Somebody posted on here the directions on how to clean the burner orifice in the Dometic 8501 (sorry I forgot who it was) and it was a big help to me, but I wanted to make some changes that reflect the newest 8501 (2018 model) which appear to be different from the original poster's RM8501L: (I used his original instructions today to clean mine (even though I don't believe it was dirty in a brand new camper but I've had trouble getting the LP to cool as well as the electric options)). Thanks for walking me through it, but I needed to make some adjustments to your directions because of changes to the new Dometic.
Let me see if I can run through the cleaning steps I used here..... this refers to the RM8501L
1. Remove the screw securing the sheet metal burner cover.
2. Use a 7/16" open end wrench to un-screw the gas pipe nut where it enters the VALVE assembly (NOT the burner). I found that it is safer to remove the burner and pipe as one and disconnect the pipe from the burner in a controlled environment since the orifice is a little piece that fits into the burner and can easily fall out if you remove the pipe from the burner in the fridge recess. (I actually found the burner orifice does not appear to be a ruby with a hole in it and it can’t fall out. It’s all one piece of brass with a hole in it just like a jet in a carburetor.)
3. Slide the burner assembly off the Flu
4. At this point, the igniter and flame sensor are still attached to the burner. Remove the #20 Torx screw securing the igniter bracket and flatten the end of the burner where it passes through a slot in the bracket. You’ll not be able to remove the burner until you do this. The burner and pipe can now be removed from the fridge enclosure.
5. In a controlled environment (ie., where you can find stuff you drop), disconnect the pipe from the burner block and unscrew the 9/16” brass nut from the end of the orifice, then remove the orifice. The orifice is the entire brass coupling with a tiny hole in the end with the 9/16” nut on it. The hole is actually a ruby with a hole in it so that it does not erode from the gas passing through it. There appears to be no Ruby nor removable tiny orifice. It’s all one piece of brass with the number size of the Orifice stamped on it #65.
6. I used alcohol in an ultrasonic cleaner to clean my orifice. Not sure if you can just soak it and swish it around in a dish and get the same results.
7. Blow out the pipe with compressed air and also inspect the burner block to make sure nothing has made a home in there..... the burner block is where the gas jet mixes with air and then flows upwards where it ignites. There is plenty of room in there for spiders and critters.
8. Remove screw securing the "T" cap from the top of the flue and remove the cap. Remove the baffle that is suspended in the flue on a bent wire. Pass a small bottle brush through the flue to make sure it is clean and un obstructed. In my case I didn't have a bottle brush so I used a wadded up piece of paper towel and pushed it down with a plastic pushrod. BAD MOVE..... it got stuck half way down and I thought I was in serious trouble for a while. Not sure if there is structure in there or what, but I finally got it to pass all the way through and since it came out intact I figured all was well. Finish off by blowing some compressed air down the flue if you can.
9. Re-assemble and test.
My best guess is that stuff sticks to the edges of the orifice and slowly closes it off, gradually reducing the size of the flame. Cleaning restores full flame.