With the warmer temperatures coming a little bit early this year, we have seen quite a few cars coming in the shop with air conditioning problems. Once people start using their air conditioning, they make a bee line to the shop if it is not cooling properly. Usually we can hook up our A/C machine to a vehicle and tell right away what the problem is. Lower pressures usually mean an under-charge condition and will most times freeze up the evaporator or lines. A system that isn’t fully charged only means one thing, a leak somewhere. If the pressures are high, that tells the technician that there could be a restriction somewhere in the lines or components, a faulty part, or over-charge condition.
I recently had a Ford Crown Victoria police car from a local township with multiple air conditioning problems. This car had been worked on previously by some other shop and had a new condenser and accumulator installed on the car. They were complaining of the air conditioning freezing up and then not blowing cold.
I rolled our A/C machine over to the car and was about to hook it up to the high and low side connections on the car, but found something interesting. Someone had installed a stud into the high side fitting, probably to try and stop a leak. This basically left me with no way to properly diagnose the problem. Sure, I could have just hooked up the low side connector and done some tests on the system, but that really isn’t the right way to do things.
I informed the service writer that in order for me to properly diagnose the car’s problem, I would have to replace the high pressure line where the fitting had been ruined. He sold the job right away, since these guys obviously wanted to be nice and cool inside the car! I got the new high side line and installed it on the car. Now I could actually test for the real problem they were complaining about. After getting a good vacuum to hold on the system and found no leaks, I charged it with the proper amount of R134A refrigerant and ran the air conditioning. It was nice and cold, the pressures were holding steady and everything seemed just fine.
Then I started hearing a noise coming from the air conditioning compressor assembly. It was a knocking type noise that would come and go, get louder and then get softer. It was surprising to hear this since the pressures on the gauges were holding steady. Usually when there is a internal problem with the compressor, that will make the readings fluctuate pretty badly. So, in my opinion, the system was functioning ok, but more than likely they would be needing a new compressor down the road once it completely failed.
Now, since this is a township police car, money really wasn’t an issue. After describing the problem to them and the possibility of needing a new compressor sooner or later, they just opted to get it fixed right now. That was good news since it meant more money in my pocket as well.
I quickly installed a new A/C compressor on the car and got everything hooked back up, vacuum tested, and charged. It was all good, nice and quiet, pressures great, and very cold air blowing out of the vents. I’m sure the police officers who drive it will be highly appreciative!
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