Osmolator pump sounds funny....

[Kaos]

My Osmolator 5017 pump sounds funny whenever it turns on. The pump will not keep a constant speed when on. It rev's up and down the whole time its working. Any ideas as to what might cause this? I have the full length of tubing attached to the pump if that matters (but the actual head is only 3'). I have not cut the suplied tubing for the pump because I am upgrading tanks soon and don't know how much, or little, I will need. Any help would be greatly appreciated.

Great product btw.

 

[rvitko]

Are you sure it is actually reving and the pitch isn't changing simply due to some air bubbles inside? I can't think of anything that would make it rev excluding a change in voltage. Often though you get some air in the pump and the noise changes due to the bubbles. I would try tipping it upside down while it is running under water to purge any air out. If you have a voltmeter it would be useful to check the output at the terminals for any fluctuation.