1 reply to this topic

[woodsy483]

Does anyone know what kind of fuse should be fitted in the supply line to the coil of a 12v relay (pin 85).

The relay has a built in fuse on the load side (pin 30) but I have know idea what cable and fuse rating to use for the coil supply.

I was thinking of connecting pins 30 and 85 together so they have the same supply switched on from the ignition, but only the load side would be protected then by the built in fuse.

I've got some 27amp cable and a 20amp fuse in mind for the load side as it is for a facet fuel pump.

[dklawson]

Normally the coil is unfused.

However, if you are saying you will be using the output of the relay to power both the coil and an electric fuel pump, you should have a fuse rated for at least 1.5 x the total anticipated current draw BUT below the current rating of the wire you are using. A coil running continuously would draw about 4 Amps. You will have to look up the specs for your pump. The pump specs probably recommend a fuse. Add about 6 Amps to that value and you should be OK. This is a recommendation for the relay power circuit... not the trigger on pins 85, 86.

The relay trigger circuit will only draw about 100-150 mA. Fuse it if you like but as I mentioned, the normal coil power supply is unfused. A 3 Amp fuse on the trigger circuit would certainly protect the wiring and meet the relay's requirements.