Right an update
Think I have it sorted .
Changed the pump for a gates pump
Mil light still on
Changed the plug and part of the loom
Same problem .
Had the old plug and part of the wiring
So tested the pumps I had .
Ended up with 4
1 the original .ran for a second if tapped and stopped .
2 cheap ass ebay pump 20e
Ran when it got power constantly .
3 a vw pump using the original part number .was surprisingly cheap 40e but came in an original vw box all part numbers were the same and made by pieberg
When it got power ran for a few seconds and came back on every 5 or 6 seconds later .
4 .the autofactors new part 130e made by gates .same as the timing belt manufacturer.
Gave it power noting at all.
Opened it up and spam the impeller with current still nothing
Looks like it was a dud part .
Put the no3 pump on.
Ran the car for an hour
Heater perfect
Scanned the ecu and no codes at all