80w headlight bulbs load

[goltho]

Evening all,

I'm about to experiment with different headlight bulbs including >55w versions on a pair of new headlights I've obtained.

Anyone know:
• the max current rating for the dip & main wiring and also the LCM switch
• the likely maximum power rating the headlights will stand in respect of heat

I have the option of fitting relays to remove any risk to the wiring & LCM but would like to know if anyone's uprated without any issues.

And I am aware of the relevant Construction and Use regs. Thanks.

Dougie.

[xsport]

And the max power the 20 year old wiring harness will stand ! ....

[SD1too]

Originally Posted by goltho

I'm about to experiment with different headlight bulbs including >55w versions ...

Bear in mind Dougie that the LSM uses transistors (not mechanical relays) to switch the various lighting loads and we don't know how they're rated. Also, the increased current may trigger a bulb failure warning.

What you're proposing is not without risk and you wouldn't be happy if your LSM failed.

Simon

[StewartIngram]

Ever since I swapped to R75 in 2007 I have uprated all my head & fog bulbs. (Previously I had an 827, which I uprated to 130W). I've had 100W bulbs in the R75s all those years (unable to find any 130W), with no problems at all. Check the fuses (off the top of my head I can't remember the size). The formula is I= P/V (Amps = Voltage/Current).
I will add that they have been checked at the MoTs with no problems and I don't get flashed for dazzling oncoming drivers, as the alignment is set up properly, though I am aware of the regulations.

[Jamiewelch]

The main issue is the inside of the lights gets dirty, either the reflector or the bowl / lenses if projectors. Stripping the light and cleaning will have the most impact, you can only reflect so much light off a dirty surface. OEM xenons with clean bowls / lenses put out plenty of light, you would be surprised how much dirt gets inside the lights.

[goltho]

Originally Posted by SD1too

.....the LSM uses transistors (not mechanical relays) to switch the various lighting loads and we don't know how they're rated.....
What you're proposing is not without risk

Thanks Simon. It was the rating data I was after to assess the risk, but it's not hard to install a 4-relay workaround so the LSM will simply activate the relays. I definitely do not want to self-inflict any injuries.

Originally Posted by StewartIngram

I've had 100W bulbs in the R75s all those years (unable to find any 130W), with no problems at all.

Good info Stewart, thanks. I'm not so concerned about the wiring capability as the LSM. The fuses are a safeguard obviously but they'll be rated quite a bit higher than the maximum sustained current the wiring can stand. I don't want to cook it. Having said that, you evidently have had no issues with 100w uprating so that's useful thanks.

Originally Posted by Jamiewelch

The main issue is the inside of the lights gets dirty, either the reflector or the bowl / lenses if projectors. Stripping the light and cleaning will have the most impact

Morning Jamie. In fact this was where I was headed as the lights have become quite opaque again so intended to strip them rather than just treat the outsides again. The motor's bust on one side too so I had a look for another pair and found an immaculate set for not a lot of money. So thought it would be worth playing with different options while I was at it.

How's the Beemer?

[Synchromesh]

I don't know the circuit for the LSM but if the outputs that drive the headlight bulbs are semiconductors and you insert relays between the LSM outputs and the bulbs you will have to connect diodes across the relay coils so the back EMF when you switch off the lights does not damage the LSM outputs.

[goltho]

Originally Posted by Synchromesh

I don't know the circuit for the LSM but if the outputs that drive the headlight bulbs are semiconductors and you insert relays between the LSM outputs and the bulbs you will have to connect diodes across the relay coils so the back EMF when you switch off the lights does not damage the LSM outputs.

Appreciate raising the point. I've twice previously installed relay conversions (last one on my Ford Crown Vic) and fitted Schottky diodes for that reason. Nobody likes back EMF.

Dougie.

[goltho]

So here's another question for a further 10 points.

How does the car handle bulb failures? I've always assumed a module (the LSM?) continuously polls the bulbs for continuity and issues a warning when one fails, whether or not it's turned on. If that's correct (may not be), fitting a relay reutilises the headlight feed as the trigger supply to the normally-open coil contact. Would that then replicate a failed bulb and produce a dash warning?

So if that is the case:
a) would the flyback diode affect that scenario, and
b) would fitting a resistor in parallel with the diode act as a workaround?

I may be barking completely up the wrong tree but that's ok. It's why I'm asking the questions. Thanks.

Dougie.

[SD1too]

Originally Posted by goltho

How does the car handle bulb failures? I've always assumed a module (the LSM?) continuously polls the bulbs for continuity and issues a warning when one fails, whether or not it's turned on.

Assumptions are unwise Dougie. Extracts from RAVE follow.

"This function is operational only with the lighting circuits being switched 'on'."
"The LSM will check the condition of a bulb when the actual circuit for that bulb is switched on."

Simon