Relay problem

I have a light that refuses to go on.
The light switch (wall type) is connected to a relay. Now the relay won't "click". It used to work a couple of days ago. The relay has operating voltage of 24V which switches a 240V line (lights).
I would like to test (using a voltmeter) where I'm having problems. How do I measure if 24V is going through the coil/magnet.
The relay box looks like this (wires go to points A,B,C,D):
A 24V b ------------- | | | | | | | | | | C------------D 240V
When the switch is off volmeter shows 240V between C and D
When the switch is on volmeter shows 0V between C and D
How do I measure voltage in A and B?
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On Sat, 17 Nov 2007 19:50:55 +0200, Mike wrote:

If C and D drops to zero then I would assume the relay is closing.
The voltage on A and B should be 24 volts when the switch is on.
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Thanks for the quick reply.
The relay is rated 24V-8V. I'd like to know what I am getting.
What if I (using my voltmeter) connect A or B to ground Should I then get 24V on my meter.
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On Sat, 17 Nov 2007 21:05:45 +0200, Mike wrote:

Chances are it's around 24 volts. Close the switch and measure the relay input.

Shouldn't have any relationship to ground seeing the secondary of a low voltage transformer provides the voltage and is isolated to ground nor should it need to have any relationship to ground. This part of the circuit is very similar to a doorbell.
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Mike wrote:

Not neccessarily, unless A or B happens to also be grounded, which would not necessarily represent a fault.
Put your meter probes across A and B. You will probably read zero when the switch is OFF and should read 18 to 24 volts when it's ON.
If you get the 18-24 volts with the switch ON, but no "click", yet C and D drops to zero as you say, then I'm missing something.
Do you know where the low voltage source running through the switch comes from?
More details please...
Jeff
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When I put the probes on A and B and switch lights on (I am testing on a similar light set up as the problem one) the meter momentarily shows to 24V and then goes to zero. Same thing with switching off. I can't figure why? Do I have a problem with me meter. It has worked fine otherwise.
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Mike wrote:

Questions:
Are the "switches" normal toggling ON-OFF types or are they some sort of momentary push buttons?
From what you just wrote, the control voltage might just be DC and not AC and you have your meter set to measure AC voltage. That could account for the meter momentarily "jumping" to 24 volts when the coil is energized OR deenergized with DC voltage.
Try setting your meter for DC measurements, try again, and report back.
Jeff
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They are normal on-off type. I tried for DC with same result.
I believe now that my meter does not measure correctly.
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Mike wrote:

Could be...
Try your meter when set to DC by measuring a 9 volt "transistor radio" battery and see if it reads somewhere around the right voltage.
Jeff
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Back to the problem. Is the load working? If you are measuring 0 volts across the 240V contacts it indicates that the switch has closed and the load should be getting current. 240v measurement means the switch is open and load is off.
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Jeff Wisnia wrote:

Not all relays make an audible click.

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No, if A&B are the 24 volt coil terminals, you should get a 24 volt reading on your meter across those two terminals, when the switch is on, unless it's a momentary contact ratchet relay, then you'll only get voltage at the coil while you hold the switch on
wrote:

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240 V lights? Explain
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On Sun, 18 Nov 2007 17:53:48 -0500, tnom wrote:

U.K. ?
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