Fuses

[mgtf328]

I have been adding in-line fuses to my BJ8 as follows:
Fuel gauge 5A (3AGC)
Wiper 15A (10AGC)
Brake/Tail Light 5A
Number plate light 5A
Fuel pump 10A(7.5AGC)
Heater fan 7.5A
4way flasher/indicators 5A
Lights have been modified with relays as per "Let There Be REAL Light by Raymond Carbone" article; including recommended fuses.

The only lines not fitted with in-line fuses are the connections to the ignition switch and the overdrive.
Any comments on the sizes of the fuses would be most greatfully received but my real question is, that now I have fused all the lines, would it be appropriate to reduce the size of the 50A fuse and if so what would be an appropriate size.

Thanks

AJ

 

[vette]

Hi AJ. On the Big Healeys and many of the vintage LBCs surprisingly the 50A fuse is actually supplying only some auxilary equipment. This is such equipment as the Horn, a radio if installed and maybe the driving/fog lamps if installed. The other fuse which is only 35A is the one that is supplying most of the electrics of the car and it is fed from the ignition switch there-by being turned off when the key is off. These are such things as the fuel pump, heater motor, wiper motor, fuel gauge & electric tach on the BJ8. Reducing the size of the 50A fuse will not have any effect on these components as they are supplied by the 35A fuse.
Also, understanding that the things mentioned above are supplied by the 35A fuse, then your in line fuses are down stream of this fuse and if you reduce the size of the 35A fuse then you will be reducing the capacity to supply your in line fuses. Unless I have misinterpreted what you have done.

 

[Keoke]

The only lines not fitted with in-line fuses are the connections to the ignition switch and the overdrive.
Any comments on the sizes of the fuses would be most greatfully received but my real question is, that now I have fused all the lines, would it be appropriate to reduce the size of the 50A fuse and if so what would be an appropriate size.

For the Over Drive use a 10 Ampere slow Blow fuse.

The 50 Amp fuse can be replaced with a 35 amp if you want to do it.

 

[mgtf328]

Thanks for the quick response. I'm using the same wiring diagramme you posted. I've just checked and the fuse in the upper part of my fuse box connecting all the Green to the White wires (Terminals 3 and 4 on the diagramme) is 50A on my car. The lower fuse connecting terminals 1 and 2 (the Purple to Brown wires) (Horns) is 35A.

On the diagramme the Green wires are the ones that run to the wiper, indictors, fuel pump, Heater fan etc. which is where I have located the in-line fuses. I understand what you mean by reducing the capacity downstream if I change this fuse for a lower value and will leave it alone.

However, I'm a little confused. You seem to be saying that the 50A fuse I have across terminals 3/4 should be 35A is that correct? If so should the fuse between terminals 1/2 i.e. the horn and the radio which are independent of the ignition switch, be 50A and not 35A as it is on my car? In other words has someone fitted them the wrong way round. |I can't seem to find which goes where in my manual.

Thanks
AJ

 

[steveg]

The 50 amp is a slow blow type equivalent to 25 A normal fuse. Are your fuses all normal?

 

[mgtf328]

I think they're normal (UK rated) fuses. They were the same ones I had in my '54 MGTF.

I've found a reference in my manual now. It says A1-A2 = 50A and A3-A4 = 35A. Mine are inserted the other way round.

AJ

 

[vette]

The later diagrams don't show the fuse sizes, but this is a diagram of an earlier 6 cyl car which is in the Workshop manual. It shows the 35 amp fuse between terminals 3 and 4. This is the way every LBC I have worked on has been.

 

[mgtf328]

Yes, thanks for your help.
I've only had the car a month or so and I'm still checking it out. The fuses were in the other way round i.e. the 50A was where the 35A should have been and vice versa.
The horn was running on the 35A fuse and it seemed to work OK. Maybe I'll leave it that way for a while. I'll definitely put the 35A fuse back where it's supposed to be.


Thanks
once more

AJ