I haven't had a chance to read through the subsequent posts to comment, too tired. However, here is the circuit diagram.

 

OK I've checked continuity of the wiring from the relay to the headlamp and that's OK. What's happening is the voltage across the relay coil is the same on both sides so there is no current through the coil and the relay doesn't close. I tested the relay out of the socket and it's fine, works as it should. I got down to the library and chased up two wiring diagrams, one from Chilton and one from Haynes. Unfortunately they are not exactly the same even though they claim to be good for the 1998. BUT one is 1998 to 2002 and the other 1996 to 2000 so the differences may be real. Both however show something called a multiplex control unit in the circuit. I'm starting to think that's the problem because the connection from the light switch passes through that device.
Bob

 

So does that mean both sides of the headlight relay are at 12v relative to a good body ground? If so, that means either a bad ground at G401, or else a bad connection somewhere along the wire to get to that ground.

If both sides are at 0v, then a bad connection from the very top of RedBull's diagram.

 

Was this Accord purchased in the US or Canada? Does this car have the automatic lights off feature? Pin 3 of the combination light switch would have a red/wht wire if you have this feature. There would be no red/wht wire if you do not have this feature.

I think your problem is most likely the combination light switch on the steering wheel. If you have the red/wht wire at pin 3, then it is possible one of the 2 multiplex units could cause this problem.

 

Guys, using Redbull's wiring diagram I notice that relay coils have a common ground so I removed both to check the connection in the fuse panel. With both removed everything is as it should be 12V on one pin 0V on the opposite. I'm thinking I'll jumper the pins on the contacts portion of relay 1 with the light switch on to confirm everything is intact from the relay to the light bulbs. At this point I'm thinking something is stopping the current in the coil portion of the relay. On the wiring diagram it looks like that might be the passenger side multiplex CU.


Bob

 

Well I by-passed the coil in the relay, jumped the contact pins going to the fuse then the bulb. Bulb works fine under that condition, both left and right sides (two relays). That leads me to think the problem is the passenger side "multiplex control unit" shown in the circuit diagram. Apparently it is located on the back side of the passenger side fuse panel. Looks as if that needs to be accessed from under the dash board and maybe the kick panel. I need some guidance for removing those things to get to the back of fuse panel. Does the glove compartment need to be removed also?


Thanks,
Bob

 

I found a U-tube describing how to replace the cabin filters and that looks like it will give access the control unit.


bob

 

OK back to the headlight problem. I've taken the dash apart and have access to the multiplex control unit. However I can't pull it out. Does anyone know how this unit pulls out of the fuse box?


Thanks, Bob

 

1. Unplug the 24-P connector from the opposite side of the fuse/relay box that hold the passenger side MCU.

2. There are four slots in the fuse box to insert a flat head screwdriver to pry the tabs on the MCU . You can use two screwdrivers to pry the tabs loose from the fuse box.

This link show removal of the driver's side MCU; but, same concept.

http://www.hondalac.com/service/bulletins/x00-071e.pdf

 

Thanks, I got it out and replaced it with "recycled" one. Did not fix things so I've been trying to trouble shoot the ground pin connections on the coil. Tried one at a time then both. I rigged a pig tail to slide in with the coil pins and then grounded that. Short version is I next started working with the steering column switch. Pin 4 to 11 jump does not turn the lights on so I'm thinking the switch is OK. BTW the number 4 pin at the steering column (without my pig tail jumping) showed 2 V but decayed with time, #11 is a solid connection to ground. If I jump my pig tail coil connection to pin 4, everything works fine, brights, regular etc. So the problem is either in the wiring or the MCU. The wiring is labeled BLU/RED in the diagram and I found two of those on the fuse block. One comes into a connector on the outside of the block the other to a connector on the inside. Looks like the inside one goes up into the dash and over to the driver's side so presumably to the switch connector. I tried measuring continuity between them but got none. It maybe the pins I'm using to connect so I'll have to go back and try again. Does anyone have details on the connectors? I located an online manual but lots of diagrams not so clear what wires go where. Anyway primary conclusion is bypassing everything between the coil ground sides and the switch makes things work so problem is either the harness or the MCU. I can get a factory fresh MCU for $80 but I'm still not sure that's the culprit. If I can confirm the two BLU/RED wires on either side of the MCU block are in fact the wires to the coils I can jump them and see what happens. ITMT I'll try testing continuity on the wires again.
Bob