Wizard
Why is it the smallest problems are the BIGGEST PITA
I have a power supply to the cabin to run assorted items ... such as the beer fridge e.g.So you can see the importance of same.
It's switched via a relay that is activated with a rear window heater switch in one of the spare holes in the dash. This is connected to the relay via small twin core wiring. The actual wiring that does the muscle bit is at least 6 sq mm and runs the beer fridge et al quite happily.
Now this little bit of necessity has been running away quite happily for about 6 years, ensuring the fridge is at the necessary temperature to keep herself and moir happy. UNTIL NOW !!!
I noticed it wasn't working so decided to investigate. The activating supply is about 11.6V at the relay, but it won't work. Checked the relay and numerous spares on the main power supply and they work fine. Bypass the relay and all works fine.
So ... what's the go?? Is 11.6V insufficient to throw the switch ?? If so, how come it's worked fine for all those years?
I've plumb run out of ideas. Thought of replacing the activating wiring with something bigger, but can't really see the point, and it's a bugger of a job getting the wires through to the fender dash anyhow.
So ......... any ideas, suggestions ??
Cheers
Master
Make up a test light to test the voltage. A digital multi could give false readings (if dodgy relay earth etc) or test the (switched) voltage at the relay terminals when the switch is in the activated state.
Voltage needs to be tested with a meaningful load applied to it
Wizard
Thanks HC ... will try with a test lamp.
Swaggie
Test across the activating supply & earth(neutral) terminals on the relay.If there is definitely power there,relay is faulty.If no power,keep checking until you find fault,bad earth,etc
I presume you have bypassed relay at relay & fridge works fine
Last edited by scarry; 24th April 2010 at 03:56 PM. Reason: Forgot something
Wizard
Yep. Bypass relay and all OK. Connect main power supply to relay activating circuit and touch to earth ... relay switch works (audible click).Originally Posted by scarry
But won't click on activating circuit with 11.6V ???
Swaggie
You shouldn't have to touch one side to earth,it should be earthed all the time i would think?
The earth could be your problem.
AT REST
11.6V at the activating circuit? It should be close to battery voltage 12.3V. While 11.6V is quite enough I don't think you are reading it right. I suspect a weak connection in your switch circuit. Connect your relay as it was, switch on, THEN check voltage across the relay coil. Start chasing voltage losses by measuring relay earth to body, switch (both sides) to body. Always remember the load (relay coil) needs to be switched on in circuit for realistic testing.
Wizard
No closer to solving the problem
Activating switch +'ve and activated +'ve both come from same power source (downstream side of circuit breaker)
Cleaned the contacts and now get 12+V through the activating circuit at the relay. Closed switching circuit to earth .. no click. Connected earth side of relay through meter to earth 12+V but no click.
Connected relay switch +'ve to main power source supply and get click when earthed.
Both have 12+V, but only one will throw the switch ...
Wizard
Think I've got it sorted. Out of frustration, and in the absence of any other alternative. I made up an alternative of heavier twin core for the activating circuit and gave it a shot. WORKED PERFECTLY.
It would appear the switching wire must be damaged somewhere. Will show voltage but can't carry the necessary current to throw the switch.
Now to replace it .... the fiddly part I was hoping to avoid.
Thanks all for the suggestions. I was almost at the point of giving up and booking it in with someone who knew what he was doing.
Master
you only need one core to switch the relay - just find the good core and use that. I'm a lazy bugger, thats what i'd do
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