Can a Honda mechanic or even someone who has always owned Hondas and does their own work please clarify the purpose of the main relay under the dash? I'm finding conflicting descriptions. I added this to a zombie thread but no one appears to have noticed it there so I'm giving it its own in hopes of getting an answer.
I've seen descriptions that sound like all the relay controls is the fuel pump. I've also seen descriptions that make me think it can prevent the starter from turning the motor. The car has an automatic transmission and turning the key puts on all the dash lights but the engine does not turn at all.
Examination of the engine compartment revealed a ground wire that was corroded beyond belief. I replaced that with a new two gauge cable and oddly enough I get less response from turning the key than I did before. Prior to replacing the cable I got a clicking from what I assume is a relay. Now it is dead silence. The battery is fully charged. Any helpful comments?

 

Well, the main relay has two switches in it - one that controls the fuel pump, and one that also supplies power to the ECU. So, on the surface it looks like the relay does a bit more than just supply power to the fuel pump.

Your relay might be fried. You can test it pretty easily though. There might be a procedure listed in the FAQ, but in case there isn't you can try this:

http://autorepair.about.com/od/engin...nrelay_tst.htm

 

Thank you for the link.

 

There is also a DIY on how to fix them. You may not have to replace it if it fails due to broken solder joints.

Link:Main relay Fix This is for an Acura Legend but it is the same for the Accord main relay.

 

More questions. Can someone point me to a description of what components are involved in making the engine spin? Not concerned at this point about spark or fuel, just what has to work to make it crank at all. Ignition switch obviously, Main Relay (maybe), Starter Solenoid, Starter Contacts (internal). Is there a starter specific relay under the hood and if so which one is it? There are some that are not identified on the fuse/relay cover. Where do I hook up my meter and test?

 

What is your issue and what year is your Accord? I'm guessing it's a no start issue.....

When you try and start the car does the engine turn over at all?
Do you hear the starter click?

Things required to make the engine crank
• Good Battery with proper connections
• Starter - signal from ignition - goes through fuse and onto starter.
• Gear position switch - Is your car automatic or manual? The A/T accords also have a gear position switch that could stop the starter from engaging.

The engine also has to be able to turn on it's own, does the crank rotate if you turn it by hand?

You can take the starter into most auto parts stores and have it tested for free.......same with your battery.

 

see if this helps.

EDIT: I see Ghost replied.....another simple way to start, measure the voltage on the large and small wire at the starter, then work your way back.

 

Thanks guys.
For clarification, the engine does not turn at all. At first there was clicking from somewhere but that actually stopped when I replaced the corroded wire. It is an automatic.

 

Check your battery and make sure the connections are clean and tight. same with that corroded wire you replaced, check it to make sure there is minimal resistance.

 

Does it mean anything that D4 is illuminated on the gear display? Park is also illuminated. One is red, the other is blue. This is not my car so I have no idea what is normal.

 

Well if the Gear position switch is screwed then your car won't start. The Car has to be in P or N it is a neutral safety switch.

If the D4 light is on then there are transmission codes being stored on the TCU/ECU. You need to retrieve the codes same as you would for a check engine light (CEL codes).

 

I'm used to automatics that you can change the gear selection with the car not running. That does not appear to be the case with this car. The gearshift appears to be stuck in Park at the moment. I couldn't put it in neutral if I had to. What is the likelyhood that this car is toast?

 

Are Honda starters like old fashioned American starters in that if you put a screwdriver across the terminals it should engage? I'm running out of patience with this car and have decided it needs to get to a mechanic.

Thank you.

 

The car has a "shift release" next to the gear selector in which you should be able to stick the key in, press down on the key, and shift to "N".

 

That is a handy bit of information to have.
Thank you.

 

I'm also having trouble with my car starting its a 1993 accord lx. the situation was i went to a friends went out on the lake and came back car would not start just kept cranking. rolled down the windows because it was hot eventually the car started and ran fine. the car also ran fine later that night when it was not so hot. ive heard stories saying that if it gets to hot in the car it could cause the main relay to act up. what do you recommend i do to fix this? i have also had this problem on other hot days, but never took so long

 

This one I can answer. If you read the earlier responses you'll find links to everything you need. If you can solder you'll probably be able to fix it yourself. If not you'll need to buy a new relay.
The board expands and contracts with the extreme heat in the car. When this happens it causes bad solder joints to become opens until the thing cools off again. You can probably speed the process by pulling the relay out into cooler air. When the relay has an open the fuel pump doesn't start, so you can crank the engine until the battery dies, but you aren't going anywhere.

 

On the starter there are three wires. One comes from the battery. Another is a thin wire obviously used to provide a signal. The third is another heavy wire. Where does this go/come from? What should I be reading on that terminal at different times? The signal wire provides 12.x volts, which should be enough to actuate the solenoid. I tested it to make sure it goes active when the ignition switch is turned to Start.
Does all this indicate that the starter and/or solenoid is shot?

 

Pull the start and have it tested, its really not that hard.

 

I'm going to have to teach the girl how to turn a wrench. I have large, slightly arthritic hands so getting into tight spots with a wrench isn't my idea of fun. She's 18. She can handle it.

 

thank you i was almost positive it was the main relay but i just wanted another opinion.

 

I got the starter out last night after all and connected it directly to a battery and got absolutely nothing but a warm wire.
I'm at work. The wife just texted me that the starter failed at the shop, so that should be it.
I want to thank all of you regulars who helped me out with this. With luck it'll be a long time before you hear from me again.

 

This thread is helping me work thru my accord issues...this is great information.

 

"mid_life"-glad you got it.....and yes, hope not to hear from you anytime soon. Thanks for posting the results.

And I hope the kid learned a thing or two. I started with all of mine when they were around 10~12....if you are going to drive, you've got to learn to work/check on them. IMO.