Electrics

Tom Maciver · May 10, 2018

I have a 1976 Massey Ferguson 135. Every time I turn the light switch to full beam it blows the fuse in the lighting harness. I've just fitted new headlamps but they are not connected yet. It's ok on the side lamp position on the switch. Once I turn it to full beam fuse blows.

gene bender · May 10, 2018

check the current draw of the new lites

fixerupper · May 10, 2018

You have a bare wire or connection touching metal somewhere making a short. Look for cracked or worn insulation in the wiring where it enters the light shell.

old · May 10, 2018

With out the light hooked up if you turn it on full does it still blow the fuse?? Or course be 1000% sure the wires that should be hooked to the lights is placed in such a way as to not short out. If it blows with out the light in the circuit you have a short some place between the switch and the light housing

Tom Maciver · May 10, 2018

(quoted from post at 10:45:50 05/10/18) check the current draw of the new lites

This is happening without the new lights wiring being connected.

old · May 10, 2018

If that is the case you have your self a short some place in the wiring

Tom Maciver · May 10, 2018

Back to the drawing board. This thing has a cab on it and it going to be hard to trace. Thanks .

old · May 10, 2018

Pull the fuse and then take an ohm meter and check the wire to ground and if it is grounded then you might be better off to just run a whole new wire for the lights

Tom Maciver · May 10, 2018

Thanks

IanC · May 10, 2018

Add up the watt ratings for all the lamps you are trying to power, and divide by 12. You may just be trying to draw too many amps through the fuse you are using. If you have 4 35 watt bulbs that is over 11 amps without loss through bad wire, switch, or connections.

Tom Maciver · May 10, 2018

Would it work if I used a higher rated fuse? 35 amp is what was in there, or is that just bypassing the problem?

IanC · May 10, 2018

Don't go too high or you'll let the magic smoke out of the wires. What size wire are you using, and how many lights?

Steve@Advance · May 11, 2018

Look for the obvious.

The short will not likely be hidden inside the wire harness.

It will be where the wire passes through a sheet metal opening and has rubbed through, it will be where it has been pinched between hinged parts, has been up against the exhaust, mouse chewed...

Not as difficult to find as you think.

Tom Maciver · May 11, 2018

At the moment the headlights aren't hooked up so its tail lights, sidelights, and dashboard light.

Tom Maciver · May 11, 2018

Day off tomorrow so will have time to check it out. Thanks for all the info. I'll report back.????

Electrics

Tom Maciver

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gene bender

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old

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Tom Maciver

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old

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