Katolight — Diode Testing
Testing & diagnosis · Rotating rectifier diodes
From a Katolight service manual covering: 280 -- 430 Frame, 280 frame, 360 frame, 430 frame. Check it applies to your exact model before use.
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Before you start
- Never use the generator's fan as a fulcrum to bar over the engine.
- Ensure that the engine cannot start during this procedure.
Procedure
- Remove the two main rotor leads and the three exciter rotor leads from the rectifier assembly.
- Place one test probe on the diode lead terminal post and in succession touch the other probe to the lead screw hole in each heat sink.
- Reverse the probes and repeat the procedure.
- Repeat using the other diode terminal post.
Tools required
- Ohmmeter or battery light continuity tester Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Good diode: reverse biased resistance 30,000 ohms or greater, forward biased less than 10 ohms
- Shorted condition: ohmmeter reading zero or very low in both directions
- Open condition: maximum (infinity) reading in both directions
Source: Katolight service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.