Norcold 442 won't cool on LP

[Dan_East]

I have an old Norcold 442 in my even older RV. Fridge works great on 110V AC. The burner tube was rusted and the flame wasn't very big, so it wouldn't cool on LP. Yesterday I finally got a replacement burner tube (they now use a flare fitting, which I like a lot better), and installed. After running on LP for 8 hours it hadn't cooled one bit.

The flame looks good from what I can tell (not having seen any before to know what a good one looks like). It's blue, about an inch tall, and solid with no flickering.

Last night at 4 AM it was still warm as can be in the fridge, so I switched it to 110V AC. Now, 3.5 hours later, it's very cold. The metal box on the back is noticeably hotter on electric than it was on LP.

I have some theories as to what might be wrong, the simplest of which is that the flame simply isn't big enough / hot enough. The rest of my LP works fine in the camper (stove burners, hot water heater), so I presume my gas pressure is adequate. My tanks are full.

I checked the service manual and did not see any way to adjust the flame - I assume the orifice controls that based on the size of the orifice? Or is there an adjustment?

Any suggestions before I start troubleshooting and modifying things? If I can get a gauge I will check the pressure going into the fridge to see if it is correct. If it is then I might try slightly enlarging the orifice if the fridge doesn't have a flame adjustment.

[Dan_East]

Thanks for the suggestions. Please note that the burner tube and orifice is brand new.

After putting some tape on the burner tube to keep junk from going into the slots the gas comes out, I removed the flue from the top (or is that the chimney?). There was a long wire clipped to the top, and hanging from it was the screw-shaped baffle. I pulled that up and out and it was all very clean. Just some slight surface rust is all, but no flakes. I ran a wire coathanger down the tube from the top. The only thing that came out below was a tiny bit of surface rust powder from scratching the sides. There wasn't anything in the tube to clean out. I ran the coathanger up from below, and again, there wasn't anything to come out.

So at this point, considering it cools great with 110V AC, it has a new burner tube / orifice, and the chimney / flue is clean, I can only come to one of a few conclusions.

1) My gas pressure is too low, and thus the flame is not hot enough.
2) The orifice in this tube isn't the exact one called for, and it doesn't allow a large enough flame.
3) The valve in the refrigerator that turns the gas on and off isn't opening up all the way and is reducing the gas pressure.
4) There is a flame adjustment somewhere and it is adjust too low (assumption on my part there even is such an adjustment - I can't find any reference to one).

[Old-Biscuit]

Burner flame should be BLUE, STEADY and JUST REACH up into center of Flue opening
*Yellow means incomplete combustion/cooler flame temp...needs more air

If NOT....then remove burner and clean it out
Remove orifice---soak in alcohol and then 'blow dry'----just whistle do NOT use high pressure from air compressor or POKE anything thing thru opening--you WILL damage it

LP System pressure S/B 11" WC (`0.4 psi)
Orifice metered size plus clean burner/slots dictate flame size

Flue and flue baffle cleanliness dictate heat transfer
Flue should be HOT at burner area and VERY Warm at top (most of the heat generated S/B absorbed by flue baffle and be transferred to 'perk tube' which then boils ammonia solution into hot vapor

[SidecarFlip]

Sounds to me like you need to pull the flue baffle and clean out the crud inside. Probably loaded up with crud.

[DougE]

Get a cheap infrared temperature detector from HF so you can check the temperature of the top tube when in LP vs 120v mode. Note there can be a parallax issue so be sure to have the detector parallel to the tube. Also, it could be that there is so much rust on the heating area that you can't get the heat transfer you need.

[Dusty_R]

The flame should be blue with yellow tips.