Norcold N621 won't go into 'high fire' mode

You said: "the burner & tube have been replaced" What about the orifice? Sounds like the orifice needs to be cleaned or replaced.

The LP pressure should be 11.5 inches WC. You state "good". HOW can you state this? HOW did you determine it is "good". The cooling capacity between 10 inches and 11.5 inches is night and day. You will get a blue flame at 10 inches but it will NOT have the BTU's to adequately operate the refer. The fact you state "high fire" mode shows you lack the knowledge to troubleshoot your refer correctly and are just throwing parts at it. Since you have replaced all the LP parts, your LP pressure must be the culprit. IF you did not troubleshoot and paid someone to diagnosis and replace those parts---DO NOT go back to them because THEY lack the basic knowledge to repair RV appliances. Doug

Your fridge flame does not change size/intensity......flame comes ON goes OFF based on cooling needs. Length of time flame is ON is determined by t-stat setting/temps.

When you say gas pressure is 'good'.......was it measured or just assume it good because other gas appliances work (stove burners, water heater etc.)??
Gas pressure needs to be 11" WC measured at fridge gas valve with at least 50% other gas appliances in service.

With fridge t-stat set to 9 check flame condition/color
- The flame should be a darker blue inside and a lighter blue outside and should be a constant and steady shape.
- The flame should not be yellow and should not have an erratic and unstable shape.
- Make sure the flame does not touch the inside of the flue tube

How long do you run it on gas before you figure it isn't cooling?

Have you checked the 'diagnostic mode' screen

Service Manual
pgs. 19-20 Diagnostic Mode Screens

You might try:

http://bryantrv.com/docs2/docs/ncoldnnewnseries.pdf

My guess (per pg 12), the electrode to burner gap is too wide...The electrode is both an ignitor and serves as a subsequent 'prover' (verifies main burner stays lit). IF out of adjustment, burner gas valve will then fail closed (a safety feature)...I had this happen on our RV furnace - same symptoms as yours...I my case, I pulled out the electrode and reset the gap from 1/4" to 1/8" and all was fine again...OR, the electrode (having two prongs) porcelain insulator (found on one prong only) may be cracked, thus shorting out. to determine, check prongs for continuity with base (continuity meter reqd).

3 tons

3 tons

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