Odd electrical issue

Lunar-Eclipse

I bought another Z about a week ago. Today I installed my Pioneer headunit. I used the same headunit and wiring harness that I used in my last Z. I didn't cut any wires it was just plug and play. The headunit works great.

The odd thing that's happening is that now my cigarette lighters have a really low voltage. Both the passenger side one and the center console one show about 2.7V and anything I plug into them doesn't get enough juice. I pulled the kick panel and replaced the "cigar lighter" and "power socket" fuses. They didn't look blown but I swapped them anyway. No change in the voltage reading. Something else I noticed is that there was a fuse in a place where the diagram shows there should be nothing. I don't know if that's relevant but I thought I'd throw it into the mix.

I looked at the cigarette lighters electrical diagram in the service manual and it shows that both sockets get their power from the same source. Since both show the same voltage level then I'm assuming the problem is upstream.

Since I'm getting some voltage I'm thinking it's either a partially melted fuse or a damaged wire (I'm really hoping it's a fuse). Is there another fuse panel I should be looking at that would also handle the cigarette lighter?

Can I just remove the fuse and stick my volt meter in the fuse panel to see if it's dishing out 14V?

Could someone post a picture of their kick panel and engine bay fuse boxes so I can confirm that everything looks right on mine?

Thanks in advance.

SouthArk370Z

Check the voltage at the fuse block. If volts are good there, then you probably have a wiring problem.

Since you have some volts at the sockets, it may be the power management is not turning the sockets on and you are seeing leakage through the transistor.

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RonRizz

Might want to look into the ground on those as well. I don't know if they are grounded in the same spot, but if they are both throwing the same voltage reading I would assume they are. A simple check would be to ground your tester to a spot other than the outer ground ring on the socket. Start with the simple, I always say.

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Lunar-Eclipse

Okay, I tested again with different ground points and I'm getting 2.4V with the car turned to "On" and 3.8V with the car running.

I also tested both the "cigar lighter" and "power socket" connections at the kick panel and I'm getting 2.4V as well. That's a lower reading than yesterday so I think the problem is getting worse.

It looks like the problem is further upstream. According to the electrical diagram in the service manual (PWO-2) the next thing up is fuse block/junction box M1 (PG-112)in the engine bay. It looks like M1 is a single chunk of fuses that can only be removed as one piece. Looking through the window at the top of the fuse block it doesn't look blown. Do I have to replace this whole thing to be sure?

The electrical diagram breaks down the M1 fuse block further (PWO-3) but it's beyond my understanding of electrical diagrams.

Any suggestions?

grant

Just to ensure it isn't your head unit and harness, unplug them and check the voltages at the outlets. That would eliminate any odd differences in the harnesses. Something is loading up the circuit that wasn't there before.

SouthArk370Z

Looking at PWO-3, the "FUSE BLOCK (J/B)" is on the left side of the driver's footwell, not in the engine compartment. "M1" refers to the connector used on the Fuse Block (J/B). The fuse is a 15A in position 20 (see lid of fuse block for physical location).

Since both the cigarette lighters are "dead" and they share a common ground, I'd take a closer look at your ground wiring if you have 12V at FB(J/B) fuse #20.

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Lunar-Eclipse

And the weirdness continues...
I went out there again to test the voltage at the engine bay fuse box and it was reading 12+ volts. So I went back to the kick panel and stuck the voltmeter probe in there and I got 12+ volts. Then I went to the cigarette lighters and tested and got 12+ volts.

So I'm thinking one of two things is happening here... either there is a loose wire going into the back of the kick panel fuse box OR there is a fuse/wire that is failing once it heats up.

Lunar-Eclipse

I wasn't getting 12V at the kick panel. I was getting 2.4V and I was grounding my probe against the bare metal or the firewall.

Lunar-Eclipse

If this happens again (and from the inconsistent results I bet it will) I'm going to try Grant's suggestions and tear out the headunit and put the Bose back in.

SouthArk370Z

Plug something with an LED on it into one of the sockets and wiggle the wiring going into the fuse block. If the light is steady, then it's not a loose wire.

While you have the LED plugged in start tracing the wire(s) from the fuse block to the sockets, wiggling the wires as you go. If the LED blinks, you've found the problem.

You may have dirty fuse contacts. Pull the fuse, clean the contacts on the fuse, and re-install.

Not very likely. An "intermittent fuse" is a rarity in my experience (other than contact problems as above) and, unless you were putting a load on the sockets, heating doesn't enter the equation. But not impossible.

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Lunar-Eclipse

Hmm... I think I have a DC test light somewhere. I'll give it a shot tomorrow and let you know what I find.

Thanks to everyone for the suggestions thus far.

SouthArk370Z

Ah. That's sounds like you weren't getting power to the Fuse Block. IIRC, power to the fuse block for the sockets comes from the ACC output of the IPDM (next to the battery), but would need to go through the drawings to be sure.

Where on the fuse block did you take your measurement? If you were not on the "hot" side of the fuse contacts, you would be seeing stray voltage.

Grounds can be tricky, especially on modern cars. Try to find a place where other equipment is grounded and use that. Make sure you have a spot that is free of paint/varnish/grease/&c.


I don't think the HU is the problem. You probably knocked something loose when changing.

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Lunar-Eclipse

I was measuring from the right side of the socket. The side closest to the front of the car.

I'm pretty sure the other contact provided no reading. But don't quote me on that. I've looked at that kick panel like 30 times today.

Lunar-Eclipse

Just thought I'd post an update on this. My power sockets went out again today when I went for lunch. They were showing low voltage again.

I bought a probe on the way home and tested the kick panel. It's definitely a loose wire/contact at the panel. There are a couple of wire looms that disappear near the kick panel so I couldn't determine which one was the culprit. I did "fix" the problem by kicking the panel a few times . Power came back up to full after that.

I need to pull the plastic paneling in the footwell to have more direct access to test the wire looms. That should also let me unscrew the fuse panel to see the back of it. Just what I wanted to spend my Saturday doing