Shower pump keeps tripping fuse

I have a 1.5 bar Newteam Duraspeed twin impeller shower pump feeding a mixer shower.The pump has worked fine for the past 12 months ,though it wasn't new when installed (I got it from another job)

It is wired via a 3A switched fused spur and it takes its power from the upstairs lighting crcuit(not my idea)
Recently the pump started to take 30secs to kick in when the sjower was turned on but has now tripped the 6A breaker in the consumer unit. I was still getting power into the fcu but nothing out. I replaced the fused spur and the pump worked again but a week later the same thing has happened again.
I then took away the fcu and wired the pump straight to the lighting circuit but now the pump starts up even when there is no demand from the shower.
Is this likely to be a fault with the pump? No other problems anywhere else in the house.

yes, very likely to be a fault with the pump.

Ok. I've put in a new pump and it works okay.

BUT- I tried refitting a new fused spur between the pump and the supply from the lighting circuit and there's no power going out to the pump again-and it was a brand new fused spur with a new 3amp fuse.

What's that all about? can't be a second faulty fused spur surely?

I have had to remove it again to get power to the pump.

I doubt there was anything wrong with the first fused spur.

Have you tested the fuse?

Have you tested the load side of the spur?

Are you sure no power is getting to the pump?

The reason I say these things is that it could be that the pump is not kicking in because you have a low head problem with the water supply to the pump. Is it a positive or negative head pump? Is there much distance between the shower head and the cistern?

there is no power on the load side of the fused spur- i've tried about 4 different fuses in it- p'raps i keep picking the same one up and putting it back in each time!
When i bypass the fcu there is power all the way and pump works fine.
The plumbing side of it is all sorted and previous pump worked ok for 12 months.
Just wondered if it was common for fused spurs to malfunction? - as I came across one the other week supplying a boiler-it just didn't work and it wasn't the fuse. New one sorted it.

Double check connections in back of spur. Could be wired incorrectly etc

Ok, just checking. If you have measured no voltage on the load side and have tested the fuse (before and after fitting it!) then it must be a faulty fcu, unless as pointed out you have it wired up wrong.

These things do go wrong, but not normally new ones.