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MG TD TF 1500 - Halogen headlamps draw a lot of current...

Last week, a headlamp blew and I had to upgrade to new halogen lamps (I went with the 6024s that others here recommended).
Yesterday I got the electrics finished and the ammeter reinstalled and working.
When I turned on the lights, the draw was nearly off the scale! The meters fine, it registers a tiny draw with lights off, and charges correctly showing a positive amperage when the engine is running (lights off).
But when I turn on those lights, its using a LOT of current, so much so that even with the engine running fast it is still showing a slight negative draw.
I read some threads where this was discussed, but I didn't hear any solutions.

My options would appear to be:
1) Find an old set of working sealed headlights using less draw. "Grandfathered" legal but not bright, hardly desirable.
2) I believe it is possible to install a H4 bulb assembly, and buy 2 35w H4 halogen bulbs - normally used on ATVs - but which I am told are not DOT legal anymore on the road. Not legal, not bright, but nobody's going to arrest me.
3) Install 35w HID lamps (which generate 20,000 volts). Cost maybe $300 total, and I'm concerned that with my positive ground vehicle, one frayed wire could do major damage to the entire electrical system. Very bright, NOT legal.
4) LED headlamps - at $300 each, very expensive but bright and legal.
5) Only drive during the daytime.

As far as I know, my generator is the original one. Is there anything I can do to boost output? Can they be rewired to generate more power? Are there replacement generators out there?

Any other suggestions or solutions to this issue?

Thanks again for the input!
Geoff Baker

Geoff, new Sylvania H6024ST Silver Star lamps only draw 65 watts (each). That's just over 5 amps, or about 11 amps for two of them. I would think that your generator should be able to handle with ease at normal speeds.
Have you ever checked your ammeter? Bud
Bud Krueger (TD10855)

Geoff -
There is no reason why "halogen lamps draw more current", except that the particular lamps are over wattage. For some years the standard has been 60/55W, both on H4 and sealed beams. What do yours have stamped on the back?
60W is nominally 5A @ 12V, real measurements can vary. Lamps themselves can vary by 10-15%, depending on who made them. Higher system voltage gives higher amps draw if you are simplistic, but higher V also means higher filament resistance, which gives lower A. Higher V gives MUCH more light. Measure both A & V if you want to know what is going on. Good wiring and relays for the headlamps can help a lot, and reduce loss through heating as the headlamp power runs through less miles of wire and switches.
Two of these would be 10A draw, plus a few A for the rest of the car.

The generator is rated 17A @ 13.5V at the generator, @ 2000rpm, 19A for later cars. Again, run the proper checks for output and regulation. The WSM assumes standard fitting, and does not give actual generator rpm, but that info must be around someplace. Smaller pulley on generator can help, if you don't use high rpm, and it might be that you have a bigger than stock one fitted over the years. But pulley changes screw up the tach drive ratio.
The system should handle the lights as long as you don't drive like a little old lady, or let it idle for extended periods. Big batteries help here - ever notice that cars with primitive electrical systems have huge batteries?

There are sealed beams available that are rated lower, like 50/40, but they are largely obsolete, and may not come in halogen, thereby reducing useful flicker to even less. Again, some MC may use them, so there might be halogen sealed beams at other ratings. Better fix is H4 lamps, and bulbs of your choice. H4 are available in many combinations, for MC and Vintage car use. You need to find a specialist supplier. I can't remember who, but I have recently seen all combos of H4 like 60/50, 60/40, 50/35, 40/35 etc. Might try Candlepower Inc, and there is an Australian supplier of esoteric H4 bulbs to fit vintage cars and MC and all the variant lamps they used.

FRM
FR Millmore

FRM, I'm driving a car thats older than I am aged wiring, weak lighting (compared to any modern car) antique braking systems and an underpowered engine. I should also replace the 30 year old tires soon.

Of course I drive like an old lady!! :)

Seriously, thanks for the info. I'll look through archives on ways to test the ammeter, and info on the generator.
Geoff Baker

The ammeter looks good. I could run another one in series to test it, but here's what I see on my 20 amp meter.
All electrics off, the ammeter balances not quite at zero, it's reading a negative 1 amp.
When you turn the key and it turns on the electrics, that barely changes.
When you turn the signal lights on, it goes up to 3 amps.
When you turn the main lights on, you hit about 12amps
With high beams, it's 13-15... quite a swing for a second, then it settles back down

This all sounds roughly correct for the draw 65x2 /12v gives you approx 11 amps, plus brake and turn lamps and other electrics in the circuit.

But I think it's now significantly higher than the old lamps which were non-halogen 6012s. On the other hand I didn't take any readings so I'm going on hazy memory there.

I am a bit concerned that with all lights on (high beams) and the engine running it's not generating enough power to charge; but on regular beams I think it appears to at least hold even.

I really should replace the wiring. I've done MOST of the wiring behind the dash (half was melted off or frayed when I started) but upon opening the headlamp buckets, for example, I found three bare sections of cracked wiring in one bucket alone! It's probably much the same throughout...

But that's for another time. Next project: wheels and tires.
Geoff Baker

Fletch is right on. Low beams are 55 watts. At the nominal output of the standard 13.5 volts, current draw should be 4.1 amps X 2 = 8.2 amps, and any good generator should be able to easily handle this.

As I indicated in another thread, I find that my ammeter will swing to the + side, when I hit about 2,000 revs, and I feel comfortable under most driving conditions. I obviously, avoid idling on the battery.

Living in the country, I frequently use the high beams, and occasionally look down at the ammeter, and I don't recall it ever dropping into the - side.

Fletch has also alluded to other possible remedies, but I suggest you might have a leak. Check and clean all contacts between the switch and the headlamps. Also, check the grounds of the headlamp bowls. You could always hard-wire a separate ground directly to the battery to check, if the ground is suspect.

Switching to the H4 shouldn't make any difference. Furthermore, I don't find the H4s as bright and 'clean' as the 6024H lamps.

Gord Clark
Rockburn, Qué.
Gordon A Clark

Thanks, Gordon. I'll check the headlamp bowls first - as I mentioned, I already found cracked wiring I had to tape up, maybe I missed something! At any rate, when high beams are on I am in the negative no matter how high I run the rpms, so something does seeem to be wrong, based on what you are saying.
Geoff Baker

Geoff -
The fact that the meter reads -1A at rest is a sign.
Is that with the battery disconnected? If so, the basic movement is out of kilter, possibly in a non linear way.

Ammeter is a voltmeter reading a drop across a shunt. If there is any bad connection inside the meter, ie at the shunt, then all readings are suspect. Does the meter get warm when everything is on?

The effects of bulb filament temperature, a consequence of delivered voltage, are tricky. It may be that if the voltage is low, the actual amperage used is higher than the basic calculation, because the resistance is lower, because the filament is too cool. And you still get crappy light!

Basic test: Hot, running at 2200, fully charged battery, everything ON. Measure at gen, D to earth, that's reference V. Then measure at the point of interest, hot to earth, should be the same, or within .25V for heavily loaded circuit like lights. The critical point for lights is bulb hot to bulb earth at the bulb. If not within .25V of ref V, measure at other points until you find the voltage drop(s). You can find drops by measuring across any section of a (loaded - ALWAYS) circuit, say from one side of the ammeter, or a switch, to the other, should be zero. Two rules: any hot to any other hot = zero, same for earths. And, any hot to any earth = reference V.

FRM
FR Millmore

geoff, i did not do any of the electrical math..but i run warner halogens and with the engine at idle i show a 1 amp draw and when i turn on the headlights it goes to 2 amp draw. with the engine above 1200 rpm i have a positive indication on the amp meter after starting and placing the headlamps to on. regards, tom
tom peterson

It is possible that your regulator (control box) is cutting the generator output back when the lights are on. Look at the generator if the service P/N is 22256x then it is the 17 Amp. version. If the service P/N is 22265x then it is the 19 Amp version. If the model No. is C40xx then it is the 22 Amp. version that was on Sprigets.

The Lucas regulators were supposed to respond to the current draw but I've never seen one that did it successfully.
Cheers,
Bob
Bob Jeffers

Tom P. -- Your description of the ammeter readings is confusing to me. What does the ammeter read when the hi beam headlight is turned ON without the engine running? (Ignition off).
Sincerely,
Bob
Bob Jeffers

hello bob, i can't vouch for the accuracy of my ammeter, but with the swich on, car not running, the ammeter shows -1 amps, turn on the headlamps and it shows -3 amps..high beams -4 amps. same indications i see at 700 rpm idle.
you know way more than i do about sparks, but i assume, this is too low an rpm for the generator to make enough juice to close the cut out relay.
the information i was trying to convey in my post..which other here did in a more thorough way...was that his electrical system should not have a problem running halogen headlights. regards, tom
tom peterson

Hello Tom,
Your attempt to show that the headlights should still show a positive charge is correct as far as I know. It was the -2 Amps that got my interest when the lights were on.

The Lucas ammeters are very primative instruments. They should not be relied on for accurate current flow. But they do show which way the current is flowing, just not how much (accurately).

It seems that the Lucas regulators were not very current sensitive, they seemed to reduce current into the system when they even got close to the rating of the generator. Therefore the regulator couldn't keep up with the increased current requirements of today's cars.

The modern solid-state conversions will cause the generator to put out more current up to the limit of it's capability than the Lucas system. But remember that the Lucas system was designed in the 1930's when there was no other way to do things. I'm just D**n glad nobody asked me to design a regulator with the technology available in the 1930's.
Cheers,
Bob
Bob Jeffers

Limora of Germany sell an alternator in the same style of housing as the old generators, but with modern power output. Cost is about 500 Euros. Maybe there is an outlet for this product in the USA ?
Remo Peter

Remo,

Does it have the Rev-Counter threaded boss on the end? OK if you're driving an MGB, but the T-Series is all-mechanical.

I don't doubt that its not top quality, but price has to be considered, especially when one can pick up a 2-wire 50amp alternator for around $40 (€25), and its very easy to rig a set-up.

But what about a rev-counter? I read that someone is producing a mod to a Yank alternator, that will mount the rev-counter drive to the end, but forgot where I saw it.

Gord Clark
Rockburn, Qué.
Gordon A Clark

Note that the ammeter measures what is going to/from the battery. So, if the battery is fully charged, it will not show a + reading, only zero. You normally only see a + just after starting, or after extended low rpm with an electrical load which has been drawing power (more than the gen can supply), when it would have been showing a - drain. The + reading will be representative of the degree of battery discharge that happened, usually low. High + always means the battery is low/defective, or the charging system is deranged, which will soon mean both faults to deal with.

FRM
FR Millmore

The alternator supplier was Jerry Felper.
DBA British Auto Electric
2722 E. Carnival Ave.
Anaheim, CA. 92806

Hope this helps.
Cheers,
Bob
Bob Jeffers

After reading about the LIMORA alternator in Remo Peter's contribution, I visited their website. The alternator looks like a generator and they do have a model with connection for mechanical tachometer. Part number: 481152. Output is 40Amp. The car has to be converted to negative ground first, which is very easy.
The price for the alternator is steep: 698 Euros

http://www.limora.com/index/lang-2/lkz-195/markenid-3/katnr-183/kat_sprache-2/lang-2/hrubnr-1558/rubrik-4752/functiontpl-virtueller_katalog.tpl,x-a.htm
I. M. Fodor

This thread was discussed between 08/03/2011 and 11/03/2011

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