High resistance on stock fog light ground wires?

[Hokie]

I added aftermarket fogs and am wiring them through my stock fog wire wiring (same wattage as stock).

I went to adjust them today: put my wrench on the mounting nut, it grounded out against the frame and blew the fog light fuse.

I check the ground circuit and and I've got really high resistance. The lights were working just fine, but the whole mounting bracket was energized

Other than running a new ground, why the heck is my stock ground loop soo friggin' high resistance?

(Oh yeah, the stock fogs worked just fine when I pulled them off)

 

[Turdle]

It sounds like your wires are crossed--and you actually have 12v+ hooked to the ground of the fog lamps-or at least one of them--

Re check the wiring-using the frame as the ground reference-

 

[Hokie]

It sounds like your wires are crossed--and you actually have 12v+ hooked to the ground of the fog lamps-or at least one of them--

Re check the wiring-using the frame as the ground reference-

Hmm, lemme try to explain this again

I unpluged the stock fog lamp wires (where they plug at the body, next to the ABS sensor plugs)

Going into the stock wiring (with my lights removed from the circuit), my voltage reads 12V and the ground reads high resistance

EDIT: wait a tick, the bulb does touch the body of the light, I may have those reversed (the wires were cut on the fog lights). Still doesn't answer why my stock ground wires see really high resistance.

 

[Turdle]

Ah--
the fog light switch has a resistor and led inside it-and completes the ground path from looking at my schematic--

 

[Hokie]

Thanks JT

I'll probe around with the meter some more. That schematic will help when I wire my fogs to come on with the parking lamps (and stay on with my high beams)

 

[Hokie]

Re-did the wiring going to the fogs (swapped wire for wire) and the case of the light isn't at 12V anymore

Still can't figure out why my ground loop resistance is so high though. I haven't changed any of the stock wiring, but the lights seem to work fine.

 

[parad1mg]

maybe the size and the length of the wire going from a 12v source going to the low beam thing that bridges it then goes to the dash panel switch then goes back out to the fog lights up front. that contibutes a lot to current resistance. or maybe some circuits just doesnt want to be fiddled with. had an instance once that i tapped something from the steering column multi-switch as a trigger and the device worked but when i put it all back and closed it up it blew a fuse and next thing i know i was getting a negative voltage reading on it. started from a simple tap then ended with rewiring one side of the column multi-switch. a definite pita. just my $0.02...
anyway, i always make a separate harness whenever i add aux lighthing.. makes everything easier while giving that quality custom work.

 

[Hokie]

maybe the size and the length of the wire going from a 12v source going to the low beam thing that bridges it then goes to the dash panel switch then goes back out to the fog lights up front. that contibutes a lot to current resistance. or maybe some circuits just doesnt want to be fiddled with. had an instance once that i tapped something from the steering column multi-switch as a trigger and the device worked but when i put it all back and closed it up it blew a fuse and next thing i know i was getting a negative voltage reading on it. started from a simple tap then ended with rewiring one side of the column multi-switch. a definite pita. just my $0.02...
anyway, i always make a separate harness whenever i add aux lighthing.. makes everything easier while giving that quality custom work.

I didn't tap/custom wire anything

I have high resistance on the stock wiring. I unplug the foglights and from that plug its stock wiring that shows high resistance...

Its wierd

 

[parad1mg]

I didn't tap/custom wire anything

I have high resistance on the stock wiring. I unplug the foglights and from that plug its stock wiring that shows high resistance...

Its wierd

>> maybe the size and the length of the wire going from a 12v source going to the low beam thing that bridges it then goes to the dash panel switch then goes back out to the fog lights up front. that contributes a lot to current resistance. <<

what i'm trying to say is that a high resistance in a wiring junction or outlet terminals like a stock fog light socket, are usually caused by a couple of things:

-poor splices anywhere in the circuit
-loose or intermittent connections anywhere in the circuit
-corroded connections anywhere in the circuit
-inadequate seating of wire in the slot connection on backwired “push-in type“ receptacles and switches.
or the most common one - The wire does not meet code standards (not heavy enough gauge for the length of the run).

this in turn can lead to both current and voltage drops. Voltage drops are not usually significant enough to cause a bulb not to light up. pair this with inefficient current draw and it will most likely produce a high resistance circuit holding up a huge load on that particular wiring then blows a fuse (if equipped with one). Or it maybe as simple as what jt said, casing getting shorted out.

on that ground loop issue, try installing earth-grounding wires or what they call hypergrounding. it helped in my case when i got a better reading when probed from different chassis ground locations. its not really that high of a priority to do this but after seeing that the grounding points connecting the -battery to the body ground to be that small i decided to do one myself.
Maybe this can help for your ground loop with a high resistance? it all varies on different cases/situation.

Well, atleast your foglights are now working.