NISSAN Pictures of how I replaced the interlock relay on my 87-95 Nissan Pathfinder with manual transmission.

After 10 or more years in service, the Pathfinder suffers a common starting problem. I would turn the key and it made a clicking noise but the engine wouldn't turn over. I'd turn the key a few times and then it would catch and run fine. I tested the battery and alternator, both fine. I cleaned all the corrosion off the battery and replaced the corroded ground cable, but this didn't help.

Then I replaced the interlock relay.


IGNITION-Switch is where I turn the key by the steering wheel.
Interlock-RELAY is the thing by the battery, which sends high current to the starter. It makes sure the clutch is depressed, and that the key is turned, before it will power the starter.
RELAY-Switch is inside the Interlock-Relay, between terminals 87 and 30.   The relay closes this switch to power the starter solenoid.
Juice goes from (+) battery -> to ignition switch -> to interlock relay -> to starter.
Pathfinder starter relay original wiring Diagram

Then this happened:

But first, lets pay some bills:

  1. Parts List:
    • Radio Shack 12 volt 30 amp automotive relay
    • 14 gauge wire
    • 12 gauge wire
    • wire connectors
    • wire cutter/stripper tool
    • electrical tape

    New Pathfinder Starter Relay

  2. Spliced about 6 inches of wire onto each connector on the relay. Used the thin wire on the electromagnet terminals (85 and 86), the thick wire on the switch terminals (87 and 30).

  3. Located the old interlock relay. It is a blue plastic box on the side of the engine compartment right behind the battery. Mine was burned by acid from the battery. Pulled the relay down, off its mounting bracket. It helps to remove the battery or at least move it over to have some room to work.
    Pathfinder Starter Relay Location

  4. Cut the wires that run to the relay. Left enough wire sticking out of the wire harness so I can splice new wire onto it. Removed the mounting bracket.
    Old Nissan Pathfinder Starter Relay

  5. Spliced the new relay in. Thick wires to thick wires, thin wires to thin wires. It is just a magnet and a switch, so polarity does not matter (As I understand it).
    New Nissan Pathfinder Starter Relay Rewired

  6. Taped it all up. Secured it to the side of the engine compartment with a screw from the mounting bracket into one of the old holes. Turned the key and the engine should start.
    The new switch didn't help much, so maybe the fault is in the old wiring, and not the switch. Therefore I rewired the interlock-relay directly to battery.
    New Nissan Pathfinder Starter Relay Mounted

  7. Next I sold out to make 02ยข so I can fulfill my lifelong dream of owning a 1986 944 with blown head gaskets.

    But no minivans!

  8. Then I finished my beer.

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Disclaimer: The technical information in these documents is provided without any warranty whatsoever and at no cost.   All information is in general terms and is not meant to apply to your particular situation, be current at the time you read it, or even be correct in the first place.   Improperly maintained vehicles can lead to serious injury, death, or unavoidable accidents. The author is not responsible for any errors on this site, and does not make any claim at all about the validity, safety, or veracity of the information contained on this website. Any work you choose to do or not to do on your vehicle is done at your own risk. The information on this site is not intended to serve as a replacement for professional advice, professional workmanship, dealer service, union labor, or psychological counseling.   The author disclaims any and all liability directly or indirectly arising from the application or use of any information or idea contained on this or any other web site.   By opening this page, you agree to never sue anyone ever or allow anyone to be sued on your behalf.   The appropriate professional should be consulted regarding your specific condition. does not take responsibility for the information posted on other sites to which it links.

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Last modified: 11/22/2014