OK here's the deal. I have a Master Disconnect Switch on the Ground side of my Battery. This is pretty much the only way it can be done at this point. I have a Console with a CB radio and Stereo as well as some charger ports and a couple other electrical things. In order to hold the Presets for the Stereo I have a relay that keeps power to the Preset power lead when the Master Disconnect is off and ground that runs directly to the Battery bypassing the Master Switch. Trouble reared its head when after getting everything installed I made what is now clearly a BIG mistake and hit the Starter button while the Master Switch was in the off position. Seams the Starter really wanted to make that run down for FISH AND CHIPS as it managed to find a Ground through the Stereo and the 18ga ground wire in the console. Well the Magic Smoke came right out of that little wire and thats that. Any idea how to retain the Ground side Master disconnect and still be able to power the presets in the Stereo. And yes I know that if I never touch the starter button with the Master Switch off I have no problem I also know thats not likely. And at the cost of a Stereo and a bunch of work to fix the oops I would like to avoid it.
why do you need the disconnect to be on the Ground side? actually, why do you need a master disconnect that isn't really a master disconnect?
Its more about the fact that the Master Disconnect IS on the Ground side. That's the way we do it on the Dump Trucks at work so I did it that way on my 48 Willys. As well as being physically better placed. it puts it in a place easy to reach from outside the hood without being visible unless your up under the Fender. Why do Drag racing cars have Master Switches? TO SHUT THE POWER OFF IN CASE OF AN ACCIDENT or Electrical fire. As this Hot Rod is a 48 Willys Jeep it can get into all sorts of trouble where being able to shut the poser off would be a good thing. Obviously when I wired it up I had no thought the Starter could find a ground through the Stereo. Or I would have tried to figure something else out. Which is what I am here asking help with. To figure that out.
Presets and memory for your radio take diddly squat out of the battery !! Why do you have a relay ? have your radio and CB go to a chassis ground and power off the battery direct with a 5 amp or less fuse!!
yeah, I have one on my Barracuda. It shuts off ALL the power when needed, as well as shutting off the engine. I don't have one on my Chevy II, which has done a lot more racing. It's allowed to not have one, because the battery is still up front, and it only techs to 10.0 ET. You are trying to do something else....and I don't really understand all the reasoning behind what you're trying to do. I do understand that you want to be able to shut off all power if needed in an emergency, I think that's a fine idea. But you also seem to want to use it as a regular on/off switch for the battery...for most circuits...and I don't understand why you seem to think that it should be on the ground side. That does not make any sense to me. I can see it on an industrial vehicle that doesn't need a radio, etc. But on a street car, you should make the electrical system robust enough that you don't feel the need to disconnect power to it all the time. Yes, I've had a few cars that I didn't feel comfortable leaving the battery connected when I wasn't around, so I understand that, as well. bottom line: either put the disconnect on the hot side, or don't use it unless you really need to--and in that case, don't have anything bypassing it, like a stupid radio memory wire.
Hmmmm. If I interpret this correctly, the relay controls 12vdc+ to the preset memory lead for your stereo. You also have (had) a 18gauge wire running from a ground in your console, directly to the battery negative. If I'm correct, the direct ground wire is part of the problem. The starter circuit found a ground from the block, through the body, then the stereo, and on through that 18 gauge wire, because the primary ground through the disconnect was open. There was no protection for the stereo at all, on the ground side. The relay-controlled power lead for the presets probably is fused, but it doesn't influence the start circuit at all. (Assuming my thought process is correct.) The best I can suggest is to put a 2-3 amp fuse, no more than 5, in the new 18 gauge ground wire for that console. In this manner, you'll still have a functioning ground, and will have some modicum of protection for whatever is mounted in the console, as long as it doesn't draw more than the fuse's rate. I can not guarantee that a similar accident won't destroy your stereo again, but at least the current draw through the ground will be limited to the fuse's rating. If you could somehow isolate that console and equipment from the rest of the chassis ground, and run a dedicated, fused ground wire for it, then the start circuit would have no ground path that way, and you would be safe, but that's easier said than done. BTW; Kudos on a quite sanitary electrical system. Nice use of a bus bar on the positive side, and well-routed wires. (At least, what we can see in that pic.) Roger
Now, from a practical sense, where do you think a fire is going to happen in that vehicle? I suspect the engine bay, which will allow flames to spread out under the fenders, greatly reducing, or completely eliminating your access to the disconnect. Just my 2 cents, and it could be wrong.....Roger
NOW Roger You have something there that actually helps. If I fuse the Stereo ground then the fuse will blow long before the amperage the starter was drawing through the little wire can burn it up. I could even use a circuit breaker so it could just be reset. I'm seriously going to look into this as a way to easily fix my problem. I can stand in front of the rig and reach the Master switch. Fire would have to reach down clear under the frame to be able to then come up on the outside of the Inner fender. Should that be the case no electrical switch is going to do squat. The only hope would be the two fire extinguishers I carry being shot through the radiator or up under the grill.
Nice job detailing the wiring and engine compartment. Where did you find the triple connectors for the battery? Wish I could help you but I'm an electrically challenged individual...............
[QUOTE="ekimneirbo, post: 14147430, member: 298431"Where did you find the triple connectors for the battery? [/QUOTE] With the threaded post a 1/8” thick copper bar works great.
(I'm seriously going to look into this as a way to easily fix my problem.) Yes, just fuse the wire to cb and radio. If you try to start it with the disconnect off it will just blow the fuse. Keep the disconnect on the negative battery post.
As the battey has Stud type posts it was easy to as said by jimmy six to just use some 1/8" thick Copper bar stock and some 3/8" Brass bolts and nuts to make the multiple connections. A tip if your hardware store doesn't have the Brass nuts look in the plumbing supplies they are used for Toilets.
Fair enough. As I said, though......I can't guarantee that your stereo won't still get damaged. If it's sensitive enough, you're still going to try to pull 200 starting amps through that ground wire for 1/100th of a second. There may still be an issue with that fuse or breaker, though. If you have a 5 amp breaker in there, and your stereo pulls 8 amps at high volume, you're going to find yourself singing to a silent radio when it's the most embarassing..............in traffic at a stop light, while you're trying to listen to what I call "power music". (For me, that's 80's bands like Def Leppard and Aerosmith.) Roger
There is good chance (certainty) that the fuse will not protect the stereo circuitry before it blows.
The Jalopy Journal
