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Unlocking the compressor Lock up, PT. 2

By Richard Hawkins, MACS contributor

This is part four of a series of articles about compressor lockups. If you have not read them yet, they can be found here.  Part 1, Part 2 and Part 3.

Last week’s article ended with the following:  “Now let’s fast forward to about a week later and a sub 32° F morning with ice on the windshield:  I went outside, started the van up, turned the defroster on and went back inside and ate a nice breakfast.  After about twenty minutes, I came back outside, switched the defroster off and tuned the heater on and went on my way.”

Now fast forward another 2 or 3 days. 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.

With the hood open, the noise was louder, and it was coming from the area where the A/C compressor is located. That is on top of the engine. Looking at the compressor, I noticed something that was a major concern. The front of the clutch hub was discolored. Listening a bit closer, I was able to confirm that the noise was indeed coming from the A/C compressor. The A/C was not turned on and the clutch was not engaged, so that indicated it was not an internal compressor noise. That meant the clutch was either dragging or the clutch bearing was noisy.

Please see pictures #1 and #2

Picture #1:  With the compressor located up high on the engine, it was easy to tell where the noise was coming from.

Picture #2:  The hub on my compressor clutch looked very much like the one in this picture. That is a sign that the clutch has gotten extremely hot due to slippage.

I turned the engine off and examined the clutch closer. The gap was normal so that eliminated a clutch gap issue, which was very unlikely anyway. But there was something else that was very noticeable. There were lots of little metal filings which were clinging to the clutch. This is always an unwelcome sign because it indicates excessive wear has taken place. Please see picture #3

Picture #3:  Metal filings clinging to a clutch hub are an unwelcome sign.

The next step was to try to rotate the clutch hub. It would not budge. My worst fear was confirmed: The compressor was LOCKEDUP. BUT WHY? About 10 days earlier, the A/C was working fine on that 70-degree day, and it had not been turned on since.   Now there was noise coming from the clutch, the clutch hub was discolored, there were metal filings clinging to it and the compressor was locked up.  Something major had occurred.

It was about a 5-minute drive to home and that WHY weighed heavily on my mind, but no answer materialized. After arriving home, I took a ratchet and socket and moved the belt tensioner just enough to slide the belt off the compressor pulley. The next step was to rotate the pulley by hand to determine more about the condition of the clutch bearing.

There was looseness detected in the bearing and it felt rough when rotated.  I needed to drive the van on a trip later in the week and did not want to experience a bearing lock-up. That meant the problem needed to be addressed right away. I didn’t have a compressor that fit the van, but did have one that had the same type of clutch on it.  The next step was to remove the pulley (which of course contained a good bearing) from the spare compressor and install it on the compressor in the van.

As I was completing the job, it hit me what had happened and my first thought was:  You Knucklehead, you caused this compressor to lock up.   

Please check back in next week for an analysis of what had occurred.

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