I have the battery in the trunk and want to install a shut off switch to make it all legal. If I run a #6 wire from the alternator to the switch what do I do with the other wires? I looked at the wiring diagram from MAD enterprises and I am now more confused than before. Somebody help me please.
You may be able to get by with the 6 gauge wire, but when I put the battery in the trunk on my I car I believe I used 4 gauge. The problem is the voltage drop you experience is greater the longer the battery cables are. The larger cables allow you to move more amps. Try the 6 gauge and see if it works ok. OK, If you want the switch to shut off the engine while it's running this is how it needs to be hooked up. With the battery in the trunk, connect the negative terminal to the frame( make sure you clean the frame and have a very solid connection). You also need to connect a heavy gauge wire (a regular battery cable will work here) in the engine compartment from the frame to the engine block. Next install the battery disconect switch so that the terminals are a safe distance from any thing metal on your car. Connect the positive battery terminal to either one of the terminals on the disconnect switch. Connect the other terminal of the disconnect switch to the the heavy gauge wire that connects to the big lug on the starter solenoid. (For external voltage regulator) Now you must disconnect the wire that comes out the the voltage regulator that supplies the charging voltage for the battery from the alternator. This wire must now connect to the positive battery terminal in the trunk (use a 10 or 8 gauge wire). (For internal voltage regulator) There should be only one wire comming out of the alternator. Connect this wire to the positive side of the battery and to nothing else (use a 10 or 8 gauge wire). Things to be aware of. If you set up your disconnect switch this way when you shut off the switch the engine and all electric items will stop working. Every souce of power will be dead in the engine compartment except for the wire that connects from the voltage regulator/alternator to the battery. If you only disconnect the main battery cable and don't move the wire that charges the battery to the other side of the switch the car will continue to run when you shut off the switch (the altrenator will continue to supply voltage to everything that needs it as long as the engine is running). Hope this helps.
Thanks for the help Kelly. I have an internal voltage regulator. Heres a question. Does the wire that is now going to the alternator get disconnected? In other words, is the ONLY wire going to the alternator just from the shut off switch, or do I now have 2 wires going to the back of the alternator? You probably made this very obvious, but I still need to ask. o No:
The only wire coming out of your alternator should be connected to the positive battery terminal, or the shut off switch terminal that connects to the positive battery terminal.
OK, I tried wiring my car but it won't shut off unless I disconnect the 2 wires on the side of the alternator too. If those are disconnected then the alternator doesn't charge o No: The only way I can get the car to die with the alternator charging is to splice into the coil wire... but that can't be too good can it. The only wire to the back of the alternator comes directly from the battery now. I also tried it from the shut off switch. Any thoughts here would be appreciated?
If your car has an internal voltage regulator it should only have one wire going to or coming from the alternator. I'm not sure what the 2 wires on the side of the alternator are for. Can you take a pic of the alternator and firewall so I can get a look at it? If you have an external voltage regulator things are a little different. The idea is that you need to have the battery and the charging system on one side of the disconnect switch and everything else in the electrical system on the other side.
Just wanted to get my name on this post so that I don't lose it :Brow: (and to let you know I am following it). If I have any specific questions once I try some of this I will let you know. K PS - my car has the battery in the trunk with a cutoff switch but it doesn't kill the motor.
Rob, What year is your car, and did you convert it to an internal voltage regulator. If not it is most likely an external voltage regulator. Here are some pics from my 68. The red arrow is the voltage regulator on the firewall. I converted my 72 to an internal regulator. I used a 1 wire alternator that I got from Jegs, it was an east coast auto electric brand. It only had one wire that came out of it. Let me know which voltage regulator you have.
your alternator has more than just 1 wire coming out of it but they are the feild wires that provide the same fuction as the ones that run to the external regulator. A true 1-wire alternator will only have one wire coming out of it but relys on the internal stuff for its voltage sensing. While this doesn't help the problem, something I'm likely to face aswell, it might help clear up some of the confustion. The GM internally regulated stuff is a 3-wire alternator just with an onboard regulator not a firewall mounted one. I'd like to know how to fix this as I also have a trunk mounted battery and will need to install a switch.
Yep - me too. My alternator has three wires coming out of the plug (where the blue arrow is shown) in addition to the one big red wire (green arrow). I'm going to get the motor back in the car and get it running before I try any of this. K
OK, here we go. On General Motors 1973-1987 with Delcotron alternators. This is an internal voltage regulator alternator. It has 3 wires that attach to it. The big red one on the back and two smaller ones on the side. Here is what happens. The smallest wire (usually brown) is energized by the ignition switch. It energizes the field around the stator so that the alternator will produce current. When you hit the disconnect switch current flows backward through this wire (the smallest one) through the ingnition switch and powers the fuse box. This is backward from how current usually flows. To stop this from happening you need to install a diode in between the alternator and where it connects to the ignition switch. This is easily done at the back of the alternator. The diode only allows current to flow in one direction. It looks like a black resistor with one white ring around one end. You want the end with the ring on it to point toward the direction you want the current to flow, so it would point toward the alternator. You wont find the diode at Auto Zone. Look for it at Radio Shack or an electronics supply store.
Wow thanks for all the replies! My car was converted to an internal regulator, but I think none of that matters now since it appears as though I can get a diode and get this thing done!!! Thanks for all the help and sorry I didn't respond sooner.
Any tips as what to look for as far as ratings for the diode. Things like voltage (12v I know) but what about any kind of amperage flow/draw etc....
A diode is a diode is a diode. They are all the same. Unless you are talking about zener diodes, but we don't need to worry about that. Just go to Radio Shack and ask for a diode. They are tiny, and come in a pack of 10 or 15. The last time I bought some it cost me 50 cents for the pack.
Thanks Kelly. Just to clarify, are you saying that if I add this diode it will fix the "run on" problem (or do I still need to do the rewiring you mentioned in your earlier post)?
The diode alone will not fix the problem. You basically need to have all sources of power on one side of the main disconnect switch, and everything else on the other side. This includes the large red wire that comes out of the back of the alternator.
Ok, got it. Like I said earlier, I'm going to get the engine back in the car, get it running and then start making some changes. K
So no need to worry about them burning out due to the amount of current flowing through. Also what size positive cable do you run from the battery to the starter? Does it make a difference on the number of strands in the wire? On the neg side can you run from the battery to the frame with one cable and then another from the frame to the engine block or should you run a single neg cable from battery to engine block? Sorry to be asking so many questions but I'm doing the same thing to my Century.
Grounds: Battery to Frame Engine to Frame Body to Frame and/or Battery, or Engine Diode, if my understanding is correct, the diode will stop the current supply instantly, that kills the engines, no engine running no current load so no power through put build up backwards, as far as the fowards..... no idea. I melted the insulation off of a 2-ga cable to the starter from the front mounted batt on my 65 Riv. I'd go 0-ga for a starter cable from the trunk as you can never get too big, but you can certainly get too small.
The diode will be fine. The bigger the wire the better. I used 4 ga on my car. You need to use a bigger cable the longer the cable is so that you can move enough current through it. The more strands are better also. You can run one long neg cable from the battery to the engine block, but it has to move just as much current as the pos cable, so it will need to be just as big in diameter. I chose to use the frame of the car to save weight, plus you can use a regular battery cable because the two cables on either end of the frame are very short. As was mentioned earlier you should make sure to ground the chassis to the frame or block. The factory used a braided wire from the firewall to the block, but I replaced it with a larger diameter wire.
