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humphshumphs
19th January 2015, 18:45
Hi All,

Daft question really, I am about to add an addition 12volt socket to the cubby hole and want it only to be live when the ignition is on.

I've done plenty of wiring in the past (made wiring looms for kit cars) so no issues there, but was just thinking about do I put the fuse before the relay or after it?

It will be placed in the supply feed, but for the life of me I cannot remember the correct side of the relay to place it :eek:
fraz59
19th January 2015, 19:46
no expert but I would think if the supply to the relay had a blown fuse, then the relay would not function...so just a guess at fuse on relay supply
COLVERT
19th January 2015, 21:15
After the relay so that when the relay switches on, your connection will become live.

However don't overload the relay. Also see if you need to upgrade the relay supply fuse.
Jakg
19th January 2015, 21:20
Obviously it depends where your actually getting your supply from - but surely the unfused part of the cable should be as short as possible?

Otherwise, what if (somehow!) the relay fails and shortcircuits?

EDIT - I have 2 main sources of extra power in my car - one is a ginormous power cable for my ICE setup, fused about 6 inches from the battery and then fused again as the cable is split and goes down in size, and one is a slightly smaller (but still large) power cable used for all the extra electrics (inc an extra 12v socket) which is fused about 2 inches from the battery. Therefore this is fused well before any relay.

EDIT2 - I pulled a relay off my car yesterday where the power input pin had corroded right through and so the cable was flapping around free! Thank goodness everything else was insulated, and of course fused...
humphshumphs
20th January 2015, 05:53
Thanks for the replies people. :bowdown:

I thought after the relay was probably the correct place.

I shall be using a 40amp relay, but only ever pulling probably a max of 5amps.

The feed is a large cable from the battery to the boot that I have taken a 'spur' off (this cable is fused probably 3" or 4" from the battery with a 60amp fuse so covered there as well.