Ford — Alternator Output Test - On Engine
Testing & diagnosis
From a Ford service manual — check it applies to your exact model before use.
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Before you start
- Alternator output terminal is connected to battery at all times - use care when connecting test equipment
Procedure
- Check drive belt tension; place transmission in neutral/park and set parking brake.
- Make tester connections as shown (Output Test); ensure field rheostat knob is at OFF.
- Close the battery adapter switch, start the engine, then open the battery adapter switch.
- Increase engine speed to approximately 2000 rpm; turn off all lights and accessories.
- Turn field rheostat clockwise until 15 volts; turn master control until voltmeter reads 11-12 volts.
- Holding master control, turn field rheostat clockwise to maximum, then master control counterclockwise to 15 volts.
- Observe ammeter; add 2 amperes to the reading to obtain alternator output.
- If rated output not obtained, increase engine speed to 2900 rpm and repeat.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Rated output 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.