Weird electrical issue

[Vinnie]

Hi Guys

I've got a weird electrical problem with my HZJ79. I've done a series of tests:

1. If the headlight are off and I press the brake, the brake lights come on but also the instrument panel's background lights come on and the "lights on warning" alarm sound.
2. If I take out one of the brake light globes and perform test 1 above, everything "seems" normal. (It can be either globe, and I have swapped the globes between the two brake lights.)
3. When the head lights or diving lights is on and I press the brake, the instrument panel's background lights comes on and the lights on warning sound, but the brake lights do not come on.
4. If I unplug the harness that goes to the rear of the car (include all the rear lights, the internal light, door switches etc.), it again seems normal. This however could just be masking the issue, as test 2 seems to indicate some dependence on the current draw.

I've also had the wife press the pedal down while I wiggle all the harness' and wires I had access too, that did not do anything.

At this point I'm thinking a ground wire is broken somewhere and some weird ground currents is causing other circuits to be energised.

I'm trying to work out a plan of attack for the coming long weekend to suss it out and would really like some suggestions.

Cheers
-Vinnie

 

[Shayne]

Seems a cruiser quirk across the range a bad earth in tail lights causes all sorts of mysterious behavior with my 90 series i ran a wire from bulb to chassis while i waited for new bumper lights to be delivered .

 

[StarCruiser]

As Shayne says, try connecting a wire to the earth connection on each side for the tail lights and connecting this to the bodywork somewhere. Make sound connections and see what happens.

I think you are right about the missing/ poor earth being the cause.

 

[Vinnie]

Cheers guys, I'll try the suggestions after work tomorrow. Would be great if it clears it up!

 

[Shayne]

Could be as simple as changing rusty bulbs i bought new lights because i could only remove 1 out of 4 bulbs the rest being welded with rust .

 

[uHu]

Absolutely lack of earth to tail lamps.

 

[wobbly]

No.3 could be interesting!

 

[StarCruiser]

No.3 could be interesting!

Yes, now that has had me thinking. My first thought is that it is a bad earth somewhere however No 3 could possibly point to a wire that's been melted or otherwise shorted to another. I doubt very much that this is the case but if there has been any work recently done on the truck it may be worthy of investigation if the temporary earth to both tail light clusters doesn't solve the problem.

Does it have a tow bar and trailer socket? Sometimes water gets in and causes all sorts of havoc in the back of the socket.

My money is still on the bad earth connection.

 

[Shayne]

And if rust makes an earth live ..............

Tow socket is a good shout i think on most cruisers it shares the tail light loom and is wired in behind internal paneling just in front of the rear passenger side tail light .

 

[Vinnie]

Thanks guys! Running a separate earth wire to the shell of each light assembly complete clears up the problem!

I took the light assembly apart and notice that though an earth wire is fed into the assembly, it connects to a spring which may or may not make connection with the assembly (and thus the outside / earth on the globe). This wire seems to be the only ground connection for the light assembly and it is only twisted on as well. It is a newly installed Tray (about a year old) with brand new tail lights, so honestly did not expect this kind of shotty work. It seems to me that I got lucky for it to work this long.

It's probably worth checking all the grounds point and ground impedances this weekend. Some of the metal parts of the light assembly also seems heavily corroded compared to other bits (supposed to be brand newish). I'm thinking the poor grounding was effectively causing some electrolysis to occur.

Again, thanks for the help chaps, greatly appreciated!

 

[StarCruiser]

Sounds like somebody replaced Toyota workmanship with Toy Motor workmanship and parts.

Interesting symptoms and glad it's on the road to being sorted.
Sounds like if you make that connection good then all will work out well. Dependent on the quality of the light units of course. Thanks for posting the results.