I'm out of ideas

[jblueridge]

If you have electrical knowledge please read this thread I started on the 70's forum.
Thanks

(Dim?) Wit's End

 

[jblueridge]

My wiring diagram states that major grounding points can be found "under the front pillars"
Anyone know where exactly I should look?
Under the truck?

 

[sved]

Do you have a power outlet box located in the engine room ? You can check some 24v connections there.It is a black square box.
ACC
IGN
+B

f you don't have 24V on the ACC and IGN it is clear that you do not get 24V to the keyswitch Which could mean that the white fusible link is not supplying 24v to the ACC .
Your horn switch is grounded on the steering column .

 

[sved]

Here is the diagram for your horn

 

[jblueridge]

Thanks!
I checked the 3 fusible links and power is getting through them. I replaced them a few days ago.
The fusible link were Blue, Green and Yellow.

 

[sved]

isn't the wire which comes from the yellow link a white coloured ?
Your domelight is also powered by that fuse/wire.I understand that one don't work either.
The horn is powered through the green fuseble link(red wire)

 

[jblueridge]

You are correct. The wires that the fusible links connect to are Read White and Black.
Dome light, stop/brake lights and horn/hazard fuses are getting power when the key switch is Off.
With the key switch on ACC, those 3 circuits and the Cig lighter and Door have power at their fuses.
When the key switch is turned to Run, all of those circuits lose power at their fuses.

None of the other circuits in the fuse box have power with any key switch position.
I had taken the Aux power box out of the engine bay months ago.
I checked the plug's connections. I don't know which wire is which but one had constant power, a second on came on with the key switch on ACC. Both of those circuits show no voltage when the key switch is on Run.

I unplugged the key switch and tested wires. The black wire, which I think is the power from the battery, shows no voltage. The black with red stripe wire has 24.8 volts. The others have no voltage at all.

I went back to the fusible links. All show power getting through from battery.

 

[sved]

about the power outlet box

ACC blue-red
IG Black-yellow
+B white

 

[sved]

ignition switch

24v from fusible link =white wire
ACC = blue-red
IG = black -yellow
start = black-orange(your red ?)

 

[sved]

you said you exchanged your starter/ignition switch ? youre sure it is the right one? or connected correctly ?

I quess you have a JDM BJ74,is it auto or manual?

 

[jblueridge]

I see now that the wire colors leading from the loom to the switch are not all the same colors as on the leads for the switch.

From firewall Switch pigtail
White Black + Red
Black-Orange Black
Blue-Red same (blue red)
Black-Yellow Same ( black-yellow)
Black-White same (black-white)

So yes, the white wire carries 24.8 volts from the battery.

Yes, it is the correct switch, exactly like the old one.

BJ74 manual (5 speed H55F)

I was frustrated and I went to the battery to check for current draw. I removed the leads from the battery positive and placed the ammeter in line, in series. Only a tiny current draw.... 3ma.
I switched the meter to measure volts. I got 24.7 volts across both batteries with no leads connected. When I connected fusible links and again measured across battery terminal, the voltage was less, down to 22V. Removing that lead brought the voltage back up to 24.7.

I don't know if that is significant.

 

[sved]

did you have that voltage drop (22v)with the key in off position ?

 

[sved]

here is a diagram of your key-switch.
in off there should only be 24 v on the white wire(AM)
in ACC there is 24v on the blue-red and ofcoures the white which is 24V supply
in IG there is 24v on black yellow and ACC and the white supply
on start (ST2) there is 24v on black-orange.

black-white (ST 1)goes to EDIC ,but you don't have that

Horn and hazard is circuit A (fusible link red wire)
Dome lights is circuit B (fusible link white wire)

 

[jblueridge]

I used the info from the 13BT manual to check the starter switch circuits. They checked out correctly.

I can't recall if the switch was on or off when I got that voltage drop.
I'll repeat that later on today.

I have the switch separated from the key device. I turn the switch with a screwdriver.

 

[jblueridge]

As i wrote in the 70 series forum, when the starter key is on Run, the white ignition lead is causing a major voltage drop when I measure across both batteries.
I would say that is shorted out, but the ohmmeter shows no continuity between that white wire and ground.

 

[sved]

Time to pull some fuses.Start with the Engine fuse and do the same test with the key in run.

 

[jblueridge]

Pulling fuses is a good idea!
Too dark now.
I'll hit it again tomorrow.
Thanks for sticking with me.

 

[jblueridge]

Easter Break is over. Back to work at 10am.

I have quit. A tow truck is coming to take it to a FJ55 owner's shop.

Thanks for all the help.

I'll report back when (if?!) they fix it.

 

[sved]

Did you ever get to pull some fuses to see what that would give ?

 

[jblueridge]

Yes. Engine fuse, Charge fuse, ummmmmmm, There were about 5 in all that seemed to be involved with the strange change in voltage at the batteries.