wattage on resistor?

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Forum Name: Lights, Neon, LEDs, HIDs
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URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=104211
Printed Date: May 14, 2025 at 3:36 PM

Topic: wattage on resistor?

Posted By: kirin
Subject: wattage on resistor?
Date Posted: April 23, 2008 at 5:58 PM

Hello, I am fairly new and trying to make use of LEDs, resistors in my old tool box.

Can anybody help me how to calculate the wattage of two resistors connected like

Series ? and Parallel ? for example, if two 1ohm resistors(1/4 wattage carbon type)

in both cases, the wattage will be /14+1/4 = 1/2 wattage?

Thank you for your assistance in advance

Replies:

Posted By: i am an idiot
Date Posted: April 23, 2008 at 6:27 PM

Unless you are connecting a boat load of LEDs to a single resistor, you should not have to worry about the wattage of the resistor.

Yes you are correct in assuming that the 2 1/4 watt resistors will yield 1/2 watt of capacity.

Posted By: kirin
Date Posted: April 23, 2008 at 6:47 PM

Thank you i am an idiot for your reply and advise, very much appreciated.

Since I have so many resistors, thinking of modifying turn signals to LEDs I have to also put some resistor in the flasher relay box to avoid high flasher(blinks very fast).

I have replaced the original thin metal with 1/4 carbon resistors(1ohm resistor x 4 parallel) in the replay box and fixed the high flasher problem but I am concerned that each 1/4 watt one ohm resistor may not

holding the current flow in the relay box ? so parallel of 1/4 carbon one ohm yied ONE watt ? would this be enough?

Posted By: i am an idiot
Date Posted: April 23, 2008 at 7:42 PM

I think that a standard 1156 bulb is a 12 watt device. I would think that you would need something closer to that handling capacity. If the 4 1/4 watt resistors are giving you the correct flash rate, just leave the blinkers on for a minute or so and check the resistors for heat, if they are not getting too hot then you will be OK.