All instruments died

[MadProffeser]

I just got my 77 Celica liftback inspected and on the way back the key falls out of the ignition. Not a huge deal I thought, seen it on other cars, I put it back in but no instruments came on. No blown fuses. I just want to see what some of you think it might be before I go digging into my dash. I hate electrical bugs.

[93celicaconv]

Make sure we all clearly understand what you have here:

You were driving, engine running, key in the ON position, and while driving, the key falls to the floorboard. Right?

Engine stays running, key is out, you put the key back in the ignition, and at this point, you discover no instruments are functioning. Right?

What happened afterwards? Did you turn the key to the OFF position, and did the engine stop?

Did you turn the key to the START position, and did the engine start? Did the instruments work at this point?

[MadProffeser]

Driving, engine running, on position. Going down the road key falls to floorboard.

Engine still running. I reach down pickup the key put it back in ignition. All while in the ON position.

Got home turned key to OFF engine stopped, removed key. Took initial inspection.

Put key in, in OFF position. Turned key to on, engine started, no instruments.

Thinking it might be the ignition itself, but not sure.

[93celicaconv]

For sure your key lock cylinder is bad (it should not allow a key to be removed while in any position other than the OFF position). The tumblers in the key lock cylinder evidently have jamming up and allowing the key to become free to fall out, which is not a good thing.

I don't have a wiring diagram for a 77 Celica, but most Toyotas have 2 contacts in the ignition switch that close when the key in is on the ON and START position, called IG1 and IG2. The instrument cluster is fed off of the IG1 circuit. The IG1 circuit also feeds the rear window defogger, the back up light circuit, the power window circuit, the turn signal circuit, the auto antenna circuit, the windshield wiper circuit, the cruise control circuit, the shift lock circuit (for automatic transmissions), the sunroof control circuit, and the air conditioning circuit. To the degree your 77 Celica has any of these items, these items should also become none functioning when your instruments no longer work. If they do, then you need to also replace your ignition switch (not the key lock cylinder that holds the key, but the electrical switch at the end of the ignition key lock cylinder).

So, if this happens again, check out some of the other items installed on your Celica mentioned above and see if they work. If they all do not, then your switch is bad and needs to be replaced.

[MadProffeser]

Well I still have no instruments but my turn signals, windshield wipers, & back up lights all work fine.

So you think it's the ignition switch not the ignition lock?

[stepho]

I had a similar problem on my wife's '87 Honda.
There is an electrical switch behind the key barrel.
After 20+ years, the contacts on the switch can be worn away.
I pulled it apart and deposited some solder blobs on the contacts but of course such a cheapskate repair job last only one year.
Eventually replaced the switch.
But having said that, I don't think it is your problem because the engine still runs.

Here's a wiring diagram for the '77.
http://autos.groups.yahoo.com/group/...ng%20diagrams/
(might have to register first)
The IG pin on the ignition switch feeds the engine fuse, which feeds the main relay, which feeds the heater fuse, which feeds the instruments (among other things) via a thick LR (blue with red stripe) wire.

Buy a cheap multimeter ($10-$15 at auto shops) and trace along that path (connect the black terminal of the multimeter to a bare metal part of the body).
With the switch in the iG position but the engine off (ie, don't start the engine), you should see +13.8V along that entire path.

Note: our older models only have a single IG instead of IG1 and IG2.

- Stepho

[93celicaconv]

I was thinking something must have changed between 1977 to 1993. I can't open your link to see the wiring diagram.

The ignition lock cylinder (at least on 90's Celica models) is purely mechanical - put the right key in it and you can turn it. The fact that your key fell out is an indication you have a mechanical problem with the ignition lock cylinder.

When the ignition lock cylinder turns, it rotates an electrical ignition switch. From what Stepho said, though, is certain cirucuits on your IG circuit work, so the ignition switch itself is working. There must be a problem further downstream of the ignition switch. Perhaps a dedicated fuse or a wire that open circuited.

Really strange that mechanically, an ignition key fell out, and then electrically, your instrument cluster no longer works, all at the same time. Very unusual.

[MadProffeser]

After looking over the wiring diagram I think its the main relay or a ground came off some where. Had some turn signal problems a few days ago & might have done something while messing with it. Not sure but I might have shorted across the metal housing of the main relay.

Haven't got to trace the wire from the ignition switch yet(might not be able to till the weekend). Just thinking.

note: to view the wiring diagram at the above link you have to register.