The Stovebolt Site Forums The Shop Area The Electrical Bay Amp gauge ground

Hi guys,
I’m putting new gauges in my 48 gmc. The current owner converted the truck to 12 volt and none of the original gauges worked so I bought a refurbished 12 volt gauge cluster. When I was removing the old cluster there was a a ground from the one side of the amp gauge to the post that sercures the gauge to the dash. So my question is since going to 12 volt is that ground still needed?
Thanks

Your 48 could be a positive ground system. Don't know if you converted to alternator and etc.

The terminals on the ammeter are not grounded. So no, don't do that. It may have a "negative symbol" (-) but it's not ground.

You may actually have a volt gauge which does have a terminal to ground.
The wiring of an ammeter does not change when converting to 12V. Unless it was wrong to begin with.

"The current owner"?????? Is that not you? Do you mean previous owner?...and let's don't use the word "current" while we are discussing this

"Positive smoke check" in 3- - -2- - - -1- - - - -!
Jerry

Sorry for the typo bartamos I meant former owner. I am the current owner and the conversion was done by the former owner. Switch was made to a alternator and I’m really trying to figure out what they did. Wires are cut everywhere and I don’t know that much about wiring.

OK, no problem. Other than the gauges question, does all the rest of the 12V conversion look OK? Is it a negative ground system? Assume it runs good? Just doing new gauges?
Nice looking truck Jim.

I suggest that you get the books out and delve into how the relatively simple wiring systems in these trucks are supposed to be connected to everything. Given your example of the "grounded ammeter wire" should cause you to distrust, with extreme prejudice, anything else which the previous owner has done to this truck.
Only YOU can prevent forest fires caused by previous owners of Stovebolts.
Carl

The truck runs great, the lights work and that’s about it. It is now a negative ground system and the alternator seems to be charging the battery but I haven’t had it long enough to be sure. There are cut wires everywhere and I’m not experienced with electrical work so I’m struggling with understanding what he did and didn’t do. And Carl is right about my biggest worry which is driving down the road and my truck starts on fire. Not that I want to but would it be wise to remove all the wiring and start from scratch? Any advice would be helpful, thanks!

If you are worried about cut wires shorting-out, put cap-nuts on them.

It's hard to say if a complete rewire is necessary, Can't see what it all looks like. Remove all the cut wires. Follow them. See what they used to do. This will help with knowledge and confidence. Read the tech section here to see what should have been done during 12V conversion and see if it all was done.
1. Ballast resistor
2. VR or no VR
3. 12V bulbs
4. Voltage reducers where required
5. 12V coil

For me, a 12V conversion would include a new fuse panel. This would eliminate fire danger. I don't think you have any fire danger but fuses are really the best idea. For my trucks, which I don't drive a lot, I always take off the neg battery cable during parking at home. Not that I can't wire properly, I just can't sleep properly.

These old truck designers were not hip to fuses. Add them to everything as you go. Wiring, in general, is the same up thru and past the 70's. So study a 60-66 diagram or 67-72 diagram and see how a fuse panel is wired as well as the rest of the trucks. They just used more connectors and, as said, fuses. The foot start vs solenoid is also a difference, but the same idea.

You can, of course, start over using a kit with a prewired fuse box. That is not hard with our trucks because there are not that many wires. The kits are divided (by you) into bundles for the various "systems". Routed, cut to length and terminated. Easy.

Bundles from fuse panel.
1. Starting and running and charging

2. Gauges and gauge lights

3. Front lights/dimmer.............. turn sig if present?

4. Rear lights/stop.................. turn sig if present?

5. One-off, or switched single wires, like: horn, lighter?, radio?, dome, wiper?, heater motor and a direct hot wire or two (fusible linked)

The light switch is involved with some of 2, 3, 4, 5

The grounding portion is not included in the kits. That would be mostly the metal of the chassis, motor and body. This is very important to the job.
It is a part of wiring that never gets proper attention by beginners.

Thanks, that info really helps me. It gives me a start point and specific areas to go through. Thank you for taking the time to write that out.

You are welcome. Just a general outline. Nothing to be afraid of. Power comes in from battery to a distribution point (ammeter or fuse panel or terminal block). Some power is direct: to ignition switch, alternator and headlight switch. Those should also be "fused" by the use a of a fusible link. From the distribution point they go thru the various switches to the draw. Everything has a switch. The draw is a bulb or a motor or accessory.

If you have a turn signal switch. The turn signal bulbs and stop bulbs (filaments) are controlled by that switch and it's associated flasher. If you need help in that area, let us know.

In a real old, original system there could be almost NO fuses. This MUST be updated. An unfused example is: a direct wire to one ammeter terminal, other ammeter terminal to switches/draws. Normally a non fused shorting/overload event is an insulation melt down. Old cloth insulation does not melt, it may burn. If something sparks near gas fumes, it burns. Seldom happens. If there are no fuses, something else has got to give! Best to be safe than sorry.

Plain Jane wiring harnesses made specifically for your application are available from many vendors for less than $150 bucks or so.
It will be easier and safer to rip out all of the old wiring and installing the replacement harness. This is taking into consider your admitted lack of "experience with electrical work".
There is no need to try to learn what the last guy did wrong. His grounding of the ammeter lead is enough information for me to conclude not to trust any thing else in the system.
bartamos has given you an extensive list of items to help you along the way in terms of what to look for. (Don't let his uppity Arizona Rancher facade fool you. He knows his stuff.)

Carl
cattle flatus intermediator

Thanks Carl, as I methodically go through each numbered area as bartamos pointed out I get more confused as to what was done. I’m leaning towards starting over. Thanks for the advice