Rheem Criterion II has 1 flash

Wojo

Seems like it's fine after the 1 hour lockup, once it runs for a while though, it will fire up a few times & lockup. The furnace is approximately 7yrs old. Could the limit switch be bad? If so, can I check it with a DMM for continuity once it locks up? Pretty sure it should be normally closed. And, what else can it be?

Poppyloppy

Sounds like it may be the high limit ( on the heat exchanger wall to the left of the inducer assembly). Check it as soon as it faults out. Yes it should be closed and show continuity.

Subcooled

This series will attempt 4 tries for ignition then lock out for an hour and will show by one flash code that it's in lock out.

With no full model or serial, no telling what you have, such as direct ignition or hot surface ignitor. This unit could have 4 different main boards in it as well.

If HSI then it can be older type that proves rectification through HSI and fails proving it if the resistance is to high (ohms).

If DS system then maybe flame sensor dirty or spark gap issue.

Could be dirty cross overs,low manifold (least liker's) and so on. Not much to go on with what you provided.

Wojo

Sorry about not enough info, I was half asleep when I posted. It is a RGPH-07EAUER. Sold my place, got married 6 months ago & moved in her house with the boys. She just told me that the furnace was doing the same thing about a year or two ago. She called the place that installed it & all they did was just clean it. That's about all the info that I can think of along with the included pics. Thanks in advance

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Wojo

Forgot to add S/N
FD5D302F470208103

hvactech126

clean the flame sensor..............

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Wojo

Might be a stupid question, but is it better to clean it with alcohol or use a green scouring pad? Don't really want to ruin a coating if it's sensitive to abrasives

hvac benny

use a green scouring pad, aka a "scitchbright pad". Do not use sand paper or alcohol.

Wojo

I scuffed the sensor with a green pad. The sensor did have a line around it like it was a bit eaten up. All back together now & waiting to see what happens. Maybe, I should invest in a flame sensor. Was not really that dirty though. Thank you

Wojo

Just posting a ThankYou. Cleaned the flame sensor & it hasn't locked out since last night. Sensor does look a little pitted & I probably should get another one. Thanks again, the chill is out of the house finally.