Strange hazard switch behavior (1 Viewer)

[Dr Gil]

My hazard lights started flashing while I'm driving without touching the switch. When I turn off the ignition the hazards lights keep flashing.
Pushing the switch off and on has no effect on it. It does this for about 3 minutes and finally the hazards turn off on their own.

I later open the door and hazards lights once again turn on. This time, I disconnected the battery for 5 minutes and I'll reconnect and hope I reset something.

This has happened only 2x in 5 months. Both times I noticed the hazard lights turned on as I was slowing to a stop.

 

[Rusty Marlin]

You have a short in a harness. The hazard switch goes directly to ground, so somewhere between the switch and the lights a new path to ground has been formed. Do you have the electrical manual....you're gonna need it.

 

[Dr Gil]

You have a short in a harness. The hazard switch goes directly to ground, so somewhere between the switch and the lights a new path to ground has been formed. Do you have the electrical manual....you're gonna need it.

Yes, I have an electrical FSM. Are you saying a short between the hazard switch and the dome lights is where to look for this short?

 

[Rusty Marlin]

I stand corrected, the hazard switch doesn't go directly to ground. When "off" it directs power from the turn signal fuse to the flasher relay.
When you activate a turn signal, power flows through the hazard switch, through the flasher relay, directed by the turn signal (lt or rt) and then through the appropriate bulbs to ground.
When "On" the hazard switch takes power from the haz-horn fuse and directs it through the flasher relay, back to the hazard switch where pin 9 provides power to pins 5 and 6. These bypass the signal stalk switch and power all the turn signal bulbs.

Maybe it's just a bad hazard switch.

 

[Dr Gil]

I stand corrected, the hazard switch doesn't go directly to ground. When "off" it directs power from the turn signal fuse to the flasher relay.
When you activate a turn signal, power flows through the hazard switch, through the flasher relay, directed by the turn signal (lt or rt) and then through the appropriate bulbs to ground.
When "On" the hazard switch takes power from the haz-horn fuse and directs it through the flasher relay, back to the hazard switch where pin 9 provides power to pins 5 and 6. These bypass the signal stalk switch and power all the turn signal bulbs.

Maybe it's just a bad hazard switch.

I'll run a meter on it. That theory is possible considering how many times I've pulled that dash bezel off and on and strained those wires to the switches.

 

[BILT4ME]

Do you have an alarm system on this?

 

[Dr Gil]

Do you have an alarm system on this?

No alarm system that kills the ignition, but there is a door locking module that takes a wireless FOB

 

[BILT4ME]

No alarm system

Then I would think flasher relay.

Since Toyota switches the ground side, I would also say you have a ground wire shorting somewhere on that side of the switch.

 

[Dr Gil]

Then I would think flasher relay.

Since Toyota switches the ground side, I would also say you have a ground wire shorting somewhere on that side of the switch.

Yes, someone else on 80 Series FB site mentioned that. I'll just looked it up and it's in the driver kick panel I believe. Is that correct? How would I test the flasher to see if it works properly? This problem has happened 2x in 5 months.

 

[BILT4ME]

Yes, someone else on 80 Series FB site mentioned that. I'll just looked it up and it's in the driver kick panel I believe. Is that correct? How would I test the flasher to see if it works properly? This problem has happened 2x in 5 months.

I think the horn and flasher are the same one, but not sure.

 

[Dr Gil]

I think the horn and flasher are the same one, but not sure.

Here is the pic I found

 

[Rusty Marlin]

Then I would think flasher relay.

Since Toyota switches the ground side, I would also say you have a ground wire shorting somewhere on that side of the switch.

But if there was ground between the switch and the bulbs, the bulbs wouldn't flash and the fuse would blow.

 

[BILT4ME]

See attached wiring diagram for flasher. You seem to have one more below. It looks like it is unique to it's location and type.

 

[BILT4ME]

It's possible the trailer wiring harness that is known to fail could be doing this.

I'm going to have to bail on this one. I'm not an electrician. There are others here better suited than I.

@jonheld ?

 

[jonheld]

See attached wiring diagram for flasher. You seem to have one more below.

For some reason, the 1996 FSM doesn't show the circuit opening relay that is attached to that relay block in that drawing. The 1991 version shows it, albeit a different relay and different design.
However it is shown on page 19 of the 1996 EWD.

 

[jonheld]

It's possible the trailer wiring harness that is known to fail could be doing this.

I'm going to have to bail on this one. I'm not an electrician. There are others here better suited than I.

@jonheld ?

I agree with @Rusty Marlin. The only ground that is "switched" in this circuit is the flasher relay load. All other switches are on the supply side. I would start with the hazard switch itself and move on to the switch harness from there.

 

[Dr Gil]

It's possible the trailer wiring harness that is known to fail could be doing this.

I'm going to have to bail on this one. I'm not an electrician. There are others here better suited than I.

@jonheld ?

@jonheld When you say it's possibly the trailer wiring harness. Are you saying to check the OEM wiring with 3-connectors? Or check the aftermarket wiring harness with the control box with the 7-pin connector?

 

[ppc]

Look at the aftermarket harness and control box. The diodes in the control box can fail and the wiring harness to the trailer connector can get damaged.

 

[Dr Gil]

Look at the aftermarket harness and control box. The diodes in the control box can fail and the wiring harness to the trailer connector can get damaged.

I just disconnected the control box and harness. The control box is swollen. It sits near the exhaust, so I guess over the years the heat got to it.
I'll assume for now, that is the problem.

 

[jonheld]

@jonheld When you say it's possibly the trailer wiring harness. Are you saying to check the OEM wiring with 3-connectors? Or check the aftermarket wiring harness with the control box with the 7-pin connector?

I did NOT say that it could be the trailer harness.
Given the original description of the issue, something is supplying voltage to the supply side (pin 2) of the flasher relay causing it to flash with the ignition off. It has to be coming from pin 7 of the hazard switch because nothing else in that circuit is hot with the ignition off.
Even if the brake lamp circuit (constant hot) was backfeeding into this circuit, the lamps might illuminate, but the flasher relay wouldn't fire.
The hazard switch is the main component in this circuit. With that removed, there can be no turn signals or 4 ways.