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Stereo makes loud crack and turns off and engine cuts off shortly after being started

Medic2038

New Member
Joined
Aug 10, 2019
Messages
10
Location
Pittsburgh
2006 TJ, 4l auto

So I had 2 electrical issues come up twice so far. Both times were independent of each other, and happened at random. The only thing I'd noticed that was it was on 2 of the warmer days we've had this fall. I'd recently replaced my dying PCM, and I'd read some similar issues were resolved from that. Both issues have occurred once before the PMC, and again once after. I'm kind of don't even know where to start with trying to figure this out. Battery is new (got it last year), and recently put new terminals on there (they're nice a snug/don't move).

So the 2 issues are
  1. Stereo makes a loud crack, and turns off. The entire console looks like it loses power (clock is off/resets to AM). Both time this happened is while I was driving, but didn't notice anything else. It was daylight so wasn't able to see any flicker, or if I lost any lights or anything on the cluster.

  2. Engine cut off shortly after being started. Happened once right after starting, immediately. I started the engine, and then everything cut off completely. On restart everything was fine. The other time it happened it was about a minute after I first started it and was turning around on my street. I'd put it in park, restarted the engine, and everything was fine.
I haven't done anything with any of the electrical system (outside of swapping out sensors), so all of the wires are still original and about 14 years old.

Appreciate any help/suggestions you guys might have!
 
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Medic2038

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Joined
Aug 10, 2019
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10
Location
Pittsburgh
So just happened again tonight. Drove to Lowe's and came back out. Put the key in the ignition and it cranked for a second before all if the electrical systems went dead. After a few seconds the cluster light came back on, the clock was reset. Started up and drive home just fine after.

I figure it's a short if some sort, but how do u track it down?
 

PatMc

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Joined
Oct 14, 2019
Messages
24
Location
Long Beach CA
I would start with a voltage drop test on your ground side.

Get a helper and a Voltmeter. Set the meter to DC volts, touch one probe to the negative battery terminal (not the cable end...the round thing sticking out of the battery) and the other probe to a clean spot (grind the paint off in a spot near where the ground straps bolt to the firewall) on the body.

Start with turning the headlights on, see what the meter reads.

Turn on more interior loads and see what the meter reads.
 

Goatman

TJ Addict
Supporting Member
Joined
Apr 23, 2019
Messages
1,832
Location
Upstate NY
Definitely sounds like a short in the main harness. A "crack" or "snap" is a pretty good indication of that compared to just a loss of continuity.
 
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Medic2038

New Member
Joined
Aug 10, 2019
Messages
10
Location
Pittsburgh
@PatMc I'll give that a try. It'll also give me a chance to check the condition of the ground there. Wasn't sure if that would cause the issue or not, but if the other bolts are any indication it might have some rust on it.

@Goatman @Chris How would I go about troubleshooting that? I have an analog multimeter, but that's about the extent of the electrical tools I have.
 

Jerry Bransford

TJ Guru
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Nov 9, 2015
Messages
12,288
Location
Escondido California
Electrical shorts blow fuses, wiring, and/or cause the magic smoke to be let out of the circuit, I strongly doubt it's a short. To a non-electrical type a short is the cause of all electrical issues but they're rarer than most realize.

I'd be looking for a corroded or loose connection on a larger gauge main supply wire. Take a look at the big ground connections like to the engine block too, and take a look at where the battery connects to the PDC at the side closest to the battery, under that small plastic snap-on protective cover.
 
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Medic2038

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Aug 10, 2019
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10
Location
Pittsburgh
@Jerry Bransford Thanks! Yeah I'm definitely not an electronics experts by any stretch. Good point, yeah there was no smoking/burning smells or anything like that.

The main battery ground (I think?) connected to a big bolt in the firewall... I took off and cleaned up with the dremel wire wheel. Also did that for the ground strap at the hood and firewall on the other side. The metal and bolts both were a bit crusty with salt/junk, and a tiny bit rusty so got them to nice and shiny again. I had to come in for a few minutes but looking at the block ground next.

I didn't see anything that was loose. Battery terminals and cables don't budge. How should I be testing these wires? When I tried the negative to the ground bolts like was suggest above, I didn't get anything. When I do positive to the bolts though I'm seeing about 14v on the multimeter.