JCB Backhoe.

[Brian Bobb]

This may seem like a silly question but this is the second time we're buying a solenoid(25/996301) with no ohms reading so it always short out whenever it is energised. Could this be manufacturer's defect or when the electrician energised it on the work bench caused them to short out?

 

[Delmer]

A coil shouldn't be energized without the core in place, the core boosts the resistance of the coil. Without the core, the coil will draw too much power and burn out. That's what I've always thought anyway.

 

[Brian Bobb]

So him just having a screwdriver would have caused them to burn out like that? He had some other solenoids and energised them without the core and there wasn't any short and it magnetised when he put a metal rod in the center. So we shouldnt have him test the new one but rather install it on the machine?

 

[Delmer]

I really can't say if a screwdriver would keep it from burning out or not. Why don't you just test the resistance if you're worried about the new coil?

 

[Brian Bobb]

I really can't say if a screwdriver would keep it from burning out or not. Why don't you just test the resistance if you're worried about the new coil?

There was no resistance when he first checked it before energising it.

 

[jcb jeff]

I guess the + and the - are the correct way round?

 

[Brian Bobb]

I guess the + and the - are the correct way round?

There was no + or - indicator on the solenoid off itself but they went according to the wiring of the backhoe. Shouldn't the coil have a resistance reading at least?

 

[Tinkerer]

Shouldn't the coil have a resistance reading at least?

Yes it should.
An open or semi-open circuit in one of those coils could show resistance depending on the ohm meter setting used.

 

[geminijo]

A solenoid is just a coil of wire and should have fairly low resistance ranging from a few ohms to a few hundred ohms depending on the number of windings and the size of the wire.If you're reading infinite ohms than you have an open coil.If you're reading zero ohms with your meter on rx1 scale then you have a shorted coil.

 

[Brian Bobb]

Yes it should.
An open or semi-open circuit in one of those coils could show resistance depending on the ohm meter setting used.

That one was giving zero ohms

 

[Brian Bobb]

A solenoid is just a coil of wire and should have fairly low resistance ranging from a few ohms to a few hundred ohms depending on the number of windings and the size of the wire.If you're reading infinite ohms than you have an open coil.If you're reading zero ohms with your meter on rx1 scale then you have a shorted coil.

It was giving zero ohms when he tested it but still tried to e energise it. So it was a shorted call after all. Thanks.

 

[geminijo]

It is sometimes difficult to determine the difference between a low resistance coil winding and a shorted coil if your using a meter that isn't real precise.

 

[Brian Bobb]

It is sometimes difficult to determine the difference between a low resistance coil winding and a shorted coil if your using a meter that isn't real precise.

Even though it is a DMM?

 

[geminijo]

If it's an inexpensive meter it may not have the sensitivity to show the difference between a few ohms and a shorted condition.Put the meter on the lowest resistance scale ,usually Rx1 and touch the two meter probes together.You should read zero ohms.If you also read zero ohms when you go across the solenoid then the solenoid is probably shorted

 

[Brian Bobb]

If it's an inexpensive meter it may not have the sensitivity to show the difference between a few ohms and a shorted condition.Put the meter on the lowest resistance scale ,usually Rx1 and touch the two meter probes together.You should read zero ohms.If you also read zero ohms when you go across the solenoid then the solenoid is probably shorted

It was an inexpensive meter. We did exactly that and got zero ohms. Just waiting for the new solenoid to get here.