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Discussion Starter · #1 ·
Hello, I have a 92 S10 4x4 & the IGN"GAU fuse blows every time I turn the switch on, my Speedometer, gauges don't work & my alternator doesn't charge. I have 12.65 volts on that slot. There is no surge when I cut the switch on & the multimeter reads 12.65 every time. I have also unplug every plug that I can think of or get to including the wiring harness from the IGN switch, & it still blows. The strange thing to me, is how does the IGN switch work when it is unplug? Yes as soon as I cut the switch on it blows the fuse. How is this possible? Are there another set of wires from the switch that I'm missing? I have a strong mechanical mind but honestly I am stumped on this one. I have also taken the gauge cluster out with no luck. Thanks & Anyone that can help me solve my problem will be my HERO for a day!!!
 

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2001 GMC Sonoma crew cab 4x4, 4.3L automatic
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Page 10 is the wiring diagram you need.

I recommend getting your alternator checked for a short circuit to ground. If memory serves, a lot of auto parts stores can test these for free. Could be a shorted diode, and checking the alternator is a LOT easier than looking for a short in the harness!

I found this and a lot more on the first post in the “If you need Wiring Diagrams” sticky topic at the top of this Electrical/Lighting forum.

Let us know what you find!
 

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Discussion Starter · #4 ·
Page 10 is the wiring diagram you need.

I recommend getting your alternator checked for a short circuit to ground. If memory serves, a lot of auto parts stores can test these for free. Could be a shorted diode, and checking the alternator is a LOT easier than looking for a short in the harness!

I found this and a lot more on the first post in the “If you need Wiring Diagrams” sticky topic at the top of this Electrical/Lighting forum.

Let us know what you find!
Hello, & thanks for the post. I took the alternator & had it tested which turned out to be good, so I'm right back to square 1. I am completely baffled about the IGN switch, how is it possible to be disconnected from the wiring harness & still blow the fuse when I cut it on? Also Thank you for the wiring diagrams, I will go over it carefully to see what I am missing. I have never encountered a problem that has stumped me in a way this wiring has. When ever I find out what the problem is I will definitely post what it was. I welcome any & all suggestions!!!
 

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Discussion Starter · #5 ·
My 92 S10 started blowing the IGN/GAU fuse after many hours of chasing down wires & leads I finally found out which wire is blowing the fuse. Now my problem is I'm not sure what the wire goes to. There is a clear or white junction box at the bottom end of the steering column at center top. There are 2 connectors that go to it one is blue & the other is black. The blue has 4 wires pink, purple, red, & brown. The pink wire is the one blowing the fuse. Does anyone know what this wire goes to? I have looked through every drawing & manual that I can find, but can't find the junction box or wiring diagram for it. If I knew what went to this pink wire I would be able to find the short. It is also a larger gauge wire I would say 14 maybe even 12 gauge. Here is a picture of it. Any help would be greatly appreciated.
Electrical wiring Cable Computer hardware Electrical supply Gas
 

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2001 GMC Sonoma crew cab 4x4, 4.3L automatic
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Rectangle Slope Parallel Font Pattern

If you remove the Ignition / Gauge fuse shown above, do you have +12.6V on what would be the side of the fuse toward the alternator and 0V on the other side of the fuse?

If you put your meter on the Ohms range, do you read 0 ohms on the side with 0 volts?


This is the Power Distribution diagram for a 1994 S10, hopefully they’re very close.
Rectangle Schematic Font Parallel Engineering

The alternator is in the lower right hand corner and following the Pink / Black wire up to the fuse panel there is the gauge fuse.

On the other side of the gauge fuse the Pink wire goes up to the ignition switch.

With the IGN / GAU fuse removed, does the turn signal flasher and /or the backup lights work?

Do you see less than an ohm to ground on the bottom of the IGN / GAU fuse to the right?

Assuming you do, that zero ohms is what we have to track down. The Instrument Cluster has already been removed but the fuse still blows, correct? If so we can eliminate the IC as the source of the short circuit. The wiring harness to the IC could be damaged, see if it’s been rubbing against something.

Every module and it’s wiring harness on the PNK / BLK wire could be the culprit. Divide and conquer. I’d find Power Distribution Center A and pull the fuse or circuit breaker 33 (or 39?) and see if that gets rid of the short.

Some wiring is more vulnerable than others, such as the switch on the transmission or the heated Oxygen Sensors.

Let us know how it goes.
 

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Discussion Starter · #8 ·
View attachment 368921
If you remove the Ignition / Gauge fuse shown above, do you have +12.6V on what would be the side of the fuse toward the alternator and 0V on the other side of the fuse?

If you put your meter on the Ohms range, do you read 0 ohms on the side with 0 volts?


This is the Power Distribution diagram for a 1994 S10, hopefully they’re very close.
View attachment 368922
The alternator is in the lower right hand corner and following the Pink / Black wire up to the fuse panel there is the gauge fuse.

On the other side of the gauge fuse the Pink wire goes up to the ignition switch.

With the IGN / GAU fuse removed, does the turn signal flasher and /or the backup lights work?

Do you see less than an ohm to ground on the bottom of the IGN / GAU fuse to the right?

Assuming you do, that zero ohms is what we have to track down. The Instrument Cluster has already been removed but the fuse still blows, correct? If so we can eliminate the IC as the source of the short circuit. The wiring harness to the IC could be damaged, see if it’s been rubbing against something.

Every module and it’s wiring harness on the PNK / BLK wire could be the culprit. Divide and conquer. I’d find Power Distribution Center A and pull the fuse or circuit breaker 33 (or 39?) and see if that gets rid of the short.

Some wiring is more vulnerable than others, such as the switch on the transmission or the heated Oxygen Sensors.

Let us know how it goes.
Hello & & let me start off by saying thank you. Now either I'm a big dummy or my brain is fried from trying to figure all this out, but I'm including another picture except this is the wires from the ignition & there is no pink wire coming from it. Also if you look to the top of the picture the yellow looking junction box that is where the pink wire connects. Am I missing something or is it so easy I'm overlooking it. Before I can do any testing I will have to plug back all connectors & sensors. So if I am loosing my mind please say so & maybe explain it in layman's terms. Again thank you for all your help.
Electrical wiring Gas Cable Electrical supply Motor vehicle
 

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Have you disconnected everything that is connected to that fuse?
Rectangle Font Parallel Pattern Number

Also humor me and unplug your heater blower motor. Theoretically it has it's own fuse, but power to that fuse goes thru the ignition switch.
 

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Discussion Starter · #10 ·
Have you disconnected everything that is connected to that fuse?
View attachment 368924
Also humor me and unplug your heater blower motor. Theoretically it has it's own fuse, but power to that fuse goes thru the ignition switch.
Thanks man, my truck is VIN Z so it doesn't have some of the relay's & or sensors, but I will try the blower motor just to see what happens. I will let you know what I find out.
 

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Discussion Starter · #11 ·
View attachment 368921
If you remove the Ignition / Gauge fuse shown above, do you have +12.6V on what would be the side of the fuse toward the alternator and 0V on the other side of the fuse?

If you put your meter on the Ohms range, do you read 0 ohms on the side with 0 volts?


This is the Power Distribution diagram for a 1994 S10, hopefully they’re very close.
View attachment 368922
The alternator is in the lower right hand corner and following the Pink / Black wire up to the fuse panel there is the gauge fuse.

On the other side of the gauge fuse the Pink wire goes up to the ignition switch.

With the IGN / GAU fuse removed, does the turn signal flasher and /or the backup lights work?

Do you see less than an ohm to ground on the bottom of the IGN / GAU fuse to the right?

Assuming you do, that zero ohms is what we have to track down. The Instrument Cluster has already been removed but the fuse still blows, correct? If so we can eliminate the IC as the source of the short circuit. The wiring harness to the IC could be damaged, see if it’s been rubbing against something.

Every module and it’s wiring harness on the PNK / BLK wire could be the culprit. Divide and conquer. I’d find Power Distribution Center A and pull the fuse or circuit breaker 33 (or 39?) and see if that gets rid of the short.

Some wiring is more vulnerable than others, such as the switch on the transmission or the heated Oxygen Sensors.

Let us know how it goes.
Hello again, OK I tested the circuit the way you said. First I have 12.4 V on the alt. side & 0 V on the other but I have 2.0 ohm's also the back up lights work, but not the signal, but I have not connected everything back together yet. If my memory serves me right, With 0 V on the one side shouldn't the ohm's read infinite? Or am I wrong for thinking that? I'm about to have a meltdown. I hate to be such a pest but I honestly don't know what to do. I have found out that with the pink wire unplugged the truck will not crank but with it plugged in the fuse blows but the truck will start.
 

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Discussion Starter · #12 ·
Have you disconnected everything that is connected to that fuse?
View attachment 368924
Also humor me and unplug your heater blower motor. Theoretically it has it's own fuse, but power to that fuse goes thru the ignition switch.
OK I did unplug the blower motor & it still blows the fuse. I have chased down every pink & black wire on my truck & yet I'm still having the same problem. This is day 4 working on the same issue. I'm about ready to take a long walk off a short pier...LOL...There's too many things going on that don't make any sense, I feel like Johnny Five & I'm about to short out. I don't even know what else to try.
 

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Are there any signs of a previous owner having done any wiring "improvements"? Like an after market radio that was not installed using Metra connectors or a remote start or keyless entry or security system? Often times wires get incorrectly connected when those devices are installed. Especially by DIY-ers.
 

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Discussion Starter · #14 ·
Are there any signs of a previous owner having done any wiring "improvements"? Like an after market radio that was not installed using Metra connectors or a remote start or keyless entry or security system? Often times wires get incorrectly connected when those devices are installed. Especially by DIY-ers.
A tach & 3 small Sun gauges, oil, water & volts. I put a stereo system in it but I have had the truck 2 years & everything has been in it that long & longer. Plus I have disconnected everything. There are strange things going on that don't any sense, I am not a master mechanic, I used to think I had a little knowledge, but I'm not sure anymore, this whole ordeal has dummied me down. I even took every fuse out & replaced them one at a time just to see if a short to ground would be on that circuit but nothing happened. With the large pink wire connected & the fuse blown the truck will crank & run, but with the fuse in & good & the pink wire disconnected the truck will turn over but not start. I wish I could find the schematic's on that 4 wire plug that has the pink wire. Thanks for the help
 

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The ignition fuse is to power items when the ignition key is in the run position. It does not supply power to the engine ignition system.

The electrical plug with the four wires in your first photo appears to be one of the connectors for the ignition switch. The pink wire sends power to the ign/gauges fuse, the turn/bu fuse, the ecm fuse and the ignition coil.
From your description all is well up to the ign/gauges fuse point indicating that the short circuit exists after the ign/gauge fuse.

Olddeerslayer is correct about disconnecting everything that is connected to ign/gauges fuse that are shown in the electrical drawing that is in his post.

I just wanted to add that the ign/gauge fuse has 4 accessory wire plug-in sockets on the face of the fuse panel, designated by the square boxes labeled A on the schematic that olddeerslayer posted. Often these jacks are used to install power to aftermarket radios, sometimes with bad wiring techniques. Be sure to disconnect these plug-in wire connectors to eliminate them during testing.

Scott
 

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Discussion Starter · #17 ·
Hello Scott, I'm Tim, thanks for the help. I have went through every schematic several times to make sure I haven't missed any culprit. I have also taken every fuse plus the jacks out of the fuse box except the IGN/GAU fuse & it still blows. Then I put them back in 1 at a time, trying to see if something happened, but nothing changed. I have taken the ALT to have it checked & it is good. I took the starter off & checked it & the wires & all is good there. I know the coil & distributor is working. The turn signals & back-up lights are working. I have taken the speedometer & gauge cluster out, I have unplugged every module, sensor, & plug starting at the rear transfer case & coming forward. Would I be wrong thinking that the short has to be a direct link to the pink wire & not one of the circuit's that branch off since i have no problems with any other circuit? The only direct links according to the last drawing are the IGN coil, the turn signals, &the BU lights & since all of this works could it be the fuse box? I would hate to think that is what it is but there is nothing left to try. Also is there a way to test the fuse box? Thank you for your time!!!
 

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Hey Tim, Let's start from the beginning.
Are you saying that your truck worked perfectly and then one day for no apparent reason this problem just started?

Had there been other unrelated work done to the truck recently?

Does the truck start, run and drive with the ign/gauge fuse removed, excepting the devices on this circuit?

In your post #5 you said “There is a clear or white junction box at the bottom end of the steering column at center top”. That would be the ignition switch. Your photo in post #5 shows one of the ign switch connectors. There are four wires on the connector, the red wire comes from the battery (always powered) and supplies power to the ignition switch. The the pink wire (only has power when the ignition switch is in the run or start position) leaves the switch and powers the ignition coil and 3 fuses, (ign/gauge, turn/backup and ecm1).The ign/gauges fuse output wire has a pink wire with a black stripe (pnk/blk).

Let's assume that everything on your truck is working properly except the ign/gauges fuse and do a basic checking of the obvious things first.

Alternator, unplug the connector with two wires, a pnk/blk wire and a brown wire.

Cruise control SW, unplug the cruise control switch under dash by steering column, 4 wire connector with a pnk/blk wire, 2 dk blu wires and a gry wire.

AC comp relay, unplug the AC comp relay (should be located on the firewall). It will have 5 wire connector with a pnk/blk wire, a red wire and three more wires, probably dk grn.

Unplug the instrument cluster connector at the back of gauge panel. Yes, there is a pnk/blk wire in the connector.

With these items disconnected does the fuse still fail?
 

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Discussion Starter · #19 ·
Hello Scott once again, first let me say that I have had the truck for 2 years & never had a problem. Now I will explain how it started. 9 days ago I was driving when I noticed the speedometer wasn't working, but I didn't pay it much attention until I noticed that the gas gauge wasn't working either. Well I found out what fuse was blown, replaced it & everything was working fine, until the next day. So I'm driving & I saw that the speedometer wasn't working again. I stopped & got a pack of fuses replaced it & started to drive off when I saw that the speedometer wasn't working, I stopped & put another fuse in & I heard it blow as soon as I cut the switch on, from that point on every fuse I have put in it blows as soon as I cut the switch on. For the next 7 days I tried every bit of advise that I was given & read about. I went as far as unplugging every thing that had a wire running to it. That is how I found which wire was blowing the fuse, but nothing I did helped me figure out why it kept blowing the fuse. Fast forward to today. I found this local guy that solves auto wiring problems. I went & saw him today, after explaining what was going on, he pointed out a problem that makes no sense to him or me after he said it. OK, with the pink wire plugged in the fuse blows & yet it will crank & run. He said with the IGN fuse blown it should not run, but it does. With the pink wire unplugged it will turn over but will not start. So he told me to make me a fuseable link & run it from the hot side of the battery & take the other end & touch it to the pink wire unplugged, if it blows the fuse it is in the wire & trace it down, but if it doesn't blow stick the hot wire to the pin that the pink wire goes to & if it blows it would be from the switch. I thought finally I'm going to get this figured out, well the story of my life, neither way blows the fuse. So I thought it fixed itself but when I put the pink wire back in & cut the switch on the fuse blows. The guy doesn't know about the outcome yet, I will talk to him tomorrow. Do you have any idea, other than the Gremlin theory because I claimed that one(LOL)? Also do you know why the truck starts when the fuse is blown? Any help will be greatly appreciated!!! Stay safe & Thank you for your time Scott. I hope that I'm not to much of a burden.
 

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I had a similar problem with my 1991 S10, 2.8L. I finally got a hold of a GM dealer wiring diagrams book, there was a single wire to a sensor on the right side under the engine on the belt driven "air pump" that was broken and touching the frame, it would blow the fuse as soon as you turned the key on. This wire was not shown on any of the wiring diagrams I found online.
 
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