Electrical Pains

kilo_z71 · April 15, 2009

I've got a 96 Silverado Z71, and none of the courtesy lights, side view mirror motors, or cargo lights worked, so I replaced the fused and it blew right away. And I don't know if its related but the volt gage on my dash never reads 14 V unless its a cold morning start, even then its only there for a few minutes. Another thing is that before I start the pick-up the clock will read fine, but after starting it up the clock resets almost everytime.

I replaced the alternator, but didn't really change anything, and the battery is a red top Optima, almost 4 years old, but never have had a problem starting the thing up. Any ideas? Thanks.

Silverado_Monkey · April 15, 2009

I've got a 96 Silverado Z71, and none of the courtesy lights, side view mirror motors, or cargo lights worked, so I replaced the fused and it blew right away. And I don't know if its related but the volt gage on my dash never reads 14 V unless its a cold morning start, even then its only there for a few minutes. Another thing is that before I start the pick-up the clock will read fine, but after starting it up the clock resets almost everytime.

I replaced the alternator, but didn't really change anything, and the battery is a red top Optima, almost 4 years old, but never have had a problem starting the thing up. Any ideas? Thanks.

That definitly a short. You need to get your hands on a schematic and also look around the cab for any fraid wires that could be contacting each other or a ground... Looks for blacken wires, or loom...

The clock thing is strange too, did all these things start at the same time? Have you added any accessories lately? Could it be releated to any thing like that? Any accidents, that could have caused a short?

pennzoil29 · April 15, 2009

I've got a 96 Silverado Z71, and none of the courtesy lights, side view mirror motors, or cargo lights worked, so I replaced the fused and it blew right away. And I don't know if its related but the volt gage on my dash never reads 14 V unless its a cold morning start, even then its only there for a few minutes. Another thing is that before I start the pick-up the clock will read fine, but after starting it up the clock resets almost everytime.

I replaced the alternator, but didn't really change anything, and the battery is a red top Optima, almost 4 years old, but never have had a problem starting the thing up. Any ideas? Thanks.

That definitly a short. You need to get your hands on a schematic and also look around the cab for any fraid wires that could be contacting each other or a ground... Looks for blacken wires, or loom...

The clock thing is strange too, did all these things start at the same time? Have you added any accessories lately? Could it be releated to any thing like that? Any accidents, that could have caused a short?

rodram · April 15, 2009

Yes, you have a short circuit problem... and shorts are truly a pain to trace... bad enough when you cause it yourself (like I have installing radio/stereo.. ) but even worse if it is a worn wire insulation or crossed connection somewhere ....

Try removing all the bulbs and isolating the things (ie., mirror motors) that are not working and then try another fuse.... if the fuse survives, then replace or reconnect each item one at a time until the fuse goes again.... it sounds a bit mickey mouse trial and error, but if you take it to a shop at $90/hr they are going to spend your money doing exactly the same thing...

Good Luck!!

kilo_z71 · April 15, 2009

It all started with the lights, then the volt gage, and clock. Havent added anything lately, I actually removed some KC Lites.

So just take out all the lights and disconnect everything attached to that circuit, and just stat connecting things until I find the one thing that blows it? If the fuse blows with all that stuff disconnected, what does that mean?

Any ideas on the volt gage? Could the short be affecting it? When I accelerate the gage goes up a little bit, but not to 14 V. When I turn on blinkers, or roll a window up/down, turn the wheel hard in one direction, the lights dim.

rodram · April 15, 2009

Who do you call????? GHOSTBUSTERS!!

You have some weird stuff happening, but yes it could ALL be from a short or more than one short... even the voltage gauge.

If you fry the fuse with everything disconnected then there is a whole lot more trial and error to proceed on. ... then the problem could be on a lead wire from the fuse block to a light base or to a mirror motor or whatever ... you would really need a wiring schematic for the truck for everything that is on the affected fuse circuit ...

Using an ohm-meter to detect current (nothing sophisticated.. you just need something with an analogue needle gauge to know if something is shorted to a ground to complete the circuit or not):

.. start at the fuse block (dead side of the fuse) to the truck chassis somewhere and presumably it will detect current (that is why your fuse goes poof)

.. keep moving down various branches of the wiring harness and check if there is a short (ohm-meter detects current from some point on the wiring to some chassis ground point) at any point along wiring harness

.. depending on switches being in on-off positions, you can start to eliminate branches of the wiring with no problems (no current in the ohm-meter - then no short), and hopefully zero in some part of the problem area.

Again... Good Luck!

kilo_z71 · April 16, 2009

Who do you call????? GHOSTBUSTERS!!
You have some weird stuff happening, but yes it could ALL be from a short or more than one short... even the voltage gauge.

If you fry the fuse with everything disconnected then there is a whole lot more trial and error to proceed on. ... then the problem could be on a lead wire from the fuse block to a light base or to a mirror motor or whatever ... you would really need a wiring schematic for the truck for everything that is on the affected fuse circuit ...

Using an ohm-meter to detect current (nothing sophisticated.. you just need something with an analogue needle gauge to know if something is shorted to a ground to complete the circuit or not):

.. start at the fuse block (dead side of the fuse) to the truck chassis somewhere and presumably it will detect current (that is why your fuse goes poof)

.. keep moving down various branches of the wiring harness and check if there is a short (ohm-meter detects current from some point on the wiring to some chassis ground point) at any point along wiring harness

.. depending on switches being in on-off positions, you can start to eliminate branches of the wiring with no problems (no current in the ohm-meter - then no short), and hopefully zero in some part of the problem area.

Again... Good Luck!

So take a lead of my ohm meter stick it in the fuse slot, and put the other lead to a ground and if there is a short it should read current, meaning I have a short, right? Then, leave a lead on ground and move the other lead between different branches of the circuit, and if it reads a current then the short is in that branch, if no current then no short? Is that right?

rodram · April 16, 2009

It sounds like you are are the right plan ..... let us all know if this works out...

You can't lose. All it will cost you is a little time and you might be able to isolate the short

wd4lam · April 17, 2009

I love GMT forums!

The above advise is good!

Let me add, that while you're under the hood looking for chaffed wires, clean any ground connections to frame and chassis you find. Part of the headlight wiring harness probably grounds to the radiator cradle.

Did I mention I love GMT forums?