Short Circuit/Fuse blows when turning ignition

[vumarkwells]

Hi,

I've just removed my dash on a S2 to recondition. When putting it back, I've put all the wires back in, but now the fuse for the ignition coil keeps blowing everytime i turn the ignition on. Has anyone had the problem before? It means I'm getting no power to my ignition coil, but everything else seems to work fine. I've looked at the wiring diagram which seems to say that the ignition coil is linked to the tacho and then to an earth. Does anyone know where the earth goes for the S2 is on this loop (how it gets to the chasis).

Any help much appecriated.

Cheers

[Gerald-TVR]

Cant help with your exact query but would suggest that you check the yellow connector between the ignition switch and the rest of the wiring its a regular fault

[Sweet Thunder]

Behind the dash, the same type connector is used for several instruments, you may have switched connectors? AFAIK the plug for the speedo is the same as for the tacho. The car won't run with the tacho disconnected.

[vumarkwells]

Thanks for this.

The yellow connector has been fried somewhat. The black connector going into the yellow one has melted slightly as well.

Do you know whether this would cause the ignition coil fuse to blow? And also what the cause of this melting is? Bit concerned that if I replace this it will simply happen again.

Last question - do you know where I can get a replacement (for the yellow connector)?

Believe everything is connected correctly as all instruments appear to be working and engine will run if I power the ignition coil directly from the battery.

Thanks again.

[Le TVR]

Supply for the coil comes from the tacho.
Pull the plug from the tacho and see if the fuse still blows.

Did you disconnect the tacho plug when you ran the motor with the supply to the coil direct from the battery?
Was the connection made direct to the coil or the other end of the ballast resistor?

[vumarkwells]

Hi, engine ran with tacho connected. I powered the coil directly.

I haven't tried disconnecting the tacho, but will try this - thanks.

[Le TVR]

vumarkwells said:

Hi, engine ran with tacho connected. I powered the coil directly.

That rules out a short in tacho and related supply wiring. The battery volts would arrive at the tacho via the ballast resistor (only 1 ohm).

Did the 15A fuse blow when the ignition was switched to on or when switched to start?

[vumarkwells]

The 15A blows when the ignition is turned to 'on' - can hear the click.

Do you know if a short can be caused in the yellow connector mentioned above?

Cheers

[Le TVR]

The only thing I've heard of with the yellow connector is the loss of supply, not short circuits.

Best way to check for short circuits is to get a 12V bulb with some long wires attached. Connect one wire to battery + and touch the other wire to the 'suspect' connection. If the bulb lights then that point is grounded.
Pull the tacho connector and see if this bulb lights when you touch the white wire connector. If yes the ballast resistor supply wire is shorting somewhere and would give the fault indicated.
If no, do the same with the red wire. If the bulb lights then the tacho supply wire, or tacho itself is shorting.
Do this with a new 15A fuse and ignition off.

Edited by Le TVR on Tuesday 9th February 12:27

[vumarkwells]

Many thanks. Will begin 'hunting the short circuit'.

Will let you know what it was when solved.