Honda Accord, Civic Main Relay Intermittent Starting Problem: how to fix a stalling or dying car. rant content frame

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Main relay location for all civic models

*Civic relay is located above the dash fuse box.

Civic relay location


92-95 CIVIC MR DEMO gif format

85-91 CIVIC MR DEMO gif format

other main relay links::




IGNITER Igniter troubleshooting


How to repair the Main Relay.

The relay's solder joints dries, crack and separates from the circuit causing an open circuit. The joints is subject to heat generated by the fuel pump. The joint is then allowed to expand and contract and subject to vibrations. For this repair project you will need a:

main relay

Bare-bone relay,

a 15-30 watt soldering iron and

 a Rosin core solder (higher silver content preferred)

a solder wick or

a De-soldering pump 



How to solder correctly

How To Desolder: Tool required: vacuum pumps (solder suckers) or solder wick.

How To Solder:  Tools required: a 15-30W soldering iron and thin rosin core solder.* Here's more soldering examples.

*Note: Many people chose a higher grade solder with a higher silver content (Radio Shack) to minimize the chance of a cold solder joint. 

Begin by prying open the main relay:

Clip----->main relay Stick a flat small flat screw driver in between.


  1. Stick a small flat head screw driver in between the wall flap (a clip) and the relay base.
  2. Do not go in too deep. Pry it open just slightly
  3. While holding it still, use the same screw driver, pry the other side.
  4. While holding it still (and cleared of the locking edge) pull the relay straight out, or forward.

Warning: Do not stick the screw driver too deep inside. You may damage the relay's mechanical or electrical parts.

Quick Step 1: Desolder the relay lead. 

Desolder using pump

Desolder using wick


Step2: Heat lead with a soldering tip while applying rosin core solder to the component lead and solder pads. 


Step 3: Clean with steel wool, inspect for imperfections then coat with lacquer to prevent oxidation. 


Step 4: Install onto the vehicle in a lower location, easily accessible in the future. You work is done.

When a fuel pump demands more current, heat would be generated as a result of increase resistance in the contact points. In this case the relays will act as heat sink. This is a sign that it is worn. The picture below explains why. When a relay contact becomes corrupt, caused by arcing or other means electrons will converge in poorly conductible space. Replace the relay if you suspect that it runs too hot. By not doing so, you can run the risk of another solder joint failure. 

   Sometimes a fuel pump may run endlessly due to the relay contacts welded together. Another term for this is resistance welding.

Current flows from left to right


Drill holes to run cooler

Figure 1.1 This picture shows how several holes may be drilled on the side of the case to vent the flow of heat and allow the relay to run cooler. Many  have suggested that holes will not affect the relay after new, proper solder application. "The problem lies in the bad solder application (caused by the wave solder process by Mitsuba.) Once the solder joints have been properly repaired the relay should last the life of the car."  

Also note that your relay may run warmer indicating that you may end up with the same symptoms. More holes will not work if your relay is worn.

Why holes?


Click to show drawings and wiring measurements.

TROUBLESHOOTING scroll down :v

Relay must have these wires to be considered a main relay suitable for this test. If so, measure the voltages to see if they are as specified below. Voltages reading taken while Main Relay is still attached.

For most Accords:

1) Blk/
yel Should have+12 volts with ignition ON
2) Blk Should be grounded always
3) Yel/blue Should have +12 volts battery, always.
4) Yel/blk Should be +12 volts with ignition ON
5) Blu/Red (auto only) Blk/grn (manual only) Should be+12 volts at START
6) Grn/blk Should be ground temporary with ignition ON
7) Yellow Should have +12 volts temporary with ignition ON

If all readings are okay except on either pin 4)ECU-Injector or pin 7)Pump then the relay is dead.

Use a test light on the flashing wire below to see if your fuel pump is being supplied with current.

The blinks show a power loss.

How relays work


This is a demonstration of the main mechanical relay. As power is supplied to the coil wounded metal core, a magnetic reaction occurs which pull in the contacts inward. Several resistor are added in parallel to the coils (not shown) Shunt diodes are also used to prevent ECU damage from induced high voltages (not shown.)


+12 volts is equivalent to 11.5 to 14 voltage, when ever mentioned here. +12 volts is not the best term. The correct term is battery voltage.

Honda Accord Main Relay

Red (auto only) Blk/grn (manual only)

More relay diagram ...


How to spot dry open jointsTo quickly fix your joint squeeze your key inward and downward - works for 20 days

Press your key against the surface to seal the joints temporarily.



Contact see author's rules. Last updated 2-10-05


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