Back Feed Frustration

A problem that crops up once in a while is back feeding. When it does happen, it can be a real pain to find and fix. Simply stated, back feeding is a condition where the electrical signal or power going to one component (load, switch, panel, etc.) goes somewhere unintended and powers another component. When this happens it is often, but not always, within one of the lighting circuits and often involves LED's.


Now, before you start blaming LED's, they are often involved because of the extremely low amount of power it takes to light them. A low level back feed might have existed since dirt but was never noticed when an incandescent bulb was being used since the bulb wouldn't light up. But replace the bulb with an LED and it shows the back feed problem quite clearly (pun intended).


Why back feeding? 


First possibility, it indicates an electrical "leak". That is, a switch or other devise that is supposed to stop all electrical flow isn't doing its job completely. Replacing the switch is about the only way to figure this problem out but sometimes the replacement does the same thing. Argh!


A second possibility is a literal back feeding. When we think of electrical circuits, the electricity is supposed to flow in one direction - and ONLY one direction. But those pesky little electrons don't know any difference so if they see a voltage differential or, especially, a sneaky way to "go to ground", they are on their way at the speed of light... well, close to it.


And the 64 million dollar question... how do we get rid of the problem?


Finding and replacing a leaking switch is a success story, so that's one fix. 


If the problem is literally back feeding where the electricity is flowing the wrong way and causing the problem, then a diode can be your cure. A diode is a one way electrical gate, allowing the current to flow one way but not the other through a wire. Make sure you're using a properly sized diode. We have them in 1 amp, 6 amp and 85 amp versions. 85 AMPS! Yes, radiator fans love to back feed. But radiator fans are a whole other blog post for the future.


If all else fails, you can often use a relay to isolate the problem circuit. By putting a relay in the feed circuit to the component receiving the back feed, the relay will cleanly turn the flow of electricity on and off - 100%. As long as the back feed isn't large enough to trigger the relay, the problem goes away.


Ultimately, finding the source of the leak or back feed is best. Otherwise a drained battery can sometimes be a painful result. So, dig in there and try to figure it out. But as an alternative for many a back feed problem, try a diode or relay. It might just make your day.


Watson's StreetWorks     http://www.watsons-streetworks.com