry out the recovery, fitting and recharge.

Because opening the circuit lets in atmospheric moisture, and the drier contains a desiccant whose capacity is finite. Once saturated it releases moisture back into the system, where it combines with refrigerant and oil to form acids that corrode components from inside and can freeze at the expansion device. Replacing it whenever the system has been open is standard practice for that reason, and it is inexpensive relative to what it protects.

No. Vehicles are designed for a specific refrigerant with specific oil, pressures and seal materials, and the service fittings are deliberately different sizes so that the wrong fluid cannot easily be introduced. Some newer refrigerants are mildly flammable, which changes leak detection and recovery procedures. Retrofitting from one to another is a specialist operation rather than a top up decision. Check the label under the bonnet and use what it states.

Only where the numbered section agrees. Routing follows the packaging of the specific vehicle, fitting types differ between joints, and heat pump vehicles carry sections that conventional versions of the same body do not have at all. A line that is nearly right sits under tension or chafes against structure, and it will fail there. Read the number from the old part, match it, and use the quote form with photographs where the reference brings back nothing.

A clip that has broken or been left off, almost always. These lines are secured at intervals so they cannot move against structure, and once a clamp is missing the pipe vibrates against a bracket or an edge and wears through over months. That is why the repair includes restoring the routing and the clips rather than simply fitting the new section. Check every clamp along the run while access is open, since one missing clip creates the next failure.

Yes. Refrigerant lines are formed to a single routing and crimped at the factory, so they are ordered by number rather than by description, and the less common ones wait for a quote. Send the reference and say which end of the circuit it serves, suction or discharge, since the two carry different diameters. Ask for the O ring set with it. Every joint you open needs new seals of the correct material, and refrigerant grade rings differ from ordinary rubber. If the system was open to atmosphere for any length of time, add the receiver drier as well.