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MG MGB Technical - Lamp 'question(s)'

Good evening,

A "question(s)" for you about head lamps for my 1979 mgb roadster...

Currently I have a mixed pair... one is a regular sealed beam, and the other is a halogen sealed beam.

I never (or seldom due to my age) drive at night.

When I was doing a light check today to make sure everything is set and ok for my Watkins Glen trip, I noticed the difference in brightness and color of the bulbs.... first time I ever checked them in the garage with the door closed and no other lights on. Always before I checked the lights outside... kind of a "duh" I know because I have owned the "B" for 8 years now.

The plan is to change both lamps at the same time to sealed beam halogen.... will these work ok with the electrical system, wires, and alternator... these are all original??

And would a local auto store carry these lamps (Auto Zone, NAPA, etc...)??? Hate to pay extra for shipping if I can buy local.

Of course, if I had unlimited resources I would install a nice pair of the crystal clear headlights, or a set of Hella Halogen.... but retirement dollars only go so far... so it will be halogen sealed beams.

Looking forward to your replies, enjoy your evening, and if you see me on the road going to Watkins Glen... give a wave!

Don 1979 MGB Carmine Red from Penna.
Don

Don
Just got two halogen sealed beam headlights (brand is GE) at the local Wal Mart. They were about US$9.75 each and went on the 1977 B Roadster I recently purchased with no problem at all. Enjoy your trip to the Glen-don't forget to check out the wonderful International Motor Racing Research Center on Decatur Street.
Richard Miller

Hi Richard!

Thanks for the information I never thought about going to Wal Mart.... just down the road from where I live. At $9.75 each should be a better deal than at Moss $12.95 each plus shipping. I can save enough money to buy a can of wax.

I am going to be part of the "Knapp Tour" and we form up at the Motor Research Center... GREAT place to visit.

Drive safe!
Don
Don

If you keep the standard wattage you should be fine. However if uprating the wattage you should fit relays (and filament fuses) as the extra current can easily cause problems with the main and dip switches and connections. But adding relays even with standard bulbs should still give a useful increase in brightness. And have you checked the voltage at the lamps? It's quite possible the dimmer appearance is caused by bad connections in the wiring at the front of the car, in which case different lamp units (and relays) will make little difference.
Paul Hunt 2

Hi Paul, thanks for the info. My plans are to install regular sealed beam halogens. Just about ready to do the project now.... what should the voltage at the bulb be at?? I have a tester and will do it the time of installation.

Looking forward to your response.

Don 1979 MGB
Don

In a perfect world the same as the battery or alternator voltage. But in practice there will always be a little voltage drop, and as connections and components get older this increases. In original wiring there can be as many as 18 or more connections and components in the headlight circuit, that is the 12v supply as well as the ground. To measure the voltage at the headlight you need to do it between the supply and ground terminals of the bulb holder itself. You can also measure from the alternator body to each of these as well, and that will tell you how much is being lost in the 12v supply (by subtracting it from the voltage on the brown at the alternator) and how much in the ground directly. This last will need the meter switched to a lower voltage range as (hopefully) you will only be measuring tenths of a volt. You will need to do this for each beam at each headlight as some of the connections are unique to each, and if one of these is bad it will make that beam dimmer than the other side. I suppose I'd like to see no more than 2 or 3 tenths of a volt lost, but wouldn't be surprised if it is closer to a volt or even higher.

I rewired a 1980 and fitted relays to the (uprated) headlights and the owner said the difference was amazing. Whereas as before when he switched from dip to main or vice-versa there was a 'blackout' period as the 'new' beam faded in, afterwards it was instantaneous i.e. as it should be. Brightness was also much improved.
Paul Hunt 2

Don

There are a couple of reasons to add relays to the headlight circuit. First, it decreases the current through the switch, increasing switch life. And, as Paul mentions, it minimizes the voltage drop in the circuit to the headlights. I have added headlight relays in my 72 GT using Hella relays with the built-in fuze holder and am happy with the results. Of course I also added Cibie headlights with higher power bulbs. Lighting is great.

FWIW

Larry
Larry Hallanger

Thanks Paul and Larry for your replies! Now I need to know a "little" about the relays.....

Where do I get these relays... Moss, V.B., or ?

Where abouts do I add to the wiring (in wiring diagram)?

Just want to make sure I do it right.... looking forward to hearing from you again soon.

Don 1979 MGB
Don

Generic relays are fine from any of the usual sources, doesn't have to be MG parts houses.

Have a look at http://www.mgb-stuff.org.uk/wn_electricsframe.htm and click on 'Lighting' and 'Uprated headlamps - Relays and Fuses' for info and schematics.
Paul Hunt 2

Hi, Nice to see someone else from San Diego! I have a 1974B And a number of years ago I pulled my regular Lucas headlites and put on a set of halogen lites from my local Kragen store. They have worked beautifully for me and give much better lite. I do miss the Lucas name on them tho. I also ran a wire and switch so I can run automatic daytime running lites when I choose to. Are you in the San Diego MG Club? We meet first tuesday each month.
Robert Ekstrand

Robert

Yes, I have been a member for about 10 years. Look for the mineral blue 72 BGT. I also drive, or will when I get the hydraulics rebuild completed, a pale yellow 58A.

As a side note, for "daytime" running lights I got the european style H4 Cibies with the integral parking light. I use Hellas on the A.

Larry
Larry Hallanger

Don,

If you're going to be at the Glen look me up on Friday. I will be judging the concours and have my 66 B there as display only. Stop by and introduce yourself. I will talk if I can, but if I'm judging at the time I will have to just say Hi. Morning is usually a litle better and less hectic but by about 11 we start to judge the cars. I'll also have my car in the show out at the track on Saturday.

Hope we get a chance to link up and say hello.

George Hershell
George R Herschell

This thread was discussed between 24/08/2007 and 31/08/2007

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