Starter Solenoid

This procedure covers the removal and replacement of the starter solenoid on a 1972 Ford F-100 with 302ci V8 engine, including battery disconnection, solenoid removal, and electrical connection verification.

Warnings

Tools required

Parts

• Starter solenoid × 1 — Ford C1AZ-11390-A or compatible aftermarket

Preparation

1. Park the vehicle on level ground and apply the parking brake.
2. Ensure the transmission is in Park (automatic) or Neutral (manual).
3. Turn the ignition off and remove the key.
4. Allow the engine to cool if recently operated.
5. Gather all tools and the replacement solenoid before beginning work.

Procedure

1. 1

   Disconnect the battery
   Open the hood and secure it. Using a battery terminal wrench or 1/2" wrench, loosen and remove the negative battery cable from the battery negative terminal. Move the cable away from the terminal and secure it to prevent accidental contact. Verified detail (On Ford trucks of this era, the fender-mounted starter relay/solenoid is almost universally located on the PASSENGER side inner fender near the battery, not the driver's side. Ford routinely mounted the solenoid on the same side as the battery.): The starter solenoid (starter relay) on the 1972 F-100 302 V8 is mounted on the inner fender well near the battery (typically passenger's side), separate from the starter motor.
2. 2

   Locate the starter solenoid
   The starter solenoid on the 1972 F-100 302 V8 is mounted directly on the starter motor itself. The starter assembly is located on the passenger side of the engine block, near the bellhousing. Access may require working from underneath the vehicle or through the wheel well. Use a shop light to clearly identify the solenoid on top of the starter and its connections. It is a cylindrical component approximately 4 inches long with electrical connections on top and a cable connection on one end. Use a shop light if needed to clearly identify the solenoid and its connections.
3. 3

   Document electrical connections
   Before disconnecting any wires, note or photograph the wire positions. There are typically 3 connections: a small wire terminal for the ignition switch signal (S terminal), a small wire terminal for the ignition bypass circuit (I terminal, if equipped), and a large threaded stud for the cable to the starter motor. The input side has a large cable from the battery positive terminal.
4. 4

   Disconnect the starter motor cable
   Using a 9/16" socket or wrench, remove the nut securing the large cable that runs to the starter motor. This is typically on the solenoid's output terminal. Carefully move the cable terminal away from the solenoid stud to prevent accidental contact.
5. 5

   Disconnect the small wire terminals
   Remove the small wire connections from the S terminal (ignition switch wire) and I terminal (bypass wire, if equipped). These wires typically use push-on spade terminals that pull straight off, though some use a small nut (approximately 1/4") — use the appropriate wrench if a nut is present. Keep track of which wire goes to which terminal. Keep track of which wire goes to which terminal. Verified detail (If the small terminals are push-on spade connectors (typical for this Ford solenoid), there are no 1/2" retaining nuts; and if nuts exist they would be much smaller than 1/2".): If push-on spade terminals, press them firmly onto their studs; if small retaining nuts are used, install and tighten them securely with the appropriate small wrench.
6. 6

   Disconnect the battery positive cable
   Using a 9/16" socket or wrench, remove the nut securing the large battery positive cable to the input terminal of the solenoid. Carefully move the cable terminal away from the solenoid.
7. 7

   Remove the solenoid mounting hardware
   The solenoid base flange is typically secured to the fender well with 2 bolts/screws, which also provide the ground connection. Using a 1/2" socket and ratchet, remove the mounting bolts and carefully remove the solenoid from its bracket.
8. 8

   Clean electrical connections
   With the solenoid removed, inspect all cable terminals and wire connections for corrosion. Use a wire brush to clean the battery positive cable terminal, starter motor cable terminal, and all mounting studs on the new solenoid. Apply electrical contact cleaner if available to ensure good electrical contact.
9. 9

   Install the new solenoid
   Position the new solenoid in the mounting bracket on the fender well. Ensure the terminals are oriented correctly for easy cable routing. Install the 2 mounting bolts and tighten securely by hand, then snug with a 1/2" socket.
10. 10

    Reconnect the battery positive cable
    Place the battery positive cable terminal onto the input stud of the new solenoid. Install the 9/16" nut and tighten securely. Ensure the terminal is seated fully against the solenoid body before tightening.
11. 11

    Reconnect the starter motor cable
    Place the starter motor cable terminal onto the output stud of the solenoid. Install the 9/16" nut and tighten securely. Verify the cable routing does not interfere with any moving parts or sharp edges.
12. 12

    Reconnect the small wire terminals
    Reconnect the small wire terminals to their proper positions on the solenoid: the ignition switch wire to the S terminal and the bypass wire to the I terminal (if equipped). Install the 1/2" retaining nuts and tighten securely. Double-check connections against your documentation from step 3.
13. 13

    Reconnect the battery
    Reconnect the negative battery cable to the battery negative terminal. Tighten the terminal clamp securely with a 1/2" wrench or battery terminal wrench.

Reassembly

1. Verify all electrical connections are tight and properly routed.
2. Ensure no tools or parts have been left in the engine compartment.
3. Verify the battery cables are securely connected and terminals are clean.

Verification

• Turn the ignition key to the START position. The engine should crank normally with a strong, consistent cranking speed.
• Listen for a solid click from the solenoid when the key is turned to START, indicating proper engagement.
• Verify the engine starts normally and the starter disengages immediately when the key is released to the RUN position.
• Check that all warning lights function normally and there are no unusual electrical issues.
• Inspect the solenoid area for any signs of arcing, smoke, or burning smell during cranking.
• After successful start, turn off the engine and check all connections one final time for tightness and proper routing.

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