Tunze Osmolator ATO Optical Sensor Replacement

rvitko · Sep 12, 2025

They are in stock, the website only lists stock in Germany, but if you order it will ship the next business day. Not in stock even means very little, it menas it is not packaged and ready to go that day, they definitely have hundreds of them but someone will need to pack it so they list it as not in stock as it won;t ship for a couple days.

If it is less than 2 years old it is under warranty, I would need a receipt and serial number for warranty replacement.

Clarkjw2002 · Sep 12, 2025

Thanks! Will order a few. I’ll see if I can find the receipt. Pretty sure I didn’t buy until my main tank was on but it’s possible it’s nearing 2 yrs if I switched out the 3152 earlier.

In either case, I don’t mind the cost since I can swap out myself.

I guess at some point I’ll need to switch to the osmolator 3. Is there a connector I can put on the currently plumbed turbelle pump I have (it doesn’t have a plug but the two wires that need hooked up to the ATO). Otherwise I would have got the new 3 instead of the 3155. Don’t want to have to remove the pump from the half inch PVC until it needs to be replaced. But I could I guess.

Genvid · Sep 12, 2025

how can i buy a new sensor, it says it is out of stock

Clarkjw2002 · Sep 12, 2025

Genvid said:
how can i buy a new sensor, it says it is out of stock

Just put in the cart and check out. I just ordered 3 of them from the link above.

If I can find a receipt I’ll get another under warranty.

Genvid · Sep 12, 2025

I still click on the order, instead of the basket, nothing happens

Clarkjw2002 · Sep 13, 2025

Not sure I understand. On the product page, click on the little yellow cart square to add to your cart.

Then scroll to the top of the page and click on the little yellow cart symbol at the top right (which now should say 1product beside it because you added the sensor). This opens your cart page where you can change quantity and click update. Or click order at the bottom of that page and it takes you to the next page for ordering details.

Worked on my iPhone and I just tried on my Mac using Safari. Think I had to scroll down to see it on my phone though. If this doesn't work maybe try a different browser?

rvitko · Sep 15, 2025

The Osmolator 3 will only work with the included pump which can handle 20ft.

Clarkjw2002 · Sep 15, 2025

I know. That’s the pump I’m using but I bought it before the osmolator 3 was out. It was an “upgrade”. I swapped it out for the normal stock pump for the 3155 and 3152 so I could plumb into half inch PVC. The only difference is my pump doesn’t have the 3 pin plug on the end of the power line that the 3154 requires.

Clarkjw2002 · Sep 15, 2025

Back to topic. Surprisingly, I found my invoice for the 3155. Was bought in Sep of last year. How do I go about getting the sensor replaced under warranty?

rvitko · Sep 15, 2025

I would just need the receipt and serial number for the warranty replacement.

Clarkjw2002 · Sep 17, 2025

PM sent.

P-Dub · Oct 14, 2025

Hi @rvitko.
I have an old (2017) Osmolator 5017 with the pump. It appears that my optical sensor has finally bit the dust as it is sensing that it is submerged when, in fact, it is dry. As I understand it, the older models are not able to have the optical sensors replaced, as the time to recalibrate, solder new components, capacitors/ resistors, etc, makes it cost-prohibitive. Is there a way to buy just a replacement controller and not the power source, or do I need a new one of those as well?
Standing by and thank you for your time.

Radiant · Nov 11, 2025

Im ripping my hair out, I would really appreciate some support. I purchased a tank this year from a fellow hobbyist. One of the pieces of equipment is the tunze osmolator 3155. Right away I replaced the pump because he told me it need to be replaced. When I tried it on my system the pump worked fine but no matter how I positioned the sensor it always indicated water level low and would fill until the emergency float switch activated. Yesterday I received my replacement sensor, I installed it without any problems. Now with the new sensor I am having the exact same problem. No mater how submerged the sensor is the unit always undated water level low and turns the pump on. The only exception is when the float switch is engaged and the alarm sounds. I do not have a receipt and am not expecting a replacement, but this is driving me crazy. Please, please, any support is so greatly appreciated

Hollywood_REEFER · Feb 11, 2026

Hello, seems like I found the right thread. My 5017 sensor finally gave up. bought the unit in 2019, looks like I need a sensor. where can I buy and is it direct plug and play?

rvitko · Feb 13, 2026

Sorry I am late to reply, R2R was down for me Wednesday morning and then I just got sidetracked.

The date of manufacture will be critical here. If it was made after Oct 2019, you can just buy the sensor and it is plug and play, before Oct 2019 it needs to have a resistor replaced and updates to the software so it need to come in. If your controller has a black tag on the cable with the two clips the pump connects to it is post Oct 2019, if their is instead a silver tag on the back of the controller it is pre Oct 2019, either tag has a 6 digit number which will likely be something like 2019xx and that is the year and month it was made but the serial number tags on the cable started Oct 2019. If it is really close, like August or September 2019, it would be worth sending a photo of the circuit board in good light as you may already have the updated board, they seem to have started showing up late August.

Hollywood_REEFER · Feb 13, 2026

rvitko said:
Sorry I am late to reply, R2R was down for me Wednesday morning and then I just got sidetracked.

The date of manufacture will be critical here. If it was made after Oct 2019, you can just buy the sensor and it is plug and play, before Oct 2019 it needs to have a resistor replaced and updates to the software so it need to come in. If your controller has a black tag on the cable with the two clips the pump connects to it is post Oct 2019, if their is instead a silver tag on the back of the controller it is pre Oct 2019, either tag has a 6 digit number which will likely be something like 2019xx and that is the year and month it was made but the serial number tags on the cable started Oct 2019. If it is really close, like August or September 2019, it would be worth sending a photo of the circuit board in good light as you may already have the updated board, they seem to have started showing up late August.

Thank you for the reply. it has a black tag on the 2 clip wires. so, I'm guessing it's a simple sensor replace. I been looking everywhere to get one and I haven't had any luck. can you point me in the right direction? Thanks in advance, Gabe

rvitko · Feb 16, 2026

https://shop.tunze.com/us/Optical-probe-for-controller-5017/5017.300

Hollywood_REEFER · Feb 16, 2026

rvitko said:
https://shop.tunze.com/us/Optical-probe-for-controller-5017/5017.300

Thank you!!!

RandyM728 · Apr 1, 2026

rvitko said:
We do sell these sensors, but since a calibration is required when it is changed, they are only sold installed. The part is $29.49, the only other charge is shipping. If you send only part 5017.000, controller with sensors, no magnets or other parts, it greatly reduces shipping, controller only will fit safely in a small flat rate priority mail box and mail for $8.65 or can be sent first class mail for around $5. Include your contact and return info in the box.

Tunze USA
305 Victor St
Austin TX 78753

Are you able to replace tunze osmolator 3 water level sensor?

rvitko · Apr 1, 2026

Any Osmolator 3 would be under warranty, the sensor/controller assembly is replaced as a unit, I would need details of what is wrong, a copy of the receipt and the serial number from the tag on the cable for warranty.