1991 chevy s-10 electrical gremilins, short to ground, hair puller!?

Question

1991 s-10 with a 4.3 v6. Test light across negative terminal on battery to cable has a dead short. Short is worst with ignition switch to run. With off a slight short is still there which I can make go away by removing radio. I have checked ground and is good to block and chassis. Big short goes away when the wires (3 that bolt to terminal on back) of alternator are removed, but still present when wires are touched together without being on alternator. The wires go to the ignition switch, and the battery. I took apart the ignition switch and cleaned, no luck. I have full wiring diagrams and have traced wires to no avail, everything I check has no resistance. I know there is a short to ground, I know that it affects many cicuits (it started with the door jamb switch). The brake lights , the headlights,the cruise control switch, the radio, the dimmer switch, and the alternator is affected. I am very capable at tracing wires/ fixing shorts, but I am stumped. Any suggestions?

I pulled every fuse out already and had ecm 1, and 2, radio , acc, ignition, and there was one or two others that would make the light go dimmer when removed. So I know it has to be a dead short to ground. I am am just stumped as far rreally where to start as it affects so many cicuits. I have opened and cleaned and tested most of the switches in the cicuits that produced a dimmer light when fused was removed. The only was to get the light out is to remove the radio and disconnect the wires from each other that go to the alternator. This truck has no AC just a dummy pulley, no aftermarket add ons, its stock. It seems as though every time I think I have it figured out it affects another circuit. I have tried all the tricks I know off including using a short finder (dont buy one of these you can make it for like 10 bucks) and evn that doesnt seem to be working. Then again I might not know how to use it properly. AWWWWW lol

This is where it gets hair pulling, no fuses are blowing. I thought alright the only thing left is the starter so I took it out still a dead short. It is affecting so many circuits that in short of replacing the entire wiring harness I couldnt go wire by wire because of the mass chaos. I did try to start cutting grounds and going straight to chassis, but after doing the 3rd one and still having the short I didnt see the point of goint on. Is it possible to have the ignition siwtch short out internally? I took it apart by unbeding the tabs, cleaned all the contact points, and examined it but it looked good to me. I took apart the headlight and dimmer switch, the mulit function switch in the steering column as well with the same treatment.

Just for shits and grins and the fact that its only 13 bucks I a, going to buy a new ignition switch. WHen I turn the switch to the off position the short is not there, when it is in run it is and only there. If I disconnect the ignition switch there is no short untill I turn on the headlights, step on the brake pedal or turn on the hazards. I know I havent been perfectly clear as far as the order of things but have limited space to work with so I apoligize. I know its a dead short to ground, it has to be to affact som many systems. The engine groun to the block and to the firewall show no resistance I.e. good. The grounds going to individaul components have very high resistance which to me makes no sense. I am trying to find the main gound splice, but is hard without removing the dash.

Answer 1

i own a repair shop ,and you are very knowledgeable on this subject ,i have ran across the same problem before on a 96 model try doing this,try pulling the fuses one by one with the test light hooked up,and it showing a short,also look closely at the air conditioner relay,these will stick on even if the key is off,the one i had ,did have a bad air relay on it,but i found it by pulling each fuse one at a time until the test light went off,that's all i can tell you,you know about as much about that one as i do,good luck with it.

Answer 2

If you can't follow the wires inch by inch and check for short, I would say replace them and bypass the old wires...many times a short is in the harness or some obscure location and short of replacing the harness, just replace the wires with labelling and run them through the same conduit or attached to it with tiestraps. You could also put a circuit breaker or fuse of the correct amp rating in the wires to see if it blows the breaker/fuse and maybe pin down which wire has the short..then trace that wire to short. Check for pinch points or wires run under bolt heads or tight wires against metal contact points...anything where the wires may have the insulation worn off. Check neutral safety switch also.

Answer 3

Try disconecting the ignition switch and see if you still have the short if you don't then that is probably it. Also try checking the continuity of the wires at the swich to each other if they have continuity they are shorting together.