Ok here is the scoop.
My 1991 honda accord has been having the following issues for about a year.
1. Car will stay running with the key out only when the parking lamps or headlights are on. (even the automatic seat belts work. no radio or other acc though)
2. Fuel gauge will not read and the Fuel low light comes on at random independent of level of fuel in the tank.
3. Instrument cluster and internal night lighting stays lit dimly when the headlight and parking lights switch is in the off position but comes on full bright when the switch is turned on. The dimming function does work when the headlight/marker light switch is in the on position.

Problem #1 lead me to remove my remote starting unit since the lights providing ecu and other power were interfering with its operation. All wires were disconnected to it and safely secured. Verified they are causing no shorts and have no influence in the problems.

The car operated for over a year with only the above problems after disconnecting the remote starter.

Now i have a very infuriating problem.
For some reason the dang gauge's will not come on unless the marker lamps or headlights are on!!! No Tach, no speedometer, no temp gauge, I need to replace the fuel sending unit i think so im not worried about the fuel gauge right now.

I have tried a 2nd cluster and the result is the same.

I dont see any where in the diagrams where the lighting circuit could feed power this way except for the dash FB and Integrated control unit.
All other acc work with just the key on.

Also the gauges, Ecu, and other engine related devices power up when the marker lights and or headlights turn on, but no acc do.

Have traced all wiring from the dash to the FB and can find no shorts. Did find some "dirty" connections but cleaning them had no effect. I even went as far as to pull out the dash and check the entire Harness........

Expert advise would be much appreciated ;-)
I have poured over the wiring diagrams for the better part of 4 hours tracing this problem. I can see no connections between the systems and have found no shorts after an extensive tear down.

 

Clear the above quote up. Can you turn the key off, pull it out of the ignition switch, and the car still runs?

 

Exactly.

1. Start the car with the key.
2. Turn on the headlights.
3. turn off the key and remove.
4. Car stays running.
5. Turn off the headlights and the car will shutdown.

And no turning on the headlights does not start the car. That would be funny though ;-) It does though power up the gauges, seatbelts, and other engine related stuff. All other ACC like the stereo, heater, etc remain off with the key out and off.


UPDATE
It looks like this is no longer the case. The car will now no longer stay running with the key out in the above situation.
But the gauges will not power up until the headlights or parking lights come on.

 

That is very strange. When strange stuff happens, I would look at the grounds.

There is an important ground on the thermostat housing. I would unbolt it and clean the bolt and eyelet with a wire brush or sand paper to ensure you have a good ground.

Since you had a remote starter, I would make sure that is not supplying power to a wire going to/from the ignition switch. There is a wire harness that goes from the ignition switch to an electrical connector under the dash. You may have to remove the cover around the steering wheel to trace it.

You should check for voltage or ground at the electrical connector of the ignition switch on each wire. The wiring diagram should show you what wires have voltage from the battery.

I don't know if you have to remove the ignition switch to unplug that electrical connector. There are some videos on how to replace the electrical portion of the ignition switch on a honda on YouTube. The hardest part will be remove the security bolts that hold in the ignition switch. Most videos are for the 94-97 accord, but the 90-93 will be similar.

The other item that I would consider replacing is the electrical portion of the ignition switch. Turning off the key should cut power to the distributor and shut off the car. Now the remote starter would have bypassed that, so that is why I suggested testing the wires before replacing the electrical part of that switch.

 

Ignition switch it self and all related harnesses check out.
Also everything there has a good path to ground.

The ignition switch has always cut power it self to the proper wires when the key is shut of and removed. There is a feed some where else between the lighting circuit for the parking lamps / headlights to the ignition run position circuit that i just cant seam to find. No shorts that i have been able to find ringing out each wire in the whole dash harness with a tester.

Checked the ground at the thermostat housing, was good but cleaned it anyways.

Dismantled the Dash FB to check for internal shorts but there were none, just some dirty connections.

Getting ready to pull hair out.

Least i still have the gauges with the headlights on.

Is there a more detailed schematic of the instrument cluster and related actual physical diagram of the wiring for the cluster/dash/electrical?

 

I found a 93 shop manual that was for non-us accords (I think). The wiring looks very similar, if not identical to the US accords.

Copy and paste this link into your browser:

rapidshare.com/files/346513877/62SN700.PDF

That may help a lot. You want to see if you are getting 12V from the wire from the ignition switch to the cluster.

The 94-97 shop manual will have different pinouts, so that won't help.

From your description, it sounds like a problem with the ignition switch, possibly shorting out due to wear. I don't like suggesting throwing parts at a car though, so that is why I suggested testing the wiring.

 

I will give it a go testing it again using this diagram.
Much appreciated. That diagram is just what i was looking for.
Has more detailed info than my diagrams.

Ill post the results of testing in the am.

 

Ok Tested the Ignition switch.

All leads have voltage only when they are supposed to and none are malfunctioning.
So that rules that one out.

Car has changed though, Now the vehicle will not stay running with the key out and Headlights on.

The problem still remains though that none of the gauges will work unless the headlights/parking lights are on.

Everything else functions correctly.

 

Do any lights on the gauge work? Let us know which ones.

Are you pretty good with a volt meter? Do you know how to test for continuity, voltage, and voltage drop? Do you know how to back-probe a connection?

I'll try to give you some basic tests to do to figure out what is going wrong.

 

All lights Work on the gauge cluster when the marking lamps/headlights are on.
All indicators work regardless of the headlights being on or off WITH the key in the on position.

Hope im good with a multimeter;-) Electrical control system designer by trade ;-)

Yes I am good at checking for all the tests you mentioned, minus one. Have never heard of a back probe. Do you mean tracing?

Any tests you may have to help me out would be awesome, What i don't know how to do already i will learn!!