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MG Midget and Sprite Technical - Would you fuse a headlight circuit

I am in the process of replacing the headlight main and dipped beam circuits with relays before the winter.
The contact points in the steering column switch are so tiny I don't really trust them to work consistently enough on full headlight current. I plan to use the existing circuits to "trigger" two relays which I will mount on the inner wing, near to the headlights themselves..
So, should I install a fuse in the main feed supply to the relay and do I need to do anything special to stop there being a momentary blackout as I switch between main and dipped beam?
Any advice on how to do this properly please?

Guy
Guy Weller

I'd add a fuse just to be protected from any potential damage from a failed relay or short circuit. As far as the "blackout" I wouldn't be concerned, it will be so quick as to not even be noticed. Remember that "speed of light" thing.
Bill Young

Here's a link to Paul Hunt's website. It is mainly about MGBs but has a lot of relevance to midgets, also.

It deals with fitting relays to the headlamp circuit and also fusing.

http://www.mgb-stuff.org.uk/electricstext2.htm#uprated
Dave O'Neill 2

THe MGB Technical page just had this discussion. Look at "Intermittent Headlight problem". Paul Hunt recommended a fuse for each filament (4 fuses total).
David "I have one fuse on the supply" Lieb
David Lieb

Guy. Headlight circuits were not fused because, if the fuse went out, you found yourself driving along, perhaps at quite high speed, with no illumination. Bad show. Especially if one is "tigering" along a windy, back country road. Because of this danger, the headlight system seldom (never?) had a fuse associated with it. (I am not sure what modern cars use for their lighting circuit.)

I have, in something over 40 years of driving, never had a headlight circuit overheat and burn up the wiring.

It seems to me that, if one decides to insert a fuse into the headlight system, a couple of decisions must be made before doing so.

First, is what impact will this have on my insurance if I have to submit a claim after having the fuse blow? Will my insurance cover such a situation or will the insurance company declare the coverage null and void because of this modification?

Second, if I am going to install a fused circuit, knowing that fuses fail more often than headlight circuits burn up, what am I going to do for some form of back up system? Perhaps some fog lights or driving lights wired into the circuit in some fashion? Some form of illumination, if only a single light, that would be available, either manually or automatically, in the event of failure of the primary lighting system would be desirable.

I understand the desire to "upgrade" the old wiring with something "more in the modern style". But, there is an old Bantu saying, "Before you replace the old ways, make sure you have something of value to replace them with". Perhaps worth considering.

Les
Les Bengtson

Les,
I see your argument for not including a fuse in the main supply, although I was thinking of something of the order of 80 amps.
I can see less of a problem in fusing each filament separately on the down-stream side of the relays. But this is just the sort of discussion I was wanting.

Dave and David; thanks I will check out the MGB info.

Guy
Guy Weller

I agree with Les' argument against fusing the head light circuit for the reason that if the fuse blows, you can be left in the dark at a most inopportune moment. That said, what is to keep a short circuit in the lighting circuit from turning the wires in the circuit into unintended fuses and leaving one in the dark? A 80 amp fuse is probably less apt to blow than the wires used for the lighting circuit, thus being useless for protecting the wiring (which is what fuses are really intended to protect). Perhaps the way to protect the wiring in the lighting circuit regardless of what happens, would be to have a fuse for each side. It is highly unlikely that a short circuit would occur on both sides at the same time, particularly if one used relays - one for each side. Finally, keep in mind that we could play the 'what if' game all night long and for every scenario that could be prevented with a fuse (or without a fuse) there is another scenario that will defeat the fuse. In actual practice, in over 50 years of driving, I have had the lights shut down on me exactly one time and that was a case of some SPO (Stupid Previous Owner) who installed circuit breakers in the lighting circuit, only he chose the current rating based on the low beams. Brilliant! When I hit the high beams while driving on a twisty mountain road, the lights went out - OH S--T!!! The following day that particular circuit breaker got removed and tossed. Cheers - Dave
David DuBois

Agree with posts above/below.

It makes sense (if you're going to use fuses) to insert them as near to the battery as possible, to protect the highest %age of the wire.

If you are using 2 feeds from the battery in this way, it would make sense to have one feed for n/s dip and o/s main, and vice-versa for the other feed; this way, a blown fuse always leaves the other side lit.

You might consider using 2 change-over relays such that their normal operation (signal to relay coil 0v) switches on the dip-beam; and applying 12v to this coil changes the relay to on / main beam. (This makes the current dip-beam wire redundant, BTW.)

A bulb switched off cools off more slowly than one switched on heats up. So when you switch to (say) main beam, the dip filament glow dies away, and a fraction later, the main filament heats up quickly. Add to this the persistence of vision (and other tricks by the brain) and we don't perceive a dark period. (Check out your 300/500W security light - when switched off.) A relay won't add any significant change to the timing.

A

Anthony Cutler

I think what I will do is use a single heavy wire from battery to the relays - which will be located near to the front of the o/side inner wing. I will re-connect the existing blue/white and blue/red wires from the steering column headlight dip switch to trigger the relays, one for main and the other for dip.
I will then put 4 fuses -one for each filament - close to the relays and these will protect the wiring from there forwards with negligible risk of all the lights failing at the same time.
The only remaining question is whether in addition to the above to add a single heavy duty fuse near to the battery. I was guessing at 80amps for this which would only blow if there was a major earthing fault in which case the lights would all go out anyway! But maybe 80 is too high a rating to provide any benefit. Perhaps a 60 would be a better compromise.

Guy
Guy Weller

If you are running an alternator and have ample amps then wire up the headlight dipped circuit by passing the dip switch. Then use the dip switch to switch main beam on and off.
So as soon as you put headlights on dipped beam is on all the time and when you switch to main beam dipped stays on and main beam comes on as well .
Will give you twice the light output down those dark country lanes .
You will have to put a relay on Main Beam circuit as on main beam you will be drawing twice the amps through the light switch.
Never had an issue myself on burning out double filement headlight bulbs by using both filements at once .

Roy
R Mcknight

Roy, that's a thought! But I already have 130 watt main beam filaments (55 on dip) so the lighting is pretty good.

What has set me off on this is that a few weeks ago my main beam stopped working. It was just poor/dirty contacts in the steering column mounted switch and easily repaired. But in the process when I had the switch apart and the lights on I realised just how very hot the internal parts of the column switch get when in use! Maybe because of my high power bulbs but whatever - not good!

Guy
Guy Weller

With high wattage bulbs, or when using both dip and main beam together, it would be a good idea to increase the gauge of the earth wire, too.
Dave O'Neill 2

Guy, aren't 130W headlight bulbs illegal?
David (davidDOTsmithAT stonesDOTcom)

I don't think so, as long as the dipped beam ones are limited to 55W
Guy Weller

Are you sure the bulb is rated for both filaments heated at same time?

A
Anthony Cutler

sorry to hijack, but i am also considering safeguarding and upgrading my lights... what specs should i be looking for for relays for the headlights? (and fuses if i decide to incorporate them) i don't really know what amps should be running to the headlights.

I will add to the discussion that the only failure i have ever had on the headlights for my 73 midget has been the switch burning itself out.

thanks!
C
Chris Edwards

Guy
i have a extra thick gauge feed wire from the start realy to a small 2 fuse box on the inner RH front wing
from there i feed 1 (will soon be 2) relay for the main beam (headlights and 2 spotlamps) works perfectly the extra one to be added if for the diped beam just because i might switch to halogenblubs in the future

Chris
if you know the watage and voltage you can calculate the amps

just devide the wattage through the voltage and get the aps then you go and sit on the safe side fot the relay and a bit more margin for the fuse

example Guys main beam bulbs are 130 watts running at 12 volts
since you have 2 bulbs the total is 260W

260/12=21.66
so you get a relay of at least 25amps and fuse it a 40 or something (on switching in curent can peak higher)
Onno Könemann

With high wattage halogens I burnt my stalk switch out at a very inopportune moment - 6am on a country in France in the fog.

Since then (1992ish) I also have the main/dip/fogs on relays. I broke into the the std circuit just after the stalk multiplug. So the stalk operates the relays...and the relays feed the lights via the orifinal loom wiring form their. I didnt go for relays on the main/dip on the basis they didnt have before and I didn't want loads of the slightly nasty in-line fuse holders which can cause as many problems as they solve (and I was on a student budget at the time). If I was doing it again I would rewiew from scratch around larger fuse boxes and include them.

My Relays are on the bulkhead but the master cylinders. Recent picture after far more substanstial additions etc to the wiring.
http://www.eatworms.org.uk/album/album2.php?album=Midget-Dash&mode=page&index=9
Dean Smith ('73 RWA)

Guy's
On the lighting subject, what are the legalitys of HID conversions? and has anbody done it? recommend it?

Best Regards,

Howie.
Howard Wright

Not Legal.. http://www.dft.gov.uk/pgr/roadsafety/drs/hidheadlamps.

On your own head be it. I see an MOT failure coming on.

Roy
R Mcknight

And here http://www.youtube.com/watch?v=yVuSSdZNsZw
R Mcknight

I am not using HID Xenons (Discharge)which produce that horrible blue/white light. Mine are just high wattage Halogen filament bulbs. They have been through several MOT tests without problems, being checked each time with the same sort of equipment as shown on that Autoexpress video. The testing station say that so long as they are correctly fitted and don't exceed 55w on dipped beam, then they are legal. Apparently there is also a date of manufacture -which I forget- after which the legality of using different non-standard aftermarket bulbs changed.

Actually I must check the bulb wattage before I select the fuses. I thought they were 130/55w which were the highest available. But I have an idea that I opted for 100/55w instead as I wasn't, at that stage, planning on upgrading the wiring! But it isn't surprising that the column stalk switch internals are getting too hot to touch!
Guy Weller

Hi Guy , not saying your 130w bulbs are illegal just Howies query on HID conversions. Agree 55w dipped are the brightest you can use , but i dont think there is a rule on main beam . Example my Discovery on Main beam is 110w per lamp .
Roy
R Mcknight

Guy

I have the standard sealed beam headlamps in my Frog that I fitted when I built the car. What units did you fit to enable you fit halogen bulbs and what changes did you have to make to the wiring?(apart from what you are proposing now)

John
John Stephens

John,
I just replaced the sealed beam units with units designed to take a replaceable bulb. I think they were made by Wipac but I just asked at my local Partco suppliers. No alterations to the wiring (yet) other than fitting the matching multiplug dodah for the bulb holder/connector.

Roy,
No I wasn't being defensive about your post. There are too many cars around with defective headlights of one sort or another. Maybe it is just our cars are too low but I am constantly being really dazzled by other cars driving right up close behind and especially noticeable with those Xenon HID lights! And then there are the cars with only one headlight which can look dangerously like a motorbike. Oh, and the muppets who think it is cool to drive with fog lights on in clear conditions! Grumble, Rant, Grumble!

I understand that as from 2010 (or 2011) all new cars will have to be sold with constantly on running lights, like Volvos. Personally I think that is a bad idea. The extra lights in daylight conditions just adds to the excess of "information" one already needs to deal with when driving. It removes the useful opportunity to use lights to warn of additional hazard, or signal to other drivers. And worst of all, it removes the universally accepted use of headlights on a motorcycle to alert and differentiate from other traffic.



Guy
Guy Weller

John. Here in the US, you can purchase a halogen sealed beam headlight at most auto parts stores. There are, still, a sufficient number of vehicles on the road using the 7" sealed beam headlight to make a halogen version worth producing. Back in the mid-70s, a friend installed the 7" round Bosch halogen headlights into his MGA. This used the replaceable bulb system with the bulk of the headlight being the reflector. I bought the car from him in 1978 when he was going over to England and I was back in the US and needed a car for several months. The system worked fine for a number of years.

The sealed beam halogen head lights available in the US were designed to work with the old, existing wiring harness and do not require upgraded wiring to work safely. I have been using them for about 20 years with no problems.

Les
Les Bengtson

And the sealed beam halogen's are useless

well at least the ones my midget and on the GT when we imported them from the UK

Changed for seperate reflector and normal bulb!(way more logic why throw away a complete reflector when the bulb had died)
And it greatly improved the night driving experiance.

Guy where can you buy those 55/130W bulbs?
Onno Könemann

Onno,
I just got them at the motor factors (Partco) in the local town - about 5 years ago
Guy Weller

Onno, sealed beams are not allowed in holland.
Alex G Matla

I know Alex
and rightly so!

i just want the bulb with the bigger main beam

but when i imported my car's they both had them fitted.
and both worked like crap.
And i hate the principle of throwing away the whole unit when only the bulb is broken in these polution minded times i thought the would be forbiden

Guy thanks i will check localy
Onno Könemann

You know why? 'cause it won't fit in a glove box, and you got to have a spare in your car.
Alex G Matla

Ono. I have not been able to do a side by side comparison of the halogen sealed beam vs the halogen 7" round headlight having the replaceable bulbs. But, I have been able to do a direct test of the standard, incandescent, sealed beam headlights vs. the halogen sealed beam headlights. The halogen sealed beam headlights produced a brighter light which traveled further on full beam (high beam).

Thus, if you found the halogen sealed beam "useless" I would have to ask, "In comparison to what?".

Les
Les Bengtson

Les

As i said in comparison to a normal bulb (non halogen) in a proper head light
Onno Könemann

Guy
I'm a bit late coming in this thread but a suggestion if I may on hooking up your lights.
By using a double relay the low beam relay can be wired direct from the headlight switch so that they are on all the time when the lights are turned on and then the high beam relay can be wired from the dipper switch. Hooking them up like this gives you low beam when dipped and both low and high when on high beam getting rid of them little dark spots out there. Fuses are a definate no no in my opinion but a circuit breaker could be fitted to each circuit seperatly. For safety reasons these are a lot better option as they will turn back on in a short space of time. Also with the lights hooked up as suggested,-- While travelling along on hi' beam it would be very unlikley that both circuits went down together.
Hope this helps Willy
WilliamRevit

If you have both Main and Dip on at the same time with uprated bulbs check the current rating of your earths very carefully. The earth lead from the light cluster is probably not rated for both for a continuous period.

(Worringly if you flash whilst on dip beam..both are lit concurrently so you may have the same issue though by definition it should be for "a flash" only)
Dean Smith ('73 RWA)

This thread was discussed between 09/10/2009 and 13/10/2009

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