Caterpillar SR4B — Rotating Rectifier Block Diode Test
Testing & diagnosis
For the Caterpillar SR4B, from the Caterpillar service manual.
Applies to: Caterpillar SR4B
Before you start
- Shorted diode can damage exciter rotor
Procedure
- Set digital multimeter to diode range and remove all leads
- Test forward bias on each diode (black to positive, red to AC terminals)
- Verify readings between 0.4 and 1.0
- Test reverse bias (red to positive, black to AC terminals)
- Verify overload (OL) readings on reverse bias
- Replace rectifier block if any reading is outside specifications
Tools required
- Digital Multimeter 6V-7070 Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Forward bias 0.4-1.0
- Reverse bias OL
Full service-parts list: Caterpillar SR4B →
Source: Caterpillar 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.