Technical Dipped Headlamp Failure Does Not Activate Bulb Failure Warning

[s130]

This is an FYI post.

As per title I've just had to replace my N/S dipped beam headlight bulb after it failed. I had no bulb failure warnings!

Additional tip/info.

Getting to this bulb does NOT require headlamp / bumper removal!

You do however have to:

1) Remove the top cover of the auxiliary fuse box just behind headlamp
2) Lift the plastic clip that holds/positions the top of neck of the windscreen washer bottle and then slide the neck to the left (as viewed from front access position)
3) Bulb tap locates top most
4) Girly hands preferred. Mike Tyson or Bruno will have problems.

 

[Davren]

As per title I've just had to replace my N/S dipped beam headlight bulb after it failed. I had no bulb failure warnings!

Bulb failure modules don't usually apply to headlamps. Manufacturers assume the driver would notice when a headlamp bulb was out by the lack of beam on the road.
.

 

[s130]

Manufacturers assume the driver would notice when a headlamp bulb was out by the lack of beam on the road.
.

Odd assumption especially based on the number of cars I see with headlights out. Even more so, especially in Italy where it is now law that you have your headlamps on at all times on major roads (unless you have daylight running lights)

Talking of aftermarket / self fit DLRLs I wonder how long it will be for the MOT to properly test them. To be legal they have to have a minimum brightness for day use and no other lights shall be operative and when night or other lights operative they MUST dim.

I've been dazzled a few times now by these aftermarket DIY DLRLs at night.

Also now more people are running their fogs illegally as DLRLs.

 

[BrianMcL]

And an odd aasumption given the vast array of sensors on everything else in the car. 5 on the front doors and 2 on the wing mirrors for example!

I too would just have assumed that the headlights would have a sensor too but then nothing surprises me about the Croma.

My big question is which way up to put the bulbs - brown cables to the left or right, top or bottom, the headlight itself doesn't seem to mind but other drivers do.

 

[s130]

My big question is which way up to put the bulbs - brown cables to the left or right, top or bottom, the headlight itself doesn't seem to mind but other drivers do.

Yes I initially struggled with this as the bulb seemed to fit at any angle. However careful inspection suggested TAB uppermost. So retried both tab up and down and despite being very similar it is tab up that is correct, confirmed by checking the other side.

Another regression in modern designed stuff. :yuck:

 

[dave]

mine fitted with tab down same as the ones i took out think i'll remove airbox to get a better look

 

[dave]

looks like tab up is right, I've been driving with upside down bulbs for ever then :shrug:

 

[s130]

looks like tab up is right, I've been driving with upside down bulbs for ever then :shrug:

Do you have any Australian heritage?

Well I'm not surprised both you and me got confused and had difficulty in getting the correct alignment as there is no "positive" location mechanism.

Thankfully the difference is about 1mm, possibly 2mm, but unlike older dual filament bulbs the bulbs are 360 degree open (long axis) and beam direction relies upon the reflector. So upside down is not a real big issue but just yet another confusion thrown in to make an otherwise job frustrating.

 

[BrianMcL]

Thanks again guys.

I'll have a look at mine at the weekend weather permitting and see which way up they are.

 

[s130]

Well if my aging memory serves me correctly when I looked in my Croma Handbook just a few days ago I think the picture/legend showed the tab uppermost.

Either way being able to fit in any orientation a "keyed" / tabbed item is indeed very confusing and dare I say sloppy designed.

One saving grace. You don't have to take the bumper off like on the Fiat Stilo and many another car including a few Volvos that would lead you to believe they were the bees knees of lighting.

 

[g8rpi]

Hi,
Picking up my Croma on 02/01/15 But was reading the manual in advance and had noticed it does say that the lights warning does not include dipped or mainbeam headlamps. As an electronics engineer I woud suggest that, apart from the fact it should be obvious to the driver, one reason for not detecting the headlamps is the higher power and current. This would require larger current sensing resistors. Also higher power halogen headlamps are more sensitive to the voltage drop across the sensor reducing the light output. One advantage is if you want to fit aftermarket HID lamps you don't have to worry about the lamp failure warning coming on.

 

[s130]

Another Electronics Engineer. No disrespect as that has been my profession since the 1970s.

I must have missed that mention/advice/warning in the owner's manual that headlights were not included in the bulb warning system.

Having said that "detection via voltage drop across a sensor" is primitive 60s/70s diagnostics especially in this digital age of advanced systems, CAN bus, etc, etc.

Not to worry. I have a backup plan courtesy of our national police force. "Excuse me Sir. Your headlamp is not functioning. Were you aware and can I be of any assistance?"

 

[BrianMcL]

Not to worry. I have a backup plan courtesy of our national police force. "Excuse me Sir. Your headlamp is not functioning. Were you aware and can I be of any assistance?"

It does just give them an excuse to pull you over anyway. Is this one of the "7 days to get it fixed" things?

The weather here looks pretty settled (very cold but clear and dry) so I'm going to do a bit of investigating on mine to see why everyone coming towards me feels obliged to flash their headlights at me. Odds that the bulbs aren't in the correct way up?

 

[s130]

Not sure being the wrong way up/down is going to make that much difference. Unlike older style dual beam bulbs with inbuilt deflector shroud on the dipped beam, these single filament H7 bulbs have 360deg radiation around the axis with only the bulb tip blanked off to stop direct forward light. Beam pattern/position is done by the headlamp unit reflectors.

When I was trying to get the bulbs in there was very little difference in the resting position with tab up or tab down. I'm not sure a small tilt along the axis is going to make that much difference.

Suggestion. Park facing wall/garage door. Turn headlamps on and mark beam positions. Now switch one bulb to opposite tab position. Turn back on. Can you see a marked difference in beam position? Would be great info for us all.

 

[g8rpi]

Having said that "detection via voltage drop across a sensor" is primitive 60s/70s diagnostics especially in this digital age of advanced systems, CAN bus, etc, etc.

Hi,
While using a resistive current shunt to detect lamp failure dies seem crude, it works and is the basis for most lamp failure detection circuits. In modern designs with solid state, rather than relay, switching the "resistor" is often built into the switching device. The switching devices are typically MOSFETs with additional circuitry integrated onto the die. Trade names are ProFet and SmartFet (just two examples). These may be controlled by, and their status reported back by, a CAN bus, but CAN does not itself include current sensing. Other options for current sensing are current operated relays (e.g. a reed switch with a few turns of heavy wire) or Hall effect devices. Both of these detect the magnetic field generated by the current. These cost more than resistors so are not as popular.
The Croma uses relays for the headlights (non xenon) and the body computer (solid state) for side lights etc. This expalins the functional difference.

Robert.

 

[s130]

Agree

Another way is by using a high frequency pulses / wave line termination techniques. If the line is not terminated then the pulse is reflected back to sender at almost full amplitude which can then be detected. This method requires no inline sensors,coils, no smart bulbs etc.

Also unlike trying to located a cable fault position, which gets quite complicated, we only need to trigger based on terminated or not and as a headlamp bulb is not far of a short circuit compare to an open circuit detection becomes a lot easier.

Now to do this properly I guess it would be expensive to have a pulse sender/receiver per line. I would envisage a single sender/receiver with a multiplexer. This way when the ignition is turned on the body computer does a faster sequential scan of all required line and then signals the failed/open circuit lines without having to attempt to power-up a bulb/device. Of course when later the driver turns say the sidelights on then the single line test is done before applying the power. Or variations there of etc.etc

Nice little undergraduate / trainee project.

 

[g8rpi]

Hi,
Maybe we should move this to an electronics forum

. While reflectrometery is a valid technique, I first used it in the early 80's, it would be difficult to apply in his case. The wiring is not constant impedance and the lamp lmpedance changes with temperature. Another issue is access to the line. You need to monitor with the lamp on and in this case the supply end of the line is typically terminated in a low, but uncontrolled impedance. This will attenuate both the transmitted and reflected pulse. You could add an inductance at the supply end but thats an extra component and losses. The current industry standard is either integrated "smart" FET switch sensing or hall effect sensors. One other method is to turn the switch off for a moment and measure the circuit resistance. This is easy to do with PWM applications such as LED drivers.

Robert.

 

[s130]

Heee Heee

I guess we can start the Croma redesign forum.... with subsections

Electronics & Mechanical & Bodywork.

Regarding constant impedance yes this is an issue BUT if the test is done cold (i.e.) before full power is applied then we are talking about a nominal variation say from -20 Deg.C for our Russian/Swedish friends and +40deg.C for our hotter climate friends. This compares to the many 1000s of deg.C of an active bulb so the there is a much larger "impedance window" compared to the inherent wiring loom and inline connectors.

Anyway this is all electronics fun just in time for the New Year

 

[BrianMcL]

Both bulbs in the correct way up so I'll just have to adjust the heights using the adjusters on the headlights. At least that's straightforward enough.

 

[Granvilleb]

I had the LH dip bulb fail and on replacement the locating tab groove is not easy to find. I thought I had fitted the bulb correctly and noticed in the dark that the beam was at 45 degrees. Got it right the second time. I changed the RH bulb as it is the same age. Not as simple. Take out the air filter box and then it is easy.
As for DRLs. Us oldies may remember the Mini rally cars being removed from the Monte Carlo Rally because their driving lights were too low. The headlights on a Mini were only 24 ins high. In UK regs. any light below 24 ins can only be used during adverse weather e.g. fog or driving snow. Can we now believe that the brain dead in Brussels have changed our reg.