Did as you suggest and wired a lamp in series across the A1 & A2 coil connections and now the contact closes once. No chattering.
What does that suggest please?

Note:- This is with a 240v 40w bulb. Tried it with new energy saving lamp (11w) and the contact chatter was the same as before.

http://en.wikipedia.org/wiki/Inductance

What's that, part of an Open University course? Way, Way above my level Fred!
Maybe my question, rather than asking what it suggests having wired in a lamp which helped with my problem, I should have asked "In very simple terms, what can I now do about it as an alternative to keeping a lamp wired in"?

unless I am really out of practice, the relay will only be working when the supply is made to the A1/A2 contacts, which will activate the coil in the relay and switch on/off the M1/M2

the remote device should be switching the relay on/off at the A1/A2

there is no motor in the relay, but I am talking about the motor you are switching on/off via the relay. although this may be rated at 300w constant running load when it first starts up it will, for a few milliseconds or more pull an initial load far in excess of the 300w. This is called "current inrush". That is why sometimes the wrong fuse fitted can keep blowing. or a relay will chatter as it tries to protect itself due to too much initial load, which evens out once the item settles down...

you need an electrician, cost about €40/hr with a bit of luck no more than an hour.

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nah, basic electrical knowledge.
and an ordinary twisted wire lamp is not the same as a power saving lamp which is actually a form of fluorescent. which is why old style dimmers are not recommended for use with these new power savers.

Your initial thought might be right Biffta.You will find that if you have a pulsing supply a relay will most of the times pick up this up by.A lamp or a fan might not pick this up...As if you are on the down pulse the lamp might not have time to go dim before its back on the up cycle also the fan might just keep on turning bit slower but maybe not enough for you to notice.

+1

I wonder if this relay is 'chattering' at 50 cycles per second

40 Euro's an hour for an electrician expensive......the 'value' of a life ?.....priceless

Perhaps the supply to the coil is mistakenly connected to the normally closed output of the relay contacts? This would disconnect the coil supply as soon as the relay is engaged, disengaging the relay which re-energises the coil, resulting in endless chatter.

If your remote controller is digital then it may not be supplying a sinusoidal input which your relay primary expects. It may be providing a pulsed signal instead, the effect that a light bulb in the circuit may be that because of its reluctance (qv inductance too) it is providing sufficient smoothing of the signal to operate the relay correctly. Pure speculation. You may need to put some sort of ?reactive/capacitive ballast? (damn I can't remember the right word) in the circuit to replace the bulb.

I think you're spot on Mike. I now believe I'm sending out a pulsed signal which is causing the contacts to bounce in and out.
After much sweating, I've decided to abandon the idea, much to the relief of my wife.
If nothing else I've learned about relays and their uses so it's not all been in vain.
A very big thank you to all who have advised me in this matter.