Electric shock

[Oldman]

Hi
ok this is a strange one. I have a mk2 with a manual gear box with overdrive. The problem is that sometimes I get an electrical kick from the gear stick when turning off the overdrive.. sometimes it will blow the fuse other times it doesn’t. I’ve checked the two cables that run from the gear stick switch to the connection under the centre console and they are ok. There is no kick when the overdrive comes in and none when it drops out
thanks

[Wheelz]

The shock will probably be the high voltage inductive kick back from the OD solenoid when it turns off. Not normally connected to the gear stick but would be if the supply feed was shorting, which would also explain the blown fuse. Remove the switch and put some insulated sleeving or tape around the leads & terminals.

[jbuckl]

The shock will probably be the inductive kick (back EMF) from the OD solenoid when it turns off. Not normally connected to the gear stick but would be if the supply feed was shorting, which would also explain the blown fuse. Remove the switch and put some insulated sleeving or tape around the leads & terminals.

Make sure there is earth continuity…. If there isn’t, that’s when it uses you as an earth and you get a shock.

Surprised a 12v system can do that though!

[DZP]

Hi,
You should not be feeling an electric shock from 12v and definitely not blowing a fuse.
Could you be generating static from another source e.g. nylon seat covers or something you are touching/wearing and then earthing yourself when you touch the gear level?
Next time, before you touch the overdrive switch, earth yourself first by touching something metal. If you get a shock, then it is static.
Static can be high voltage, but is very low current and hence is very unlikely to blow a fuse.
regards,
Den

[DJT]

Wires running inside gear-lever to switch have chafed insulation, so shorting through lever.

[Philip Wardle]

90% certain that Wheelz is right about the back EMF. This effect ( L di/dt) is present in any inductive component, and even though we are only dealing with a 12V DC supply the instanteous EMF voltage can easily be >> 50 volts and is enough to shock if there's an insulation failure. It is the back EMF which causes problems such as arcing, pitting and failure of contacts in window lift switches on the Stag. This degradation is clear to see if you dismantle a switch - you can see the arcing if you operate it under load whilst on the bench.

[Oldman]

The shock will probably be the high voltage inductive kick back from the OD solenoid when it turns off. Not normally connected to the gear stick but would be if the supply feed was shorting, which would also explain the blown fuse. Remove the switch and put some insulated sleeving or tape around the leads & terminals.

[Oldman]

Hi
Thanks to you all for your thoughts regarding the electric shock. I will check all the wiring from the solenoid to the gear stick and the overdrive switch. Hopefully that will dirt the problem I will let you know
many thanks all

[Oldman]

Hi
just want to thank Wheelz for his thoughts about the electric shock. After checking as ll the wiring I found a problem with the earth and the Lucas connector which look ok but the internal wire had broken once replaced no electric shock. Thanks for pointing me in the right direction.

[Wheelz]

Hi
just want to thank Wheelz for his thoughts about the electric shock. After checking as ll the wiring I found a problem with the earth and the Lucas connector which look ok but the internal wire had broken once replaced no electric shock. Thanks for pointing me in the right direction.

Good guess eh

[richardthestag]

To help prevent against the wire chaffing through again, I bind the wires tight to the gearstick just below the hole where they come out. insulating tape etc will do the job. The idea is to prevent the wires moving in and out of the stick during gearchanges.

Pleased you got to root cause