About 18 months ago when I installed my new radio and ran mostly new wires, I used an existing ground. Checked it, made sure it was good, hooked up the radio and no problems. It's been fine for all this time.

(side note: the people I bought the car from were hacks, they cut a whole bunch of the wires in the radio/counsel to install a slap shifter. The ground wire was part of this, not sure where it came from or where it went but I did verify that it was a ground)

Yesterday, I took the radio out and cut the ground wire to splice in another lead for a switch. I got done, neither the switch nor the radio worked. I checked everything out, turns out the ground is now bad. All I did was the wire, cut it & solder another wire to it. I cut the solder out and checked the wire only, still no ground. So somehow, between cutting the wire and putting back together, the ground stopped being a ground.

The other odd thing...as I was testing it, I hooked up a string of LED lights, the positive to the battery and the negative to this ground. When you first turned the key on, the lights would flicker for maybe 0.5 or 1 second, then go right back off. So it's like the ground was a ground for a split second and then stopped. I ended up hooking the ground to some steel behind the radio and now both my switch and radio work again, but I'm very curious as to what could have caused my problem. I'm hoping someone can help me.

The second part of my question is, after driving the car I noticed that the temperature gauge was pegged at 260 when it normally never gets above 220. I opened the hood, verified that the fan was running. I used an infrared heat gun on the radiator hoses, the upper hose was 180 and the lower was like 160 if that means anything. Just wondering if this ground issue could be affecting that gauge, too? Other gauges seem to work okay. After shutting the car off, I did hear the antifreeze gurgling back into the overflow so maybe the car was overheating though I didn't see any antifreeze or steam.

 

 

It's all about resistance and current. Your smaller ground may have been great for just the radio, which is <5 Amps in most cases, but may not have sufficient contact to carry more current. I don't know what sort of switch you hooked up, but perhaps you doubled the load on the ground (current will be a constant throughout the whole circut, just like your battery cables, both sides have to have the same capacity) and the ground did not have the capacity for both. Try cleaning it throughly at the body/frame and ensure you use clean, paint free hardware. As for the temp gauge, make sure you did not mess with any other wires, but it's now grounding out somewhere, perhaps it had something to do with whatever the switch was for?

 

The temp gauge/overheating issue was something entirely different, that has been fixed.

I agree with what you said about the ground, but when it didn't work I unhooked all of the wires & checked it from the source - still nothing. At that point, no items were hooked up - no switch, no radio. The only thing I can think of is, when I was messing with the wires I might have pulled on it too hard and dislodged it from somewhere. The people that had the car before me didn't do anything very well so it's possible the ground was loose when I began...

The only part that I don't understand is, when I turned the key on and the ground would have ground momentarily, like for just a split second. My experience has been that if it's hooked up, then it's hooked up and if not then it's not. No in between.