Cummins/Onan WC4-10S-5 — Fan Belt Tension Adjustment
Maintenance · Fan belt and idler pulley
For the Cummins/Onan WC4-10S-5, from the Cummins/Onan service manual.
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Before you start
- Too tight a belt will have a short life and cause unnecessary wear on the water pump bearing; a loose belt will slip and fail to drive the fan and water pump fast enough.
Procedure
- Loosen the idler arm mounting bolt and the adjusting screw lock nut.
- Turn the adjusting screw right or left to increase or decrease tension as necessary.
- Tighten the adjusting screw lock nut, then the idler arm mounting bolt.
- Check that belt can be pressed inward 3/8 in when a pressure of about 8 pounds is applied midway between the pulleys.
Tools required
- wrenches Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 3/8 in deflection under about 8 pounds pressure
Source: Cummins/Onan 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.