Solenoid blows LED

Hey guys - I'm stumped here. I'm using a 90amp continuos solenoid to power a heavy duty electric fan on my ford bronco. I have a dash switch that activates the solenoid.     I have an LED wired to the switch (it attaches to the same post that the wire is connected to that goes to the solenoid to activate it. The fan and everything works fine , but it blows the LED when I flip the switch. Someone told me that it may be the back EMF from the solenoid that is causing the LED to blow. I had a person recommend me using a relay between the dash switch and the solenoid. Would this remedy the problem? I'm definitely not an electrician, but any help would be greatly appreciated.

A Relay will not fix the problem.

It will do the same thing. A Solenoid has a Coil and so does a Relay. The solution is a Diode across the coil of the Solenoid or relay.

Here is why:

As a relay power is applied it energizes the coil.

This creates a Magnetic field around this coil when power is on the wires.

When you take power off of the coil this magnetic field collapses and causes a voltage spike in the wires in a reverse polarity from the original.

A clamping Diode will give this spike a path to ground. A Diode is like a check valve that lets voltage flow in only one direction.

Here is an example on Diode used to protect Transistors

Check out our Diode section Here https://www.the12volt.com/diodes/diodes.asp

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !

Thank you so much for the advice - I was planning on using a relay which would have just ruined another expensive LED. I'm more or less electrically incompetent, so you can you walk me through which diode to get, which way to wire it,etc. The solenoid I have is basically a starter solenoid with 4 posts. Main Power in, Main Power out, switch in, and ground. I've never used a diode before, so can you spoonfeed me or draw a diagram or something? Do I get it at radio shock, solder it on, etc? Thank you so much for the help. This has been driving me crazy for days..

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !