How to wire master disconnect?

How do I wire dual master disconnect switches? I want one in the car and one outside. I need to cut the alt. and the battery from either switch. Can anyone give me some insight as to whether this is possible? I have been thinking about this all day and I just can't get it sorted out.
 

Ron McCall

Supporter
Dean,

Just make sure this sytem isolates the battery completely, ie all elec. loads should go through it, including the starter load.

Here is a quick sketch of one, some people may prefer to control the relay with the ground wire though.

S
 

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Bill:
You would need to run the switches in series, and they would both need to be on to complete the circuit. I know that sounds obvious, but the point I am making is both switches need to have direct battery thru them with the cabling becoming a problem.
If you have ever been around big machine tools or some other systems they have a disconnect placed in various places to disable the machine's power remotely. This is essentially what Pantera is talking about. It allows you to use a small wire like 14ga. to operate a contactor that switches the power close to the battery. This eliminates the heavy cabling and losses associated with the run lengths. The switches are set up so that any one will disable the contactor thereby cutting the current, and the contactor can be wired close to the battery and the load, eliminating long fat cables. The drawback is the contactor requires power to stay engaged, not much, but enough to hold the solenoid in. If you you have EFI or any other system that requires power for memory you may need to run a separate power lead to bypass the disconnect and maintain your settings. The solenoid needs to be a continuous duty unit and I am sure that if left on will kill a battery overnight.
Of course if you shut it off after each drive that is not a problem. Sorry to be long winded, but one more note and that is the switching for the solenoid needs to be live at all times or it will not pull the switch in, so there is no complete disconnect with the remote system. If you do the manual switch system, and keep them close you can minimize the cabling, but it will still need to carry full load to operate the starter, so there is a minimum size you can use.
Good Luck
Phil
 
I was wondering if there is any reason that a battery disconnect could be used on the negative side of the battery instead of the positive. I am useing a manual dissconect switch and the negative side would be alot less distance for the cable to run.
 

Mike Trusty

GT40s Supporter
Lifetime Supporter
I'm using the same solinoid activated disconnect switch as Ron(Pantera1889) and it works great.

Phil: The first unit that Ron suggested from Ron Francis does NOT require a holding current when activated. It only uses current during the translation of the switch so it will not drain your battery when the battery is being bypassed. I believe the second suggestion does and I would not use it for that reason.

Besides having a switch inside and outside I went one step further and took the power for the switch off of the load side(car) which means that when either button is pushed the switch isolates the battery and can NOT be turned back on from either switch. This is a great security feature. I placed a small hidden switch that gets its power from a small wire directly from the battery that has a 3 amp fuse protecting it to reactivate the disconnect switch. When the disconnect is activated there is only about 12" of heavy gauge hot wire in the car except for the 3 amp fused wire to the hidden switch.

If you have digital injection and ignition I would suggest that you do not switch the ground. Jack Houpe can explain this better than me and Kirby Schrader can atest to the fact that you should not switch the negative with lots of electronics.
 

Jack Houpe

GT40s Supporter
I was wondering if there is any reason that a battery disconnect could be used on the negative side of the battery instead of the positive. I am useing a manual dissconect switch and the negative side would be alot less distance for the cable to run.

If you have just a distributor (non electronic) and a carburetor then you might get by with it but if you are using any electronic equipment (msd, efi, or any electronic controlled devices) then you are going to have feedback after you disconnect the ground from the car. When you remove the potential (battery) from the circuit (the car body) then all the stored voltage feeds back in a reverse direction through all the other electronic components (reverse polarity) and will cause damage to the computer and some very crazy things will start to happen.
 
Guy's

I hope no one misunderstood.

I would not control the neg. terminal of the batt.

My suggestion on some peoples preference was how the RELAY is controlled.

Some may prefer to control the relay by switching the ground instead of power. (terminals X1 & X2)

Also I am not familiar with a relay that is not either N.O. or N.C.

The relays I have used require power to either open them or close them.

The one shown in my W/D is using DC power to hold it electrically closed when its control switch is closed and powering the cars elec. sys.

It is a normally open (N.O.) relay.

Regards,
Scott
 
Just received this promo from American Autowire. It is an ad for Master Disconnects with a twist that makes it different from the others. Something to consider.

<table style="width: 440px;" width="440" border="0" cellpadding="5" cellspacing="0"><tbody><tr><td rowspan="1" colspan="1" width="100%" align="left"><table style="margin-bottom: 5px;" id="content_LETTER.BLOCK17" width="100%" border="0" cellpadding="5" cellspacing="0"><tbody><tr><td style="color: rgb(92, 120, 140); font-family: Verdana,Geneva,Arial,Helvetica,sans-serif; font-size: 10pt;" rowspan="1" colspan="2" align="left">LifeLine from American Autowire.
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The Lifeline enables users of a Master Disconnect Switch to retain a small amount of power for memory circuits common in fuel injection computers, radio presets, and clocks. The Lifeline is "self-resetting", eliminating the need to replace a fuse when the user tries to start the vehicles before first switching the Master Disconnect to ON. The Lifeline is a memory circuit retainer that will automatically reset after the electrical load is significantly reduced or if the Master Disconnect Switch has been switched to the ON position.
Find out more about the:
Lifeline
Remote Lifeline
20.jpg

</td> </tr> </tbody></table></td> </tr> <tr> <td style="background-color: rgb(255, 255, 255);" rowspan="1" colspan="1" valign="top" width="100%" align="left" bgcolor="#ffffff"> <table style="background-color: rgb(108, 133, 145); margin-bottom: 5px;" width="100%" bgcolor="#6c8591" border="0" cellpadding="0" cellspacing="0"> <tbody><tr> <td rowspan="1" colspan="1" height="1">
</td></tr> </tbody></table> <table style="margin-bottom: 5px;" id="content_LETTER.BLOCK11" width="100%" border="0" cellpadding="5" cellspacing="0"> <tbody><tr> <td style="color: rgb(92, 120, 140); font-family: Verdana,Geneva,Arial,Helvetica,sans-serif; font-size: 10pt;" rowspan="1" colspan="1" align="left"> American Autowire wishes you a happy Spring and hopes to see you at one of the many shows we will attending this
</td></tr></tbody></table></td></tr></tbody></table>

Bill
 
In the hand drawn diagram above the alternator output should be moved to the battery side of the disconnect switch or the ignition system will recieve power from the alternator when the switch is turned off and the engine will continue to run.
 

Howard Jones

Supporter
Wayne is correct. The best way to do the alternator output wire is to run it back to the positive post of the battery. Then run the 12V battery main power wire ONLY to the "off" side of the master switch. From the "on" side of the switch run a heavy wire to the main buss for the rest of the cars systems. You should also run the main starter power from the "on" side of the master switch also. This way no matter how the car is wired otherwise the master battery power off switch will in deed turn off the battery (12V) completely to the rest of the car.

As an aside. The alternator will continue to charge the battery as long as it is turning but it will not feed 12V's to the rest of the car's system such as the ignition/spark box. This is the main point in fixing a main power switch off car keeps running problem.
 
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