Frequently Asked Question

Why do Horst Miracle Probes work, while the regular probes don't?

Normally, electrical communication between a PLUS probe and a MINUS probe goes through the water and excites an LED. ( Light Emitting Diode) After a tank has been used a couple of times, the wall of the tank gets coated with sludge.  This causes all LEDs to turn on even when the tank is empty.  False conductance is established between the negative and positive stainless steel heads of the probes over the "with sludge covered" rubber grommets and plastic walls. The Horst Miracle Probes interrupt this electrical path because the probe stem is covered with Teflon tubing which prevent that from happening.  Teflon is the most slippery material and self cleaning.


Can I use Horst Miracle Probes on any RV holding tank?

Horst Miracle Probes can be installed on all RVs that are built to RVIA, CSA and IAPMO standards


How do you install the Horst Miracle Probe?

Remove existing probes out of the usual 3/8" diameter holes and replace them with the Horst Miracle Probes.  You can push the threaded portion of the old probe into the tank.

Optionally, you can also choose to drill 3/8" diameter holes next to the existing probes.  Push the new probes into the 3/8" diameter holes and tighten first nut to make a good leak proof seal.  Connect wires as they were.

Because black tank probes have a 'roof' above the probe to prevent toilet paper from covering the wire, be sure to orient the roof by rotating the exterior threaded electrical stud so that the milled flat section on the end of the stud is down, and the roof is up.


My tanks are hard to access, what should I do?

If it's difficult to access grey and black water tank, simply take your RV and your Horst Miracle Probes to your local RV service station.  Tell them that you would like them to replace the current probes with the Horst Miracle Probe.    The directions are included on the package, and are very straight forward.


I'm not getting a reading after installing the probes.

If you are testing the tank with fresh water or soft water, there may not be enough connectivity in the water to make a reading.  (Remember, these are for waste tanks, and waste water has conductive elements in the water.)  You can add a teaspoon of salt to your fresh water, which should solve this issue.

If you are still having an issue, double check to make sure that the wires are correctly hooked up. You can see a visual at the bottom of this page: https://www.rvprobes.com/howitworks.html

It's also possible that you may have an issue with the monitor, and not the probes.  To find out if it is a monitor issue, do the following:

1- Disconnect all wires from the tank and measure resistances in Ohms between the common (white) and the three level probes with no water in the tanks. It should read infinity on the Ohm meter

2- Measure the resistance between the wires while they are disconnected from the probes.

     Between green and yellow should be about 120000 ohms

     Between orange and green should be about 68000 ohms

     Between orange and yellow should be about 188000 ohms

Typically the resistance between the common probe and any of the individual probes while submerged and with no wires on them should be about 10000 ohms to 100000 ohms depending on the water. This must be done with an analog ohm meter.


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