Dead Dometic RM8501

I'm going to check that very same thing on mine when I get it back from the service department (of course a lot of that test depends on your hearing! LOL)

Paul, There are a lot of variables and I doubt there is any "Normal."  If it's 70 degrees outside the temperature in the fridge will be a lot different at any setting than if it's 100 degrees outside.  And we found out today that it makes a BIG difference if the unit is IN the Pod or sitting on a test bench.  Because of the refer being in a slide-out, they unable to put a roof vent (which would be a lot more efficient) and these Dometics apparently lose a lot of efficiency just because of being mounted in the RV.  Dometic will tell you the only way they accept temperature readings is if you are doing the "water test."  That is, a glass of water in the fridge with a bulb thermometer in it.  It's the only way they'll accept readings from a service department (as my service department told me today after they've been talking to Dometic service directly).

I didn't realize the service and diagnostic manual I posted was not for the 8501, but you're right, it does have a lot of information in it.

Paul, thanks for the step by step instructions.   

Most helpful!

I so appreciate the level of knowledge and the willingness of this community.

Thanks 

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.  

3.  Remove the screw securing the burner to the flue and then remove the pipe from the valve.  

4.  At this point, the igniter and flame sensor are still attached to the burner.  Remove the screw securing the igniter bracket and 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 carefully remove the orifice.  The orifice is basically a cupped washer with a tiny hole.  The hole is actually a ruby with a hole in it so that it does not erode from the gas passing through it.  

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.  I am also not sure what is actually the best solvent to use.  I have seen alcohol, carburetor cleaner and soap and water mentioned, but I don't know what we are trying to dissolve.... dust and dirt, or something gummy from the gas?  There are plenty of warnings online to NOT use any sort of implement to poke through the orifice, since you can damage the opening.  

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.  

I am trying to figure out how to gauge the cooling efficiency.  Since there is no indication of when the flame is on and no way to determine what the stabilized duty cycle is, I can't figure out how to tell if I am completely back to normal.  But it SEEMS to be normal.  

Paul

This past weekend, the problem reappeared. Cooled fine on AC, but not on propane. My best guess is that somewhere along the road I got some dirty LP and this is the reason I have had to repeat this procedure several times. Easy to do, but a filter would be better.

This AM, I repeated the cleaning above. It's cooling fine now on LP (after about two hours running). This time I am measuring boiler temp with infrared thermo @ top of boiler mantle. Perhaps I can use this temp as a diagnostic tool in the future. Seems to be holding steady @ 280-284.

fred