Stray Voltage?-long winded

I own an old farmhouse where the wires are the old silk/cloth wound type. The whole house has these encased in the flexible metel conduit. The conduit is attached at the access and is the 'ground'. In addition to 'grounding' at the box, there are 3 points that I know of that are 'grounded' to iron pipes embeded in the earth. I went to wire a new light fixture that is switched. I killed power, removed the old fixture, and turned power back on. I have one of those 2-prong 90-300V circuit testers. With the switch on, I touched black and white and the tester lit brightly. I then touched black to 'ground' on the box, and the tester lit brightly. I then touched white to 'ground', no light. So far so good...
I then turned off the wall switch. I touched black to white, and got a faint glow! I touched black to the box and got full power!
I then pulled the switch plate and tested the lines to the switch. Absolutely no power at the switch, it is all ground. I unhooked one wire from the switch and tested the black wire at the fixture again. Full power from black to the box, but a faint glow from the white wire.

My questions are:

1. Isn't it supposed to be the 'hot' wire that is switched?

2. Where could the white be going to ground with it disconnected from the switch? Inside the conduit?

3. How dangerous is this? It has been working for 50+ years so far...

Thanks in advance for any and all thoughts, and I apologize if this is not the correct forum for this question.

I want to assure you all that the service entrance is a modern 100amp access installed in the early eighties by a master electrician. It is correctly grounded to a 6 foot copper rod at the meter (which was not grounded when I moved in). At that time I voiced some concern about the older BX wiring. The Master did quite a bit of looking and continuity testing and assured me that the BX was in very good, serviceable, condition. He also stressed that the new 'system' was much safer in that the old wiring had all been connected through 2, 30amp fuses. Now the house is supplied by 10 individual, 10-15 amp breakers (not including the 1 double breaker for the well pump).
I have the utmost respect for electricity and its dangers.

Thank You All Again!

I should have added that you do have a serious problem with this circuit. This one circuit has to be corrected and the rest should be tested to see if any more exist. It's the way it's wired is the seriousness of the problem. If you have one wired this way, one can assume you have more!!!

As they say, this circuit is an "accident" waiting to happen.

T_Bone

However, if this information is news to you...you should definitley contact an electrician!

"Hire an Electrician Before You Burn Your House Down"

Now if Jim K, Ray M41, Davido, Jim WI, and ironhead: Will e-mail me, I will explain why ALL of you are wrong on what you said to this post, of how this circuit works and how to correct the problem, what each of you missed and why one should NOT give out electrical advise over the internet, provding that each of you will post back here too Salmoneye after I have convienced you why I'm right, so that others may learn of why you can NOT give advice on high voltage (over 24v as defined by NEC) circuits over the internet without writing a book!!!

What I do NOT want each of you to do is post the correct answer on this post so someone "might" kill themself or a loved one thru a miss-understanding of directions.

If I'm wrong, I'll post here that I don't know what HE** I'm talking about!!!

This is not the place to learn about high voltage electricity!

Salmoneye, Please hire a qualified electrician as by your post you are beyond your skill level for this job. Learn from watching what he does! And no I will not tell you whats wrong with your circuit! and I hope no one else does!! Atleast that way You'll be here for this Christmass!!

T_Bone

--->Paul

1. There is one 'cable' at the switch. There is a black and white at the switch.

2. I have found a receptacle (outlet) that is on the same circuit, but have not pulled the plate to look at the leads.

If I am undersatnding the replies, this could account for the 'slight' ground that I found in the white wire of the box for the fixture (even with the switch off), if I had something plugged into the outlet such as an instant-on Television with a capacitor? The 'hot' at the fixture might go to ground through the TV? Should I unplug everything and test the 'hot' at the fixture again to see if the slight ground is not present?

Thanks Again!

PS Davido: I would really appreciate it if you could e-mail me the diagram! I do not think that the wiring is in bad shape. I have done a lot of renovations of old apartment buildings and I have seen 'bad' wiring before. It is just that I have never put a tester on anything before, and this surprised me.

2. Given that you describe the old style cloth insulation and a glow from the bulb, I suspect an insulation breakdown inside the conduit. It could be at the box for the fixture and might have happened when you moved the wires while removing the fixture. Old insulation breaks fairly easily.

3. The incorrect wiring on the switch is dangerous because you think the fixture is off when it's not. That's the only real danger since the you indicate that the black is the hot wire as it should be.

The question you need to ask yourself is just how much of the rest of the wiring is wrong? I wouldn't be surprised to find a few other things (and maybe something really bad).

I think I'd be doing a bunch more checking to figure out what else is wrong.