Tempest At5K Resistance Tester

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Part# 08-07462
MFR Model# AT5K


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.



Frederick F Verified Purchase


October 19, 2022

Burgess A Verified Purchase


April 12, 2022

Some folks have complained of the price, but to me it is well worth it for the convenience and accuracy. I highly recommend having one. I rotate and test my plugs every 50 hours on my O-540. Having this tester has made checking the resistance a breeze.

William B Verified Purchase


November 4, 2021


Sandro P Verified Purchase


May 30, 2021

Would prefer a built in OHM gauge on the unit, but the unit is well made and should provide years of good service. It is easy to use

Paul T
October 5, 2019

Works great, simple and quick. No reason not to check plugs when they are out when you have this great little unit. You can accomplish the same thing with an ammeter but not as quick and easy. Im happy with it, highly recommend.

October 13, 2017

Works as described. It would be 5 stars, but it is overpriced for what you get.

West C Verified Purchase


June 22, 2022

This unit is battery powered. Nothing in the manual stating what type of battery, no instructions for changing battery. No portals for plugging in a recharger. No info on expected battery life. Appears back side is removeable, small screw driver required, presumably giving battery access. The unit is well made. Easy one-click spark plug placement on center post. Then one click insertion of wire tester into unit. One button to activate unit, red on-light appears. Touch the lead end of the wire tester to spark plug electrode, get a reading. Green light good, red light fail. Works great. Great peace of mind if youre self-maintaining the plugs. Would give it 5 stars if not for the battery uncertainty.

March 22, 2021

Both O-rings pulled off on the first plug. Other than that it works great. I found the faulty plug that had been bothering me right away. What a time saver.

Tom F
July 29, 2019

Seems to work well, very easy to use.

Glen B
December 10, 2018


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Does this Tempest AT5K resistance tester work on Champion plugs as well as Tempest?

Yes, both plugs types will work fine with this tester.

Q: Will this Tempest AT5K Resistance Tester work with both massive and fine wire plugs?

Per the supplier: Yes, it will work with both types of plugs.

Q: How is the Tempest AT5K resistance tester powered?

This is powered with a 9V battery.

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