Had a clutch failure on an A-6.
A little backround.
System was rebuilt last summer and worked until I had a deer strike last winter. In the winter I replaced the clutch pulley as I didn't have the right one at 1st. The system takes the less common 5 5/8" x 1/2" belt pulley that was used in the 60's, but well into the 80's on ag equipment. I originally could only find the 5" x 7/16" belt pulley. When the correct pulley was installed a new pulley bearing was installed at the time.
When the deer strike happened, it was well below zero, and although the condenser cracked, it was not a sudden release of pressure and the pressure was very low anyway due to the cold temps.
Because of the slow release, the lack of any evidence of oil escaping, when the unit was repaired, no oil was added.
Last week it got warm enough to use the A/C and had some belt squeal when the compressor tried to start, but once it was going it cooled well. When I stopped, I tightened the belt and all was good... so I thought.
The next day, it quit working. When I got home I found the clutch in pieces and the pulley bearing shot. The belt never stopped turning and there was no belt squeal. The system has a high pressure cut-out and two low pressure safety cut outs. (one each on the high and low side)
Two scenarios come to mind, either the clutch started slipping and heat built and burned the clutch and bearing, or the bearing failed and took out the clutch. The reason I don't suspect the clutch slipped is, A) it never had before even at much higher head pressures, B) it was cooling well and the truck has an oversize condenser and the head pressure is always low.
Oil slugging of the compressor is a possible cause of clutch failure, but with no oil being added to the system since when it was working well last summer, I can't see that being the cause. Any blockage in the system would trip the high pressure safety on the compressor outlet.
I'm leaning toward a failed bearing however unlikely that is, as the cause. Once the bearing failed and the pulley was no longer held in tight alignment, the clutch slipped and rapidly failed due to heat build up. The epoxy in the clutch was burnt to the point it fell out, and the bearing was toast. The rubber coupling bond to the driven disk had separated (looks to be a heat related failure).
All indication are the compressor is fine, it turns over by hand easily but not without a little resistance, as one would expect with a charged system. The pressure shows ambient temp, so I don't believe any loss of refrigerant. The low safeties are very effective and shut the system down before any significant loss would be detected.
New Ag clutches are available, but cost as much as some rebuilt compressors. Unfortunately the heat damage is so severe that no part of the clutch is re-useable. Amazing that it made it the 1000 miles with the bearing in taters.
I guess my question is: has anyone come across a bearing failure as the PRIMARY cause? esp a new (less than 6 months old) bearing? Most times it is a slipping clutch and the related heat that takes out the bearing, in this case I don't think that is what happened.
A little backround.
System was rebuilt last summer and worked until I had a deer strike last winter. In the winter I replaced the clutch pulley as I didn't have the right one at 1st. The system takes the less common 5 5/8" x 1/2" belt pulley that was used in the 60's, but well into the 80's on ag equipment. I originally could only find the 5" x 7/16" belt pulley. When the correct pulley was installed a new pulley bearing was installed at the time.
When the deer strike happened, it was well below zero, and although the condenser cracked, it was not a sudden release of pressure and the pressure was very low anyway due to the cold temps.
Because of the slow release, the lack of any evidence of oil escaping, when the unit was repaired, no oil was added.
Last week it got warm enough to use the A/C and had some belt squeal when the compressor tried to start, but once it was going it cooled well. When I stopped, I tightened the belt and all was good... so I thought.
The next day, it quit working. When I got home I found the clutch in pieces and the pulley bearing shot. The belt never stopped turning and there was no belt squeal. The system has a high pressure cut-out and two low pressure safety cut outs. (one each on the high and low side)
Two scenarios come to mind, either the clutch started slipping and heat built and burned the clutch and bearing, or the bearing failed and took out the clutch. The reason I don't suspect the clutch slipped is, A) it never had before even at much higher head pressures, B) it was cooling well and the truck has an oversize condenser and the head pressure is always low.
Oil slugging of the compressor is a possible cause of clutch failure, but with no oil being added to the system since when it was working well last summer, I can't see that being the cause. Any blockage in the system would trip the high pressure safety on the compressor outlet.
I'm leaning toward a failed bearing however unlikely that is, as the cause. Once the bearing failed and the pulley was no longer held in tight alignment, the clutch slipped and rapidly failed due to heat build up. The epoxy in the clutch was burnt to the point it fell out, and the bearing was toast. The rubber coupling bond to the driven disk had separated (looks to be a heat related failure).
All indication are the compressor is fine, it turns over by hand easily but not without a little resistance, as one would expect with a charged system. The pressure shows ambient temp, so I don't believe any loss of refrigerant. The low safeties are very effective and shut the system down before any significant loss would be detected.
New Ag clutches are available, but cost as much as some rebuilt compressors. Unfortunately the heat damage is so severe that no part of the clutch is re-useable. Amazing that it made it the 1000 miles with the bearing in taters.
I guess my question is: has anyone come across a bearing failure as the PRIMARY cause? esp a new (less than 6 months old) bearing? Most times it is a slipping clutch and the related heat that takes out the bearing, in this case I don't think that is what happened.
Comment