blowed dome light fuse

Good day.I have a question.I have come accros a few cars where the domelight is not working and when I check there is no extra loads connected to the circuit but the fuse is blowed.I replace the fuse then everything works for a long time.now I think,if it was a short,it would have blowed emediately.does fuses pop after a while just by itself?and what makes a dome light bulp blow by itself,while it is getting their amount of voltage needed.Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

Like any fuse blow, it's usually due to a fault. But fuses do fatigue, usually more from thermal cycling but also due to higher currents (hence the general lifecycle advice to normally load fuses at no more than 70-80$ of their rating). Other problems like open-circuit intermittents accelerate thermal cycling fatigue. That was not uncommon with festoon dome bulbs. Intermittent (load) shorts do the same but worse - the longer the shorts, the faster the fail. (Short circuits should blow fuses within seconds.) Bulbs blow for the same reasons tho shorts have no effect other than the resulting on-off thermal cycling. Dome lights tend to suffer more vibration than other vehicle lighting, and festoons tend to be more prone to vibration damage. Re the above, it often amuses me how people blame bulb failures on shorts. What short? It's usually due to vibration and bad contacts; intermittent shorts tend to be rare.

Thanks Old spark,I think the hotwire of the domelight mustve been pinched somewhere and touches the body now and then (vibration) causing a short.because it doesn't blow immediately.sometimes takes months before the same person tells me the fuse blowed again.Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

I agree. It's a long run and often loosely secured so it can rub. And then there's roof & hook screws... The grounding door switch faults are easy - the light comes on ad hoc but often on bumps. That's for insulation failure etc and won't effect the fuse - other than the added thermal shocks. Self-resetting circuit breakers can be a solution tho care is needed - they should NOT be used in cases of intermittent shorts (ie, hotside insulation failure) because they can repeatedly cycle on & off until either they or the wire catches fire. But MAYBE for a short every few weeks or months... hoping that that does not increase in frequency or duration.

Thanks for the advice!Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.

In many North American domestics, particularly GM, the dome light fuse is also the lighter fuse. Lots of people put various devices in the lighter plug. Like phone chargers, etc. While the load may not be enough to cause an overload, a mechanical problem with the plug creates a short. I find blown dome fuses all the time. Usually in vehicles that power an accy or lighter outlet with the dome fuse.

I will check it out from now on.and yes one of them mentioned that his lighter is nolonger working,so ill ask him to check the lighter out aswell now that I have replaced his fuse.Do it once,do it right - This means no short cuts. You never get paid twice for having to do the job twice because it wasn't done right the first time.