CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Is it safe to do electrical work on car in rain or snow?

Need to back probe a headlight with a multimeter with lights on. It is snowing out. Is this safe?

In general is it safe to do electrical work on car when standing on a wet ground or in snow.

It’s safe on 12V systems, not anything more (any higher voltage).

1 Like

It is safe. Your tires prevent your car’s chassis/unibody from having a path to the ground. Ergo, you cannot be part of a circuit because the tires isolate the car from completing a circuit.

If part of you does create a circuit path it’d be within the car’s chassis/unibody itself, just as it would in dry weather. And your biggest danger would be in banging your head when reacting. Electricity is only dangerous if it’s of sufficient strength to overcome your body’s natural resistance to current flow AND it travels a path that interferes with your bodies signals, like through the neural pathway that controls your heart. A multimeter contains nowhere near sufficient energy, and even a car battery would only do this under a very rare set of conditions if ever.

But if you hear thunder, save the project for another day.

1 Like

It should not be a problem. The voltage on a car except for the spark plugs is only 12 volts. The reason it is not safe to work on house wiring while standing on damp ground is that one side of the house line is called the neutral. This side of the line is attached to the earth. If you touch the ungrounded wire the path for the current to the ground goes through you. If you are standing on wet ground it is possible for lethal amount of current to pass through you.

1 Like

Your warning about working on house circuitry is very well stated and necessary.
It could be disastrous for anyone to take the comments on working on the car and apply them to working on house current.

Well done.

1 Like

@the_same_mountainbike Thanks for the compliment. I remember well the days when one side of the power line was connected directly to the metal chassis of inexpensive radios and even some television sets. If the wall plug was inserted so the hot side went to the chassis, one could receive a shock by touching the chassis. If the plastic knobs were missing, one could be shocked just touching the control shafts. How this design got Underwriters Laboratories approval is beyond me. More expensive radios with a power transformer did not have this problem as the transformer isolated the radio circuitry from the power line.

1 Like

LOL, I remember not too many years ago when I kept getting shocked in the winter every time I’d touch some of my light switches… especially with that polyester robe on.
These switches had metal boxes, which were grounded per code, with the switch bodies grounded to the boxes per code. The static electricity on me would get so high it would jump 1/8" or more to the switches heading for earth ground. I stopped it by replacing the metal switch plates with plastic plates and the screws with nylon screws. I still wear the robe.

1 Like

While 12 volts is very unlikely to electrocute you and in most cases touching it doesn’t even produce an electric shock sensation, there is a real danger from the high amps a car battery can deliver. A 12 volt car battery can turn your wedding ring red hot in just a few seconds of short circuit current. I met someone who had to have his ring finger amputated because of this kind of accident.
Always remove the ground cable from the battery before doing electrical work on a car. You can leave the positive cable hooked up.
The reason to remove the ground cable is that if you short out the wrench to the chassis, you don’t produce a short. Once the ground is disconnected, hitting the chassis with the wrench while removing the positive wire won’t produce a short.
Remember, remove the ground first, and connect the ground last.

2 Likes

There is no danger of being shocked when working with 12 volt headlights.

However High-intensity discharge lights (HID) operate at high voltage, do not try to probe the high voltage circuits with a meter. Do not switch on the headlights with an access cover removed from a headlight.

In general there is no danger working on vehicles with 12 volt systems however hybrid cars have systems with greater then 400 volts. These should only be serviced in a dry environment by trained technicians using proper equipment. The high voltage circuits on a hybrid vehicle can include the A/C compressor and the power steering.

1 Like

I always thought to keep the battery ground on and take the power + off. My thinking was by removing the power, you are removing the electricity. Live and learn.

it may be safe, but if there is snow, then it’s waaaay to cold out to be working!!!

#DesertDweller

2 Likes

It’s not the voltage that kills. It’s the amperage that fries you.

Tester

You need both; enough voltage to overcome your skin resistance and enough current to do any damage. You could grab both posts of a 12 volt car battery with soaking wet hands and nothing would happen.

1 Like

I don’t think I’ve ever heard of anyone being shocked enough to be killed when working on a car. At least not from the car itself, and conventional designed cars. Anybody got electrocuted probably that was from some accessory equipment being used, shop lights, electric tools, etc. Like pro musicians getting electrocuted from their audio equipment, not an entirely uncommon thing during 1960’s and 70’s rock concerts as I recall. (Remembrance of those times somewhat hazy tho … lol …)

As for the shock hazards of the car itself, there’s high voltages in the ignition system that could potentially shock you enough to stop your heart, esp if you happened to have an already defective heart, and you were touching both the HV source and the chassis ground at the same time. Having wet hands could increase that risk I suppose.

Has anyone here ever been shocked by 12V on a car? I haven’t.

Firstly, voltage and current are not separate things. They’re two variables in the same equation, along with resistance. Current is the flow of electrons when voltage (potential) is sufficient to overcome resistance.

I have over the years seen a few people get “zapped” working on cars. Occasionally someone dreaming of their previous evening will inadvertently let their hand or forearm short the battery to ground. The result is the contraction of the muscles through which the current flows and sometimes a reactionary jerking back of the arm. They might get a small burn mark, but the only real danger is in hitting their head or arm against something in the engine compartment. That too does occasionally happen. 12VDC is insufficient to overcome the total resistance across a normal person’s chest, so electrocution is not possible. And it definitely won’t overcome the resistance to the feet… even if they’re wet.

Do magnets near electrical wires cause any reactions?

Why am I asking this? I used two small magnets for a tin cover over some electrical wires on a ceiling fan.

I don’t know but somehow that just does not sound like a good idea. Doesn’t the cover have screws to hold it in place. Any thing electrical should be done properly and if not it could effect an insurance claim, call an electrician and have put to code.

If you place the under side of your forearm across the battery terminals you will feel a tingle. 12 volts is not enough to “zap” anyone.

You might find this link interesting. It not only answers your question, but provides some explanation.