Deuce light switch overheat?

[hunderliggur]

Driving to PA from MD yesterday and the three level light switch became intermittent after 1 1/2 hours of driving. It would flash twice for a turn then shut off. I was running with all my lights on but when it shutoff no lights works at all. After about an hour of being off it would flash 4 times then off. Is there an auto reset thermal breaker or something? I am camping in PA and need to drive home in a week. When the lights are out not even brake lights work. I have TMs on the iPad but I did not find this in the troubleshooting. If someone has a manual and page it would help, or any other advice. Thank in advance.

 

[cattlerepairman]

Yes, built-in self resetting circuit breaker. A wire chafed through at one of the lights maybe?

 

[hunderliggur]

I'll check, thanks!

 

[DieselBob]

If you turn the lights on now just sitting do the stay on or go out almost right away ? If they are going out right away try it in the service park setting which would eliminate the headlight circuit. Does your truck have any extra lights installed. It could also be that the circuit breaker in the switch is bad. You said in your post that it took an hour for it to reset. That's a long time.

 

[cranetruck]

The rating of the light switch CB is 20 amps.
Do the smart thing and separate the headlight circuit from the rest of the lights. It is not fun when it happens at night.

 

[m-35tom]

I didn't realize the switch was made by Lucas! You need a new switch, 1 hour is way too long.

 

[m16ty]

I've had a switch short out internally before. The contacts inside the switch got out of whack and shorted out.

 

[ducer]

Lucas electric "THE PRINCE OF DARKNESS".

Denny

 

[cmpman]

I have found some of the newer generation of switches sufferred in their design. The heat of having nearly 20 amps of current running through them causes the little thermal circuit breaker in the switch to melt the plastic/nylon plate that it is built into, resulting in failure of the lighting circuit. Older switches used a bakelight plate which was not susceptable to the melting.

You can open up your switch to determine if it's the circuit breaker. There will be one screw in the back of the switch. Sometimes it is covered with a dab of silicone. Remove the screw, then pull back the rear housing to reveal the guts of the switch.

It is possible to bypass the circuit breaker inside the switch, but you would want to install an external circuit breaker to the power coming in to the switch. Without it, you would be tempting fate. The simpler method, is, of course, that you replace the light switch.

 

[hunderliggur]

Ok, more trouble shooting at the campsite. The switch is fine with just the service lights. When headlight&clearance lights are on, trips in about 4 seconds, but resets in just a minute or two. Still trips with turn signal connector disconnect and/or headlights removed. And the switch in the headlight position. Going to check the headlight wiring for shorts since they are disconnected right now. Or it could be the clearance. It may have overheated and melted since I was powering a trailer clearance and brake lights at the time. The trailer clearance lights may have put just too much continuous load on the circuit. I'll be pulling the switch later to check. Have to do this while volunteering for radio communications for the Creation Festival with 50,000 of my close Christian friends in the middle of nowhere. Deuce goes on a road trip this morning with the clearance lights to set up directional signs on the highway. Keep the great suggestions coming, you all are a great help!

 

[cattlerepairman]

I replaced most lights with LED; this greatly reduced the amperage flowing through the switch. Not much help where you are, right now...

 

[hunderliggur]

Tried field repair of the switch yesterday, broke a Bakelite tab reassembling. Only blackout drive lights now. NOS switch from TNJ Murray on its way to the middle of nowhere, PA (Shirleysburg) for delivery tomorrow.

 

[hunderliggur]

Got a NOS switch from TNJ Murray today. Still overloads with headlight/clearance lights. Wiring checkout tomorrow. Still have turn/stop do I can get home more safely.

 

[197thhhc]

Check the grounds for the headlights. Dirty grounds cause high resistance which makes for higher current draw. Even if they look good I would take them off and clean the mating surfaces. Good luck to you.

 

[welldigger]

Check the grounds for the headlights. Dirty grounds cause high resistance which makes for higher current draw. Even if they look good I would take them off and clean the mating surfaces. Good luck to you.

I'm pretty sure that's what cooked my led taillights.

 

[cranetruck]

Check the grounds for the headlights. Dirty grounds cause high resistance which makes for higher current draw. Even if they look good I would take them off and clean the mating surfaces. Good luck to you.

Actually, higher resistance will reduce the current, but increase the voltage drop across the junction and leave little or no voltage across the light filament (=make it dim).

Most LED lights have built-in voltage regulators but will "blow" if the voltage is to high.

 

[cattlerepairman]

Actually, higher resistance will reduce the current, but increase the voltage drop across the junction and leave little or no voltage across the light filament (=make it dim).

Most LED lights have built-in voltage regulators but will "blow" if the voltage is to high.

Interesting. Could that be the reason for the common "1/2 of the LEDs are out" GROTE taillight issue? I just replaced one of my rears for that very reason. Ground appeared to be fine, but...

 

[cranetruck]

Don't know anything about that, I'd bench test the units under ideal conditions before installing, if it was me.
Plastic tail light housings may need more than one terminal grounded (mounting screw).

 

[Dodge man]

Be careful with your troubleshooting. Most of the circuit breakers used in switches aren't made to handle repeated overloads and you'll find that the reset time will quickly get longer and longer as the CB wears out. The life expectancy for CBs of that type is frequently measured in tens of cycles before they fail completely. That's why in MOST applications, CBs are a separate unit from the switch. But in headlight switches they're combined for safety reasons.

You'll get more accurate results if you use a amp meter (with fuse protection!) to bypass the headlight switch. It will let you check each circuit in the lighting circuits individually and will also give you repeatable results.

Tip: I used to have a problem like this in one of my Dodges where lights would all go out without warning. At the time I lived in a dark, dark area and when the lights went out I couldn't see ANYTHING. There's no feeling in the world like driving now a narrow road with trees close on both sides at 40-50 MPH and suddenly not being able to see ANYTHING! Luckily I had installed a set of fog lights on a completely separate circuit and those saved my bacon.

 

[hunderliggur]

Well, I found the problem and got home safely. The 24V to 12V converter for the trailer lights had failed, and when power was applied (off the clearance light) it would overload. Bypassed the unit using a feed for 12V from my PCMDS unit. I may want to just use that in the long run. Thanks for everyone's assistance.