New driving lights switch...

[deilenberger]

hi Don......yes....those thick wires go on one end to the fuse box and the other end to the battery with the relay in between.....the lead wire that goes to the battery has a 30amp inline fuse.....the only wire that is left goes from the fuse to the switched sercuit which in my case is the maintenance port wire....I took detailed pic's of the install....once i get them over to the computer, I will do a new tread on the Centech box install (detailed)....as far as i have seen nobody has done that to the detail that is nesessary for the person that has never done anything like this before.......

OK - good deal. BTW - I'd suggest a free Photobucket account for photo hosting. It works quite well.

my question actualy was about the driving lights.....if I already have my setup with the fuse box and relay, can I just hook up the lights to the fuse box and then put a switch on the lead wire that goes from the box to the lights? or am i completely off base here and would need another relay, etc.....

thx....alex

The answer is no. The switch is not designed to take the current the driving lights draw - and without a relay you'd be passing the full current through the switch. The wires are WAY too small (would probably start heating up, which drops voltage, and could melt the insulation), and in this case - I suspect the switch contacts are also too small.

You need another relay to accomplish this. Feed the switched contacts for the relay off your fuse box, and you can power the coil (via the switch at the bars) off the fusebox also, but make it a control circuit, perhaps 1A.

[Graf]

...got it....thank you Don!
one more question......there are 20amp, 15amp, 10amp x2, and 5amp fuses......can you give me an idea what i would use for what..(aux lights = ?amp fuse, GPS = ?amp fuse, etc....)....it also seems that i could connect 2 devices (farcles) to each fuse on the Centech box for a total of 10 devices....am i wrong?

thx....alex

[deilenberger]

Ya know.. sometimes I hate this website (long message just lost..)

OK - what size fuses. For things like lights, take the rated total wattage (2 x 35W = 70W or 2 x 55W = 110W) and divide by 12.6. Add a fudge (safety factor of about 25%, or even 50% if you're confident in your wiring skills). 70W/12.6V=5.5A - so a 10A fuse would be fine. 110W/12.6V=8.7A, so a 15A would be fine.

Small current devices like a GPS use the same forumula if you can find the Watts they consume, if not - see what size fuse comes with them from the factory. You can put several small-current devices on a single fuse as long as the total doesn't exceed the fuse rating + 25%. Only problem with that is when the fuse blows - having more than one circuit to track out makes troubleshooting a bit more difficult.

You also shouldn't exceed the overall rating of the fusebox (60A for the Centech) or the main fuse you put in the power feed to the fusebox. You used a 30A fuse - that would allow for 2x55W driving lights, plus GPS, and heated gear - all running at the same time. That's about what I have on mine, and I've had no problems. (Heated gear = 160W = 12.7A, lights = 110W = 8.7A, GPS = about 0.5A, total Amps = ~ 22A. 30 Amp fuse is more than adequate.)

The rule of thumb is - you're not protecting the device (if it shorts out) - you're protecting the wiring to the device. The idea being, if the device shorts out you don't want the wiring overheating and melting down.

[Graf]

....Don, as always i am amased at the knowedge you have.....you are a real asset to this forum and the people here....thank you so much for taking time to explains all of this for me (and others)

alex...

[icecave]

And there's Murphy's Law to contend with when dealing with fuses AKA The rule of Protection: If you install a $0.50 fuse to protect a $100 component, the $100 component will blow to protect the $0.50 fuse.

While saving the wire and a potential fire due to a dead short, I would like to hope that the fuse (less extent the wire) is protecting the charging system or battery from a large current drain in the off chance I used the wrong wire gauge (too big) and have a low impedance short.

[parkec]

The switch looks GREAT!! really good.

Much better than reaching down behind my left leg to toggle my motolight switch. Frankly I've been thinking of gluing a sequin to my front fender skirt so I see if the lights were on.

gotta say I am having a real problem not calling my dealer and ordering the parts right now. I don't know why I'm resisting. I know I'm going to do it, yes I am...aaaaaggggggghhhhhhhhhh. don you are evil. The onlyy possible thing stopping me is - - wifey is down stairs

[deilenberger]

The switch looks GREAT!! really good.

Much better than reaching down behind my left leg to toggle my motolight switch. Frankly I've been thinking of gluing a sequin to my front fender skirt so I see if the lights were on.

gotta say I am having a real problem not calling my dealer and ordering the parts right now. I don't know why I'm resisting. I know I'm going to do it, yes I am...aaaaaggggggghhhhhhhhhh. don you are evil. The onlyy possible thing stopping me is - - wifey is down stairs

You can order from Max BMW on-line..