100w Headlamp bulbs

Just noticed this on their website.

The Important Info:

*Specification: Xenon superwhite off-road upgrade bulbs

*Designed to Fit: The vehicle listed above

*Road Legal: These bulbs are NOT road legal

*Plastic Lenses: Safe to use

*Guarantee: 6 months as standard

Damage to the wires at the bulb connectors by overheat is when the headlights have been left on with the engine switched off, as the car is not moving the heat generated by the bulb and the lack of airflow in that area plus as the battery gets flat the voltage drops so the amps increase.

Most modern car manufactures have the headlight wiring relayed so that the ignition has to be on for dip and main beam to be on; so it’s not possible to leave the headlights on 'unless you're daft enough to leave your keys in the ignition and switched on with the engine not running’

Unfortunately on the TF you can have the headlights on full with the ignition off.

I had to fit a headlight bulb to our Passat and was amazed at how small the size of the wires at the bulb connectors are, possibly 0.5mm sq, on this car you can only have sidelights with ignition off, no headlights.

If you wanted to modify your wiring to prevent the wires overheating you could fit a relay in the IND/WL circuit (the warning light signal from the alternator) so when the alternator is on station (charging) the relay contacts are made giving a feed to the dip and main beam control circuit.

This idea is what the caravaners use so they can charge the caravan battery when the engine is running but as soon as the alternator is not charging the circuit is broken (I think they call it a preferential charge or split charge relay)


Anyway my eyesight is crap for night driving and I have never found a guide dog that can run fast enough; so I let the better half drive at night (also a good idea to let her drive so I can have a few beers)

Hmm. Some things to think about there. Not sure how much cooling effect you get in a fairly sealed unit, and headlights should be designed to work while stationary, but it is possible. Also I would have thought the connectors would be designed to take the current with the engine off, although money can be saved by pairing the cable down to it's bare minimum. Every penny saved matters when you are selling thousands of cars.

Most melted connections I've dealt with have been down to overrated or cheap lamps being fitted.

This has sparked an interesting debate.
Clive hit the nail on the head with my melted connectors. The melting was caused by the poor quality oem plug becoming loose on the bulb spade connectors.
I changed them to good quality connectors - no more problem! :yesnod:

David Aiketgate wrote: This has sparked an interesting debate.

Groan.

An interesting use of the word "interesting"... :whistle:

I'm interested to learn why you are interested enough to assert that my use of the word 'interesting' is interesting?

It is interesting that you ask about my interest in your use of interesting as a word...interesting, indeed.

cjj wrote:

John and Sue wrote: Sorry, as an Electrical Engineer, couldn't let this one go.

Headlights are usually used when the engine is running. So the battery applied voltage is around 14.4 Volts. Due to alternator input.
So Ohms Law gives 200/14.4. Just under 14 Amps.
55W x 2 gives just over 7.5 Amps.
So Clive's figures are correct when engine off. If you are dopey enough to have your headlamps on when the engine ain't running.
The cables will probably still overheat with 100 W lamps, but depends on the csa of the cable. May be ok.
Just saying.

Really?

It was only a rule of thumb.

But if we are going this route then maybe you should have mentioned effects of temperature and worked out the resistance of the cable lengths. Maybe you should take into account also that you design a circuit for the worst operating scenario, so the driver could sit with headlights on and engine off, which would be around 12 - 12.8V

Thought that would get a bite! :broon: thought you knew me better by now!
yes, any sane designer apples worst case conditions to circuits regarding ambient temperature versus resistance. But we're talking MGR here, the people that bring you cassette storage in a factory CD player equipped car. Etc etc.

Oh, and Ohms Law isn't a rule of thumb: it's a series of mathematical absolutes. :yesnod:

Spoken like a true engineer.

12V was used as a accepted voltage for the sake of ease of calculation and to not overcomplicate the issue, which was to show the correlation between power and current. It wasn't intended to show an exact value of current, just to show that putting 100W lamps in would almost double the current.

My "Flawed" example showed that, and so did your eloquently engineered version.

Current ( ) company noted, in my experience, while engineers are good at their purpose, they tend to overcomplicate what can be a simple explanation.

cjj wrote:

Rich in Vancouver wrote: I used to run 100W high beam bulbs on the rally car, never had a problem. Also ran some big mother Cibie long range driving lights again without a problem. Mind you it was a 1989 Skoda so probably had better wiring than an MGF :coat:

I did similar on my Ford Sierra and the light control stalk burned out, at night, with 100 miles left on my journey. The only thing that worked was flash, so did the rest of the journey with my hand on the flash. Obviously went black ops when a car was coming the other way, but it was 3am. Still not sure the stalk wasn't a coincidence, but hey, you never know.

Mind you we only ran the car on winter rallies, sub-zero temps and all that so there was lots of cold air flow particularly over the lenses. Might have been a fluke that the circuit didn't burn up somewhere out in the wilderness! :hgf:

Gawd those rallies were fun!

cjj wrote: Spoken like a true engineer.

12V was used as a accepted voltage for the sake of ease of calculation and to not overcomplicate the issue, which was to show the correlation between power and current. It wasn't intended to show an exact value of current, just to show that putting 100W lamps in would almost double the current.

My "Flawed" example showed that, and so did your eloquently engineered version.

Current ( ) company noted, in my experience, while engineers are good at their purpose, they tend to overcomplicate what can be a simple explanation.

Nice one Clive. :broon:
I actually started as a humble apprentice power station sparky 40 years ago this September. After doing night school off me own bat the Generating Board kindly sponsored me on a part time degree course at Leeds Uni in the 90's. so after many years of hating Engineers...... I became one!

Now a Chartered one, and a member if the IEE an' all. But don't blame me for the Regs: a different bunch, that. :yesnod:

So, I could talk sense in the earlier stage of my illustrious career. Though many might disagree. :yesnod: