I have installed the new horst probes in my black tank easy job and haven't verified their accuracy yet..if you do it plan on replacing the electric ends on the wires cause they are different.
Installed Horst probes about 2-3 yrs ago. I still have same problems with inaccurate readings. Called company and was told that I still needed to wash probes when I dumped. Should have stayed with factory probes and saved my money.