I've searched around the forums, and I've found threads similar to my problem, but none were exactly like mine, and all of them came out with different solutions. I realize I may be re-posting a problem, so bear with me.

1985 Chev S10 Blazer 4x4 2.8l Automatic.
Every time I turn the ignition to start, the 20 amp GAU/IGN fuse pops, and all my gauges go dead. The motor still starts though! I've replaced the fuse 3 or 4 times, but it doesn't matter; the thing still pops right when I turn the key.
I looked in the owners manual and that fuse serves the gauges, ignition, rear defogger, and transmission.

I've seen solutions anywhere from shorting O2 sensor to replacing the computer I sure hope it isn't that...

Anyways, I hope you guys can help me out, because I cannot do electrical for the life of me and I cant spend $200 for a mechanic to look at it.
Thanks!!

 

I would start by looking for the easy things, down on the starter is a smaller wire in the bundle, its an ignition wire I beleive - have a look for that one grounding out somewhere on its way to where it goes into the firewall and relay.

Fuses blow when there is a short (grounded wire) in the system. Its gonna end up being a chafed wire, or broken wire somehwere, just root around and Im sure you will find it. Giveaways will be exposed wire and black burn marks. If you wanna waste some fuses, you can have someone else plug em in and turn the key while you are underneath looking for the spark and listening for it it may be kinda hard to hear it over the fuses popping though. You can use any size fuses for this task.

 

this is kinda a side problem im having too, my transmission has been acting up and also this fuse was blown too. heres the steps i got off identifix.com

1 locate the bulkhead connector c100 on the drivers side near the brake booster. remove the pink/black wire from the cavity b2 and then plug the connector back in

2 if the fuse still pops with the pink/black wire removed from the connector unplug the cruise controle module rear defogger switch rear defogger relay, daytime running lights instrument panel cluster and rearview mirror and retest

3if the fuse still pops locate splice s200 near the steering cloumn above the brake switch inside the wiring harness. disconnect the wires from s200 one at a time while testing the fuse

4 if the problem is gone when one of the wires is disconnected check that wire using a ohm meter to each of the devices unplugged to locate what the wire powers up and check the wire from s200 to that electrical device for short to ground.


so in other words have fun. this is for a 93 s10 though so i dont know if its going to be the same for you. i hope this is my problem cause mines just a offroad truck so any of that defrost or anything else can just be cut and removed

 

Its the o2 sencer shorting out. Mine was doi g the same thing. Try unpluging the 02 sencer the one on the pipe. And let me know if it stops

 

to quote my other thread....


"This sounds like the IGN/GAU fuse. This fuse controls the alternator charging, o2 sensor, transmission (with fuse blown, it forces 3rd gear. Awful for starting from a stop and high revs at highway speed), gauge lights, and the warning buzz for the key being in. This fuse used to blow on me every time I took it wheeling, got very frustrating.

Start by checking the fuse. it's a 20-amp located in the fuse box in the driver's side footwell and it is labeled IGN/GAU. After you replace the fuse or verify it is good, you need to start looking for the short.

My short (which is also the most common) was as the wiring harness leading to the trans goes between the firewall and the transmission. If you look down directly past the distributor, towards the underside of the car, you should see a big loomed harness running to the underside of the car, which is most likely pinched between the trans/firewall and causing your problem.

If you verify a pinched harness in there (even just a little bit), start by unplugging the o2 sensor, the large connector that goes into the transmission on the passenger side, and the small connector that goes into the transmission on the driver's side. Then you can pull some (but not all) of the harness back towards the top of the motor, which should net you enough room to see if there is any bare copper. The wire that is vital to the systems you are talking about is PINK/BLACK, but I found 17 bare/shorted wires when I got my harness visible.

Easiest way to repair is to get as much harness up from underneath the car (the large connector for the trans wouldn't fit between the trans/firewall for me. If you jack the trans maybe you could get it through, but you'll see it won't yield much help. Next, under the glove box inside the car you'll find where the harness comes into the car and to the ECU. Unplug it from the ECU and feed the harness/plug through the firewall into the engine bay. Next you can take the harness/plug and pull it up and over the exhaust manifolds, again moving towards the distributor. This will be as far as you can get the wiring, but should put the pinched wiring at about hood height, at the distributor. Now you can lean over the motor (or sit on the motor if your 130lbs soaking wet like I am) and start repairing your wire.

Re-install in the reverse order, and be sure to use a few zip ties to keep the harness towards the passenger side of the car where it goes between the trans/firewall. You'll see that as you go towards the passenger side, the gap gets bigger for the wiring harness. By keeping it towards that side, you should be clear of this problem forever.

Feel free to PM me if you have any questions. I wish I had pictures from my repair.... "

 

just realized this was a resurrected old thread....one of two of them....

 

LOL, Not only can the person who brought it back to life not spell, but read either.