Ignition Switch

[Percy TR6]

Hi All... following a nice day out in the car last week, I stopped for a coffee and when I came back out it wouldn’t start. The key was simply turning in the ignition switch!

Looking at the back of the switch I could see that the brown wire had melted the insulation at the spade connector. This must have been an issue for a while as the innards of the switch had perished too!

New switch ordered but 2 questions:

1) What would cause this to overheat? A bad connection I assume but is it safe to assume that was down to a failing switch or problem elsewhere?

2) In replacing the spade connector on the brown wire, what should it be rated at? I’m assuming 30A - though I am not sure I know why I think that. 

Cheers,

Steve

[Waldi]

Steve,

I would not assume it is the switch. Before connecting again to the battery, try to find the cause. Otherwise a repeated failure may occur. A safe method is to remove a battery pole and install a light (2 or 3A) fuse in line. Remove all (3) fuses. And disconnect coil and pump.

Then connect and switch the contact on. If the fuse does not blow, install a 10A fuse on the pole and 1fuse (1 of the 3 you removed). Switch all end-users on and off one by one. If ok, remove the fuse, install the next and test the next circuit. If you have an amp meter, put it in series with the  temporary 10 A fuse, the fuse will protect the meter, most meters are rated 10A.

More educated members will hopefully add, but this is what I would do.

Waldi

[RobH]

+1 for Waldi's suggestion.   You do need to do a thorough inspection and test of all the switched circuits, to be safe.

If it all checks out OK,  the failure could have been a bad connection on the switch which overheated due to "I squared R" loss or, since it was the brown input terminal which melted rather than on the output side of the switch,  it is also possible that something went wrong mechanically within the switch itself and shorted out. 

The size of the new spade connector will depend on the diameter of the wire. It is the wire which is current-rated and the spade needs to be the right size to make a good mechanical connection to it. 

 

[astontr6]

18 hours ago, RobH said:

+1 for Waldi's suggestion.   You do need to do a thorough inspection and test of all the switched circuits, to be safe.

If it all checks out OK,  the failure could have been a bad connection on the switch which overheated due to "I squared R" loss or, since it was the brown input terminal which melted rather than on the output side of the switch,  it is also possible that something went wrong mechanically within the switch itself and shorted out. 

The size of the new spade connector will depend on the diameter of the wire. It is the wire which is current-rated and the spade needs to be the right size to make a good mechanical connection to it. 

 

 Have you got a high torque starter motor? I had a similar problem with a Wasp one which a shorted out the ignition s/w. It transpired that it should have been wired through a relay as they put 41 amps across the s/w contacts? There was no mention of this in their fitting instructions? But when they tested it there was something wrong and they gave me a new one. It was out of warranty. So I cannot complain too much!

Bruce.

[Andy Moltu]

The solenoid on the wasp solenoid shouldn't draw that much current?

It might spike transiently to 30 A  or so but generally less than 10A whilst engaged which shouldn't overload the switch.

[PeterTRR]

Steve

Regarding your problem i had the same issue last year,the cause was the alternator  it even burnt the wire to the distributor at the fuse box.

John.

[astontr6]

14 hours ago, Andy Moltu said:

The solenoid on the wasp solenoid shouldn't draw that much current?

It might spike transiently to 30 A  or so but generally less than 10A whilst engaged which shouldn't overload the switch.

That's not what it says on their fitting instructions? It clearly states 41 amps!

Bruce.