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More (effing) boat electrics. Help!

outdoordan

Well-Known Member
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Joined
Dec 5, 2012
Messages
294
Not a high stakes problem but its got me stumped.

12V DC

12v fused (3A) from engine battery (on constant trickle charge from pv cell) showing 12.9V

Live to bilge pump via float switch (tested several times) working fine.

Earthed direct back to battery for the moment.

Bilge pump when connected direct to pos and earth runs fine, pumps strongly.

When switched on via float switch it runs not and just makes a slight buzzing noise. Volt meter from pos out float (to motor) and neg out from motor when float switch in on position reads 0.8V

Leave voltmeter clips attached to terminals and remove motor from loop reading is 12.9V

Im giving up and going for a gin in the garden
 
Connect your voltmeter inline and check the amperage draw when the float switch is connected and in the on and off position. If it acts like a latching switch then no the circuit should be open when float is down. However, as the switch is normally connected to a manual override there could be a back feed. Option c is rig up a halogen car headlight bulb in lieu of the float switch and see if it stays lit all the time.
 
Probably bad float switch. To make sure you check only float switch, leave pump connected as normal and try shorting between in and out of float switch. If then the pump runs fine, the float switch is the problem. E.g. corrosion on contacts inside.
 
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