Multiple accessories off ignition switch

[noodle]

Hi All.

Just about to get my new truck and after owning my previous 4x4 complete with a birds nest of wires throughout the
cab I want to make sure this one is done neatly & safely.

One query I have is when wiring multiple accessories off an existing ignition wire (for a signal to switches / relays) is it necessary to upgrade the the wire itself or is the draw so small it is insignificant.

To give you an idea of the accessories :
2 compressors into relays
Gps into relay
Auxillary Power Outlet into relay
Rear Lights into relay
Driving lights into relay.

I want to limit as much as possible the amount of wires entering the cab.

Cheers

[-Scott-]

I recommend you install a "master relay" to switch "accessories" power to all your accessory relay coil circuits.

[noodle]

So would run an ignition wire to a relay "Master" and then run a cable to another relay, jack off that to another etc ?

Thanks

[-Scott-]

Pin 87 of your "Master" relay becomes your new "ignition" wire. Everything you would normally connect to "Ignition" connects to the output of the "Master" relay instead.

[chimpboy]

I agree with Scott. Also, consider what to use as your trigger wire. It's a small thing but it's good if you use a trigger that isn't live during cranking. That is if you stall the engine and need to start again, all those extra accessories switch off during the cranking.

[stuee]

I agree with Scott. Also, consider what to use as your trigger wire. It's a small thing but it's good if you use a trigger that isn't live during cranking. That is if you stall the engine and need to start again, all those extra accessories switch off during the cranking.

I've been thinking of installing a time delay circuit for this, mainly for my thermo fans. If I go to start the engine while its still hot they turn on as soon as I turn the ignition to on then die right down when I crank the engine over, so I've been thinking of installing a delay circuit of some sort that will prevent them running for 5-10 sec. Might be a useful feature to incorporate into this master relay circuit.

[Dooley]

I recommend you install a "master relay" to switch "accessories" power to all your accessory relay coil circuits.

I don't know if it's necessary with the current draw anticipated.

However I think it's a good idea more for if something shorts the ignition wire, instead of having many circuits going all over the place that could be the culprits, making it a bit of a headache to troubleshoot, it would be much easier to fault find and provides a level of isolation, plus reduces the chance of it happening as you've got far less wire that is actually directly connected to the ignition.

But that's just my 2c.

[chimpboy]

I agree with Scott. Also, consider what to use as your trigger wire. It's a small thing but it's good if you use a trigger that isn't live during cranking. That is if you stall the engine and need to start again, all those extra accessories switch off during the cranking.

I've been thinking of installing a time delay circuit for this, mainly for my thermo fans. If I go to start the engine while its still hot they turn on as soon as I turn the ignition to on then die right down when I crank the engine over, so I've been thinking of installing a delay circuit of some sort that will prevent them running for 5-10 sec. Might be a useful feature to incorporate into this master relay circuit.

My idea (not yet implemented) was a changeover relay that is hooked to the starting circuit. It would be NC to ignition power, and goes open when you crank the starter. Then use that as the power supply for your temperature switch or fan relay.

That's if you don't have a wire that is already set up with 12V at the right times (I think some cars do, for example for air con and the blower fans). Accessories usually goes off with starting, but it is also on when you don't want it to be.

It's just an idea, I haven't put it into practice yet

[krusty182]

I have read an idea that seemed to make sense to me for this tyoe of situation where you don't want accessories to have power until the engine is running. If the vehicle has an oil pressure switch which switches to negative, you can use this as the negative for your relay, so that the accessories relay coil won't get power until the engine has developed oil pressure.

Can also be used to improve a basic dual battery set-up using a cheap "solenoid" type relay, to delay connecting the two batteries until the engine is running.