Water pump 12v (1 Viewer)

[Taff015]

Hi all,

after some collective advice please?

My water pump isn't working. I've changed the fuse and I'm getting power down the wires. I thought the pump was cuffed and removed it. just to confirm my suspicions, I hooked the pump up to a 12v battery and it works......

My only though is that all the microswitches on the taps are shagged or could this relay be the culprit? If so, will any 12v 5 pin relay do?

Thanks in advance

Paul

 

[autorouter]

How to test a 4-pin relay. Use a multimeter to measure the resistance (ohms) between any two pins. When you find a value between about 10 and 1000 (ie not zero and not infinite) then you have found the coil pins.

Apply 12V to the coil pins. The relay should click as the contacts close.

If it's a standard relay, the resistance between the other pair of pins should go from infinite to zero when the coil is powered, and go back to infinite ahen the coil power is disconnected.

will any 12v 5 pin relay do?

Any 4-pin relay will do. If it's a 5-pin, You need to find the coil pins by the method above, then find the other pair of pins that are infinite resistance with the coil unpowered, and use those. Ignore the fifth pin.

 

[tonyidle]

Here you go:

You shouldn't have a connection to 87a for your application.

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[Taff015]

Thanks guys. I've ordered some off amazon that have the same numbers on the bottom! I do have a feeling though that this is the toilet relay!!

I may have to faff about some more!!!

 

[autorouter]

If you can get at the wire near the tap, there will be a 2-way connector for the microswitch wires. Separate the connector.

Use a multimeter to measure the resistance of the microswitch, at the connector terminals. it should be zero (or very low, 0.5 0hms or less) when the tap is open. It should be infinite when the tap is closed.

The other side of the connector can be used to test the rest of the system. If you short the wires at the connector, the pump should fire up, and should go off when the short is removed.

 

[tonyidle]

Your new relay isn't wasted. If there isn't a pump relay install the one you bought - it's a very worthwhile mod.

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[Taff015]

Your new relay isn't wasted. If there isn't a pump relay install the one you bought - it's a very worthwhile mod.

I've bought a new pump too thinking the original was cuffed. Thank the internet gods for Amazon's return policy!!

 

[autorouter]

If it's a 5-pin, You need to find the coil pins by the method above, then find the other pair of pins that are infinite resistance with the coil unpowered, and use those. Ignore the fifth pin.

No, sorry, that's not enough. Two pairs of pins will have infinite resistance with the coil unpowered. But only one of those pairs will have zero (very low) resistance when the coil is powered. That is the pair to use; ignore the other pin.

 

[tonyidle]

No, sorry, that's not enough. Two pairs of pins will have infinite resistance with the coil unpowered. But only one of those pairs will have zero (very low) resistance when the coil is powered. That is the pair to use; ignore the other pin.

Or see my picture in post 3?

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[tonyidle]

A relay is just a switch. In this case when you throw the switch it moves the lever 30 from 87a to 87 and is known as a changeover switch (or SPCO single-pole changeover). If you replace your finger with a coil that when powered will move the lever 30 in the same manner you have a relay. The coil magnetises a fixed lump of metal that attracts lever 30 and causes the movement. The point of all this is that the coil requires a very small current to magnetise it (around 0.15A) but the switch contacts can handle 20A to 30A. So the winky little microswitches on the taps have to handle whatever the pump requires (probably 3A - 4A) at present. With a relay in use they'd be handling 0.15A. And that isn't the whole story: switching a motor OFF causes quite a large spark that slowly erodes the microswitch contacts whereas the relay has big fat contacts that are much less affected. Add in the fact that current doesn't now have to find its way all around the taps to get to the pump and you're onto a winner. That relay and its colleague the 4 pin version (no 87a) is the most common relay in automotive use.

 

[Taff015]

A relay is just a switch. In this case when you throw the switch it moves the lever 30 from 87a to 87 and is known as a changeover switch (or SPCO single-pole changeover). If you replace your finger with a coil that when powered will move the lever 30 in the same manner you have a relay. The coil magnetises a fixed lump of metal that attracts lever 30 and causes the movement. The point of all this is that the coil requires a very small current to magnetise it (around 0.15A) but the switch contacts can handle 20A to 30A. So the winky little microswitches on the taps have to handle whatever the pump requires (probably 3A - 4A) at present. With a relay in use they'd be handling 0.15A. And that isn't the whole story: switching a motor OFF causes quite a large spark that slowly erodes the microswitch contacts whereas the relay has big fat contacts that are much less affected. Add in the fact that current doesn't now have to find its way all around the taps to get to the pump and you're onto a winner. That relay and its colleague the 4 pin version (no 87a) is the most common relay in automotive use.

Thank you, much appreciated