Ford — Field Relay Test
Testing & diagnosis · Alternator regulator
From a Ford service manual — check it applies to your exact model before use.
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Procedure
- Remove the regulator from the vehicle and make the connections shown (Field Relay Test).
- Slowly rotate the field rheostat knob clockwise from the maximum counterclockwise position until the test light comes on.
- Observe the voltmeter reading at the moment the test light comes on - this is the relay closing voltage.
- If the relay closes immediately, push the red button between the meters and repeat the test.
- If closing voltage is not to specification, replace the regulator.
Tools required
- Rotunda ARE 27-38 tester Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Closing voltage see Specification Chart
Source: Ford 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.