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Symptoms of a short?

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Old Jul 18, 2014 | 07:26 PM
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Default Symptoms of a short?

Hello,

I have a 2004 silverado z71 crew cab and the gauge lights along with the climate control screen sometimes go out. When they do, I can tap on the dash above the gauge cluster and they will all come back on. I took the dash mostly apart and did not immediately see any shorts but I could not get a good look at most of the wiring as it went back down towards the firewall. Once or twice the truck would not crank so I held the key in the start position and tapped in the spot on the dash above the gauge cluster and it started right up.

My question is, if there is a short in the gauge cluster panel, could this cause the other symptoms downstream (climate control screen and buttons not to light up and ignition seemingly not receiving power)? I know there is an issue in the gauge cluster because the fuel gauge does not work properly ever, and the rest of the gauges have read incorrectly before.

Thanks for you help guys and girls,

Trey
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Old Jul 18, 2014 | 07:54 PM
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sounds more like a loose ground (or other connection) then a short, a short would usually blow a fuse.
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Old Jul 18, 2014 | 07:57 PM
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Oh yea, there was a blown fuse at one time as well.
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Old Jul 18, 2014 | 09:47 PM
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those clusters (at least the ones in the diesels anyway) have a known issue, I know on my dads old 03 (sold it a few weeks ago) he had to send the cluster off to have it rebuilt and I vaguely recall other signs of this cluster issue caused problems with the A/C and electronic 4x4 buttons.

here is something I just found with a quick google search of the phrase 04 silverado instrument cluster recall

http://www.gm-trucks.com/forums/topi...luster-recall/

I would say you should check in on the different truck forums and see what people say, also while your there look into the "4-high mod" all you have to do is a a diode (comes in like a pack of 3 or 4 from radio shack) that is used to "jump" one of the pins on the headlight relays that will keep your low beams on when you turn your high beams on, which gives you much improved lighting.

Basically this video minus the second one running to the DRL's:
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Old Jul 18, 2014 | 09:55 PM
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Originally Posted by Daniel Richards
those clusters (at least the ones in the diesels anyway) have a known issue, I know on my dads old 03 (sold it a few weeks ago) he had to send the cluster off to have it rebuilt and I vaguely recall other signs of this cluster issue caused problems with the A/C and electronic 4x4 buttons.

here is something I just found with a quick google search of the phrase 04 silverado instrument cluster recall

http://www.gm-trucks.com/forums/topi...luster-recall/

I would say you should check in on the different truck forums and see what people say, also while your there look into the "4-high mod" all you have to do is a a diode (comes in like a pack of 3 or 4 from radio shack) that is used to "jump" one of the pins on the headlight relays that will keep your low beams on when you turn your high beams on, which gives you much improved lighting.

Basically this video minus the second one running to the DRL's:
Thanks for that man- unfortunately, my truck would be out of the recall specs due to mileage and age. It does confirm there was a problem with clusters tho.

NEW DEVELOPMENT- the "reduced engine power" notification came on and wouldn't let me go faster than 25mph. I turned the truck off and on a few times and it went away but then came back after driving a little.

I have a thread going on performance trucks too. Both have given some good ideas so far. Keep them coming! I've gotta figure this out tomorrow.

Thanks
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Old Jul 18, 2014 | 10:08 PM
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he never had anything like that, but he did have the ABS and BRAKE (the parking brake light on the dash) come on at the same time and the speedo start jumping 5-10 MPH variations and some other things and turned out to be his transfer case was shot.

what you describe is a "limp mode", try hooking it up to an OBD2 scanner and see what codes it's reporting, probably some sensor going out somewhere.
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Old Jul 18, 2014 | 10:11 PM
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It won't scan because it can't connect - likely because there's no power to the port :/
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Old Jul 18, 2014 | 11:21 PM
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I saw on another forum where someone had similar issues, including the truck going into limp mode and a new / rebuilt cluster fixed it. Going to put one in tomorrow, assuming a local parts store in Amarillo has one in stock.

Keep the ideas coming. I'll update this post when I fix the issue.
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Old Jul 18, 2014 | 11:55 PM
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No power to the aldl (diagnostic port) is usually caused by a blown fuse for the cigarette lighter or power outlet on GM products.
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Old Jul 18, 2014 | 11:57 PM
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Could a short in the cluster cause the cig lighter fuse to blow?
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Old Jul 19, 2014 | 11:13 AM
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The term "short" is being used incorrectly a lot in this thread. So here is what a short is:

"Short" is a contraction of the phrase short circuit. A short circuit occurs when the wiring is damaged in a way that allows power to flow directly to ground bypassing the load (device) it was intended to power - the circuit is "shorter" because it doesn't flow through the load. With no load between the power source and ground, the current flow immediately rises to the maximum that the power source (battery or alternator) can produce which is way more than the wiring can handle. That's why we use fuses. The fuse is designed to blow and break the current flow before it can melt the wires and cause a fire. Fuses protect wiring not devices.

The most common cause of a short (other than dumbass wiring modifications) is having the insulation on a power wire break due to old age or from rubbing on some surface. The non-insulated portion then comes in contact with grounded metal (body, dash, fasteners, etc.) causing the current to short circuit and (hopefully) blow a fuse.

Shorts are not intermittent. If you can bang the dash and things work again then it's not a short - it's a loose connection somewhere or a defective device.
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Old Jul 19, 2014 | 12:18 PM
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Originally Posted by WhiteBird00
The term "short" is being used incorrectly a lot in this thread. So here is what a short is:

"Short" is a contraction of the phrase short circuit. A short circuit occurs when the wiring is damaged in a way that allows power to flow directly to ground bypassing the load (device) it was intended to power - the circuit is "shorter" because it doesn't flow through the load. With no load between the power source and ground, the current flow immediately rises to the maximum that the power source (battery or alternator) can produce which is way more than the wiring can handle. That's why we use fuses. The fuse is designed to blow and break the current flow before it can melt the wires and cause a fire. Fuses protect wiring not devices.

The most common cause of a short (other than dumbass wiring modifications) is having the insulation on a power wire break due to old age or from rubbing on some surface. The non-insulated portion then comes in contact with grounded metal (body, dash, fasteners, etc.) causing the current to short circuit and (hopefully) blow a fuse.

Shorts are not intermittent. If you can bang the dash and things work again then it's not a short - it's a loose connection somewhere or a defective device.
Thanks for that. I do understand what a short is - I was asking if a short in the cluster could cause the other effects. If I bang on the dash, theoretically, could if be causing a wire with damaged insulation to contact a ground thus "shorting" the circuit intermittently? Albeit, a loose connection may be more likely.

So let's rephrase the question - could a lose connection or short in the cluster itself cause the other issues? Intermittent loss of power to ignition, the diagnostic port, blown cig lighter fuse?

Thanks
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Old Jul 19, 2014 | 02:16 PM
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Short answer... No. (pun intended)

No, if you bang on the dash and it caused a short, it would only happen once because the short would cause a fuse to blow and there would be no power for it to happen again.

No, a loose connection in the instrument cluster could cause loss of ignition but not the ODB II port or cigarette lighter because those circuits don't share power with the cluster. Both the OBD II port and the lighter run off the same CIG/ACCY fuse so the blown fuse would account for the diagnostics port problem. It is possible there is a short in that circuit or the fuse could have blown because of something getting into the lighter socket itself, shorting the contacts.
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