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MG TD TF 1500 - Fuse replacement....

When my car came out of the barn, it had 35 amp Lucas fuses... i checked the archives and found the "English - N.A." fuse difference. Picked up a box of 15 A north american fuses as i seem to remember my MGA used 15's.
The other day one of the original Lucas ones popped (brake light/turn signals).
I replaced it with one of the 15's and it went after a few minutes... funny... i tested the circuit by putting on the turn signal and holding the brake on for a minute or so... anyway... can't seem to "make" it pop... it just pops after a given time.
In the archives it is mentioned that 17's are also used...?
Would like to determine if i have a problem, or if the fuse just isn't quite heavy enough?
gordon.b.lawson '53TD

Gordon - Basically, the British 17/35 amp fuse will not blow at 17 amps and will blow instantaniously at 35 amps and above. Anywhere in between those two levels of current, the fuse will blow if the current remains at that level for a long enough period of time, with the period getting progressivley shorter the closer the current level gets to 35 amps. American fuses come in a variety of different types foa a given current rating. a 15 amp instantanious blow fuse (also considered a instrument fuse) will blow at 15 amps. A standard 15 amp fuse will withstand about a 150% overload for a short period of time and a 15 amp slow blow fuse will withstand a 300% overload.

Now that you know more about fuses than you ever wanted to, you still don't have an answer to your question. To determine if you have a problem, you really need to put a ammeter in the circuit and read the current being drawn with both the brake lights and turn signal on at the same time. Since it may be difficult to find a ammeter to read above 17 amps accurately, you may need to check the current drawn by one of the bulbs and multiply by 4. That said, I would suspect that you have an intermittent short somewhere in your wiring. Unless you are using some very high powered halagon bulbs, with all four bulbs on at the same time the current being drawn should be no greater than about 8 amps. Also, since the turn signals use the same filiment in the tail/brake light, there is no additional current being drawn by them when the turn signal is on (in fact it is less since one of the brake light bulbs is being turned on and off by the turn signals), just by the front turn signal bulb.

I think that my approach to the problem you are experiencing would be to get some British 17/35 amp fuses and put them in. If the problem persists, start looking for an intermittent short.
Good luck - Dave
David DuBois

Thank you for the lesson in electrics... and here i thought that if you left a socket empty, all the electricity would drain out...!!!!
There is a vintage Land Rover dealer about 4 minutes from the barn... (ever seen a cardboard box filled with original "in the wax paper" 1950's windshield wiper motors?... Just like ours (lucas) but sort of smoother corners...?) Anyway... he will have the original Lucas fuses...
Funny... the last time it blew, i had just put it in reverse... like someone hooked up a back up wire to the transmission (????) for the Lucas back up light....hmmmmm.
gordon.b.lawson '53TD

If you have the original Lucas fuses - I have not seen them in years - just solder a thin wire in the groove. Those fuses are meant to protect from a short, and the thin wire would do.

Denis
Denis L. Baggi

Gordon,
"if you left a socket empty, all the electricity would drain out...!!!!".....
Can we sell that back to the power companies?
"like someone hooked up a back up wire to the transmission" ....see a mechanical "switch" under there anywhere?
I put a period Lucas reversing lamp on the TF ...but it works from a switch I have installed under the dash. I also use it to "flash" "cellphoning/bookreading SUV's"
when they get a little too close for comfort! I orginaly had a "landing light" out of a lear-jet in it for a bulb...but it was slightly "overtaxing" for my genny and the OSHP (Ohio State Highway Patrol) "requested" I remove it after I lit-up I-270 for a couple of miles one night! It was,however, most effective at getting rid of a tailgater durring the test run!
Cheers,
David 55 TF1500 #7427
David Sheward

David - "most effective at getting rid of a tailgater durring the test run!" Is that the individual in Ohio who claims that he was blinded by an alian ship on I270 one night? Cheers - Dave
David DuBois

David Seward,
Your transmission has a fitting for the optional back-up light switch. This was used on some non-T application.
Years ago I saw the switch in the Moss or Abingdon Catalog and I ordered one. If you look there is a rather large plug on the transmission and on removal the back up switch screws in, and it is activated when the shifter is in reverse. Some T-cars were fitted with the switch and the Lucas back-up light.
Don Harmer

Ah Ha.... I just signed on to update the fuse thing...
I put in a 20A this morning and all day used my turn signals and brake lights... sometimes alone, sometimes together... all was well....
At the end of our run ( http://www.niagarabritishcarclub.org/queen/queen.html ) i returned to the barn and stopped.... made sure my signal was off, put it in reverse and ..... POW.... it popped. This has been where it has popped the last 5 fuses... It has to be put in reverse... I didn't see any wires when i had it up on stands...but i wasn't looking either... Where would it be if it was there?
gordon.b.lawson '53TD

Don... thank you for the info... went to the Moss site and sure enough, there was the part number and illustration (#138).. and it ls still available.... I didn't look up in that area of the transmission and will check it tonight...
gordon.b.lawson '53TD

It protrudes at the l.h.s. of the gearbox. All the TD's I have seen have it, though there might be no wires coming out.

Denis
Denis L. Baggi

Don,
Thanks ...I did not know that was there!
Might just have to crawl under there this winter and hook that up!
Dave, Could be ...it was very bright..but the headlamps got pretty dimm!
David
David Sheward

Denis,

Here's a picture of mine. http://pg.photos.yahoo.com/ph/eford321/detail?.dir=/4e2d&.dnm=3ee8.jpg&.src=ph&.tok=phHcE8BB6zQsnYw3 (ignore the color, the flash makes it look very red!)

I got the optional plug! I might order the switch before I put the tub back on the chassis. Does anyone know which lucas light would be period correct?

Evan
Evan Ford - TD 27621

This is the Lucas one on mine.... very similar to the license plate light, except larger and a clear glass lense facing the rear (duh)..

http://www3.sympatico.ca/gordonblawson/td/backup.jpg
gordon.b.lawson '53TD

Am taking the car out for a run on what might be the last sunny/semi-warm fall day... took a couple photos of the Lucas back up light.
Think the bracket attached to the bumper support was pretty "shop made". Think it might be better on the RHD license plate position, however, at some point my spare tire support was welded shut on that side.

http://www3.sympatico.ca/gordonblawson/td/lightdetail.jpg
gordon.b.lawson '53TD

Gordon,

Your car looks great! That license/3rd brake lite is a neat accessory.

It looks like Moss had your reverse light assembly listed as 544-110 - under the Triumph TR2-4A. It's NLA.

It appears to be a Lucas L661 or L651. There is one on ebay: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=27383&item=2495880984&rd=1
Buy it now for $91+, ouch! (Isn't that like $5000 canadian? ;^) The weak dollar is a killer!

Evan
Evan Ford - TD 27621

Ah.... but our dollar has been climbing for a couple of weeks... it is now at $.82 U.S. Of course this means i'm not making any money on ebay sales...and our tourism dollars will decline.... Oh well...(when i was a kid, it was the other way around...our dollar was worth $1.25 U.S.)
The third brake light i really like...even if it isn't a stock item...i can tell if my lights are working by looking over my shoulder.
Those are a really nice pair on ebay....!!!!
gordon.b.lawson '53TD

This thread was discussed between 11/10/2004 and 23/10/2004

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