| PROBLEM | CAUSE | CORRECTION | 
| Knocking Noise | Possible defect in | Operate safety valve manually | 
| 
 | safety valve. | by pulling on ring. If valve still | 
| 
 | 
 | leaks, it should be replaced. | 
| 
 | Defective check valve. | Remove and clean, or replace. | 
| 
 | Loose pulley. | Tighten pulley set screw. | 
| 
 | Loose flywheel. | Tighten flywheel screw. | 
| 
 | Compressor mounting | Tighten mounting screws. | 
| 
 | screws loose. | 
 | 
| 
 | Loose belt. | Loosen wingnut and then | 
| 
 | 
 | tighten wingnut until it contacts | 
| 
 | 
 | the washer, plus one turn. | 
| 
 | Carbon build- | Have checked by a Trained | 
| 
 | up in pump. | Service Technician. | 
| 
 | Belt too tight. | Loosen wingnut and then | 
| 
 | 
 | tighten wingnut until it contacts | 
| 
 | 
 | the washer, plus one turn. | 
| Excessive | Loose belt. | Loosen wingnut and then | 
| belt wear | 
 | tighten wingnut until it contacts | 
| 
 | 
 | the washer, plus one turn. | 
| 
 | Tight belt. | Loosen wingnut and then | 
| 
 | 
 | tighten wingnut until it contacts | 
| 
 | 
 | the washer, plus one turn. | 
| 
 | Loose pulley. | Have checked by a Trained | 
| 
 | 
 | Service Technician. | 
| 
 | Pulley misalignment. | See Motor Pulley/Flywheel | 
| 
 | 
 | Alignment paragraph in the | 
| 
 | 
 | Maintenance section. | 
| Squealing | Compressor pump | See  | 
| sound | has no oil. | in the Maintenance section. | 
| 
 | Loose belt. | Loosen wingnut and then | 
| 
 | 
 | tighten wingnut until it contacts | 
| 
 | 
 | the washer, plus one turn. |