UrbanFire

I bought a new 50" LED light bar, it is rated at 300 watts, my problem is that the 40 amp relay I put in is getting hot, I am running directly from battery and using 12 gauge wire with fuse, and using 12 gauge for the whole set up, my switch is rated for 25 amps, I've tried 15,20 and 30 amp fuses and it still gets hot, the light bar did not come with a harness, and has 14 gauge wires coming out.

Any suggestions?

F150Torqued

You probably don't have a problem. Some pretty good heat from the coil of a 40 Amp relay would be normal. You can measure the current in the relay coil circuit. It might be 2 amps in a heavy duty relay (which would generate 24 watts in the small space of the coil - that would feel damn hot.

Frankly, I don't think you need that heavy a relay, although it should be rated for "continuous duty". The light bar specs should indicate how many amps it draws, and your relay contacts need to be rated about double that to be reliable.

You noted the light bar is "rated" at 300 watts. BUT, that doesn't mean it is truly that heavy a load on the battery. In fact, you state you tried a 15 amp fuse (presumably in the battery > relay contacts > light bar circuit). That 15 amp fuse would have blown at 180 Watts draw. (12v X 15a). So I don't believe the heat is coming from the relay contacts. You can measure for voltage drop across the closed contacts while the light bar is running. If there is no voltage drop, no heat (or watts) is being generated in the contacts.

scopes1980

I agree. It is normal for the relay to get hot. I would stick with the 30 amp fuse because you light could pull around 24 amps