Relays

Technical MGB discussion
lightning
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Relays

Post by lightning » Thu Jul 23, 2020 1:17 pm

I would like to know if relays used for LED bulbs are the same as those used for Halogen bulbs?
I have converted my side , stop and tail and direction indicators to LED, they are much brighter, I am very pleased and now feel confident and safer now that other drivers can see me, particularly those with LED head lights as they can obliterate rear indicators. I am now going to fit Cibe headlamps with Osram Night Fighter bulbs. I have relays for LED bulbs hence the question.

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Peter Cresswell
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Re: Relays

Post by Peter Cresswell » Thu Jul 23, 2020 4:28 pm

You need a 30A relay for headlights using 60/55 bulbs, so a relay for LED lighting (probably 5A) won't cope with the current. One 30A relay is ok to power both headlight units. Also if you use a thicker cable to run between the relay and as close as possible to the back of the headlight units, you get much brighter lights as well - and they are even better if you double wire the bulbs so the dipped beam stays on when you go to main beam! When on dipped beam at night try flashing main beam and you will see what I mean. Cibie headlight units should cope with the heat generated by doing this.
Pete
1969 MGB Roadster
2011 MG 6 TSE Magnette
2007 Mercedes SLK
Plus 32 other cars since 1965

lightning
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Re: Relays

Post by lightning » Fri Jul 24, 2020 10:03 am

Thanks for the info Peter, most helpful. Brian

Dave Wheatley
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Re: Relays

Post by Dave Wheatley » Fri Jul 24, 2020 10:16 am

Peter Cresswell wrote:
Thu Jul 23, 2020 4:28 pm
You need a 30A relay for headlights using 60/55 bulbs, so a relay for LED lighting (probably 5A) won't cope with the current. One 30A relay is ok to power both headlight units. Also if you use a thicker cable to run between the relay and as close as possible to the back of the headlight units, you get much brighter lights as well - and they are even better if you double wire the bulbs so the dipped beam stays on when you go to main beam! When on dipped beam at night try flashing main beam and you will see what I mean. Cibie headlight units should cope with the heat generated by doing this.
I find that led lighting dazzles me at night, so double wiring compounds the felony.

I wonder if double wiring is legal? Not a good suggestion for me anyway Peter.
1978 MGB GT
1931 Austin 7 RM
1955 Standard 10
1972 Ford Cortina
No modern!

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Peter Cresswell
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Re: Relays

Post by Peter Cresswell » Fri Jul 24, 2020 1:48 pm

On all modern cars, the headlights are double wired so the dipped beam remains on when main beam is switched on. This has been the case since the mid 1960s when 4 headlight systems first appeared on the Rover P6 and Triumph 2000. The purpose of double wiring (on an MGB in this case) is to provide similar headlight performance from a single unit, but as the beam pattern is dictated by the lens glass, they don't dazzle any more than a car just on main beam where the driver is slow to dip them. The dipped beam staying on with main beam merely keeps the immediate distance in front of the car illuminated, which main beam alone is not designed to do. If the headlights are correctly adjusted and providing the driver dips the lights timely, there will not be a dazzle problem .

I agree that modern cars produce much more dazzle than in days gone by. This I think is for two reasons. 1. the headlights are mounted much higher on modern cars because the bonnet line is higher, and 2. the dipped beam pattern is much broader - it illuminates both the nearside kerb and the offside equally well. These factors mean that in any older, lower car the driver will experience more dazzle, and since the introduction of Xenon lights and more recently LED lights, along with clear lens and the beam pattern being controlled by the reflector, we have had to live with the problem. I also think there is too much reliance on automatic dipping which seems to rely on oncoming traffic producing enough light to trigger a detector, so the dimmer your lights the longer you will be dazzled by bright lights on main beam.

In the case of the query here I can't find Osram Night Fighter bulbs listed but Osram do bulbs called Night Breaker or Night Racer which offer better performance from a halogen H4 bulb. They use a different halogen gas within the bulb which makes the light brighter, but the beam pattern remains the same. They are the same wattage as normal cheap H4 bulbs - 60/55W- so don't put any greater strain on the wiring and switches, but they don't last very long compared to cheap bulbs - two winters are about it!

As far as the law goes, I believe only the maximum wattage for headlights (60W) for main beam and (55W) for dipped beam are stated, so the Night Breaker and Night Racer bulbs are road legal. They are also 'E' Marked. What is not road legal are rally bulbs (sold as off road use only) which are 140/90 watts and the reason for this is the bulb is physically bigger and so are out of focus in the headlight unit so can dazzle oncoming traffic. They are also not 'E' Marked. Replacement H4 LED headlight bulbs made by the reputable automotive bulb manufacturers are also legal as they are designed to maintain the correct focus. But definitely illegal is fitting Xenon bulbs with all the high voltage transformers need to power them, as older cars do not have self levelling suspension which is required when Xenon systems are fitted.

I would still say - if you want better headlights on your MGB then firstly try better headlight units (Lucas H4 are quite good - Cibie H180 are better and Cibie Z180 - if you can find some - are fantastic) then consider relays in the wiring for main beam and use thicker cable from the relay to the bulb, but the best light from 7in round headlights will be obtained by double wiring the main and dipped beams to be on together. It does of course depend on how much driving you do in your MGB in the dark. Although I obviously know how to double wire the headlights, I am not going to provide a wiring diagram ( so don't ask!) as if a mistake is made it can cause an electrical fire. It is surprisingly easy to work out though!
Pete
1969 MGB Roadster
2011 MG 6 TSE Magnette
2007 Mercedes SLK
Plus 32 other cars since 1965

ChargedAutoGT
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Re: Relays

Post by ChargedAutoGT » Fri Jul 24, 2020 11:18 pm

I have found that the hi perf Osram and Phillips bulbs give good light, but the bulb lifetime suffers - a lot.

seem to be replacing one every year. and i never drive at night. always MOT time....
G

Allan T
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Re: Relays

Post by Allan T » Mon Jul 27, 2020 1:12 pm

Had you considered using LED bulbs instead of the Osrams? Perhaps you already are using LEDs as you say you have relays for them. But they're a huge improvement on tungstens and a large improvement on halogens, and need vastly less power than either, so I wanted to be sure you and anyone following this thread considered the LED option.

Allan T
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Re: Relays

Post by Allan T » Mon Jul 27, 2020 1:26 pm

By the way, if you have LED headlamps, the power they draw is so much lower than tungstens or halogens there's unlikely to be any real advantage from using relays either in protecting the light switches or giving greater brightness, though of course they'd do no harm.

lightning
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Re: Relays

Post by lightning » Sat Aug 01, 2020 11:11 am

Hi Allen,
Yes I have LED headlight bulbs from Classic Car LEDs that are pre-focused for MGB headlights but was a little disappointed with the result, although they seemed brighter the beam was poor, this I guess could be due to the lense, a new original style one from MGOC, Cibie lenses maybe the answer if not change the bulbs to Night Braker bulbs. All the exterior bulbs are LEDs and are well recommended with to-days motoring, they are literally brilliant, even in the daytime. I`ve yet to change the dash lights, access looks like challenge not to mention extracting bulbs that were fitted decades ago.

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Tom Brearley
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Re: Relays

Post by Tom Brearley » Sat Aug 01, 2020 11:01 pm

Peter mentioned he thought the maximum wattage for main beams was 60W and 55W for dipped. This gave me thought, as Clausager says that after 1970 sealed beam headlights ("improved type") were fitted of 75W. In fact, I can't find any legislation stipulating a maximum wattage (but maybe I haven't looked hard enough). The Road Vehicles Lighting Regulations 1989 (Schedules 4 and 5) give _minimum_ wattages for vehicles first used prior to 1986 but not maxima as far as I can see.

Interesting (ish).
1973 MGB GT (Exeter) - currently shaking down after 3 years off the road

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