TorontoTim Posted August 16, 2017 Report Share Posted August 16, 2017 I'm hoping that the clever electrical folk on here can help me. I have blown two pairs of headlamp dip beam bulb filaments recently. They ran continuously for perhaps two hours. I can't quite work out why they blew, and am hoping that there might be some ideas and experience out there. Facts: Bulbs are Phillips X-treme Vision H4 (I use Cibie lamps) - I have previously used Osram Nightbrakers, so these bulbs haven't been in a long time. I have a 4-relay system to feed the lamps, so feeds are not common (I don't think that earth wires are common, but I'll check in the morning) Alternator conversion The headlamps were recently removed for some bodywork and NOT replaced by me, but I believe that the wiring is correct (is there a wiring problem which could cause this?) I have not had any problems previously, so there must be something new........... Is it a problem with these bulbs in a hot, vibrating TR? Are they getting a sudden "pulse" of excess current that melted the filaments? If so, why? Can there be a wiring problem (feed or earth) that can cause this? Thanks in advance, Tim Quote Link to post Share on other sites
Geko Posted August 16, 2017 Report Share Posted August 16, 2017 (edited) Hola, the pair blew up at the same time or one after the other? In the former case the problem might be at the level of the relay itself (check connections 86 and 87 as it is possible to have them connected the wrong way around). In the later case I would check a bad connection ahead of the relay i.e. at the control box. Any signs of wires overheating or connector insulator melting down? Mind posting a diagram of the connections to the relay? Edited August 16, 2017 by Geko Quote Link to post Share on other sites
graeme Posted August 16, 2017 Report Share Posted August 16, 2017 Tim, Is it possible that an alternator fault is supplying a high voltage? Have you checked the voltage with the engine running? Cheers Graeme Quote Link to post Share on other sites
Don H. Posted August 16, 2017 Report Share Posted August 16, 2017 Are the bulbs extra-high wattage, Tim? Standard 60/55W H4 bulbs should last several years -- at least. +30 versions shouldn't be much different. High power versions like 100/80W will often have significantly shorter life. I'm with Graeme -- it really sounds like they've got to be over-powered. Quote Link to post Share on other sites
Waldi Posted August 16, 2017 Report Share Posted August 16, 2017 As a start I would check the voltage too, first with engine not running: you should have 12.5-13.0 V or close. Next with engine running idle, it should now be higher, than with engine running at 3-4000 rpm, the voltage should be around 14,2 V, and once the battery is fully charged, it drops a bit to around 13.8 V. Measure directly at the battery terminals. Also measure with lights off and lights on. There could be some difference between both, but not much. Waldi Quote Link to post Share on other sites
Lebro Posted August 16, 2017 Report Share Posted August 16, 2017 Tim. The voltage would have to be significantly higher than normal, filament bulbs are very good at giving a fairly constant brightness over a range of volts, due to the resistance of the filament increasing with temperature. Yes, check the voltage on the battery whilst engine at reasonably high revs, should be no higher than 15, & more likely 14 - 14.5 Other than that - poor manufacture, or just bad luck. (wrong relay connections would not cause this). Bob. Quote Link to post Share on other sites
Steves_TR6 Posted August 16, 2017 Report Share Posted August 16, 2017 My thoughts are either over voltage as above or a dodgy earth Bulbs usually fail when turned on, the inrush of current causing the tired filament to fail. A loose earth efffectively turns the bulb on and off frequently, or at least varies the current, you might not notice but the current is varying and this may cause premature failure. So check the voltage from the alternator and remake the earths, being as this started after removal and refitting my money is on the earths. Steve Ps, one other possibility is mechanical failure, are the headlamps bolted in securely? Quote Link to post Share on other sites
peejay4A Posted August 16, 2017 Report Share Posted August 16, 2017 (edited) There are reports on various forums about the relatively short life of high output bulbs. The more "extreme" the worse the problem seems to be. 2 hours does seem very short so a voltage check might be worthwhile. The TR environment being a little bumpy might be a problem too. Ordinary Nightbreakers seem to be OK in Eric. Edited August 16, 2017 by peejay4A Quote Link to post Share on other sites
ctc77965o Posted August 16, 2017 Report Share Posted August 16, 2017 Fake lamps? Quote Link to post Share on other sites
TorontoTim Posted August 16, 2017 Author Report Share Posted August 16, 2017 Thanks for the suggestions - I'll check some things and report back. Some answers to questions in the meantime: - bulbs are standard wattage, 55/60, but are the "high output" ones listed above - both appeared to blow together. I was actually driving on the highway at the time, so can't be sure (it was raining). Note: it was NOT raining the first time this happened (so I don't think it's a water ingress problem) Tim Quote Link to post Share on other sites
TorontoTim Posted August 16, 2017 Author Report Share Posted August 16, 2017 Checks so far reveal... - Lamps are screwed in securely - not wobbling about causing mechanical failure (that doesn't eliminate TR4 "character" vibration, of course). - Earths are not common in any way (other than both going to the body). I remade at least one of these within the past 10 days, so I'm fairly confident of it. - However, I did discover that both battery terminals were loose. It's possible that this caused small and/or rapid/momentary loss of earth or full current to the bulbs, creating the on-off thing that Steve refers to, above. - Voltage seems to be as expected (i.e. not unduly high from the alternator). Having said that, if it's an intermittent problem causing a short "spike" then I wouldn't catch it... Next test will be to put in regular H4 bulbs and see what happens there. Tim Quote Link to post Share on other sites
RobH Posted August 16, 2017 Report Share Posted August 16, 2017 Its just possible that a loose battery terminal was the problem Tim. You haven't told us what car this is but if it has an alternator, the regulator uses the battery as the 'reference' and a periodic loss of that voltage may have caused the alternator output to surge considerably above the normal level. Quote Link to post Share on other sites
TorontoTim Posted August 16, 2017 Author Report Share Posted August 16, 2017 Thanks, Rob. TR4 with alternator conversion. Quote Link to post Share on other sites
ianc Posted August 16, 2017 Report Share Posted August 16, 2017 Are you certain that only one of the two filaments in the bulb is activated at a time? If something were awry in your relay box, might you be powering both filaments in a bulb? - in which case, life would be drastically reduced. Ian Cornish Quote Link to post Share on other sites
Steves_TR6 Posted August 16, 2017 Report Share Posted August 16, 2017 Loose battery terminals could cause alternator output spike i guess. Hopefully thats is and no further consequences! Quote Link to post Share on other sites
TorontoTim Posted August 16, 2017 Author Report Share Posted August 16, 2017 Battery terminals tightened. New, ordinary (therefore CHEAP) H4s installed. Ian, good thought, but I'm pretty sure it was only dipped beam - these bulbs are BRIGHT so I like to think I'd be aware of both filaments being on (also, only dipped beams have blown; not sure whether that confirms or not). I'll report back. But don't that stop you sharing a dynamite suggestion in the meantime!! Quote Link to post Share on other sites
Alec Pringle Posted August 16, 2017 Report Share Posted August 16, 2017 Hi Tim, long ago I managed a foul-up by somehow creating a situation by which the dip worked OK, but main brought on both filaments - the bulbs lasted but mere hours ! Misrouted relays, my own fault. I've also had the loose battery terminal problem, that flickering of power massacred bulbs, about 3 sets until the penny dropped. Cheers, Alec Quote Link to post Share on other sites
TorontoTim Posted August 16, 2017 Author Report Share Posted August 16, 2017 Thanks, Alec. I'll check the wiring anyway, but I didn't have the main beams on at any point so don't think that's the cause of my problem. Good to know that you've seen the loose battery terminal thing before, that might be the cause, so I'm hoping we have a winner there. Cheers, Tim Quote Link to post Share on other sites
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