A couple of days ago a buddy of mine calls me for help with the refrigerator in his 96' camper (in his Cummins powered truck). It has an electronic controlled 9100 series, and all the other LP appliances work perfect (so I presume regulator is ok).

A relative of his used the thing for the first time this season, and the fridge wouldn't work (on LP) however when he got it back it ran fine on AC.

I turned it on, and set it onto LP, and I could hear it try to ignite, until it kicked on a blinking light, which I looked up- failure of burner unit, essentially it failed to ignite.

I pulled the burner cover, and it was pretty dusty, but all looked to be in good condition, not corroded, and I doubt it has many hours on it. My buddy came up with a can of compressed air, and I shot some up the flue, but didn't get anything (no rust, bug nest, dirt).

I then pulled the ignition/sensor probe and wiped it and the burner off, then blowed out the burner. I put the probe back in, turned the thing on, and it immediately lit with a nice, even, steady blue flame. I could see that the heat from the flame seemed to draw a draft up the flue, and well centered.

Shut it down and restarted a couple of times, each time it lit instantly and had a perfect bright blue/pale blue flame. Shut it down, put the cover back on, and turned it on and it again burned great.

I thought since it ran on the 110 heating element, now that I have a great looking flame, problem must be solved. I didn't pull the burner to clean it with alcohol since the flame looked so good. I also didn't clean the flue or baffel, since it apparently requires removing the unit from the camper, and it seemed to be clean.

Anyway, they went out and used it, and he calls me back to say the freezer part works fine, and keeps everything frozen, but that the refrigerator part doesn't get cold. That even the fins in the back aren't warm to the touch?

I'm confused. How could the freezer part be working good, but the refrigerator part doesn't get cold? It's all part of the same cooling unit

Can anyone point me in the right direction?

 

Low amonia/ freon charge ? I don't know what these units use.
Is it possible the flue/baffel is partialy blocked and not letting the heat go up far/ fast enough to cool sufficiently? Does it make ice cubes?
Is the fridge door shutting squarely? Mine does not seal well , unless I push a little on the bottom corner.
Missing insulation perhaps on the refridgerater area ?

 

Thanks for the reply. It is an ammonia absorption type refrigerator (powered by heat, no compressor) and I didn’t see any sign of a leak. I guess I assumed the cooling unit was good, since he said it ran well under 110 volt heater. Since the cooling unit works well with the 110 heater, I expected it would also work well with the heat from a good flame. Perhaps the cooling unit is marginal (on both 110 and LP) and he only became aware of poor performance when out in the heat? The cooling unit can’t be recharged, and would have to be replaced if it were bad.

From what I understand, if these units get run for any length of time when they are significantly un-level, some of the refrigerant can get “cooked” because the slant prevents some of the refrigerant from returning to the boiler. Then chunks clog some of the internal passages, and you end up replacing the whole cooling unit.

Good thought on the door seal, and also the flue. I think I will check the door seal, and also make sure the light turns off when the door closes (they put off a bit of heat). Other than that, I suppose all I could do is pull it out of the camper, and clean the flue and baffle.

I downloaded a service manual, though it wasn’t too much help. There is a procedure to put the computer into diagnostic mode, but it wasn‘t showing an error once I cleaned the burner. I thought about setting it to display the reading from the thermistor that tells the brain what temp the food compartment is, but I don’t think that could be the problem because the brain is sending power to the gas valve to run the LP burner, so it must be sensing that the temperature reading from the thermistor is not satisfying the desired “coldness” set on the control panel?

Anyhow, I guess I will hope that I find something in the flue, or door seal, or the magnetic switch that shuts the light off. Otherwise, I guess I’ll have to tell my buddy to go find somebody with more brains… (Like a real service technician, probably for an expensive replacement of the entire cooling unit).

The more I think about it, the more I think you may be onto something: Something partly clogging the flue that I couldn't see without pulling the whole fridge... That would be a good explanation for good performance under 110 volts, and iffy performance on propane even though the flame looks perfect...

 

Most absorption units work better on propane, as the heat is more intense. There is sensors galore in the newer ones, and come to think of it the 9100 is auto controled temperature wise. As far as the freezer working and the bottom not, I would lean towards the auto sensor for climate control. There is also a heater in the fridge that controls ice build up that sometimes go awry and warms the bottom to much. You are right about the level and the ammonia not flowing freely,and the overhead campers suffer the most as they are not always kept comfortable level when used, such as parking when stopping for a short bit. You might try the local RV dealer for some advice before taking it to them. Goodluck,,Rick

 

you've most likely already seen this, but if not it might help.




http://www.rvmobile.com/welcome.htm

 

Thanks, guys, for the help.

I told my buddy I would get with him on Sunday to have another crack at it.

This is one of the totally electronic controlled jobs, and when you put it into diagnostic mode, it can display incoming voltages (for ad and dc), whether it detects the door open or not, what temp reading it is getting from its sensor, whether the heating elements are on, and how many amps they are drawing... I suppose it wouldn't hurt to scroll through all of them, and while I'm at it I'll put the temp probe into a glass of ice water and make sure the reading changes appropriately.

Quote "Most absorption units work better on propane". I figured that would be the case, which makes me think Duelin is onto something when he suggested partly blocked flue/baffel...

Anyway, thanks again!

 

www.gasrefrigeration.net Go to the fault diagnosis section. This might help also. Goodluck,,,Rick

 

Well, I went down and worked on it today. Blew out the flue from both ends, nothing blocking it. I pulled the burner, and the oraface tube, and soaked them in alcohol. I put the computer into dignostic mode, and all the readings looked good (put the temp sensor in a cup of icewater, and reading dropped promptly from the 90's). Door seals look good.

My girlfriend's dad is about to retire from a natural gas company, and he worked LP before that. He lent me a remote temp probe, so I could shut it in the fridge and monitor how it does w/o having to open the door and let the "cold" out. Then I left for 3 hours to tear down part of my cyclone fence (bought a 5th wheel yesterday, and need to get it off the street).

When I came back, the temp probe was reading 50. Ambient temps were in the mid to upper 90's and the camper was out in the sun. Looks like everything is working good!

I was really glad to help out this friend. He is retired state trooper, working in a coffee shop, going through a divorce...

Anyway, thanks everyone.