Make An Aftermarket Solenoid Work With A Starter

Be aware of some slight differences when installing an aftermarket solenoid in your vehicle.

A vehicle solenoid functions as a heavy-duty switch that receives a voltage signal from the ignition key and bridges that electricity to the starter motor. A starter solenoid endures a lot of heat and voltage every time the vehicle starts. The longer the starter cranks, the more stress on the solenoid, wires and starter motor. Sometimes the solenoid can fail by itself. Aftermarket solenoids have become available for nearly all factory manufactured originals. A DIY repair person can adapt an aftermarket solenoid to work on his vehicle by paying attention to some differences in terminal locations and overall configuration.


External-Mounted Solenoid

1. Place the vehicle in “Park” or “Neutral,” according to your transmission type. Apply the hand or foot brake. Raise the hood and disconnect the negative battery cable with a wrench and socket. Look for your external solenoid to be mounted on the firewall or fender well in the vicinity of the battery. Trace your positive battery wire to its location. Use a socket to remove the two large red wires; the battery wire and the wire going down to the starter.

2. Remove the small wire on the solenoid with a small socket, which might be marked with an “S”, standing for “Signal.” It functions as the control wire that comes from the ignition switch. The “S” wire might pull off manually from a pressure connector. Use a socket to remove the two mounting bolts that hold the solenoid to the fender well. Match up the aftermarket solenoid to the old one. Instead of one small terminal found on the original solenoid, the aftermarket version might have two.

3. Mount the aftermarket solenoid on the fender well and insert the mounting bolts. Tighten the mounting bolts with a socket. Place the two large red wires back on their respective posts and screw the nuts on them by hand. Tighten the nuts with a socket. Place the small wire onto the “S” terminal of the aftermarket solenoid — do not place it on the extra “I” terminal.

4. Tighten the wire nut with a socket. In the case of a pressure fitting, push the small wire over the post. Reconnect the negative battery cable and start the engine.

Starter-Mounted Solenoid

5. Set the vehicle in “Park” or “Neutral” and apply the emergency brake. Disconnect the negative battery cable. Raise the vehicle and place jack stands at both ends underneath the frame. Use a shop light underneath the vehicle to locate the starter. Remove any skid plate or plenum cover impeding access to the starter bolts. Turn the front wheels if the drag link obscures the view. Use a socket to remove the main battery wire on the solenoid-mounted starter.

6. Use a small socket to remove the other small wires on the solenoid, keeping track of what posts they attach to and their letter designation. Refer to your owner’s repair manual for help on identifying the wire posts. Use a socket to remove the main starter mount bolts. There could be two or three bolts. Look for an upward-mounted bolt, if you can not find the third hidden bolt. Pull the starter out of the vehicle from underneath.

7. Use a socket to unscrew any braided ground wire — called the field coil strap — that connects from the solenoid to the starter motor body. Use a screwdriver or small socket to remove the solenoid bolts where they connect to the starter. Some solenoids require you to loosen the solenoid bolts only, then twist the solenoid housing to pull it off. Pull the solenoid off the starter.

8. Place the new solenoid on the starter body and screw the bolts in by hand. Tighten the bolts with a socket. For the twist design flange, set the solenoid against the starter and twist it so its tabs slide underneath the flange ends. Tighten the solenoid bolts with a screwdriver or socket. Reconnect the braided wire to its post and tighten the nut with a socket. Slide under the vehicle with the starter.

9. Push the starter back up into its mounting surface and start the mounting bolts in by hand. Tighten each bolt sequentially until the starter sits flush with the bell housing. Wiggle and turn the starter if you have trouble engaging the starter gear with the flywheel. Reconnect the main (red) starter wire and tighten it with a socket.

10. Reconnect the smaller wires to the posts from which you removed them, matching the lettering. If you have an extra “I” post on the aftermarket solenoid and no wire for it, do not hook any wire to it. Replace any plenum cover or starter shield you removed, and tighten the bolts with a socket. Reconnect the negative battery cable and test-start the engine.