4 replies to this topic

[ImagoX]

I'm needing to use a switched power source running off the main fuse box for the trigger voltage for my driving light relay. I want the driving lights to go out if I accidentally leave them on when I turn off the car (I'll hook up the headlamps in a similar fashion when I upgrade them to halogens).

I know that on the 4-fuse box, the first (top) and third fuse are connected to the ignition switch, but which side of the box should I connect my switched wire to, in order to properly complete my circuit? I ASSUME (dangerous word there, I know) that the right side of the box (as you're looking at it standing in front of the car - in other words the PASSENGER side on a RHD car) is the switched side, seeing as how there's a brown, unfused wire leading to the #2 fuse - I know that plain brown is generally the color code for unfused direct-to-battery positive.

Is this correct? Also, if I have an extra terminal on the box, above the wire that's clipped there, can I also clip to that free terminal? They look like they both run from the fused connection, but it's difficult to be 100% sure.

Last, can anyone recommend a convenient ground connection near the fuse box? I've located my relay a few inches form the box, but the relay needs a ground connection for the trigger voltage to function properly. There are some wires clipped to the screw securing the fuse box to the firewall - is this a suitable ground location? There's nothing about this being a ground in my Haynes book...

Thanks a million as always!

[stealth05]

personally mate i would go off the incoming side to the fusebox and fit my own in line fuse that way you reduce load on the fuse in the fusebox thet may be up to max already

[Ethel]

If it's just a relay it won't add much load to the circuit but it does beg the question what are the spots tapped in to?

If the wires are black 'n screwed to the body they're earths.

[ImagoX]

If it's just a relay it won't add much load to the circuit but it does beg the question what are the spots tapped in to?

If the wires are black 'n screwed to the body they're earths.

Exactly - this is just for the TRIGGER VOLTAGE for the relay... the main power for the spots is independently fused and runs from the direct-to-battery lead on the starter solenoid (based on numerous tips from here). You must never, never, EVER connect anything electrical in your car without a fuse!!

FYI in case anyone doesn't know - a relay switches open or closed when a small amount of DC current is sent across it, completing a SECOND, independent circuit (containing much more current). In this way, the actual switch in the cabin only has to handle a tiny amount of current compared to the much more robust circuit powering the actual lamps. If I use a switched power supply for the trigger voltage (usually less than .5A), then there's no way that I can leave the driving lamps on because the moment I take out the key the trigger voltage that's holding the relay closed will disappear, breaking that connection.

I just want to hook to the correct side of the fuse box so that I get a bit more protection in the form of that glass fuse. With such a small amount of current present in the wire for the trugger voltage I probably don't NEED to fuse that connection, but I'm obsessive that way. And hey, nothing;s ever caught fire in my car, or even came close to smoldering, so I guess anal-retentiveness pays off (at least when it comes to wiring).

[ImagoX]

I just want to hook to the correct side of the fuse box so that I get a bit more protection in the form of that glass fuse. With such a small amount of current present in the wire for the trugger voltage I probably don't NEED to fuse that connection, but I'm obsessive that way. And hey, nothing;s ever caught fire in my car, or even came close to smoldering, so I guess anal-retentiveness pays off (at least when it comes to wiring).

I hear from another forum, that the right side of the fuse box (assuming you're standing in front of the car - the passenger side on a RHD vehicle) gets the protection of the fuse. Just an FYI... I'll use the screw securing the fuse box to the sheet metal firewall as the trigger voltage ground. Thanks!