Ford — Alternator Voltmeter Test Procedure
Testing & diagnosis · Charging system
From a Ford service manual covering: 140 CID, 2.3 LITRE, 2300 cc, LSG-423. Check it applies to your exact model before use.
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Procedure
- Turn off all lights and electrical components; place engine in neutral; battery must be charged to at least 1.200 specific gravity.
- Connect negative voltmeter lead to negative battery cable clamp and positive lead to positive battery cable clamp.
- Record battery voltage reading.
- Connect tachometer red lead to distributor terminal of coil and black lead to good ground.
- Start engine and operate at approximately 1500 rpm with no other electrical load; reading should increase 1 volt and not exceed 2 volts above battery reading.
- With engine running, turn on all electrical equipment.
- Increase engine speed to 2000 rpm; voltmeter should indicate a minimum of 0.5 volt above the first recorded battery voltage.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Over voltage is more than 2.0 volts above battery voltage
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.