Headlights will cycle off/on

[pulsarjab]

Our 2000 Diplomat cycles the headlights off and on when the switch is turned on. Is there a circuit breaker for the lights and where is it located? The dash and parking lights remain on. Wiggling the switch has no affect.

[cbr046]

Off and on like a blinking effect or like an intermittent / bad connection?

I have the same problem.  Last occurrence I beat on the dash, wiggled the harnesses under the dash and under the transmission selector, then wiggled every relay I could find in the Front Run Bay.  This was during daytime so I couldn't see which were having an effect, but now my headlights worked for the last two 1 hour drives.  

There are suggestions to look for a bad ground under the dash . . . . I never could find a common ground bus. 

I have oval 2x5" fog lights that I'd like to turn into driving lights for the next "emergency".  All I can find are these, and they're a mix of fog and driving lights.  Good chance I can't aim them without blinding oncoming traffic . . .

https://www.amazon.com/dp/B07R7SMCZB/

- bob

[waterskier_1]

Yes, at least on Dynasty & Executive.  Each headlight is on a self-resetting circuit breaker.  They are located in the Front Run Bay. 

  - Rick N 

Casa Grande, AZ 

[pulsarjab]

That is what it is acting like. I changed to halogen and the additional draw may be causing the issue. However, both lights are in sync which would indicate a single circuit breaker and there is nothing in the front bay labeled headlights other than a 25 amp fuse. The wiring diagrams do not show anything like that either. Installed a new switch, not a fun job, will continue looking today. 

[Rikadoo]

So with original vehicle old school headlight switches, aka chevy, ford, dodge. The headlight switch had a internal breaker for the headlights, then the park lights were fused. (Spoiler alert many electronic devices were borrowed from those Mfgs in the earlie days) So it was possable to lose one but not the other. 
Try this test, when the lights fail, if your high beam switch is also your turn signil lever, at the moment the lights fail, then pull back on the stick and hold it there… AKA, flash to pass, do the lights come back on?  Yes: its most likely the headlight switch. No: you have a breaker feeding the headlight switch that 💩the bed… reason was older systems used the same power wire for the flash to pass also fed the headlight switch.

So if it is the headlight switch as the lights fail, touch the stem of the headlight switch, switch… is it 😡HOT. If so the headlight circuits may have too much resistance, if you replace the switch and it still gets hot your search for the problem still exists, cause by replacing the headlight switch, was just the symptom.

[bobdinsmore]

I had this same problem years ago when I changed to higher wattage headlight bulbs. The switch stem was very hot. Fixed the problem by installing an automotive R86 relay in the headlight circuit: Cut the wire from the switch to the headlight bulbs. Then the trigger signal comes from the switch, then ran a new wire from battery and another to ground, and the other end of the cut wire that goes to the bulbs becomes the relay output. This offloads the high current from the switch to the relay.

[pulsarjab]

Solution. First, the headlight switch was replaced to fix the panel lights and gauges not working correctly. Headlights were replaced years ago but never driving at night, was not noticed if they were cycling. The lights were always dim. After replacing the switch we decided to tackle the dim head lights. Voltage measurements showed 10 volts to lights, and after a period they would start cycling.

We replaced the light circuit with a Amazon relay kit, splicing it into the circuit and using the wires from the switch to turn on the relays. This provided peak voltage to lights and eliminated the cycling.

Thanks for all the ideas. I am very fortunate to have a great friend, Myron, that knows a lot about these RVs. He tackled this project and did a great job of diagnostics and installation. Without his help, I would not have tackled the project. The idea of re-engineering an electrical design is best left to the experts.

[Drywalldan]

On 3/8/2024 at 5:38 AM, pulsarjab said:

That is what it is acting like. I changed to halogen and the additional draw may be causing the issue. However, both lights are in sync which would indicate a single circuit breaker and there is nothing in the front bay labeled headlights other than a 25 amp fuse. The wiring diagrams do not show anything like that either. Installed a new switch, not a fun job, will continue looking today. 

When troubleshooting first ask yourself "What has changed?".  What you describe sounds like a self-resetting breaker is in play brought on by your headlight bulb change to halogen.