The 25+, "Overloaded Switches"

Let's look at circuit overloading, specifically talking about switches...

#17. You mentioned the headlight switch getting over loaded when higher wattage headlights are used. Are there other switches or circuits that often get over loaded?

Lighting circuits are common problems even if they are other than the headlight circuit. For example, people who add auxiliary lights may buy a kit with a pair of spot lights or driving lights - the kit has a switch and maybe a relay - and, if the manufacturer has done their design work right, then you are good to go. But often, one set of lights leads to yet another. If the switch and/or relay in the second set gets left in the box so that all of the lights can be turned on together, then the original switch/relay will probably be over loaded by having to carry twice the lights - and twice the amperage - that it was designed for. As always, preventing an overload requires making sure that the switch, or the relay, and all of the rest of the circuit components (wire, connections, etc.) are sized large enough to handle the entire circuit amperage load.

The other most common switch to get over loaded is the ignition switch.

#18. How can you over load an ignition switch? It just runs the car ignition.

But it also supplies power to the starter solenoid and to all of the “ignition controlled” accessories. The starter solenoid is seldom a problem (it is called a solenoid because of its design, but it works like a relay in the starter circuit). But, when we add accessories powered through the ignition switch problems can develop. Very few ignition switches are rated to carry more than 30 amps of accessory power, total. Add some new power windows and an air conditioner to your car and that ignition switch will be toast.

You can protect your ignition switch quite easily by (am I starting to sound like a broken record, yet?) adding a relay with a higher amperage rating, like our 80 amp relay. It will more than double the total accessory carrying capacity, protect the ignition switch and provide more than most cars need for their system.

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