High internal resistance in spark plugs is rapidly becoming a concern that many IA/AP's are beginning to recognize as the source of rough running engines and chronic magneto related problems. Since a growing number of maintenance facilities are incorporating a resistance check of all spark plugs, Tempest felt it would be beneficial to make it as easy and efficient as possible to conduct such a test.
AT5K Resistance Tester
Tempest has developed an easy-to-use tester that makes it very efficient for IA/AP's to test the resistance in all aviation spark plugs.
The IA/AP simply places the spark plug, barrel side down over the contact post and touches the other lead end to the firing end of the center electrode. If the light is green, the spark plug resistance is below 4kŮ (thousand ohms). If both the green and red lights are on, then the plug is between 4 - 5kŮ. This is acceptable for serviceable plugs. If the red light is on alone, this indicates a resistance value in excess of 5kŮ and the plug must be discarded and replaced.