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MG MGA - New headlamps

Bought a new pair of headlights bulbs, which it is claimed on the package that they produce an additional 80% light. The wattage stamped on the metal rim of the bulbs is 60/55. This is the same wattage as my existing bulbs installed on the car. I have not tried them out in the dark, but lit one from a battery and the light emitted is quite strong and very bright white. This was done inside the garage. My question is should I install a relay in the headlights circuit? and, would there be any risk of fire from hot wiring? Attached is a pic of the package.

Frank



F. Camilleri

If they are the same wattage bulbs then they will draw the same current as the previous bulbs Frank. So you can use the original wiring.
However,I have read that if you fit a pair of relays and use thicker wires you should get brighter lights.

One thing I would recommend, even if you dont fit relays, is that you should fit a fuse into the lighting circuit.
I have fitted one but only after a catastrophic short circuit that burnt out the front loom.
Colyn


Colyn Firth

I endorse the recommendation to include fuse(s).
There is a very informative and helpful posting in the archives by Lindsay Sampford entitled "Extra fuses re-think and re-work". Would recommend you take a look.

I fitted them recently and am grateful to Lindsay for sharing that.

Regards, Graham
Graham V

"One thing I would recommend, even if you dont fit relays, is that you should fit a fuse into the lighting circuit."

I would suggest, if you are going to fuse the light circuit use two fuses - one for each light. That way, if one fuse blows, you still have one light to get home on. When we got the MGB that we own now, it had a circuit breaker on the headlights. the circuit breaker chose a particularly dark night on a winding road with no street lights and nowhere to pull over. we stopped and hoped that no one would come around the curve we were on while I worked to get the breaker reset. Cheers - Dave
DW DuBois

Why not fuse the tail light circuit also?
Mike
Mike Ellsmore

If I recall correctly, Lindsay's diagram fuses the headlamps and side lights separately
Graham
Graham V

My single fuse protects the entire lighting lighting circuit, sidelights and headlights.

I admit that it would be better to have a multiple fuse box like Lindsays and I probably will fit one sometime.

However, fitting a single fuse is a really easy first option which, in the event of a serious short circuit, will at least protect the wiring loom and possibly the whole car from a catastrophic fire.

Colyn
Colyn Firth

The Lucas SF4 Fusebox has 4 fuses and fits the same holes on the firewall as the standard MGA 2-fuse block

I have used one of the extra fuses for lighting






Dominic Clancy

Why didn't MG fit fuses originally? Did they take the view that the danger of loosing all your lights driving at night was greater than that of a short? After all most incidents of fuses going wouldn't have caused the serious fire danger Collin experienced? I clearly I don't know the answer.

Paul
Paul Dean

I reckon mgaguru comments are compulsory reading when considering extra fuses for an MGA (start at ET-200)
http://www.mgaguru.com/mgtech/electric/electr_2.htm
Mike
Mike Ellsmore

I want to thank you all for you suggestions and advice regarding my query. I have now settled for fitting extra fuses in the lighting circuit. Playing safe as always.

Frank
F. Camilleri

One for Dominic. I'm wrestling with the best way forward on fusing on mine. Tending to go with the Guru that, given a well executed wiring system, it's not necessary or even desirable to install loads of extra fuses due the possibility of extra connection problems, volt drop, etc. So, just interested in your comment re one extra fuse for lighting. Presume you have decided that one fuse (in series with the power wire from the live side of the ignition switch which feeds the lighting switch) is adequate for all main lighting and accepting the (hopefully!) unlikely failure of all forward visibility if that fuse should go? (Rather than separate fuses for main and dipped beams.). How do you see it?
Bruce.
B Mayo

If Barney was right, modern cars would only have two fuses too, and none on lights - which is easily disproved by looking at the owners manual of your car - under the section fuses you will probably find something like the attached image. Your own modern car probably has multiple fuseboxes, each with multiple fuses and relays..

Then there's the failure mode to think about. When you get a short (such as the rear license lamp live feed dropping out of its connector sleeve), what happens?

If you have an extra fuse, it blows and gives you a fairly clear indication that something is wrong somewhere on the circuit. Without a fuse - well it just melts the wiring on that circuit, and anything else that lies alongside it until they short too, and this escalates until the power is disconnected or the wiring is all burnt out. At best it only affects the loom at the rear of the car, but that one light is also connected to the sidelights at every corner of the car and the dashboard lighting.......

Not a likely scenario? Tell that to the owners whose cars I have re-wired after exactly this scenario, or another very similar short in the lighting circuit. And one got lucky with this fault because the short was very intermittent and made his lights flicker and prompted a search for the cause. How long does it take the loom to burn out - about five seconds for the rear loom to let lots of Lucas smoke escape, than less than a minute for the rest.

So, as you can now probably guess, I am of a completely different opinion to Barney here.

If your car still has its original wiring I would very highly recommend that you install some extra fusing, because the insulation may look fine, but it's actually old and rather brittle, and waiting to fail when you least want it to. I rewired one car where even the rubber sleeves on the bullet connectors were falling apart and only staying put and not sorting to earth because the rest of the wiring was so stiff - nothing moved until it was touched, at which point the insulation turned to powder. It was plagued by reliability problems.

Better is to put in a new loom, it's actually nothing as hard as it may look, and on the way you will probably find a number of other things that are really not electrically up to scratch. On all the cars I have rewired this has been the case. (I have done enough that I can now label most of the loom without referring to the wiring diagram). A loom costs less than 200USD and a day to install if you approach it logically and no other electrical problems are uncovered. For some strange reason the headlamp pigtails are never included with the MGA loom, so order these separately.

How is my own extra lighting fuse connected? The Brown/Blue wire is routed through the fuse before returning to the switch.




Dominic Clancy

Hi Dominic,

Looking at your image attachment, I must say that it is very neat. I am sorry to say though that I cannot make heads or tails from this image. I am not an electrical guru by any means, but not too bad on car electrics, and have worked on many wiring projects and repairs over the years. I am not criticizing your diagram, but to me it looks very professionally laid out, where only professional electricians are able to follow. I am more used to simple wiring diagrams as can be seen on other sites. Is this diagram straight out of workshop manual?

Frank
F. Camilleri

Dominic. Your diagram is of a modern car fuse box layout, with which I am familiar, and not any of your cars I presume. Not sure if you are recommending that amount of sophistication for an MGA, surely not? Yet you still refer to one extra fuse on yours. Slightly confused here. Nevertheless, I shall go for one extra fuse, possibly two, in the lighting circuit.
Bruce.
B Mayo

I used the diagram from a modern car to show the layout and proliferation of fuses to counter Barney's argument that no extra fuses are necessary at all. If progress wasn't a good thing we would all be driven Model T Fords. They had no fuses at all as standard, but I believe any sane owner fits at least one.

I would strongly suggest that a fuse in the lighting circuit is a must-have, and although I used a Lucas fuse box, it's not really necessary. It would be just as good to put an in-line fuse holder into the light wiring live feed at the back of the light switch.

There is the argument that sidelight, high and lo beam headlights should be separately fused (as in the modern diagram I attached). It has a certain logic, but I would suggest having a simple approach with one fuse is a whole lot better than none at all. If you are up to the sophistication of fuses on every circuit, why not.



Dominic Clancy

We are now on the same wavelength! Thanks for your input.
Bruce.
B Mayo

This thread was discussed between 12/07/2017 and 17/07/2017

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