Electric shock from my wiper switch ??

[MY 59]

Hi all
I have not had the need to use my wipers as I do not drive in the wet, and after rebuilding the wiper motor and arm systems to ensure they worked for licensing have never used them.
However the other day I was unlucky enough to get sprayed whilst driving by a large council sprinkler wetting my 59 from front to back, and upon switching my wipers on I received a decent electric shock! And again when I switched them off??
Wiper motor has the earth strap, and I am just after any info as to why this would happen ?
Has anyone had similar ?
Thanks
Dave

[The Tassie Devil(le)]

Funny thing is I have never received any Electric Shock from any of my cars, even by holding the positive and negative terminals at once.

Bruce.

[MY 59]

I highly recommend it

[P. Manoogian]

Have you checked the grounding of the switch itself? Sounds like you are the ground. ..

[TJ Hopland]

You actually felt the shock or just saw or heard sparks?    IF you felt it it would just about have to be higher voltage from something like the ignition system or maybe radio.  Everything else is just 12v which you would have to have a lot of things going wrong to feel.

[35-709]

Static electricity?

[D.Yaros]

Static electricity?

It would seem that any static electricity would have dissipated when turning on the wipers and no shock from it would be felt on turning the switch off?

[cadillactim]

The switch completes the ground circuit. There is battery voltage at at the wiper motor when the key is on. When the wiper switch is OFF, the circuit is open. So when you touched the metal knob, you became a potential carrier of the ground circuit.

Normally there is too much resistance (insulation) in your clothing to allow the current to complete the circuit through you. Somehow you may have had a path that day. It could have been dampness on you. But more likely there is some corrosion/dirt in the switch contacts. Normally when the switch is turned ON the ground circuit immediately goes through the switch contacts because it is the path of least resistance. But a dirty contact prevents full current flow, and your body is now storing that current. When the contacts finally find a "clean" spot that current from your body moves to the new path of least resistance. That current leaving your body gives you the shock.

Likewise, when you turned the switch back to OFF the dirty spot of the contacts allowed current to enter and then leave your body causing another shock.

Check your switch contacts.

Tim

[bcroe]

When the current through the motor stops or changes, an
inductive voltage "kick" can be developed in a manner like
the ignition.  Not very dangerous,  but something is wrong
with the switch (probably grounding) that you should feel it. 
Bruce Roe

[MY 59]

Hi all, and thanks for the responses
I pulled the switch last night and stripped it,
Inside was pretty clean however the spring between the switch actuator and contact plate was crushed
I replaced it and lubed everything with Di electric grease, and still get the shock ( no noise, just shock)
May try a replacement switch if I can get my hands on one unless anyone has another suggestion
Thanks
Dave

[bcroe]

I pulled the switch last night and stripped it,
Inside was pretty clean however the spring between the switch actuator and contact plate was crushed
I replaced it and lubed everything with Di electric grease, and still get the shock (no noise, just shock)    Thanks Dave 

This is the point at which I start adding ground wires/bolts, whatever
is needed to tie the outer metal to the car chassis.  Bruce Roe

[cadillactim]

I agree with bruce, add another ground strap. Take a jumper wire from the switch housing to a good body ground. If you still get shocked, take a jumper wire from the wiper motor housing to a known good body ground.

Tim

[59-in-pieces]

Dave,
Shocking - I just had to say it - couldn't "resist".
I assume when you did your DOT MOD or what ever, you did not get the shock nor did the tester fellow.
So, it was the introduction of the water to the car that prompted the shock.
I assume you were shocked through your fingers or knuckles from the slide lever to the assembly - and not through your arm or body.
Have you done a simple continuity test between the slide lever (or washer button) to the metal assembly that holds the master window switches as well as the wiper-washer switch - at the various speed positions.
Try it with the key on & then with the key off (accessory or run modes).
If you get continuity, you have a short, since power comes both to the switch for the windows and again to the wiper-washer switch.
Let's take this off line, as there are a bunch of issues to discuss, and I know you like a good mystery - and love to work on your car, hands on - nuts & bolts.
Here is my email and that way I can send a bunch of pics that might help and not plug up the thread.
Have fun,
Steve B.
slynnbutch@sbcglobal.net

[G Pennington]

Does the shock occur only when the engine is running?  If so, suggest you check the coil and spark plug wiring to see if its rubbing against the wiring to your wiper motor.  If the insulation is bad, a spark could jump to the wiper circuit, especially when wet.

[MY 59]

Hi Gary,
shock occurs with engine off and on
however, I removed the connector from the wiper motor, cleaned and aligned the contacts and now the shock appears to be gone?
will keep experimenting

[cadillactim]

Electricity 101: Electricity takes the path of LEAST resistance. A loose or corroded connection will cause more resistance, so if there is a more direct path to complete the circuit (including your body, i.e. touching bad spark plug wire) that's where it is going.

Maybe there was excessive resistance at the wiper motor connection since the shock is gone.

Tim

[dplotkin]

Sorry Tim, BCroe got closer to the answer than you did but you are still half right. Battery current at 12 V simply cannot give you a shock you can feel. Put your hands across the battery terminals. You will live to tell about it. The only thing on a car that can send you into your opened hood is the coil and certain other components with coils, such as relays and motors. As you know the coil generates its secondary high voltage because of the collapse of the field of the primary coil which causes back EMF (electromotive force). In my telecom days we used diodes across relay coils to block this EMF from damaging the circuits behind it. The shock is a few hundred volts of back EMF from the wiper motor armature with no current to speak of and likely limited to his fingers where I think he is exposed to the hot side of the wiper motor and ground from the switch. Try a 12V test light between a good ground and the switch knob itself while operating the switch with another hand (using exam gloves!) If the light flickers or lights you know the switch itself and not just its contacts are hot.



Dan