An ignition coil steps up the voltage because of the difference in turns of wire on the primary and secondary coils. The secondary coil has many more turns of wire, so 12 volts applied to the primary coil will generate a higher voltage in the secondary dependent on the turn ratio of the 2 coils. If the ratio is 1:1000 then 12 volts applied to the primary will result in 12,000 volts from the secondary. The coil inside the relay is not a step up transformer, it doesn't have a primary & secondary coil to step up the voltage, it cannot increase the voltage.
You can touch both terminalson a 12V with your tounge? Damn man , your lady is one lucky one ain’t she!!!!!
I just confirmed, it will only do it when the car is running. You can blow the horn with the ignition 'OFF' and car just sitting there and not get a shock. If you start the engine that is when you can get a shock. The altenator is a Ford 3G with internal regulator and a Painless connector kit. I have a #10 ground, the 'GEN' lite works and voltage is 13.5ish with volt gage in the car, its all normal readings. It must be AC voltage doing it, somehow.
Was the Tiger originally positive ground? I'm wondering if there is some capacitance built up in the column that would normally not be an issue with the positive ground but now with a negative ground does create an impromptu capacitor with the horn ring becoming a lead. Another thought, find a nice dark garage or wait til nightfall, open the hood and start the car. Look at the ignition wires. Do they have a nice blue halo coming off them? Are any of the spark plug/coil wire(s) near the column or harness?
Yes, you are right. When I wired the car there was a horn relay near the front and I replaced it with a new one, connected the horns to it and that was that. Only later during a conversation with the owner did I find out he had added that horn relay for electric radiator fan. I felt it was best to leave the relay in place because I didn't want the full horn load going thu the steering colum. The original horn mechanism and turn signal had broken inside the steering column, there are no replacement pieces. I had to make a new turnsignal mechanism from a newer Triumph (so you can get parts in the future) and horn contact ring. The horn contact ring and arm are original but I felt it was best to minimize the amount of current it carried. I realize the load is momentary but a pair of horns could be quite a load and I don't think that circuit is fused either.
This subject was covered a lot at the FordBarn (lots of old positive ground cars). The conclusion was that the collapsing voltage at the horn relay was causing a spike that went searching for a ground. I suppose the coils in the horns could behave similarly. The key finding is that you won't get shocked till you RELEASE the horn button. A fun trick is resting your left arm on the window frame while blowing the horn with your right hand. The thin skin on your left forearm gets the shock, compounding the mystery.
Nope, shocks only when engine is running and horn is pushed. If you blow horn without engine running you will not get a shock. I'm about back to the coil, I have to send the car to the alignment shop so we won't be able to mess with it until tomorrow. But keep the ideas coming. Try to concieve a test for them too so we'll know.
Take the alternator belt off and start the car and blow the horn. If no shock then it's caused by the alternator. If you still get a shock try different coil.
It's "back EMF" from the field of the coil (relay or horn, it doesn't matter as both are inductors) If you have a look at a lot of small electronic relays, they have a diode across the coil (reverse biased, or the wrong way round) to short out the back EMF. Try putting a 1 amp diode across the coil, so the cathode (thats the end that usually has a stripe), is connected to the positive end of the coil.
I thought about doing that. I made the mistake of connecting the line/load backwards on some icecube relays once and wondered why they worked just the one time. I took them apart to find that diode burned up and had to fix a wire. Thats when I learned to order them with that little squiggle in the schematic, made things easier. But why does it shock only when the engine is running, any thoeries, is it AC voltage at that time where its DC when the engine isn't running?
Isn't the altenator putting out AC voltage as well as chopped up DC? Can't say I've ever checked to see.
A few thoughts on this.... Different people have different sensitivity to electricity. A lot of the 'old timers' I knew in the electrical trade when I first started didn't use meters to check circuits, they used their thumb and index fingers! Some could even tell you the voltage present, some had to lick their fingers to be able to 'feel' 120V (my father was one of those). But generally, 12V isn't enough to overcome most peoples skin's natural resistance, but there are exceptions. Meter accuracy; Fluke states in their owners manual that their hand-held meters will only 'resolve' ohm readings down to about .1 ohm and accuracy suffers at low ohm readings. If you want to know the actual resistance across a connection, use the 'voltage drop' method to calculate it. Put your test probes on either side of the connection measuring voltage when energized/closed and read the 'difference'; this is the voltage drop across the connection. Measure the current in the circuit, and these two numbers will allow you to calculate the actual resistance. VD (voltage drop) = I (current) x R (resistance), or VD/I = R. As for a AC component showing up, check your alternator. One bad diode can cause a AC 'leak' into the system while not reducing output enough to be noticeable under light loads. This 'leak' can also be well in excess of 12V. Do check all your ground paths. British cars are notorious for poor ground paths, and .6 ohm is certainly excessive. Lastly, voltage in and of itself isn't harmful; it's the current that you feel and does the damage. Current up to about 30 MA isn't considered especially harmful, although some people can 'feel' current as low as 10 MA. A typical GFCI outlet or breaker will disconnect at only 5 MA. Look up Nicola Tesla and his demonstration at the worlds fair where he held light bulbs in his hands that lit up when he applied 1,000,000 volts through his body. Current was limited to a few MA, too low to do any harm.
Alternator output is rectified to DC, though there may be some AC ripple left due to the lack of filtering in a car's electrical system. Or one or more diodes in the alternator could be faulty and leaking AC. A scope works great to identify AC riding along in a DC system, but with your Fluke meter you should be able to see it if it is present.
I don't think he'll be able to see it on his 87, but he could monitor AC voltage off a DC point. Regardless, I like the idea of disconnect the Alt, and see if it still occurs. I also like the idea to see if it is because of maybe the plug wires are causing it. Some sharp minds here leading him to the right place. Always amazed at the HAMB, just folks telling what they know from not only "car" experience, but from their profession.
Shock has nothing to do with the horn, but is caused by the horn relay's collapsing field. A capacitor across the relay will quench it. Otherwise don't drive with your bare arm out the window. OR wear a long sleeve shirt.
I'd have to agree with the idea of a magnetic field collapsing somewhere. On the other hand as Crazy Steve said people's tolerance for electricity varies a lot from one person to another. I used to work with a guy in the early 70's who would check spark plug wires on a running car by holding his finger tip to the end of the wire. His favorite thing was to zap you on the ear with the index finger of his other hand.
LOL! Yeah, we had a dog that would follow the lawnmower and constantly bark at it. My dad got tired of this, so he grabbed the dog, put one thumb on the dogs nose, then touched the spark plug lead of the running mower with his other hand. The dog wanted nothing to do with the mower after that.... LOLOL...
Then why does it only happen when the car is running? If your theory is correct, it should happen all the time, not just when the car is running.
It's not the relay..... Any CEMF that comes out of the relay won't be any larger than what went in, and most relay coils draw under 30MA.
Well I am so glad to read this thread,,,I had a 65 falcon coupe as my first car,,40 years ago , if I blew the horn while touching the alloy part of the column it would give me a hell of a boot ,,thought I was going mad ,,now I now it wasn't just me,,,
Well, I got the car back late yesterday and did some more checking. The coil is Pertronix FlameThrower III, it measured .6ohm, I checked and the nearest I had was a Mallory at .9ohm so I swapped them. The car idled better, still a little hitch in the quality of the idle but I still get a slight zing when blowing the horn. It is definately lesser. Its as if the steering column somehow is energized with ignition voltage but somehow insulated enough so that it cannot pass current until the ground circuit is completed when the horn is tooted. I meant to check it last night after dark. The idle doesn't change when you toot the horn or get the shock. Here's a pic, the plug wires run around the steering column but don't touch it. The only plug wire touching anything is #8 and I'll replace it with a 135deg boot for clearance. #8 is the plug that you have to change from an access hole near the gas pedal.
The coil voltage goes up as the magnetic field collapses when the relay circuit opens. It tries to find a path to ground through you.
Used to be an old guy around here, I think he's passed on now, could spread his fingers apart and put them on the plugs on a flathead 6 and kill it out! The plugs didn't have any boots over the terminals. I think it was a flathead 6 in a Dodge pickup, IIRC.
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