Replacing the Main Relay/Starting Relay

 

Disclaimer: Please note that I am not a mechanic or a car specialist.  This page is not for instructional use.  Rather it is an accounting of a personal experience and/or process.  Any information used from this page is solely at your discretion and I can not be held liable for any resulting action and/or damage.

Symptoms: Car will not start when it has been parked in sun or it's rather hot outside.  After a few minutes with the windows and/or doors open (cooling off the interior of the car) the car starts up without issue.

Cause:  Heat build up and the Main Relay's inability to vent this heat cause the metallic solder on the Main Relay to expand thus electricity is not able to flow across the circuit board rendering the Main Relay inoperative until the heat is dissipated.  The Main Relay is part of the starting system and controls the fuel pump.  This is why the car will not start with the Main Relay is not operative.

Tools Needed:  10mm socket, socket wrench, 10mm box-head wrench, flat-head screw driver, and a flash light.

Difficulty Scale:  On a scale of 1 to 5 (5 being very difficult) this is a 2 and only a two because of the tight working conditions (you really have to cram yourself under the dash, your head will bump against the brake & gas pedals several times during the process).

Replacement:

** Caution - your are working in an area where there are wires for your air-bags.  Do NOT cut, disconnect, pull or mess with any wires/harnesses/relays coated in yellow. **

  1. Disconnect the negative cable on your car battery (better safe than sorry)!

  1. Locate the area where the Main Relay is location.  It is located under the driver's side dash.  Please refer to the picture below:

Relay_locations.jpg (114879 bytes)

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This document is also available as a PDF file, click here.

  1. If your vehicle is equipped with cruise control you will have to remove the cruise control unit, if not skip to step 4.  The cruise control unit  is a silver, rectangular box and can easily be seen when you are underneath the driver's side dash looking up ( see the photo below).  

To remove the unit, use a 10mm socket to remove the 2 mounting bolts numbered in the photo below.  There is no need to disconnect the wire harness from the cruise control unit as the wire harness is long enough to place the unit on the floor board.

Relay_Pic1.jpg (54476 bytes)

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  1. Once the cruise control unit is out of your way, you should be able to see the Main Relay; the photo below.

Remove the 10mm mounting nut.  Due to the length of the bolt, you probably will not be able to use a socket wrench.  There is sufficient room to use a box-head wrench  to remove the nut.

Relay_Pic2.jpg (55040 bytes)

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  1. The Main Relay is held in place by 2 posts; one with nut you removed in step 4 and the second is simply a post (no nut).  You will have to slide the Main Relay mounting bracket off these two post (this sounds much harder than it is - you will easily see what you need to do to remove the Main Relay.

  1. Once the Main Relay is removed, disconnect the wire harness.  I had to use a flat-head screw driver to help separate the harness from the main relay.

  1. Install the new Main Relay is the reverse order and don't forget to reconnect your battery.

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Last updated 20 Oct 2008 05:25:50 PM