The blog article published on November 8, 2022, focused on understanding the importance of knowing the precise location of service ports when faced with a challenging A/C diagnostic issue. It…
I was driving the van home in the afternoon. It was about 45° F outside and the heater was on. It had been an uneventful 15 to 20 minutes’ drive at about 55 to 60 mph. Slowing down to make a 90 degree turn on to a different road, a faint grinding noise was heard. I rolled the window down and drove along at about 5 MPH and could hear the noise more distinctly. The next step was to pull over into a parking lot and leave the engine running and raise the hood.
I noticed the temperature inside of the van had increased a bit. Placing my hand near a vent, I also noticed that the airflow had decreased and increasing the blower speed did not increase the airflow much.
The relay was sticking in the on position and the compressor would not cycle off when the clutch cycling switch turned the power off to it.
All too often when a compressor lock-up occurs, the compressor itself is blamed for the lock-up. While it is possible for a manufacturing defect to cause a lock-up, there is usually a problem related to the service work or a problem with the system that is the culprit.
When an air conditioning system is first assembled, all components (except the compressor) are refrigerant oil free. After the system has been charged with (R-134a) refrigerant and operated, the oil in the compressor is dispersed through the lines and components. The evaporator, condenser, and receiver/ drier will retain a significant amount of oil. Refer to the A/C Component Refrigerant Oil Capacities table.
When draining oil from compressors which have drain plugs, proper draining procedures call for the removal of the drain plugs and the unit drained from both the drain plug hole and the suction and discharge ports.
The A/C system was run with the vehicle’s computer controlling the compressor. When the heat loads were changed, there were noticeable changes in the duty cycle signal being supplied to the compressor.
It is important to know the correct answer, but it is more important to know why it is the correct answer. Please picture #4 for more information on that.
Not much thought is given to compressor clutches until they fail, but they are extremely durable. I have personally owned three vehicles that had between 200, 000 and 240,000 miles on them. They all still had the original compressors and clutches, and they were still functioning perfectly.
