Headlight (low beam) not working (Nissan Tino 1.8, 2001)

[JD]

JD wrote in news:XnsA5676CECBA3FFaaaalifecom@130.133.4.11:

.....or would that overload a relay or the healight switch?

[The Natural Philosopher]

Probably.

Its almost certainly either a duff wire joint or the relay for that bulb

[JD]

Mrcheerful wrote in news:NKy8y.481307$wD3.212918 @fx45.am4:

Thanks. The trouble is that the powered side of the fuse holder is dead, even when the lights are switched on. Hence my proposed fix (pls see my message of a moment ago)..

JD

[Chris Whelan]

This any help for relay location?

Chris

[Mrcheerful]

that would put double the load on the existing working fuse and wiring, the relay is designed to power both, so that will be ok. I would try it using the existing rating of fuse, if that survives then it will be ok for a while at least.

[Dave Plowman (News)]

Right - so no volts getting to the fuse. Which means the fault is in the feed to it.

[JD]

Mrcheerful wrote in news:GCz8y.481474$wD3.472160 @fx45.am4:

Both fuses themnselves are faultless and intact. The problem is no power to the fuse (in the case of the light that doesn't come on). As for a relay, I cannot find one that has ane effect on the headlight that does work. Is it certain that there IS one for the low beam, do you think?

JD

[JD]

The Natural Philosopher wrote in news:n3ufbf$hn0$1 @news.albasani.net:

A relay would be easy to check, if I could find one. I can't find a relay that has any effect on the working lowbeam headlight. I presume that the two realys (one for each lowbeam bulb) would be at the same location.

Would both headlights go through a single relay, or is it more likely that there is one for each lowbeam bulb?

JD

[Chris Whelan]

{...]

Did you look at the link I posted earlier? It clearly lists two headlamp relays, with a diagram showing their location.

There will be one relay for dip, and one for main. It's possible that there are separate contacts on each relay for LH and RH side, in which case the fault might be the dip relay.

It's more likely that there is a single contact feeding one wire to the fuse box, which then splits within the base of the box. In that case the fault is likely to be a break under the fuse box.

Chris

[Dave Plowman (News)]

I can't think of a reason to use two relays, since standard auto ones are more than capable of handling the current for two headlamps.

Have you looked for a schematic online?

[JD]

"Dave Plowman (News)" wrote in news: [e-mail]:

I posted the Hayens schematic here:

Can anyone decipher that and tell me what the relay should look like?

BTW, I'm puzzled by that schematic, because it doesn't show any single- filament headlights. My low beam lights are separate, single-filament bulbs.

TIA!

JD

[JD]

"Dave Plowman (News)" wrote in news: [e-mail]:

I've posted one here:

JD

[JD]

"Dave Plowman (News)" wrote in news: [e-mail]:

I can;t see any ref to a CAN system in the Haynes manual.

Chris Whelan (in an adjecent reply that I couldn;t respond to within this group for some reason) sent an image of the other relay box. While the relays in my box in that location didn't correspond to the ones in the image, I took them all out and the working lowbeam headlight still switched on and off, so I guess it's none of those.

I'm baffled! SURELY Nissan would put a headlight relay in a place that's easy to locate, wouldn't they??

There is nothing in the car's handbook about relays. And Haynes shows a circuit diagram, but not the actual location of the relays.

ALL I can find is a MAIN relay (presumably meaning main beam) but that has no effect when I remove it.

JD

[Dave Plowman (News)]

Typical Haynes - trying to show every possible combination of all variants in the same diagram. How I hate them. ;-)

Looks like there are only relays involved if you have daytime running lights?

[Davey]

And the Haynes manual for my model of Renault doesn't have my engine size, the only mention is that it isn't included.

[Mrcheerful]

Haynes manuals are not even very useful as a door stop, let alone a reference. If I had the time and was paid to do it, I would visit them and point out some of the errors I have noticed from the distant past when I used to refer to them.

[dennis]

How much resistance? A working 20A fuse should read pretty close to zero with an ohm meter.

[Johnny B Good]

He was referring to the lamp filament resistance, not the fuse link.

I have a couple of 12v 55W quartz halogen capsule lamps which are probably identical to the ones JD's testing. The hot, working resistance calculates out to 2.62 ohms.

However, since the hot resistance of a tungsten filament lamp is typically an order of magnitude greater than its cold temperature, a resistance check with a multimeter on the ohms scale will be trying to measure a mere quarter of an ohm resistance value which, with most multimeters, can be damned difficult to read or distinguish from the test lead's own resistance.

Whilst many modern DMMs are calibrated to tenths of an ohm on their 200 ohms scale, thermocouple effects and test probe contact resistance make getting 'tenth of an ohm' readings rather problematical. With a lot of care and determination, I can usually get the short circuit test to stabilise at 0.6 ohms for the test lead resistance and with similar care when testing the lamp plus test lead resistance, see a 0.8 to 0.9 ohm reading on my 55W test lamp.

In practice, of course, I'm happy to see a reading that approximates a short circuit when testing such low voltage lamp filaments when all I'm doing is simply to prove they haven't gone open circuit.

In the early days of automotive electrics, it was standard practice to eliminate any fusing protection on headlight circuits to avoid the consequences of a total blackout due to a tired fuse blowing whilst driving along an unlit road.

Any resulting electrical wiring fire was deemed less of a risk than a possibly fatal collision due to a sudden blackout - the theory being that at least one of the headlamps would remain lit long enough for the driver to bring the vehicle safely to a halt, pop the bonnet release (in later vehicles) and jump out, fire extinguisher in hand and possibly a suitable wrench to disconnect the battery (or, at the *very* least, *safely* abandon the vehicle along with any passengers before the vehicle became a raging inferno).

Later on (sometime in the fifties or sixties?) the manufacturers started fitting safety fuses initially one per headlamp circuit (protecting both dip and drive filaments on each side) then 4 fuses to protect each filament or lamp. When relays started to used to control the vehicle's driving lamps, it was most likely a single changeover relay to begin with before this single point of failure was duplicated then quadruplicated to eliminate the risk of a total blackout by any one component failure.

I'd imagine all modern vehicles (circa ten years old or less) will have not just a seperate fuse link per lamp filament but also a seperate relay for each lamp filament (not just duplicate contacts on a single coil relay).

I don't envy JD's task of tracking down this particular fault. Vehicle electrics wiring diagrams are generally a total and utter shambles, seemingly designed more as a technically challenging puzzle designed to exercise the minds of individuals possessed of the intellect of the eponymous "Sherlock Holmes" character than as an aid to diagnosis by us mere mortals.

[NY]

I experienced the Sudden Blackout once, and it was very frightening. I'd just arrived back from a holiday on the Isle of Wight and was driving through the New Forest on my way back from Lymington. I thought that my headlight pattern wasn't quite right and that the lights weren't as bright as they should have been. When I came up behind another car, I saw that I was right: there was only a reflection from one headlight - the other bulb had blown. I decided to carry on to Brockenhurst (the nearest settlement ahead) where I knew there'd be streetlights to supplement the little torch I had, to help me change the bulb, since it's a bugger trying to fumble in the restricted space between the headlamp housing and the engine.

I'd only gone a mile further and the other bulb blew. I now just had the sidelights, which are no use at all the illuminate the road (eg white lights, kerbs) ahead. I drove most of the way on full beam, having to revert to blackout (apart from sidelights) whenever there was an oncoming car, and keeping well back from the car in front to avoid dazzling him. With hindsight I should have used the front fog lights but I forgot about those. Eventually I managed to find somewhere that I could safely pull off the road to change at least one of the bulbs (I just had one spare).

Late at night, there were no shops open to buy a second bulb, and even Rownham Services on the motorway only had 24V and not 12V H7 bulbs - fine for HGVs but no use for cars.

At least one bulb, fitted on the offside to indicate the boundary of my car to oncoming cars, was enough to get me home.

Now I try to carry *two* spare headlight bulbs!

[JD]

dennis@home wrote in news:56633431$0$51618$b1db1813$ [e-mail]:

Apologies; I meant to say it has "very low resistance" (as opposed to the very high resistance of a blown bulb).

JD