headlight switch gets HOT - Headlight Relay Install w/ pics - Finished

[Dr. Marneaus]

Hi friends....

after being turned on for a bit my headlight switch gets hot. Hot to the touch. Never so hot that it'll burn me...but its definitely beyond just being warm. I can feel it in the shaft of the pull knob but also on the dash board and on the threaded washer that holds it in.

Maybe related or unrelated...but my headlights still flicker sometimes. After say 20 minutes of being on all lights interior and exterior will flicker and go out and on and out, but if I shut the switch off and turn em back on now they are instantly better....for another 20 min.

That being said....I have taken apart the whole nose of the jeep and cleaned all the grounds patched any splits in the wire coating, etc. I have replaced the dimmer and the headlight switch.

I know resistance causes heat....is my next step using some electrical component cleaner on the plug at the switch and the plug at the firewall? Not sure where to go from here.

[Billygoat]

Headlight relay, get the main juice for the lights out of the switch.

Places sell kits, but you can get what you need for under $30 or so.
several write ups in the forums

[Dr. Marneaus]

does this about sum it up?

[robert_hollis]

Run one relay for brights, and one for dims. should be two gray wires coming off your hi beam switch. each one should feed the relay, then the relay feeds the headlights. Put the relays as close to the bat as possible so you have the shortest distance for big fat wires to run.

This is what they suggested on Mad Electrical. It reduces strain on both switches, and by putting the relays close to the bat, you reduce cost of thicker wire, and voltage drop.

[Dr. Marneaus]

How would you wire in 1 relay for highs and one for low? It's controlled by the floor mounted dimmer switch i thought? there is only 1 power "in" on that switch, and the switch itself controls where the power goes.

The above diagram puts the relay between the battery and the switch essentially, thus keeping the switch from becoming overloaded, and sends the power directly from the battery to the dimmer switch on the floor, and then out to the lights.

I'm not sure how one would wire it in the way you are suggesting, the relays come after the floor dimmer....do you disconnect the main power to the switch, if not how would it reduce the strain at that point? If there was a diagram, it seems like your way might be a bit easier, but i can picture how it would work. I just skimmed the mad electrical article...

What im saying, is with that setup, do you keep the wiring to the switch the same, and the normal current to the headlights is used to trigger the relays, which in turn provide better power (more direct) to the headlights? If so, how does it keep my headlight switch from heating up? I can see how it may gain performance at the lights, but i'm trying to prevent a fire, that system seems like it would still route all the power through the stock switch in the dash, unless otherwise disconnected. Or does simply having the relays in there sending the power from elsewhere reduce the load on the switch?

[Billygoat]

your diagram shows bypass the on/off switch, but not the dimmer.
You are better off to bypass the dimmer and use 2 relays on the headlights themselves, and use the dimmer switch to activate one relay or the other

[mdill]

If the switch is hot then the resistance is in the switch not somewhere else, (heat is produced at the point of loss).

[Dr. Marneaus]

your diagram shows bypass the on/off switch, but not the dimmer.
You are better off to bypass the dimmer and use 2 relays on the headlights themselves, and use the dimmer switch to activate one relay or the other

Right but the goal is to get the load off the main switch, thus keeping it from getting hot and settimg my dash on fire...the floor mounted dimmer doesn't get hot and im not overly worried about light output...I want to keep the main switch from getting hot....isn't that the purpose of that single relay diagram?

[Billygoat]

Right but the goal is to get the load off the main switch, thus keeping it from getting hot and settimg my dash on fire...the floor mounted dimmer doesn't get hot and im not overly worried about light output...I want to keep the main switch from getting hot....isn't that the purpose of that single relay diagram?

You are correct, but the floor dimmer is a know issue - ok maybe not in your area, but salty boot water in the winter around here is hard on them.

You could go with what you have shown or drop $5 on another relay and have a better system. The 2 gray wires for the lights are in the harness on the driver fender, you can cut and splice your relay's there pretty easy, and run a new 10ga wire from the solenoid over (with a fuse) in a short amount of time, if you feel you headlight plugs are good no need to replace that part of it, just change the point the point the power enters system.

[robert_hollis]

How would you wire in 1 relay for highs and one for low? It's controlled by the floor mounted dimmer switch i thought? there is only 1 power "in" on that switch, and the switch itself controls where the power goes.

The above diagram puts the relay between the battery and the switch essentially, thus keeping the switch from becoming overloaded, and sends the power directly from the battery to the dimmer switch on the floor, and then out to the lights.

I'm not sure how one would wire it in the way you are suggesting, the relays come after the floor dimmer....do you disconnect the main power to the switch, if not how would it reduce the strain at that point? If there was a diagram, it seems like your way might be a bit easier, but i can picture how it would work. I just skimmed the mad electrical article...

What im saying, is with that setup, do you keep the wiring to the switch the same, and the normal current to the headlights is used to trigger the relays, which in turn provide better power (more direct) to the headlights? If so, how does it keep my headlight switch from heating up? I can see how it may gain performance at the lights, but i'm trying to prevent a fire, that system seems like it would still route all the power through the stock switch in the dash, unless otherwise disconnected. Or does simply having the relays in there sending the power from elsewhere reduce the load on the switch?

The dimmer switch has one inlet (red) and two outlets (gray & gray w/tracer). One outlet controls lows, one controls highs. put a relay in line with each of those. That way the power going through the headlight switch AND the dimmer switch is only what is needed to power up the relay's magnetic coil (substantially less than that needed to power two headlights).

Sorry, if I come off confusing. I'm an EMT, not a teacher.

[robert_hollis]

Yes, I know this is hideous, but I'm not redrawing the entire circuit for you.
You could run a seperate fuse to each relay if you like, but I don't see a need.

[babywag]

You basically use the existing headlight plug wiring as the relay trigger to energize the circuit.
low beam wire triggers low beam relay, high beam wire triggers high beam relay.

Takes all the load off the switch & dimmer, that way you get direct battery voltage running from relay right to the headlights.

Do a google search for headlight relay wiring diagram, there are better dual relay diagrams out there than the one you posted.
Here's an example...

http://www.rowand.net/Shop/Tech/images/HeadlightRelayWiringDiagram.jpg

[joe]

If the switch is hot then the resistance is in the switch not somewhere else, (heat is produced at the point of loss).

Agreed. Clean "to bright shine status" connections at the switch. Just cause you put in a new switch doesn't mean it's good. Taiwan electrical components from auto parts stores(including Napa) all too often are pretty much junk right out of the box.

[Dr. Marneaus]

Okay that explains it a little better, but by simply providing the power to the lights from a different source (bat and relay) the load is removed from the switches even though that wiring stays the same? The relays are only going to draw enough power to click themselves on even though the original current is running through the original circuit still?

[robert_hollis]

Yup. Just because the wire's big enough to push a more power doesn't mean more power's running through it.

As they said, clean the connectors, so you reduce resistance. Also, wouldn't hurt to buy a new $20 switch, if yours is old, and shows signs of heat (warped plastic, or discolored metal).