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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - FUSES FOR TF

I am restoring my TF 1250. The fuse box has all the old paper type fuses in it. I never recall blowing one. They are all 25 amp. WHAT IS THE CORRECT AMPS, AND ARE BOTH THE SAME? Believe it or not, the operators and mechanical manuals do not specify! I see where Moss gives a choice of 35 or 50, so now I am wondering if 25 is correct. I sure like the looks of the old hand-soldered paper fuses.
Keith
Keith Murphy

Keith --- I am of the opinion that one 35 Amp and one 50 Amp fuse were used. I tried to look up where I got that idea but could not find it. Possibly it was in some of Chip Olds articles. The 50 Amp fuse was used for the horns I believe. The 35 for everthing else.

Remember that those are the British ratings, US ratings are very close to 1/2 the British ratings. The US ratings are what the fuse will carry indefinetly, the British rating is what it takes to blow the fuse in a given short time.
Cheers,
Bob
R. K. (Bob) Jeffers

Thanks Bob. I think the paper fuses I have are for US, so the 25's that are in it may be same as British 50 then? I guess if nothing blows when I hook up the car, then the 25's are ok.
Keith
Keith Murphy

U.S. "Slow Blow" fuses are also available.
They have what looks like a spring inside wrapped around the element.
The current ratings on the US SB fuse is for continuous service. The surge value is taken care of with a delay, that allows some over current before it blows.
The regular glass fuses with the straight element in them are normally OK, but loads such as a horn which has a coil winding may give some trouble, as there is an initial "spike".
Dallas
Dallas Congleton

Keith,
DO sign in as "a member" (free to join) so you can check the archives! This is one of the single "most dicussed" subjects on this BBS! There is a lot of info on the subject you will want to read up on ...(either now ...or like I did after I re-did my wiring for the 3rd time!) "Horns" are the single "largest" amperage pull on our little cars @ 50amps...followed closley by the headlamps @ 20amps that have NO FUSE! IMHO (and quite a few others on here)...one of the best things you can do RIGHT NOW is fuse the Headlamps...they seem to be the single most common component that can casuse damage (or even fire) in these cars! Do your homework now ...you will be glad you did!
Cheers,
David 55 TF1500 #7427
David Sheward

Dave,
What amperage fuse should we use in the headlamps. I have a 35 amp buss fuse in mine. Do you think that is too much
Russ Oakley

The British fuses carry two ratings. The 35 amp fuses are rated as 17.5/35 amps, meaning that they will carry 17.5 amps indefinitely and will blow right away if the 35 amps rating is exceeded Between 17.5 and 35 amps the fuse will blow in a progressively shorter time period (very similiar to the US slow blow fuses.

When adding extra fuses, such as ones for head lights, the fuse should be rated for the wire being used as it is the wire that will burn up if the current capacity is exceeded. The headlight circuit should use 12 gauge wire, which for up to a 20' run can be fused at 20 amps. If you are going to fuse the headlights, I would suggest that each light have it's own fuse so that you will always have at least one head light on if a fuse blows. I can tell you from experience, it is a terrible feeling to have the headlight go out when you are at speed on a winding country road on a moonless night. You are afraid to pull to the side, because you can't see where the side is, you don't want to stop in the middle of the road, for fear someone coming behind won't see you in an unlit car and you are afraid to continue on, because you can't see the road. All the while you are screaming at the wife, "get the flash light out of the glove compartment, but you are in the MGB and the wife is frantically searching for the glove box key in her purse - Much better to use two seperate circuits! Cheers - Dave
David DuBois

Russ,
I'll have to check, but pretty sure I ended up with a 15 on each headlamp and a 20 on my fog & driving lamps. Headlamps are seprate and fog & driving on a 3rd one for both. All are wired with 12g 3 conductor "trailor" wire with a seprate ground. I should have done a better job documenting just what I did because I still need to do some work to get it back the way it was before I had my engine re-built. Shop that did that did not get things quite right!
Cheers,
David 55 TF1500 #7427
David Sheward

Keith,

I don't know how important absolute originality is to you, but if you want to buy some real bullet-tipped glass Lucas fuses for the TD/TF, they are still available in a variety of sizes from 1 amp up to 50 amps.

These are still available from http://www.theelectricalpartscompanyltd.com/

As you have indicated, these are the paper-type.

I purchased a quantity from them at the last Stoneleigh MG Parts Show and seem to be doing the job. Also the original Lucas fuses are the only ones I found that would fit comfortably in the spare holes at the top and bottom of the fuse block.

As for the correct amperage, I can't tell you the correct fuse for A1/A2 (bottom) and A3/A4 (top), but since the horns (high current inrush) are wired through A1/A2, I can only guess that they use the 50 amp fuse and the other accessories would by extrapolation, use a 20 or 30 amp in A3/A4.

Its interesting to note that A1/A2 protects the accessories that operate irrespectrive of whether the ignition is on or off; while A3/A4 protects those devices that are ignition-on dependent

Gord Clark
Rockburn, Qué.
Gordon A. Clark

This thread was discussed on 16/05/2006

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