Back-up Lights Current Draw

[Jeff10]

Hi,

I've done some searching for the current draw of backup lights for a 1971 Bronco.

I'm running power from a different source, so I'd like to make sure it's protected. I looked at the schematic for the original configuration and it looks like that circuit is fused for 14 amps. I'd like to keep the fuse rating as low as necessary.

Thanks for your help.

Jeff

 

[Viperwolf1]

That original fuse is also protecting the W/S washer, turn signal and radio circuits. A 5 amp fuse is plenty for stock backup lights.

 

[Broncobowsher]

Quick check shows an 1156 bulb to draw 19-27 watts depending on brand. At 12.8V that could be upwards of 4.2A or so. A 5A fuse is the smallest that should work. If the wiring can handle it (and it should be) a 7.5 or 10A fuse would be better. Fuses should be based on the lowest current limiting factor in the system, not the actual load placed on the system. If the switch and wiring can take a higher amperage the system will be more reliable (less chance of blowing a fuse that is borderline capable)

 

[Jeff10]

Hi Guys,

Thanks for the feedback.

Jeff 6

 

[Steve83]

...the current draw of backup lights for a 1971 Bronco.

It's the sum of all the backup bulbs' draws at your alternator's peak output (usually ~2000RPM just after cranking; usually ~14.5VDC). So it depends on what bulbs you have installed. If they're common incandescent, look them up on this chart:



If they're LED, measure them with a digital multimeter in the 2A range.

I'd like to keep the fuse rating as low as necessary.

That's the correct goal, but it's safe to fuse up to the WIRE'S capacity, regardless of the expected load. If the load is higher than the wire (meaning you designed the circuit wrong), the fuse will protect the wire & blow before the load peaks, which is safe. If the load is less than the wire, everything will work safely. Either way: choose the fuse for the WIRE. But choose the wire for the load.

 

[RT]

When I replaced the neutral safety switch I looked inside the old one. the contacts looked pretty burnt.
I wired up a relay for the backup lights as I had plans to use extra lights. This way the safety switch only has to handle the load of the relay.

Overkill maybe, but now I can do what I want with the lights. If I ever get around to it,,,, hah!

 

[Jeff10]

Hey Everyone,

Thanks for all the great feedback.

The Bronco didn't have the back-up lights wired when I purchased it. I installed the switch in the T18 and wired from a constant 12 volt source. The bulbs are the stock bulbs in tail lights. I should have made that clear in the original post.

I agree with the comment about the relay. This alternator upgrade has resulted in quite a few wiring changes in the engine compartment. I still need to make more changes; but, I'm hoping to get things wrapped up by next week for a trip to Moab, so cleaning up the wiring even more may need to wait until we get back.

Thanks everyone for all the input.

Take Care,

Jeff

 

[DirtDonk]

Why finish now Jeff, when you can wait until the night before heading out to Utah to finish things up!!!!!!
You know... Like any EB trip!

Seems like you've had your share of finishing-up-in-Moab before if I'm not mistaken. Feel kind of strange getting it ready ahead of time.

Have a great trip!

Paul

 

[Jeff10]

Hi Paul,

Why finish now Jeff, when you can wait until the night before heading out to Utah to finish things up!!!!!!
You know... Like any EB trip!

Seems like you've had your share of finishing-up-in-Moab before if I'm not mistaken. Feel kind of strange getting it ready ahead of time.

Have a great trip!

Paul

What you said would be funny if it weren't so true.

I would probably be trying to do too much on the Bronco all the way up until the time we leave except for the fact that I have a work project that will be doing that... no time for the Bronco to get in the way.

There's always so much that I want to do to the Bronco and other things get in the way. Besides, it's more relaxing working on the Bronco in Moab! All of the electrical is working and it's driving, so getting it on the trailer for the trip won't be an issue.

Thanks for writing.

Jeff

 

[DirtDonk]

This still reminds me of the old show where the guy was out on the running boards servicing the car while it was being driven down the road.
I forget if it was "Believe it or Not" or "You Asked for It", but I think of it every time one of us has to work on their rig right up to the deadline.

Have fun in Moab for sure. Relaxing is good, whether it's because working on the rig is more casual, or it's so broken and you can't fix it there that you have to just sit around and enjoy the other side of life for awhile.

Paul