headlamp wire rating

[Griffdowg]

Wiring spots has been covered lots i know. I have just bought a pair of PIAA driving lights that are 120w ea. Im going to wire each one to a seperate 30a relay and then run them to 1 switch no problem. the feed was going to come from the full beam circuit rather than a seperate feed from the batts. but then i though, can the existing wiring handle another 240w of lighting power? and then i suppose i will have to install a higher rated fuse.

while im here, what are the advantages of the fused relays anyway? i dont understand them

once again, cheers folks!

G

 

[The Mad Hat Man]

well Griff.
Headlights are usually rated at 65watts - thats 2*65/12 Amps = 11Amps. Do yu think it will cope with an extra 20Amps? even allowing for a safety margin - unlikely and if it does fail, you will loose spots and headlights - not a good idea.
Fused relays just mean yu dont need a seperate fuse to wire in to the circuit.
Take a seperate feed from the battery for the spots. If yu wish to take the trigger from the headlight feed, then that is no problem. It will mean yu cannot switch on the spots unless the headlights are on though.

 

[Trewey]

wot Daft says.

 

[Griffdowg]

well Griff.
Headlights are usually rated at 65watts - thats 2*65/12 Amps = 11Amps. Do yu think it will cope with an extra 20Amps? even allowing for a safety margin - unlikely and if it does fail, you will loose spots and headlights - not a good idea.
Fused relays just mean yu dont need a seperate fuse to wire in to the circuit.
Take a seperate feed from the battery for the spots. If yu wish to take the trigger from the headlight feed, then that is no problem. It will mean yu cannot switch on the spots unless the headlights are on though.

thats what i thought. just asking because people say you USUALLY can for spots but presume this is for 2x 55w ones = an additional 10amps or so.

so if i use 2 fused relays i dont have to have an in-line one close to the battery? this seems easier

got it sorted, ordering from VWP now fitting next weekend.

G

 

[Beast o Bodmin]

wire in the spots individually each with relays with a remote power from main beam ALSO have a seperate switched relay from the battery that is on the dash and powers the main beam link.Place one way diodes in place in each remote feed.this will mean you can use bunnies without lights on as well.

 

[Trewey]

try to keep the fuse reasonably close to the battery - the wire between the battery and the fuse is unprotected and should therefore be kept short.
personally, I'd fit a fuse in the battery box and the relays on the inner wing, with just a short wire to pick up on the high-beam line.

 

[Griffdowg]

wire in the spots individually each with relays with a remote power from main beam ALSO have a seperate switched relay from the battery that is on the dash and powers the main beam link.Place one way diodes in place in each remote feed.this will mean you can use bunnies without lights on as well.

was just going to run the lamps seperately to their own 30amp fused relays using 20amp wire then running 5amp wire to the carling switch from the relays. feed and earth will be taken to the batt using either 40amp wire or 2 20's. fuses will be 15amp. all the wires will be held in loom tape and secured against the elements.

sound ok?

G

 

[Griffdowg]

try to keep the fuse reasonably close to the battery - the wire between the battery and the fuse is unprotected and should therefore be kept short.
personally, I'd fit a fuse in the battery box and the relays on the inner wing, with just a short wire to pick up on the high-beam line.

ok, i will forget fused relays, as i wanted them under the bonnet, but thats only half way. im also going to forget the hi-beam line switch/feed as i dont know where i would wire this to. so just going to run it as a seperate system. not going to use them unless its dark anyway! so i will certainly have my normal lights on before powering these bad boys up! looking forward to using them now

G

 

[The Mad Hat Man]

earth wires do not need to go back to the battery, they can be earthed to the body locally.

 

[Griffdowg]

earth wires do not need to go back to the battery, they can be earthed to the body locally.

that was my original thought, but i read that the original PIAA loom allows the earth back to the batt. not wanting to sound stupid, but its it an advantage to have the "power" going back to the batt rather than lost into the chassis?

or am i talking negligable bollix? uke:

G

 

[Trewey]

that was my original thought, but i read that the original PIAA loom allows the earth back to the batt. not wanting to sound stupid, but its it an advantage to have the "power" going back to the batt rather than lost into the chassis?

or am i talking negligable bollix? uke:

G

negligible bollix

 

[The Mad Hat Man]

Wot Trewy says. I spose it stops the need to drill holes into the bodywork, but it does mean loads of wires back to the battery.

 

[Griffdowg]

Thanks gents

G

 

[heggars]

the resistance would be lower and lower the current slightly "very very slightly" but as you said there would be so many bloody wires, it wouldn't be a great idea.

Saying that though you would never have a bad earth problem.