Master Switch

911_guy · Post by **911_guy** » Wed Jan 22, 2003 10:57 pm

Thinking of putting a master switch in my Jeep for my radios and scanner. Anybody done it? Ideas, suggestions? Yes? No?

nmfire10 · Post by **nmfire10** » Thu Jan 23, 2003 6:53 am

You can either get a "big switch" similar to what is used on fire apparatus or you can use a continuious duty high current relay. I personally like the relay idea best. You can use a small Double through center off switch for it. The center would obviously be off, up would be on constant, and down would be on & off with the ignition.

apco25 · Post by **apco25** » Thu Jan 23, 2003 8:21 am

I use Bosch 75amp relay power from ignition and a TSD 200amp circuit breaker. You can manual set the break to off and use it as the master switch. Works great when you have to jump start another vehicle, completely isolates your radios too.

gws · Post by **gws** » Thu Jan 23, 2003 11:19 am

I had in my last vehicle and will be installing in the new one soon a Valet switch. A key switch that will switch power off to all the radio gear.
The switch I have will be select power follows ignition, power always on or power is always off (valet) mode.

Since I already have the power control relay, the valet switch was easy to add.

jim · Post by **jim** » Thu Jan 23, 2003 2:32 pm

75 amp Bosch works great when switched by the key, but don't protect a 75 amp circuit with a 200A breaker.

apco25 · Post by **apco25** » Fri Jan 24, 2003 2:02 pm

of course not. The breaker is for the combined load of everything. Each device is still fused at the appropriate rating , same with the relay.

ptemplin · Post by **ptemplin** » Fri Jan 24, 2003 7:35 pm

And don't use a breaker as an on-off switch, either. Unfortunately, breakers are almost always affected by use. Some tend to wear in a way that they trip on a lower than normal load (safe, but frustrating); others wear in a way that they trip on a higher than normal load (not safe).

As always, use the right tool for the job. Switches are sold as switches for a reason...

kens · Post by **kens** » Sun Jan 26, 2003 7:00 pm

I like to use a timer (either Chargeguard or Copeland) set to a couple of hours. I often need the radios to stay on after I shut the motor off but it is usually less that 2 hrs.
The smaller one by Copeland needs to operate with a relay, the others will handle up to 30 amps on their own. In some vehicles (some Ford trucks) the Charguard will have a slight delay in turnon. This is due to it is voltage operated and will close only when charging voltage reaches about 13.5v.

johnnybelks · Post by **johnnybelks** » Fri Mar 21, 2003 9:47 pm

If you do install a Bosch 75a relay by the battery (properly fused, of course), and run it to a master key switch, can you leave that key switch on all the time?

I plan on doing the same thing, but I would only turn off the key switch when I was going to let somebody else drive my car, or leave it parked for more than a few days. (otherwise leave it on most of the time)

I know the Bosch relays are good, but can you leave them on all/most of the time?

jim · Post by **jim** » Sat Mar 22, 2003 7:53 pm

The 75A Bosch has a 100% duty cycle and can be left on at all times- just make sure your battery is good if it will sit for several days.

Master Switch

Master Switch

leaving relays on