My 3 lever light switch

Deadguy · Post by **Deadguy** » Mon Aug 20, 2012 11:52 pm

gets hot when I am using the dash lights/blinkers. The current draw can't be that much, maybe there is a short in the line somewhere?

Post by **wesk** » Tue Aug 21, 2012 12:24 am

The current generates the heat. If the switch feels too hot then the current passing thru it is too high.

High current is usually either a large load or excessive resistance.

A short to ground creates a high load.

A poor ground creates resistance.

Seems to me I recall you posting a problem a few months ago about bad light assembly grounds. Perhaps it is time to start scraping paint off the ground points.

Deadguy · Post by **Deadguy** » Tue Aug 21, 2012 1:00 am

Thanks Wes. I'll test the wires and see if any live ones are grounded, and I'll clean up the ones that are supposed to be grounded.

jimm · Post by **jimm** » Tue Aug 21, 2012 8:18 am

A switch can also get hot due to poor contact within the switch itself. The poor contact is resistance, and when the current from the load passes through that resistance, it generates heat. I've had this happen on a couple of '50s vintage vehicles. A way to measure this resistance is to measure the voltage drop with a voltmeter across the switch when the circuit is on. (Or measure the voltage on the input side of the switch relative to ground and the voltage on the output side relative to ground, and subtract the latter from the former - not as accurate, because you have two measurements.) The power, in watts (heat!) being generated in the switch is the voltage drop times the current. For a switch in good condition, the voltage drop should be so low that you can't even detect it with an ordinary voltmeter.

Post by **wesk** » Tue Aug 21, 2012 10:28 am

High current is usually either a large load or excessive resistance.

Jimm covers in more detail what I stated above. His notes on the switch testing are not as simple as stated. You will need a decent digital VOM, a pinout for the switch and an internal diagram of the switch contact wiring so you can first determine which circuit contacts you are going to test and which pins you are going to measure the resistance or voltage drop across.

Based on your previous responses to electrical issues on your jeep I believe that electrical troublshooting is not a strong suit for you. There fore I would suggest substituting a known good switch to see if the heat is caused by internal switch resistance.

This shows the early Bendix switch but applies to the later single plug switches by simply ignoring the test connections in the right column.

Bretto · Post by **Bretto** » Tue Aug 21, 2012 11:14 am

Before I tore into my 'disposable' single plug switch, one of the circuits in the switch had variable resistance readings when you wiggled one of the arms. I can't recall which one it was. But when I cracked the switch open, I found a few of the terminals were corroded. This goes along with what Jim had noted that bad terms can add resistance. I clean everything up and it works great now.
http://i1201.photobucket.com/albums/bb3 ... 9-7878.jpg
http://i1201.photobucket.com/albums/bb3 ... 1-7878.jpg

whydahdvr · Post by **whydahdvr** » Tue Aug 21, 2012 11:24 am

Along the lines of the replaceable 3 lever switch, I have one in my jeep, a repro version, and even when all the screws are removed it still won't come away from the inside of the dash. It doesn't feel like there are any spot welds on the screw holes and it's not coated in paint.
Any ideas on what might be hanging it up? I suppose it could have been glued or epoxied but am wondering if anyone has come across the same issue.
Thanks.

Deadguy · Post by **Deadguy** » Tue Aug 21, 2012 7:45 pm

I just recently bought a new 3 lever light switch from John at Midwest Military. If anything is suspect, it is probably the new leads to the turn signals

capescw · Post by **capescw** » Thu Aug 23, 2012 4:41 pm

The dash lamps (2) each consume 5 watts each at full brightness. If you are in the 'dim' position, an internal resistor in the light switch is dissipating about 5-8 watts, the same as a small 7-1/2 watt night light. Is that the cause of your heat?

Deadguy · Post by **Deadguy** » Fri Aug 24, 2012 9:46 am

I seriously doubt it. The switch is what is getting hot

capescw · Post by **capescw** » Fri Aug 24, 2012 10:09 am

That's what I mean,

an internal resistor IN the switch

. That would heat the entire assembly. The dim/bright effect should be easy to see.

I'm suggesting it only because the 'dim' position is the first detent from the 'off' position, and would be easy to leave in that position by mistake.

My 3 lever light switch

My 3 lever light switch

Heat source