H400 SF issue

[chef_m]

Hi. I have a 5 yr old H400 ED2 with electronic ignition. I live in Arizona, so I use it year round. It generally has been issue-free and works great. Currently though, I have an intermittent SF issue that's been popping up.

If it happens, it tends to happen when I attempt to turn it on. I initially thought it was just a loose connector, as when I opened the panel and tightened every wire I could find, it came back and worked fine for weeks. But I've recently been thinking that it probably was not a connection issue. If I flip the (external) power breaker and shut off all the equipment, it resets and comes back to life.

My theory now is that it's just a side effect of hard water and that I should remove it and clean and/or replace it. But here's the real question: which sensor is it (see pics) and how do I remove it? I've read the H400 service manual 3 times now, and it just is not clear. Yes, I could probably trace the wire pairs back to the control board and hope that the board has printing on it on the back side, but I'd prefer to do it right the first time.

So, which of the two sensors is the thermistor and specifically how do I remove it given my installation?

[attachment=1:1t40id08]H400_1.jpg[/attachment:1t40id08]
[attachment=0:1t40id08]H400_3.jpg[/attachment:1t40id08]

 

[phipsi1237]

Chef,

The 2 sensors on the right side of the header (as you face the heater) are high limit sensors. From what I can tell, the thermistor is on the left side bottom closest to the heater. I believe it's the only one with copper tubing.

To remove it, you'll need to remove the front access panel and pull it through the "firewall" after loosening it's one screw. It sticks into the header itself about 3 or 4 inches. Hope this helps.