How do I check my main relay? 87 Honda accord lxi
ok all relays
the relay is just a coil (mag) and a switch.
many relays have just 4 pins.
most main relays have 2 pins at 12v. one on the coil and one on the common contactor pin (input)
the ECU/PCM grounds the other coil pin, the mag field inside builds and the contactor closes. and the contactor ouput pin
goes to 12v and the ECU then powers up.
how to check it, is easy, use a voltmeter, (never lies , like other ways)
any DMM , even that cheap one at walfart works great.
set the dial to 20vdc.
conn, black lead to car body, metal.
conn red lead to the 4 pins, 1 at at time and key on. (no start)
if the 2 pins do not have 12v(input pins) the fuse is blown or some dork cut the wires to install some , accessory.
now see the ECU ground the othe coil pin, 0volts,
the relay is now energized, (coil must not read infinity removed)
now check the output pin on said relay, if 0v , the relay is bad.
if 12v, on this pin, well , the relay is 100% OK.
to work on cars, you must learn electrics first, then how relays work. there are millions of web pages on this subject,
ok , i went to alldata.com (so can you)
and that car has 7 pin, MAIN relay.
black yell and blue black pins are 12v keyon.
yellow wire is fuel pump (early cars have 2 relays in one)
black is ground, if open , all is dead ! must be 0v
fuel pump enable line is green-black (ecu commanded)
0v when active, most cars take cranking to go active.
the blue-red wire from crank fuse. sends 12v to pump relay coil
for crank pump action.
and last but not least is the yell-black wire, this wire runs the ECU
and all injectors. this is 12v key on. if not check all coil pins on main.
i answered in the generic and exact.
old post. but lots of old handa's still ,
all this is on alldata.com or at mitchels.
Sep 30, 2013 |
1987 Honda Accord