Checking Belt Tensioner Spring Tension and Belt Wear (Automatic Tensioner)

Belt drive systems equipped with automatic (spring) belt tensioners cannot be adjusted or repaired. The automatic belt tensioner is designed to maintain proper belt tension over the life of the belt. If tensioner spring tension is not within specification, replace tensioner assembly.

Checking Belt Wear

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Cast Stops

A - Tensioner Cast Stop

B - Fixed Cast Stop

The belt tensioner is designed to operate within the limit of arm movement provided by the cast stops (A and B) when correct belt length and geometry is used.

Visually inspect cast stops (A and B) on belt tensioner assembly.

If the tensioner cast stop (A) on swing arm is hitting either fixed cast stop (B), check mounting brackets (alternator, belt tensioner, idler pulley, etc.) and the belt length. Replace belt as needed ( see REPLACING FAN AND ALTERNATOR BELTS in Service As Required Section).

Checking Tensioner Spring Tension

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Marks on Tensioner

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Align Torque Wrench With Pulley and Tensioner

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Align Marks

A - Mark On Swing Arm

B - Mark On Tensioner Mounting Base

C - Torque Wrench

A belt tension gauge will not give an accurate measure of the belt tension when automatic spring tensioner is used. Measure tensioner spring tension using a torque wrench and procedure outlined below:

1. Release tension on belt using a long handled 1/2 inch drive tool in square hole in tensioner arm. Remove belt from pulleys.

2. NOTE: While belt is removed, inspect pulleys and bearings. Rotate and feel for hard turning or any unusual sounds. If pulleys or bearings need replacement, see your John Deere dealer.

   Release tension on tension arm and remove drive tool.

3. Put a mark (A) on swing arm of tensioner as shown.

4. Measure 21 mm (0.83 in.) from (A) and put a mark (B) on tensioner mounting base.

5. Install torque wrench (C) so that it is aligned with centers of pulley and tensioner. Rotate the swing arm using a torque wrench until marks (A and B) are aligned.

6. Record torque wrench measurement and compare with specification below. Replace tensioner assembly as required.

   Item	Measurement	Specification
   Spring Tension	Torque	20 N˙m (15 lb-ft)

NOTE: Threads on belt tensioner roller cap screw are LEFT-HAND threads