2x6125 Won't start

[barjam]

I have two brand new 6125 that I have had in my tank for a few weeks.

The problem is they refuse to start unless I bring them into some air to kick start them. All they do is clatter unless I do this. I let one of them clatter for 5 minutes to see if it would ever start and it did not.

The magnet assembly moves freely on the metal pole and there is no debris within the unit itself.

Any ideas?

After poking around on the Tunze site it looks like maybe I am missing a 3005.740 set for both pumps? I looked in the box and don't see them.

 

[rvitko]

The 3005.740 sits down in the pump at the base of the shaft, you would need to look in their with a light to see it. This piece being missing could cause this, other possible causes would be use on a wavemaker, or damage to the propeller blades or front housing. The 6125 will always start backwards and the prop flies forward and hits the front cover to correct direction, repeated on and off will break the stop tabs on the propeller housing or the ends off the prop, I would inspect those, even if no wavemaker was used, just to be sure. The disk can cause this because it is a shim, without it the drive magnet is trapped under the magnetic field and cannot move forward. Also any debris between the shaft and magnet that would impeded the smooth motion forward and back can cause this.

 

[barjam]

I looked again those parts are in there.

These are brand new pumps less than a month old and have not seen a wave maker. I inspected them for any damage to the housing or prop and see nothing. One pump will almost always kick off the guard and sometimes cause the housing to open a bit. The other pumps is slightly better behaved and starts once in a great while.

I also inspected them for any debris and found none. They haven't started since day one without help so I don't think it is a debris issue.

I don't know what else to try.

Edit:

I saw elsewhere that you mention low voltage can cause this. I measured it 120 +/ 2 at the power source.

 

[rvitko]

Can you PM me your email? I would like to email you some pics of the drive unit. My best guesses at this point are A) the drive unit is wrong, i.e. the propeller is a 50Hz propeller and not a 60Hz propeller (bigger and won't run on US power). B) the drive unit fits too tightly on the shaft, you could check this by seeing how easily it slides out, besides the magnetic field their should not be much resistance.