Ford — Starter Motor - Motor Feed Circuit (Voltage Drop Test)
Testing & diagnosis
From a Ford service manual — check it applies to your exact model before use.
Browse Ford generators & specs →
Before you start
- The heavy gauge battery input lead at the starter solenoid is electrically hot at all times. When shorted to ground, may cause personal injury.
- A protective cap or boot is provided over the battery input terminal and must be replaced after repairing.
- Always connect the 73 Digital Multimeter at the component terminal rather than at the wiring end connector.
Procedure
- Make sure the battery is fully charged.
- Connect a remote starter switch between the starter motor solenoid S-terminal and the battery positive (+) terminal.
- Connect the 73 Digital Multimeter positive lead to the battery positive (+) post. Connect negative lead to the starter motor solenoid M-terminal.
- Engage the remote starter switch. Read and record the voltage. The voltage reading should be 0.5 volts or less.
- If the voltage reading is greater than 0.5 volts, move the multimeter negative lead to the starter motor B-terminal and repeat the test.
- Remove the cables from the starter motor solenoid B-, S- and M-terminals. Clean the cables and connections and reinstall. Repeat Steps 3 through 6.
- If the reading at the B-terminal is still greater than 0.5 volts after cleaning, the concern is the positive battery cable connection or the cable itself.
- Move the multimeter negative lead toward the battery and check each mechanical connection point to locate the excessive voltage drop.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Voltage drop should be 0.5 volts or less
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.