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Thread: electrical resistance problem, can you help? |
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Thread Status: Active Total posts in this thread: 7
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acpartsman
Veteran Cruncher Martinsville VA, USA Joined: May 6, 2007 Post Count: 943 Status: Offline Project Badges: 
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I need to simulate the presence of 2 28watt 12v lights (automotive #3157) I need the car to think they're there even though they are not. I checked the net and found a calculator that said I need a 2.57watt resistor. Is this right? I don't want to burn anything up. This resistor will be powered anytime the brakes are applied and/or the turn signals are used.
----------------------------------------Also, how hot are these resistors likely to get? Do I need to mount them on the underside of the car, outside of the body? So you can further understand what I'm doing: The turn signal flasher looks for the presence of 3 3157 bulbs (1 front, 2 rear) with this load the lights blink at the proper rate. Any less load and the flasher thinks there is a light out and it goes into a fast mode to indicate a light out. Due to some customizing, I'm separating the brake lights from the turn signals and therefore need the flasher to think the 2 rear bulbs are there when they're not. Can this be done practically or do I just need to have 4 lights lying in the trunk? Any help you can provide will be appreciated. Thank you and have a beary good day.
One drop raises the sea.
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littlepeaks
Veteran Cruncher USA Joined: Apr 28, 2007 Post Count: 748 Status: Offline Project Badges: 
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Unless I'm missing something, that just doesn't make sense. If you dissipate 56 watts, you would need a 56 watt resistor. Besides, you can't just buy a resistor by the watts -- you need to specify the resistance and then get a resistor with that resistance and a greater wattage than you need. Yes, it would get very hot.
I calculated you would need a value of 4.66 ohms for the resistor. It would be very difficult to buy a 4.66 ohm resistor at, say 70 watts. Unless I'm totally wrong, I'd just use the lights, but there must be another option. Generally low resistance resistors are of the wire-wound type. |
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acpartsman
Veteran Cruncher Martinsville VA, USA Joined: May 6, 2007 Post Count: 943 Status: Offline Project Badges:
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This is so far over my head. The calculator I found on the net also said 4.66 ohm but that's the same calculator that said I'd need a 2.57 watt resistor.
----------------------------------------I was hoping there would be an electrical engineer on the boards that could explain it to me. Thanks and have a great day.
One drop raises the sea.
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Former Member
Cruncher Joined: May 22, 2018 Post Count: 0 Status: Offline |
How about replacing the flasher with an electronic one?
People pulling travel trailers end up adding an extra load on the signal light circuit without any disruption of service from their electronic flashers. No need to calculate resistance with these. |
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acpartsman
Veteran Cruncher Martinsville VA, USA Joined: May 6, 2007 Post Count: 943 Status: Offline Project Badges:
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The car already has an electronic flasher (5 conductor style). But I tried a new one just in case the new ones would operate differently, no go. My problem is I'm not adding lights, I'm eliminating. Instead of 1 front and 2 rear I will have 1 front and none on the rear ( as far as the flasher knows) My new rear signals are controled by a different circuit that receives it's signal from the front and produces no load to the flasher.
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One drop raises the sea.
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jal2
Senior Cruncher USA Joined: Apr 28, 2007 Post Count: 422 Status: Offline Project Badges:
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A quick search turns up this site, spiderlite, which has a load balancer kit that sounds like what you are looking for. If nothing else, it identifies the desired part as a 7-ohm, 60 watt, load. Also, this is probably a load coil and not a resister.
----------------------------------------note: I am not associated with this site, nor have I tried their products. This is just an example of what you are looking for which I obtained via a common search engine. |
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acpartsman
Veteran Cruncher Martinsville VA, USA Joined: May 6, 2007 Post Count: 943 Status: Offline Project Badges:
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Thank you, I'll check it out.
----------------------------------------Have a great day.
One drop raises the sea.
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