Starting to dig into certain accessories not working

Now that I have my battery issues rectified, I’m just starting to troubleshoot and repair issues with my 12 volt accessories. Currently the only thing working are brake lights, flashers and feature plug. Headlights, taillights, parking lights, signals, horn, wipers/washer are not working. I’ve tested all the fuses and they are good. I recently located the 2nd 72v to 12v converter, as I was told it could be bad, but have not figured how to get to it yet, to test it. Also, the speedometer does not work, but the instrument cluster was replaced a year ago by the previous owner.
I have the service manual and troubleshoot guide, and have been digging into it.
I’m new to these and am a little confused as to what needs to be removed to get to the areas I need to check. Any help will be appreciated.

Was told to test the 12v accessories fuses to see if they are reading 12v+ or less.
The brake, horn, flasher fuse reads over 12v. The other fuses read 11.5v. I was told that is too low and to ground the white/grey wire, but don’t know where it is located.

One dc/dc converter runs everything except the power point unless someone has messed with the wiring. I would go to the multifunction switch and see if you have 12 volts going in and if you do test for 12 volts coming out on the different circuits that are not working.

I tested the multi-function switch harness.
looking at the harness connectors, starting with the Right passenger side one, top right pin 2 has 13.4v, pin 3 11,9v, pin 6, bottom right 11.9v
Left Drivers side harness no pin 1, pin 2 11.9v. that is the only pin out of the 4 on the left and the 2 on the right, of the driver’s side harness, that has voltage.
After cleaning everything, I still have no parking, headlights, wipers, signals. operating the signal switch gives me a buzzer, but no signals. I also tested the fuses for voltage. The only one that shows full voltage over 12v is the brakes, horn, flasher fuse. Regarding horn, pressing the horn button causes a faint clicking, if I short the horn, it beeps, so I think it is a relay issue.

Follow the pinpoint tests in the shop manual. Start with the headlight pinpoint tests page 94 in the electrical section.

After that go to page 113 and follow the pinpoint tests for the horn

Thanks will do. I do suspect the multi function switch may be bad or the white grey wire needs to be grounded. The voltage on the fuses seem low, and when testing the switch with a probe, turning on headlights, signals, etc, did not register voltage on the pins.

Jump pin 3 Red/Black and pin 4 Red/Gray at multifunction switch. If the headlights work doing that the multifunction switch is bad. See page 205 in the electrical section for a picture of the connector. Pin 4 is the 12 volt feed so if the headlights don’t work doing this check for power at your jumper. If you don’t check the 30 amp fuse. See page 87 for the wiring diagram

Jumped the wires, no headlights. Power is present on p[in 4, (13.8v).
I think the multi-function switch may be fine. When I turn on the light switch the cluster light dims or goes off. When I put on the turn signal, I get buzzing. All the fuses, under hood, for the accessories are weak (11.5 volts). Was told to jump the white/grey wire to ground. Problem is I can’t find it.
Horn issue may be relay. Trying to find one now.
Thank you for the help.

When so many unrelated things go wonky and just don’t make sense, I go have a look at the ground connections.

Make sure the connection from that converter has a good clean path to the frame.

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Wise words.

I haven’t found much out there with vehicles or control systems that will dish out more random grief than one dodgy ground or common connection.

Check for power and ground at the headlights with the jumper installed. It may be a ground issue. The ground for the converter comes from the battery pack not the frame and than the converter supplies the 12 volt ground for all the 12 volt accessories. Do not use the frame for grounding.

Do not use the frame for grounding.

So like a boat, the late cars don’t tie into the frame for anything and run a separate ground for all accessories?

@David_Illingworth
Thanks will do.
Does anyone know the location and where I tap into the white/grey wire to ground?
Found the relay for the horn. OMRON Electronic Components G8JN-1C6T-DC12
Thank you for the help. I feel I’m getting closer.

It might help if you tell us which white/gray wire. Which circuit? I see a gray/white ground wire for the dc/dc relay but you have power at pin 4 of the multifunction switch so that can’t be it.

I was told by someone that the cluster grounds the passenger side relay at the grey and white stripe wire.
If I ground this wire, it should turn on other accessories through multi-function switch.
So I assume it is the cluster grey and white stripe wire.

Yes that wire supply ground to the dc/dc relay but you said you have power at pin 4 at the multifunction switch and if you do the relay is working. See page 41 and 42 in the electrical section

@David_Illingworth
This is the message Bob sent me regarding my accessories not working:
“Outside one is only for power point. One behind frame is accessories. If you have brake lights, you have power, measuring at fuses under hood would help. 12-13.6 specs, under 12 is weak. cluster grounds passenger side relay at grey and white stripe wire. Grounding this wire turns on other accessories through multi-function switch.”
So I assume I need to ground the cluster grey and white stripe wire, as my voltage is approximately 11.5v at the fuses.

Did you check to see if you have power and ground to the headlights? I’ve seen countless times when both bulbs are blown. You can jump ground to the gray/white wire if you want but if you have power at pin 4 of the multifunction switch you are just wasting your time as the dc/dc converter is what supplies pin 4 with power. Look at page 87 in the electrical section and look at the bottom of the page where it says multifunction switch and then find pin 3. As you see if you have power on pin 3 like you said you do that wire runs directly to the headlights so figure out if you have power and ground. For only 11.5 volts first make sure you’re not using the frame as your ground for your voltmeter. Use battery #1 negative as your ground. If it still reads 11.5 go to the dc/dc converter and recheck the output voltage. If it reads over 12 volts than you need to figure out where in the circuit you’re losing voltage. Possible the dc/dc relay or multifunction switch. Just follow the diagram and check voltage going into each component and the voltage coming out to see where the voltage loss is. Your headlight would still work with 11.5 volts.

@David_Illingworth
Thanks for the help and direction. I never checked power and ground at the headlights. So I will do that.
I was using the frame as the ground when checking the fuses. I will use battery 1 negative.
Thank you again.

I checked for power and ground to the headlights. There is no power with switch on, key set to drive mode, multi function switch lamp switch on. There is also no power to wipers, washers and signals.
I’m going to look at the service manual sheets more to see where to go from here. I’m totally stumped and don’t want to damage, show or blow something. With the exception of these items, (now that the horn works), the Think drives perfect.