Tunze ATO demise

JulesH · Jun 18, 2026

I have the older variant, it’s about three years old. Typical but I am away from home and my ATO according to my wife and my Apex has given up the ghost or so it seems.

It now shows a red light, I remotely switch it off and then back on, the controller makes its noise but the pump does not come on. The light turns to green then a while later switches to red. I am not sure what has failed, the controller, pump or sensor?

I am trying to remotely trouble shoot this and was wondering if anyone else had seen the same issue?

mfinn · Jun 18, 2026

@rvitko

Blitheran · Jun 18, 2026

Do you have a UV running?

Maybe try switching it off and try again. I have heard and seen the UV can throw off the sensor. Not saying this will work, but in an effort to try anything. This is something I would do

JulesH · Jun 18, 2026

No UV running, but thanks for the tip!

rvitko · Jun 18, 2026

I assume this is a 3155? If it is a red too low light, the pump is probably dead and this is plausible after a few years, this would mean it tried to pump for 10 minutes and a fill was not registered so it timed out, this can also happen if the water level is really too low so 10 minutes is not enough. A red too high light means something is going on with the float, affected by a magnet, upside down, damaged in some way.

JulesH · Jun 19, 2026

Yes it is the 3155. I switched the ATO off and on, my wife could not hear the usual pump sound. So I am guessing the pump is dead?

Kooma · Jun 19, 2026

Those have a 5 year warranty, I’d start that process with them. Sounds to me like a dead pump.

rvitko · Jun 19, 2026

Older legacy products have a 2 year warranty, the 3155 could not be warrantied for 5 years as the pump and sensors of this design will not last that long.

It likely needs a new pump, the old pump typically needed to be replaced every few years.