5c marker lights

[christopher]

on a recent trip, the marker lights would stay on for a period of time then go out. towards the end of the 1900 mile journey, they stayed on. this never happened before.
could this be a bad circuit breaker or?
the junction boxes are real clean(like new)
Thanks
Chris

[chuckdrum]

Interesting you should mention this.  Unless yours is set up differently than mine, the 5C has self resetting breakers for the lights.  My understanding is that a short in the wiring anywhere in a given circuit could cause enough heat to trip the breaker, then it will reset automatically and things will be fine until a heat-producing short trips it again.

My headlights and markers are on the same switch.  I've had intermittent headlight failure followed by what I assume is the breaker resetting and the headlights return.  I had the headlight switch replaced (it was definitely bad) but the problem returned.  A bad ground connection near the switch was discovered and repaired but the problem returned again.

The most recent advice was that the problem was very likely in the marker lights, not the headlights or the switch.  I have several marker lights that are on again/off again and I'm thinking there's enough of a faulty wiring problem there somewhere that the breaker is continually tripped.  I'ver replaced one marker fixture altogether but there are at least two or three more that are questionable.

[Iceni John]

I have dozens of self-resetting circuit breakers in my bus.   I've found that when they get old, for some of them their internal resistance increases, sometimes to the point that they start tripping off and back on by themselves due to their own internal heat.   I first discovered this when measuring voltages across their terminals  -  some CBs were losing almost one volt under load and were getting noticeably warm, then one time while I was testing them I heard one trip off and on by itself.   It came back on after a few seconds, then would trip off again in a minute or so.   If there's a short they'll constantly trip off and on, but this one was doing so much more slowly.   I dissected one of the bad ones, and its bimetal (?) strip inside that touches the stud was warped and causing bad contact, with some corrosion visible on the strip and stud.   That would be enough to make them unreliable.   Get out the DMM and measure their resistance and voltage loss.

They're only a few dollars each, so I've ordered enough to replace the bad ones and to have several spares in each amperage.   I've learnt now to always keep spares of some things in the bus, such as cube relays, these CBs, buzzers, even a D2 air governor.   Always something to deal with on older buses!

John

[Brett G]

I have dozens of self-resetting circuit breakers in my bus.   I've found that when they get old, for some of them their internal resistance increases, sometimes to the point that they start tripping off and back on by themselves due to their own internal heat.   I first discovered this when measuring voltages across their terminals  -  some CBs were losing almost one volt under load and were getting noticeably warm, then one time while I was testing them I heard one trip off and on by itself.   It came back on after a few seconds, then would trip off again in a minute or so.   If there's a short they'll constantly trip off and on, but this one was doing so much more slowly.   I dissected one of the bad ones, and its bimetal (?) strip inside that touches the stud was warped and causing bad contact, with some corrosion visible on the strip and stud.   That would be enough to make them unreliable.   Get out the DMM and measure their resistance and voltage loss.

They're only a few dollars each, so I've ordered enough to replace the bad ones and to have several spares in each amperage.   I've learnt now to always keep spares of some things in the bus, such as cube relays, these CBs, buzzers, even a D2 air governor.   Always something to deal with on older buses!

John

Had the same problem with headlights.  Breaker was just weak.  New one solved the problem

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