Need Help with an Electrical Issue (1 Viewer)

[1979 FJ40ish]

I need help with a wiring issue and hope that someone smarter than me can help me.

I’m trying to install a device in my 79 FJ40 that will have power only when the ignition switch is in the ACCESSORY POSITION AND a MOMENTARY SWITCH is being PUSHED.

I know the device works because I’ve confirmed it by running 12 volts directly to it.

I have also confirmed the device has a good ground.

I have included a wiring diagram below to show how the device is wired.

To power the device, I tapped into the power lead from the fuse box to the radio.

When I turn the ignition switch to the ACCESSORY position the radio works and the device remains off, as it should. So far so good.

Here is the problem:

When I push the MOMENTARY switch with the ignition in the Accessory position the RADIO GOES OFF and the devise does NOT work.

I hope someone can tell me what I did wrong.

Thanks

 

[mrboatman]

Check your connection at LR and fuse box. also at LR and RB and both grounds.
JP

 

[Living in the Past]

What is the load of the devise. That may help solve the problem. Your radio draws most it's power from the lead to the battery for a reason. Ignition switch is not designed for a heavy load.

 

[morganism]

Switch is grounding thru it's body, try putting a nylon spacer around it?

 

[1979 FJ40ish]

1. I don't believe there is an issue with any of the actual connections. Every connection I've made has been solder and then covered in heat shrink.
2. I believe the connection at LR & the fuse box is good else the radio would not work - ditto for the radio ground
3. I've also confirmed the ground at the device is good.
4. The instructions on the device said to protect it with a 3-5 amp fuse. I selected the radio lead because it is on a 5 amp fuse. I have NOT blown a fuse nor set fire to the cruiser during testing.
5. I can't be certain that the switch isn't being grounded through the body but I doubt it is. It is a cheap chrome covered plastic switch. I can try to check it tomorrow.

Clearly, I've got it wired wrong I just don't know where I went wrong

 

[1969FJ]

What is the load of the devise. That may help solve the problem. Your radio draws most it's power from the lead to the battery for a reason. Ignition switch is not designed for a heavy load.

Exactly, load of device is needed......

 

[Shark56]

Turn your radio off. Try it again...does the device work. If so it is the draw of the device.

 

[Solace in Solitude]

I’d use a relay... that way you can draw as much as you want (fuse it), directly from the battery, using your momentary switch as the trigger... and no longer worry about overloading OLD wiring components.

 

[1979 FJ40ish]

I ran some test this morning.

The body of the switch is definitely not grounding to the dash.

I confirmed continuity of the lead between the switch and the device

I tested the device again and it works when grounded and power is applied directly from the battery

I used a multimeter with the following results.

With the device grounded:

12V into the switch
0V out of the switch when pressed
The radio cuts off
The device does not work

With the ground wire removed from the device:

12V into the switch
12V out of the switch when pressed
The radio DOES NOT cuts off
The device does not work

With the ground wire removed from the device:

One lead of the mulitmeter connected to a good ground on the body
The other lead connected to the input of the device
12V at the device
The radio DOES NOT cut off
The device will not work because it is ungrounded

I hope this make sense to somebody because it doesn't to me. I would have thought that if I had really mucked something up I would be blowing fuses or seeing smoke.

 

[1969FJ]

Well, first off, do We need a Secret Clearance to KNOW what the "DEVICE" is ? Second, GROUND is frame. Until we know the characteristics of "device", how can we figure voltage potentials? ( The switch is NOT the issue.)

 

[Solace in Solitude]

May I presume the Y* (constant battery power) is merely to retain radio settings... not to power the radio?

If your diagram is correct, it appears you expect accessory power to BOTH the radio and the switch.

Your diagram doesn’t explain how pressing the switch turns off the radio.

Does your wiring match your diagram.

May I also presume your “momentary” switch is, in fact, a switch that sends a “momentary” pulse to your mysterious “device”, when pressed?

If so, what powers the “device” AFTER the switch is “momentarily” pressed?

If my presumptions are correct, you would, as I stated above, be better served by triggering a relay, with your switch... switch pressed would send the pulse to relay-86.

Ground to relay-85

Battery+ to relay-30/51

Relay-87 to the device

Relay-87a not used in this scenario

Hope this helps

 

[1969FJ]

Forget it, Bozo. Cannot define. Idiot. Let it go.

 

[1979 FJ40ish]

Solace

May I presume the Y* (constant battery power) is merely to retain radio settings... not to power the radio? - CORRECT

If your diagram is correct, it appears you expect accessory power to BOTH the radio and the switch. - CORRECT

Your diagram doesn’t explain how pressing the switch turns off the radio. - I can't figure it out either!

Does your wiring match your diagram. - To the best of my knowledge it does. I did the wiring.

May I also presume your “momentary” switch is, in fact, a switch that sends a “momentary” pulse to your mysterious “device”, when pressed? - CORRECT - power to the device only while the button is pressed.

If so, what powers the “device” AFTER the switch is “momentarily” pressed? - The device shuts off when the button is released. The device will NOT be used when the engine is running.

As for the power consumption the device has two thin wires coming out of it, probably 16ga. One black wire that is to be connected to ground and one power lead. The device must be fused with a 3 - 5 amp fuse. I selected the lead from the fuse box to the radio because it has power from the accessory switch position and is on a 5 amp fuse. I'm going to "assume" here that give the size of the wire out of the device and the fuse requirement for the device that it isn't drawing much power. The assume is probably going to get you know were.......

 

[KingAir Driver]

Mind Control Device?

 

[ginmtb]

I had the same issue when I was trying to connect the Illudium Q-36 Explosive Space Modulator device too! Put a few ball bearings inline with the fuse and it should then work fine. Everything is built with ball bearings these days...

 

[1911]

I had the same issue when I was trying to connect the Illudium Q-36 Explosive Space Modulator device too! Put a few ball bearings inline with the fuse and it should then work fine. Everything is built with ball bearings these days...

This makes me very angry, very angry indeed.

Marvin the Martian

• 1911
• Oct 14, 2018

 

[Solace in Solitude]

Since your “device” is apparently part of some sort of security system, I’m going to bow out of troubleshooting this and recommend you take it to a place that installs automobile security systems.

I’d hate to cause your “shields” to be down when they are supposed to be up.

Good luck

 

[1979 FJ40ish]

OK guys I don't see what difference it makes if the device is a light bulb, flux capacitor, a security device or an electric fuel pump that I intend to use to prime the carb after the cruiser sits for days and will not start without priming it.

Now that the "secret device" has been disclosed and it is wired as described in the diagram above why is the radio cutting out and the pump not working?

Solace - I do appreciate the help and I have disclosed all of the information I have about the device and how it is wired but so far no one has been able to explain why it will not work as wired.

 

[1969FJ]

What are the specs on this pump ? How much current does it allow to flow and is it grounded as you show in the hand drawing ? Can you apply direct power to it and will it run ? This seems very simple as it is just 12 volts being distributed. Is there a brand name on this pump?

 

[Solace in Solitude]

This is why I seriously suggested you take it to someone experienced in security systems.

The radio/switch branch, in the diagram, is not conditional... the two devices share the circuit.

An auto security tech could figure this out pretty quickly.