Mysterious Black Box on 1988 JDM BJ74

[Greg_B]

Here you go Bruce. Too small to be a converter imo, and while it does say Toyota it in no way looks like a factory mount (2 sided tape on some ducting).

And the PO tapped off the positive pole of the lowside battery for the radio, and that is all there is for 12V appliances on it right now Bruce?

The truck does not stay running after shut off, so if it was a turbo timer it is not working any longer...

Anyone wanna guess?

gb

 

[A2B in a TLC]

Thanks Greg!

B

 

[Diescipel]

Forgive my ignorance, but is your 74 24v or 12v?

It kinda looks like some kind of step-down transformer, but why? Home stereo amplifier take 120v X amps AC (here in the US) and turn it into X volts and X amps DC.

B

PS Whatever you do, don't cut the RED WIRE!!!! Tic tic tic tic tic tic..........

 

[A2B in a TLC]

My JDM BJ74 is 24 V. Sorry for not stating this.

And thanks,

B

 

[A2B in a TLC]

Hi Greg,

No other 12V accessories to my knowledge other than the 2 deck stereo which at this time has no power.

B

 

[Greg_B]

Here is a post about your question with the speed buzzer Bruce.

https://forum.ih8mud.com/showthread.php?t=35919

When Stone is in there, have him follow it and see where these wires, and the red tap off the lowside end up.

gb

 

[A2B in a TLC]

Thanks Greg,

That was before I bought the BJ74. Mine definitely buzzes at 105 kph. Perhaps a way to keep my foot off the peddle?

I wonder if Toyota can look up that black box part # in Canada. Or if I should post on Birfield......

There is a piece that is finned, probably to diffuse heat.

B

 

[Eric Winkworth]

I know my BJ70 24V has a step down box in it, but it is a little bigger than that, you would think they would use the same ones. The headlights actually only run off 12V but the rear lights and side lights are all 24V, your stereo ,clock and cigerette lighter are 12V. I dunno but you would think yours would be the same.

I will take a picture of my stepdown box tommrow.

 

[A2B in a TLC]

Thanks Eric,

I'm quite sure my whole system is 24V, as the JDM units were. I would be interested in seeing the module you have. Mine may not be a step down device. But it does seem elaborate and it would be nice to know.

As Greg pointed out, the PO seems to have cheated a bit and run a line off one of the 12V battery posts. I assume that was to power the aftermarket stereo. If the black box is a step-down, then why would they run the line? Unless it malfunctioned first and, instead of repairing, they added the wire?

Bruce in Tsawwassen

 

[waaz]

Hello
Just a guess, but it maybe a daytime running light module.
waaz

 

[A2B in a TLC]

Thanks Waaz,

No day time running lights installed, so that's not it.

B

 

[Landpimp]

it might say Toyota on it......but its not a OEM Toyota part, I suspect its just for use in a Toyota. That is not a Toyota part #

as to what it is........no darn clue

 

[tlcruiserman]

What about some kind of trailer light or brake module, does it have connecter for trailer hook up on the back?

Is the stereo a 24v or 12v if so could be a step down for radio

I don't have anything like that in my 74.

Michael

 

[A2B in a TLC]

Hi Michael,

The stereo is definitely aftermarket - its an Alpine, so it must be 12V. No trailer hitch or anything like that - in fact, no other accessories. The cig lighter is 24V.

I have noticed a toggle switch under the dash, so I'll try to see if the Black Box wiring leads to the toggle.

Thanks,

Bruce

 

[Jan-78FJ40]

Hi Michael,

The stereo is definitely aftermarket - its an Alpine, so it must be 12V. No trailer hitch or anything like that - in fact, no other accessories. The cig lighter is 24V.

I have noticed a toggle switch under the dash, so I'll try to see if the Black Box wiring leads to the toggle.

Thanks,

Bruce

as a molecular biologist I suggest a 'knockout' experiment-unhook it and see what's happening. that's what we do with genes where we have no clue about the function

 

[Stone]

The little black box on the circuit board with writing on it states a "Coil" and "Contact"...so that leads me to think that it's a relay of some sort...although the Coil is 12v...so I don't know what it would be switching in your Cruiser without following the wires.

It's too small for a step-down converter...those things usually have large heat sinks and vents on them as they produce a lot of heat.

The buzzer is tucked in under the dash on the left side of your steering column. It's a small black box with a mounting tab, secured by one bolt, and has a two wire harness coming out of it. It has slots for the buzzer on one end.

 

[Stone]

Took a closer look at the photos you sent me, Bruce...and it looks like there's a resistor (white box) inline to that relay, and there's something else with a heat sink on top of it (black box with fins). So, my best guess is that it is a switch (relay) that uses 12v...so the resistor is probably used to reduce the 24v input from the ignition to switch the relay which probably was used to turn the radio on and off with the ignition.

You could do the same thing with a 24v relay.

 

[crushers]

I know my BJ70 24V has a step down box in it, but it is a little bigger than that, you would think they would use the same ones. The headlights actually only run off 12V but the rear lights and side lights are all 24V, your stereo ,clock and cigerette lighter are 12V. I dunno but you would think yours would be the same.

I will take a picture of my stepdown box tommrow.

curious as to why the headlights are 12V...
disconnect the box and see if anything quits working, that might help in diagnosing what the box does...
cheers

 

[Stone]

The 12V headlights don't actually run off of a step-down converter, but are run off of one battery each to provide 12V through a fancy gizmo hooked up to the dimmer switch. That's why it's not good to run your headlights for a long time if one is blown on these rigs with 12v headlights in a 24v system, as it would cause your batteries to go out of balance and cause problems.

I believe the OEM step-down converters in the CDN BJ70s were solely for the use of the radio...and those converters often end up failing. I think the BJ60s had the same gizmo.

Greg_B knows a bit about the fancy dimmer device for the 12V headlights. Greg?

 

[Greg_B]

Greg_B knows a bit about the fancy dimmer device for the 12V headlights. Greg?

You mean the funky 12V dimmer switch that has both 12V and 24V going into it, and a whole mess of wires heading out: 12V neutral (and 12V to the low beam pin when the lights are off) and 24V high/low to one side and 0V neutral and 12V high/low to the other side to balance the batteries and make the system happy? Yup...familuare with it...

Eric, your Cdn spec 24V vehicle has the funky 12V dimmer headlight switch thing, unlike the HJ61's and BJ74's from the JDM market; nice clean 24V power to everything stock.

I think Stones guess about the relay is the closest...

gb