@@saadyzuleyman7138 Gracias!

You are certainly on the right track. High resistance readings on thermistor translates to high temperature readings by control board. Any higher resistance than this, the contol board will see it as a full open (infinite resistance) and result in E01 error. Also, make sure you spade connectors are clean and not corroded so that you have zero resistance across each connector. You don't want something like corrosion to add resistance into the equation while trying to get an accurate reading from a resistance based component such as a thermistor. Cheers!

Company should be sued.

That's intense, but you stuck through it. Nice job!

E01 is "open thermistor". Check the thermistor connectors, wiring harness, and modular connector at the control board. If all is OK, you have a defective open thermistor that must be replaced.

@Torch-lt1ry If you have hot exhaust, then your igniter is working, your gas valve is working, and your burner is burning. Let's check for water leaking into your combustion chamber and filling it to the point of covering up some of the copper tubes inside. If this happens, the fire will not be able to engulf the tubes as necessary which will result in hot, moist exhaust with relatively cold output. There are about 12 vertically oriented bolts on you manifold (6 on each side). Remove either one of the bottom bolts on the manifold and see if water pours out. If water comes out, then you have a leaking heat coil assembly that will need to be replaced.

@@pvt-pilot what’s weird is it worked yesterday and it felt like my water was getting warmer but the reading never went higher than 51. I know what 51 feels like and the pool water felt like 70 something! So today I am getting AFS error and I never here the engagement after 10 seconds or so. The service heater light comes on and the AFS light. So I looked in the blower and there was a nice nest in there at one point so I cleaned it out. I then took my gas blower and blew it into it and the service heater light turned off but I never heard or felt it engage the heater! So that is where I left it! Do you think it could be the AFS that needs to be replaced? Because if it was a bad board the light wouldn’t of gone out correct? Sorry long winded post!

I do not, sorry. Hopefully someone else on here knows how and can respond.

Then you likely have an issue with the contol board. To prove this, you can disconnect the membrane pad and use needle nose pliers or a piece of wire to short the common pin #1 on your circuit board to the corresponding pin that traces out to the button you are pressing. I don't have the pins memorized, but I can do a membrane pad replacement video and illustrate this exact concept. (I hope to have that done in the next week or so) You just have to look at the back side of the membrane pad and follow each conductor embedded in the ribbon from the white modular connector to each respective button on the pad. Take note of this and short the common pin #1 on the control board to the temperature up button pin on the control board briefly and repeatedly to simulate pressing the button repeatedly. If you can't get the control board to respond this way, you have to replace the control board. If it does respond, then your new membrane pad is also defective. You can also use an ohm meter and connect it to your membrane pad across your temperature button female hole on the white connector of the membrane pad and the other lead on the common pin #1, then press the button on the pad and see if you get a 0 ohm short. This will prove your new membrane pad to be good or bad. You should see a short on each respective button if it is good.

Sorry, I'm just a home owner sharing knowledge gained from tinkering with my Mastertemp 400. I don't have any knowledge on your Mini Max. That said, 88.8 sounds like all possible pieces of each number on the display are illuminating, like what happens at a faulty gas station sign. I might start with the control board with that scenario, but really don't want to lead you in the wrong direction.

@@Docinabox83 Fantastic!

Yes, it will heat the water quicker at 400,000 BTU as opposed to 250,000 BTU heater

@bsatchel705 It is the next likely box to check. Grab a 13mm socket and remove those manifold bolts, remove all of the sensor wires and loosen the 2 unions (inlet and outlet). The whole thing comes off as one unit very easily. Pull out the plastic wall inside the manifold, and your Manifold Bypass Valve should be right there sitting sideways in the grooves. Hopefully yours didn't break and take a ride in the pipes like mine did.