MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

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 - MG TD/TF Fuse Protection

I have commenced this new thread as a result of the responses to "Lucas 50amp Glass Fuses" where the gravity of retaining originality was subject to conjecture.

Somewhere in my memory bank I remembered good work had been previously done in this area and commenced a "Google Search".

This link was what that search revealed, it totally supports my fears that my own TF is under threat of creating a lot of "Lucas Smoke":

http://tseriesmg.blogspot.com.au/

Having gained access to a calibrated DC Tong Tester, tomorrow I will complete current measurements to ascertain whether the existing 35 and 50 Amp fuses match the protection requirements that the components in those two circuits require to prevent "Lucas Smoke". Results will follow.

Graeme

G Evans

I have added in line fuses in various different places to protect the wiring. Although a viable solution, and easier to do, some of the fuses are visible and dispersed around the car. I think the solution proposed in your attachment is much better and I am going to put it on my list of things to do during next winter's lay up.
Thanks.
Dave H
es1

I just connected my fog/driving auxiliary lights to the A switch connection. I added an inline 5 Amp fuse as these are LEDs.

I got a 10 pack of inline fuse holders on Ebay for next to nothing, it included a box of blade fuses of various flavors.

My fuse box is rather "tarnished" so I am planning to look at replacing that but I am concerned at the quality of the replacements. I feel with the tarnishing that I would be losing voltage in high current draw situations, which in my case would be headlights only. They may become LED soon too.

I don;t have a heater so not much else would draw a lot of current.

I do agree some of the wires are undersized for the fuse ratings.

Peter
P G Gilvarry

Results of TF Fused Circuits current draw test:

Horn Circuit(50A) 11.7A

Brake Light, Turn Signals, Windscreen Wiper, Low Fuel Warning Circuit(35A) 13.8A


These numbers embellish the concerns expressed in Evan's Document.

Owners who desire to retain originality might consider at very least modifying the existing fuses by fitting suitable wire sizes that provide lower amperage protection, original labeling could be retained.

Personally I have a chore to attend to, incorporate Evan's recommendations.

Graeme
G Evans

Peter

I would consider removing your existing fuse box and submerging it in "Bakers Soldering Flux" for a few hours, this will clean the fuse contacts.

Ensure you thoroughly water flush the box prior to refitting.

Graeme
G Evans

Graeme the early TD has the 9 post Voltage Regulator with fuses attached. Don't think it wise to immerse. Cheers
Peter TD 5801
P Hehir

Peter


The member I was posting to owns a TF according to his vehicle profile.

G Evans

OK. Cheers
Peter TD 5801
P Hehir

Initial search indicates Baker's not available in USA, will look for something similar.

Thanks for the heads up.

Peter
P G Gilvarry

The author begins his dialectic argument with an absurdity. That being that the cars are "under-fused" using the equivalent standard modern (American) fuses of 30A and 25A. The normal suggestion is to replace the "50 Lucas" with a 20 or 25 amp standard fuse, and to replace the "35 Lucas" with a 20 amp standard fuse. He seems to have a basic misunderstanding of how to convert from the original Lucas fuses to standard fuses, then bases his need to "re-wire" on that misunderstanding.

His next absurdity is: "Fuses are chosen based on the current load of the device they are to protect." NO, the fuses in the Lucas scheme are to protect the wiring, not the "device." Think about it; why "protect" a "device" that has already failed? What causes a fuse to blow?

Clearly you want to add a bunch of fuses, so why don't you just go ahead and do that? Many people who do understand how fuses were designed into this system settle for a relay to each headlight, to take the full current of both headlights away from the original switch.
D mckellar


Instead of only partially quoting from a document there is a need to place the statement in conjunction with:

"Fuses are chosen based on the current load of the device they are to protect. In addition, the size and length of the wire must be considered. The TD & TF have a variety of wire sizes in their harness. The majority of the wire is 14/0.30 or 14 strands of 0.30mm wire. This is roughly equivalent to 18 gauge US wire. The carrying capacity of this wire is only 8.00 Amps.
This is used for general wiring like side and tail lamps. For heavy feeds like horns, 28/0.30 wire is used with a 17.50 Amp capacity. This is roughly equivalent to 14 gauge US wire. For ammeter and voltage regulator connections 44/0.30 wire is used with a 25.50 amp capacity. This wire is roughly equivalent to 12 gauge US."

No one in their right mind would install a 35A fuse to protect wiring rated to carry 8A or a 50A fuse to protect wiring rated to carry 25.5A.

Also why fit fuses that have the capacity to pass currents far in excess of devices connected in the same circuit? I would rather blow 20 fuses than have 1mm of my wiring harness destroyed by "Lucas Smoke".
G Evans

Let me keep it simple for you Graeme.

1. You say the fuel warning light carries 13.8 amps, but give no voltage. What voltage are you talking about there, and where did you come up with 13.8 amps??

D mckellar

The 13.8A value is the combined current draw of all components supplied via the 35A Fuse. The components being;
Brake Light, Turn Signals, Windscreen Wiper, Low Fuel Warning Circuit.

I physically measured this value using a Digital DC Tong Tester Meter clamped on the input side wiring of the 35A Fuse.

My battery was supplying 12.6V during this process.

All components were operating during the measurement process.
G Evans

Graeme, you want everybody to listen to your nonsense, but you obviously do not listen, or even read what others have to say. Between this topic and the other topic on the same thing, it has been stated numerous times that the LUCAS 35 is equivalent to a 17 amp modern fuse, which is not made, and to use a 20 amp fuse. Why do you insist it is 35 amps?
D mckellar

D mckellar

If you track the content of this thread and the one titled "50 Amp Fuse"correctly you will note I am totally aware of the Lucas fuse ratings and their labeling. Even to the point that Yanks and Brits cannot agree on their fuse rating methodology.

Instead of casting aspersions get your head out of the clouds and read the total content of what I have posted plus the links to relevant subject matter.

For the sake of explanation of my measurements I used the nomenclature label contents on the fuses, I am well aware of the two criterion used to rate these fuses.

Is what you are promoting a debate or the communication of sound proven practice, I will let others judge.

Graeme







G Evans

You see what it is Graeme is nobody care's about your delirious ramblings.
D mckellar

This thread was discussed between 11/04/2017 and 13/04/2017

MG TD TF 1500 index

This thread is from the archives. Join the live MG TD TF 1500 BBS now