AlanG

Just a thought really.
There's been a few threads about this and a number of you have done it to good effect, but i'm wondering if it's really necessary.

For example, from your lighting switch,the wiring goes through a relay before terminating at the respective lamp, so why would you want to put another one in?
And why do we have a voltage drop at the lamp if it goes through a relay anyway? Is it down to thin wiring? poor relays? what?

Do you relay the lamps so that you can run higher wattage bulbs than std and so reduce the load on the std wiring? If so, why go for higher wattage bulbs in the first place if the lenses are plastic and the manufacturers recommend sticking to 60/55W because you run the risk of damaging the lenses with higher wattage bulbs?

I know some of you run higher rated bulbs with no ill effect to your lenses,(i've ran 100w bulbs in mine in the past) but it's just as i say, a thought.

Discuss.

ozzy

Well, I'm no expert (OK, you've guessed that already), but uprating the headlamp wiring involves running heavier duty cables direct from battery to bulb (albeit via a relay). The relays are just there to trigger the circuit from the OE headlamp plug (and therefore OE headlamp switch. This should, in theory, supply a full 12v for the individual lamps and avoid any voltage drop problems - this bit is open to debate and will vary between cars.

I measured 14volts at the alternator, but just over 10volts at the actual lamp itself. Now, the questions is whether I measured correctly and if so, is the voltage reading accurate. I did ask at the time and was told yes by a few auto sparks (personal disclaimer )

The main reason I wanted to uprate the wiring was to make sure my existing lamps were being supplied with the correct voltage and not to run higher wattage bulbs. I was hoping this would increase the effectiveness of the lamps, but being a lazy @rse recently I've not bothered. Oh, and I couldn't source cheap relays (well cheaper than £8 each) so the costs rose quite a bit.

The risk from these would be the additional heat from the bulb and melting your reflectors. IIRC, the advice for NOT running hgher wattahe bulbs on the OE loom was the cable and (more specifically connectors) couldn't cope with the extra current.

Stefan

AlanG

Hi Stefan

This is one of the reasons for bringing the thread up. What i would like to know is why we have a voltage drop at the lamps at all, since the wiring for the lamps goes through a relay in the first place.

AlanG

If you still want to do it (on your next car ), i can dig out the price i paid for fused relays and contact details. Quite sure it wasn't anywhere near £8 each.

David_Wallis

Maplin sell some cheap 30a unfused relays use a blade fuse with crimp connectors on..

dont forget to use a diode for back emf supression.

I would try an alternative gnd to check the voltage drop.

Otherwise is **** wiring..

Other relays may be necessary if the wiring isnt upto it.. (its no fun repairing a wiring loom that has been melted together.. lots of burnt wires - all over the car, depending on what side of the fuse the fault is )

David

ozzy

So, have you measured the voltage to your lamps Alan? You're not running those flasher units still?

I can get some cheap'ish relays, but I wanted ones that had the blade fuses built into them (just to make a tidy job). Vehicle Wring were selling them for more than twice the cost of the unfused ones

Juat wondered if that was the case with any fused relay or whether they just happened to be expensive from there.

Stefan

AlanG

I haven't measured the lamps yet Stefan but with the car approaching five years old I think it's more of a preventative measure than dealing with a problem. Same thing when i did the "earth mod", I didn't have any problem that i knew about but had the stuff there and would have done no harm in doing it. (Plus i was bored TBO)

We measured Dougies though and his is a couple of years younger than mine and there was over 2volts difference betwen alternator output and lamp.

Alan

AlanG

Still got the "flasher unit" Haven't used it for a while. T-uk was the last one to sh*t hisell when i used them.

ozzy

Even my MY99 (5yrs in May) had a 2v drop so you might be surprised.

Flashers are one of the :ccol:'ist mods I've seen yet