wiring problem?

[Matty]

Im hoping one of you knowledgable guys can help me out with a wiring fault I have. Once the engine is running im can't switch it off? There are only 3 ways to stop it...disconnect the coil wire, disconnect the F wire on the voltage reg from the dyno, or disconnect the Y wire from the voltage reg that goes to the ignition light.

I have also found that the wires to the ignition light get VERY hot (to the point where they have melted together at the bulb) and that it doesn't go out when the dyno is charging.

Where could the problem be? It has only been doing this since I connected the voltage reg to the dyno...would the incorrect polarity on the dyno cause this?

All other electrics work, and I have also checked to see if the dyno charges (which it does). ANd I have also checked all the other wiring to the voltage reg, and it checks out ok...

Has anyone got any suggestions of where the fault could be?

Here is the wiring that ive got.


http://www.minimania.com/images/wiring/ ... ring06.pdf
Cheers
Matt

[Matty]

The voltage regulator is new as is the ignition switch. If I disconnect the F wire to the dyno I can switch the engine off with the key no problem, so I know thats working.

The reason I changed the voltage reg was because the dyno used to run like a motor everytime I switch the ignition on, so I assumed the regulator was at fault as the dyno has been reconditioned.

Is there a way to test what polarity the dyno is without zapping it, or some other tests to see if something is wrong with the dyno?

[IAIN]

I will start with my thoughts !
If the dynamo runs like a motor it must be ok. The fact it did, means it's getting power to it that it shouldn't.
It looks like (from the diagram) the ignition could be supplyed through the dynamo and the charging light circuit to the ignition switch. Hence it all works ok with the dynamo disconected and why the wire got hot ?

I think some where the wiring at the regulator must be wrong.

Is the car now negative earth? Is the engine earthed ?

You could try starting the car with the dynamo disconected and check with a meter that it is charging.

[Matty]

Ive got it wired positive earth at the moment, and a strap between the block and inner wing.

Should the W and Y wires be joined together at the bulb, or should one be grounded and the other go to the bulb? Also should the bulb holder be plastic for this bulb, as im using a metal bulb holder?

[ace01]

The bulb holder must be insulated from the speedo/earth. Normally there is a little sheath that goes over the holder.

[Matty]

Ah I think that'll be the problem then! Is that the same for the oil pressure light?

I have both of the wires joined together at the centre pin then earthing through the speedo...on closer inpection the diagrams shows the wires go to either side of the bulb with no connection through the holder.

Is the sheath just a like a rubber collar?

[ace01]

The ignition bulb receives power from the ignition switch and (on a neg earth car) earths through the dynamo. When the dynamo starts rotating it produces a current. With no earth the bulb goes out.

As far as I can recall the oil light would not have a sheath.

The sheath is about 2 1/2 inches long and covers part of the cable.