Previously working Nest T-stat E298 error

[WasabiDragon]

Hi, 

   My t-stat (not sure what gen it is) has worked for a couple years and today it's showing a E298 error. I've checked the wires on t-stat and hvac unit, all appears ok. Breakers aren't tripped, it worked fine this morning. I've reset the t-stat and tried reconnecting to Google home with no luck. I will check the drain from outside later, the drain inside appears clear though. 

Any suggestions in not thinking about? 

[Patrick_Caezza]

@WasabiDragon 

The E298 error code means the Nest isn't receiving power from the HVAC system.

Here is a quick help article that offers some reasons for no power.

Troubleshoot a "No power" alert on a Nest thermostat (E298, E448 or M20 help code)  

Some simple causes of no power are,

• Condensate drain plugged
• The covers are not completely or correctly installed 
• 24vac fuse is blown on the control board in the furnace/air handler

[WasabiDragon]

 @Patrick_Caezza

I don't see where the safety switch would be to check if it's plugged. Would it be inside the top part where the pvc line comes out? I checked the small fuse inside the front panel, the thin metal stand appears intact, it has three little beads down the length of the wire (weird). I removed the front panel, replaced it making sure the switch behind it was pushed in. Thank you for your reply. I'll check it the link also.

[Patrick_Caezza]

@WasabiDragon 

That white pipe is the condensate drain, and that plastic hanger might be causing a problem. There should be a float-type switch somewhere in that pipe.

Also, that cover doesn't look like it is properly installed, but it's hard to tell.

You can check the voltage at the thermostat between the R and C wires if you have a multimeter. It should read around 24vac or you can check between the R and any function wire (W, Y, G) and read the same voltage.

[WasabiDragon]

@Patrick_Caezza

The issue was found.  It ended up being the incoming 120v wires that were behind a small metal cover that had heated up over time and melted together, causing the voltage readings to fluctuate or something to affect.  Anyway, cutting them back and re-wiring them solved the problem.  Also learned that this older unit (HEIL brand from 1991) does not have any float switches, and does not use the flat type automotive fuse, on the low voltage side, it uses the cylinder type fuse.  thank you for your help.