Electrical Problem

[Timon]

My car work perfectly one moment and the next it didn't. My turn signals on the dash were both lit up when I turned the power on. I started the car and it runs fine, but here are the issues I'm having, note everything ran wonderfully before turning the car off.

1. No headlights, they come up, but do not turn on.
2. The dash lights are extremely dim.
3. The voltage meter shows just over half when the lights are all off, but jumps down to only a few volts when I try to turn on the dash lights.
4. When turning on the defrost I get a whole new set of issues
a. The tach goes down instead of up.
b. The dash lights do not work at all.
c. The turn signals do not work.
5. When the dash lights/tail lights are on the turn signals do not work at all, but they do work when the lights are all off.

Right now I'm really confused. Everything worked only minutes ago. The engine still runs fine, but now I have electrical problems up the ass. Also to note, the tail lights, brake lights, side markers all work without any problems that I've noticed yet.

I've checked all the fuses and they're good. I also replaced the relay under the steering column and the headlamp relay. Using a multimeter I tested the wiring that plugs into the back of the headlamp and it reads 5.34 volts on all three wires.

Any suggestions? Or does anyone have, or know of, a wiring diagram?

[MR2Jedi]

Check your alternator. - belt tension , alternator connections and output. Pep Boys, O'Rielleys, Advance will check them for free.
Check battery , connections, cables and terminals.

[Timon]

Well here's an update on it:

I believe it is a short, but I'm not sure where. The reason I believe it is a short is that the dash lights go back to normal when both headlamps are unplugged. As soon as I plug in a headlamp and attempt to turn it on the dash lights go out completely and the voltage meter for my battery shows a major draw. Then if I remove the headlamp and turn the switch off and back on (keeping in mind the headlamps are both disconnected again) the dash lights work as normal, and the battery shows no major pull.

So with that in mind, I'm looking for common places for wires to break (I don't know of any), a wiring schematic, or some other type of advice that will help point me in the right direction.

P.S. I never mentioned this, but it is an '87 MR2 N/A.

[MR-Deuce]

I think you might have a ground problem. Check the engine and chasis ground wires to be sure that they are clean and tight. I poor ground wire could cause a number of odd things. also if you believe that you have a short in the the headlamps then when the headlamps are disconnected everything else should work properly. you could try a new ground wire from the battery to the altenator or from the battery to the frame. post any changes in your situation.

[Timon]

Another update:

Now the only way I seem to be able to stop the short is by disconnecting the harness on the light switch. What I want to attempt to do it narrow down the light switch itself or the wiring leaving it. I'm assuming the switch connects certain pins depending on the setting (dash light only/dash lights & headlights/headlights up, but no lights). Does anyone have the pin information for which ones raise/low, turn on/off the headlights, or turn on the dash lights.

[Timon]

I found 2 grounds in the frunk, which look fine, and of course the ground for the battery, which also looks fine.

Does anyone know exactly which grounds to check and where they are?

[MR2Jedi]

Check engine ground(s). Look at the intake side of the engine, underneath intake plenum & corners for grounds

[Timon]

I'll go do that now, in the mean time, any other grounds? Are there any more grounded in the cab anywhere? I'm mainly trying to find out how/where the instrument panel is grounded, but as mentioned I will go check the engine bay right now.