Refrigerator not Cooling ???

Topic: Refrigerator not Cooling ??? (Read 3778 times) previous topic - next topic

Re: Refrigerator not Cooling ???

Reply #25 – June 20, 2011, 08:51:45 am

Quote from: Mike Baldacchino – June 19, 2011, 10:58:12 pm

There are some old threads that explain how to feel the temps on the coils in the back to see if the ammonia is cascading down the tubes to the bottom.

Testing the Cooling Unit Testing by " Feel "
For this method of testing the only tools required are your hands! CAUTION: some of the components may be HOT! Be careful! If a cooling unit is operating properly, there should be approximately the same amount of heat in the middle sections of the boiler and absorber. A bad cooling unit will aways be HOT somewhere on the back. No heat at any location on the back after several hours could mean something other than a bad cooling unit.

Cooling unit blockages When a cooling unit malfunctions due to a blockage, the boiler section may be too hot to touch and the absorber will be relatively cool. Any blockage reduces the free flow of the solutions and will inhibit or completely prevent proper cooling operation.

Testing an Absorbsion Refrigerator Cooling Unit

Re: Refrigerator not Cooling ???

Reply #26 – June 20, 2011, 09:21:54 am

Lots of great ideas. Thanks to all.

I don't think it is the cooling unit because I have a freezer at 3 degrees and a frig at 60 F. The only thing I have messed with has been the thermister, if that's the right term, in the refrigerator area. When I was installing the "Fin Fan" I was looking for a 12V source and mistook the white thermister wire as a possible power source. I used my ever handy 12V trouble light and punctured the wire with its needle point. I saw a weak flashing light, not a constant 12V source so I am afraid that I may have shorted out the thermister with the test light. Per Bill Willet suggestion I have currently disconnected the thermister plug at the control board and the temperature is falling in the refrigerator part, down form 59 F to 46 F in less than 1/2 hour.

I hope it is as simple as installing a new thermister and not the cooling unit or circuit board. The refrigerator is in such good condition I really don't want to replace it. I will post the outcome as soon as I find out what's wrong.

Re: Refrigerator not Cooling ???

Reply #27 – June 20, 2011, 09:51:09 am

Barry, I checked the elements on the back of the refrigerator with an IR thermometer. There is no cool spot or spots. The temperatures seem pretty consistent as you move up the coils.

The tank at the bottom is 136 F.
The lower most portion of the coil is 139. As you go up the coils each coil drops about 2 degrees until you reach the top coil at 114 F.
The finned portion at the top is 135 F.

The coils on the right hand side, the freezer side, are about 3 degrees hotter than the coils on the right. I don't know if this is good or bad. I would be interested how this compares to others. Remember, I have disconnected the thermister so the cooling unit is running at full power and is on 110V AC. Inside temp of fins in the refrigerator is down to 42 degrees from the starting point of 59 degrees an hour ago.

Re: Refrigerator not Cooling ???

Reply #28 – June 20, 2011, 10:40:46 am

Kent, Looks like you are working towards a control board problem if you are down into the 40's in the box. Be patient and let it cool on manual AC for a day, may go below freezing but That's OK it will only confirm that coil is in operating condition..
Don't be afraid to install a new board. Dinosaur makes a replacement board that works great and costs about 125 bucks. Also as Bill W can tell you you can get an adjustable Thermistor that will allow you to control the temperature more precisely.

Re: Refrigerator not Cooling ???

Reply #29 – June 20, 2011, 10:57:05 am

Quote from: Gary Bouland – June 20, 2011, 10:40:46 am

Kent, Looks like you are working towards a control board problem if you are down into the 40's in the box. Be patient and let it cool on manual AC for a day, may go below freezing but That's OK it will only confirm that coil is in operating condition..
Don't be afraid to install a new board. Dinosaur makes a replacement board that works great and costs about 125 bucks. Also as Bill W can tell you you can get an adjustable Thermistor that will allow you to control the temperature more precisely.

As Bill suggested, I went online last night and the Dinosaur site says they only sell through retailers. Does anyone have any suggestion where to find the best price?

Re: Refrigerator not Cooling ???

Reply #30 – June 20, 2011, 11:15:40 am

Kent, Can't remember where I bought last one but here is a place to begin. Google Dinosaur Refrig parts for other sources.

Dinosaur P-711 Dometic Refrigerator Circuit Board

Gary B

Re: Refrigerator not Cooling ???

Reply #31 – June 20, 2011, 01:44:57 pm

Just one more thing to add about this problem. Read this from Barry's website. It's about not being level and overheating the boiler. Foretravel As I understand it when unlevel conditions are right for longer than about 15 - 20 minutes the sodium chromate precipitation can occur. According to the article this would only happen on older models and require several hours in a newer model. Is my 15 yr old refrig a newer or older model? Once it happens it cannot be reversed. This is easy enough to do when checking in at a campground, shopping, etc if you are not parked reasonably level. It seems that manufacturers could install a device that would shut off the refrigerator and sound an alarm when it is unlevel if they wanted too. It could not be something as simple as a mercury switch alone, it would have to include a timer to eliminate frequent shutoffs while driving. I try to remember to shut off the refrig when it isn't level, but many times I forget.

Re: Refrigerator not Cooling ???

Reply #32 – June 20, 2011, 04:10:38 pm

Gary, thanks for the link.

Jerry, I have never had this coach parked out of level but I have had it less than a year so no telling about the previous owner. However, from my experience and what I have read it takes quite a bit of out of level exposure to damage one of these units. I'm counting on it being my stupidity poking a hole in the thermister cable with a test light probe. We should know by tomorrow.

Re: Refrigerator not Cooling ???

Reply #33 – June 21, 2011, 09:28:57 am

The latest update is that yesterday at 8:00 AM I disconnected the thermister from the circuit board. At that time the frig had been on all night set on 5 on the cooling scale and was at 59 degrees interior temp. Outside temp that night was 78 degrees. The frig fins dropped to 39 degress within 1 hour, taken with an IR thermometer. During the day, with the thermister disconnected and the outside temp reaching 102 degrees, the frig fin's temp went up to 59 degrees and the freezer shelf was at 3 degrees. The freezer seems to be still functioning adequately.

What I don't understand is how the freezer can be cold and the frig not cold. Isn't it all one cooling unit?

Last night, with the thermister still disconnected and the outside temps went down to 68 degrees. This morning the frig fins were down to 19 degrees and the freezer shelf to -7 degrees. It will be interesting to see how hot the frig portion gets today. The outside temps here are forecasted for only 92 degrees. It would seem apparent that the thermister is bad.

Yesterday at the suggestion of Bill Willet I spoke to David Force of RV Cooling Warehouse. He certainly seems to know what he's talking about and did not try to sell me a cooling unit. He said it sounded like beyond the bad thermister, improper initial installation of the refrigerator was the primary cause of my problems. He explained that the coil portion of the unit is designed to be flush with the outside wall. This forces the air flowing from the vent door through the chimney to go up inside of the coils to pull off the heat removed from the interior of the frig. I have almost 4" of open space between the coils and the outside wall of the coach. This lets most of the ambient temperature air flow outside of the coils and reduces the units ability to cool. This is not so much of a problem in regular weather but in high heat like we are having this summer, proper flow over the coils is critical. He said most RV manufacturers make this mistake and don't baffle the chimney area properly.

My plan is to buy a new thermister and to build a box out of aluminized insulation board that will take up the space between the coils and the outside wall of the coach forcing the air flow up through the inside of the coils and finned evaporator at the top. This will also prevent the heat on the outside wall from reaching the heat exchange portion of the unit.

Any observations or opinions will be greatly appreciated.

Re: Refrigerator not Cooling ???

Reply #34 – June 21, 2011, 09:46:44 am

Quote from: Kent Speers – June 21, 2011, 09:28:57 am

T... 39 degrees within 1 hour, taken with an IR thermometer.

Kent, rather than an IR thermometer, which entails opening the door and perhaps skewing the results a bit if you're opening it several times to see if there's any change, I would suggest a wireless thermometer designed for this purpose. Amazon.com: Chaney Instrument 00985 Wireless Refrigerator Freezer Thermometer We purchased this unit (as have others) at the suggestion of Barry & Cindy, and I highly recommend it (less than $30). It has been great to keep an eye on what each side of the unit is doing - and it also displays "min" and "max," which I reset (one button push) each day to see what's happening in a 24-hr period. You can reset at any interval to follow the min/max, especially if you are making any changes. I also use a lithium battery (as recommended) in the freezer sensor. The display unit is small, and has a strong magnet - so I have it on the side of the microwave (and it never moves underway regardless of road vibration). Hope this helps.

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.

Re: Refrigerator not Cooling ???

Reply #35 – June 21, 2011, 10:10:04 am

Kent,

Yes, a good idea to verify that the refrigerator installation instructions, particularly about clearances are observed to the letter to insure most efficient cooling.

With your temperature swings, which sound to be based more on ambient temperature than any other factor, I would agree that maximizing refrigerator efficiency would be the first step. And, while in there eliminating any air space above or on the sides of the refrigerator, bringing back clearance to ideal spec, I would add two muffin fans at the top of the coils exhausting UP. You can put them on a separate switch or on a thermostat. They draw so little amps that they can safely be tied into the galley lighting/light switches.

Brett

Re: Refrigerator not Cooling ???

Reply #36 – June 21, 2011, 10:23:59 am

Quote from: Kent Speers – June 21, 2011, 09:28:57 am

What I don't understand is how the freezer can be cold and the frig not cold. Isn't it all one cooling unit?

I have almost 4" of open space between the coils and the outside wall of the coach. This lets most of the ambient temperature air flow outside of the coils and reduces the units ability to cool.

The refrigerant in the absorber type refrigerator first flows into the freezer section and then to the coil in the refrigerator section. If it picks up enough heat in the freezer, there isn't any cooling capacity left for the refrigerator. At start up the freezer section will cool down first.

I think you found the problem with the gap between the wall and the heat exchanger. There should be a block of foam between the wall and heat exchanger to force the air through the heat exchanger. My coach has it, maybe yours fell out, someone removed it, or it wasn't installed to begin with. I'm sure FT is aware that it is required. My refrigerator installation instructions mention this requirement.

Re: Refrigerator not Cooling ???

Reply #37 – June 21, 2011, 10:47:32 am

Pat: I also purchased the Chaney thermometer. it works very well. I use one in my home and in the rv. I velcrowed the unit to the front of the fridge in the motorhome as the magnets would not attach to the front of the fridge. It gives you a good idea at all times the temp without opening the doors. Another forum idea put to use. DAN

Re: Refrigerator not Cooling ???

Reply #38 – June 21, 2011, 11:58:20 am

Kent you can buy a thermistor kit to splice into the old wire. I did this. Purchased from PPL and it took only a few minutes. If I had used the complete one the refer would had to have been pulled out to access the back.

Re: Refrigerator not Cooling ???

Reply #39 – June 21, 2011, 01:19:01 pm

I have made significant changes to the air flow behind the fridge, I have installed 2 Ultra muffin fans(1500 rpm, 52 cmf, dual ball bearing) connected to a thermodisc (stc-20) on the upper boiler pipe with the thermal paste, I have also installed a Thermistor Adjuster(Dinosaur Electronics) this will allow me to dial down the temp in the fridge in extremely hot weather(Note, on some of the new Dinosaur boards there is a pot that will do the same thing as the thermistor adjuster) I have also installed 3 (Koolink 80mm,1100 rpm,19cfm fans) Quietpcusa.com on the fins inside the fridge, I changed the light switch to SPDT switch, so when the door is open the fans go off, I will be adding an on off switch to control the fans in the winter months.

Re: Refrigerator not Cooling ???

Reply #40 – June 21, 2011, 03:04:46 pm

Pat, thanks for reminding me. I had two remote thermometers in the bay. They are not in the frig.

Brett, muffin fans are ordered and on the way.

Quote from: Jerry Whiteaker – June 21, 2011, 10:23:59 am

Quote from: Kent Speers – June 21, 2011, 09:28:57 am
What I don't understand is how the freezer can be cold and the frig not cold. Isn't it all one cooling unit?

I have almost 4" of open space between the coils and the outside wall of the coach. This lets most of the ambient temperature air flow outside of the coils and reduces the units ability to cool.

The refrigerant in the absorber type refrigerator first flows into the freezer section and then to the coil in the refrigerator section. If it picks up enough heat in the freezer, there isn't any cooling capacity left for the refrigerator. At start up the freezer section will cool down first.

I think you found the problem with the gap between the wall and the heat exchanger. There should be a block of foam between the wall and heat exchanger to force the air through the heat exchanger. My coach has it, maybe yours fell out, someone removed it, or it wasn't installed to begin with. I'm sure FT is aware that it is required. My refrigerator installation instructions mention this requirement.

Jerry, I guess it makes sense but with the freezer at 3 degrees I would think there would be enough excess cooling to cool the frig down below 59 degrees. Maybe not.

Barry B. also once mentioned a block of foam between the wall and heat exchanger. I want to make sure I understand. Is the heat exchanger the finned thing at the top of the stack or is it the entire system of coils and the finned unit? What kind of foam was used? Is it a special FR Foam? Many types of Styrofoam begin to melt at 140 degrees. I have measure temps at the top of the coils as high as 149 F. Do you know what the maximum temp of the unit gets up to?

If anyone can take a photo of a proper installation, I would be very grateful.

Jerry, I don't think I can use the kit because I damaged the thermister wire where it comes out of the wall when I used my test light probe trying to find a 12V source for the fin fan. Since you have already installed one, is that correct?

UPDATE: Outside temp is now 97 F. The inside temp of the frig on the bottom shelf is 38 degrees. The bottom shelf of freezer is 18 degress. The fins in the frig are 19 degrees and the shelf in the freezer is at 3 degrees. I don't believe I have a cooling unit problem. Now, to get the new thermister, due in tomorrow the muffin fans due in next week and figure out the best way to vent the heat exchanger.

Re: Refrigerator not Cooling ???

Reply #41 – June 22, 2011, 01:06:18 am

following these Fridge cooler problems and read about the Chaney temp sensors that a few of you have bought and seem happy with, so I opened the link onto Amazon and have been reading ALL of the comments from buyers of this item. There seems to be an obvious problem with a lot of them as a large percentage have returned the item as inacurate or just plain does not work as it is supposed to. So what is the chance of getting a bad one delivered?? I would hope the manufacturer is working on the bugs it seems to have. Any comments from those of you that have them, re their accuracy??

Re: Refrigerator not Cooling ???

Reply #42 – June 22, 2011, 10:39:28 am

Kent,

As the coach happens to be here at the house, I went out to check on what type of foam it was only to discover that I don't have a foam block!!! Takes a mirror and a light to see up behind the refrig and what I looked at before and thought was a foam block is the ceiling liner carpet, rather dirty and does look like a dirty piece of styrofoam. Yes that heat exchanger is the part right at the top of the refrigerator. On my coach it is located right under the roof vent. I removed the cover only to discover that many screws have to be removed to get in there. There is also a fairly large gap at the ends of the heat exchanger. I was all wrong about FT installing a foam block. Too bad about the thermistor wire, I have done things like that. There have been times where my freezer was cold but the refrig was not very cold, not like 59 though. I suppose anything like a piece of sheet metal or plywood would work as a baffle. Something that would not catch fire is best. Some folks have said that they lined the back of the refrigerator compartment with fire resistant material. I think it was Hardy board usually used behind tile in a bath or kitchen wall.

Re: Refrigerator not Cooling ???

Reply #43 – June 22, 2011, 10:47:22 am

Quote from: John Haygarth – June 22, 2011, 01:06:18 am

following these Fridge cooler problems and read about the Chaney temp sensors that a few of you have bought and seem happy with, so I opened the link onto Amazon and have been reading ALL of the comments from buyers of this item. There seems to be an obvious problem with a lot of them as a large percentage have returned the item as inaccurate or just plain does not work as it is supposed to. So what is the chance of getting a bad one delivered?? I would hope the manufacturer is working on the bugs it seems to have.

Hi, John. IMHO, it's like reading reviews for anything you order on Amazon (or elsewhere... or even reading RV park reviews on RV Park Reviews :: Home)... take out the outliers to find the most useful information somewhere in between. One caveat with product reviews, I personally think, is that more unsatisfied than satisfied customers will typically post reviews, often skewing a general impression of the product.

I've been pleased with the product thus far (had it for about a year). I will say that I have experienced the --E-- in the display on rare occasion (short-lived, though). With regard to the concern that the manual is incomplete, I've downloaded and attached it for your perusal. It appears to cover the general operation well enough.

I did find that when replacing the batteries, it seems to be similar to my Skyscan atomic clock (which has a remote thermometer sensor).... replace the remote sensor batteries first, and then replace the display unit batteries. Even if you are replacing only one set of batteries (for example, only one remote), you should still take out and put back in the other batteries (ie, in the display unit). This is undocumented in the refrigerator/freezer product, but is documented in the atomic clock product manual.

Hope this helps with your decision.

Re: Refrigerator not Cooling ???

Reply #44 – June 24, 2011, 10:28:01 pm

Kent and others,

After getting some things out of the way, I looked through the installation instructions for my refrigerator. I have the Norcold 682, and I am sure it is the original one installed at the factory. According to the instructions, the ideal space behind the refrig is 0 to 1 inch. If there is more than 1" space, two baffles should be installed to prevent air bypass. One baffle is located at the heat exchanger at the top rear of the refrig, the other is at the absorber coils at the bottom rear of the refrig. The lower one would be just above the air supply opening. Baffles should be within 1/4" to the coils. I didn't measure but I have about 3" of space behind the refrig and no baffles. Really surprised that FT didn't comply with this requirement. The sides and top of the refrig should be sealed off from outside air which FT did do. My refrig has generally seemed to cool ok, but at times it has been warmer than desired. I thought that was just the nature of the beast. Would it perform better with baffles? I wonder if other coaches are like this? Could this be a reason for the cooling fans that so many have installed? If I install baffles, I would make them from sheet metal. I'm not sure why I thought that the baffle should be a block of foam. After thinking about it, foam would be a poor choice due to the heat. A better solution might be to build out the wall above the air supply door to fill in the space. I'm not eager to do that though. I suppose other models of absorber type refrigerators would have similar installation requirements. What do other owners have to say?

Re: Refrigerator not Cooling ???

Reply #45 – June 24, 2011, 11:20:38 pm

Quote from: Jerry Whiteaker – June 24, 2011, 10:28:01 pm

Kent and others,

After getting some things out of the way, I looked through the installation instructions for my refrigerator. I have the Norcold 682, and I am sure it is the original one installed at the factory. According to the instructions, the ideal space behind the refrig is 0 to 1 inch. If there is more than 1" space, two baffles should be installed to prevent air bypass. One baffle is located at the heat exchanger at the top rear of the refrig, the other is at the absorber coils at the bottom rear of the refrig. The lower one would be just above the air supply opening. Baffles should be within 1/4" to the coils. I didn't measure but I have about 3" of space behind the refrig and no baffles. Really surprised that FT didn't comply with this requirement. The sides and top of the refrig should be sealed off from outside air which FT did do. My refrig has generally seemed to cool ok, but at times it has been warmer than desired. I thought that was just the nature of the beast. Would it perform better with baffles? I wonder if other coaches are like this? Could this be a reason for the cooling fans that so many have installed? If I install baffles, I would make them from sheet metal. I'm not sure why I thought that the baffle should be a block of foam. After thinking about it, foam would be a poor choice due to the heat. A better solution might be to build out the wall above the air supply door to fill in the space. I'm not eager to do that though. I suppose other models of absorber type refrigerators would have similar installation requirements. What do other owners have to say?

Jerry, what you describe is very similar to my situation. I have 4" clearance between the outside wall and the tubes and 3" between the outside wall and the heat exchanger. Today I installed two of the Valterra Fans designed for this use REFRIGERATOR FANS at the top of the stack. I had to remove the vent cover but installation was pretty easy. The fans come with two thermostats so they only go on when the coils are over 100 degrees and they go off when the temps go below 80 degrees. I used two separate toggle switch so I can better control when the fans are activated.

The fridge stayed cool all day with both fans installed. I had the remote thermometer on the bottom shelf near the door, the warmest place in the fridge. At 7:00 AM the temp was 46 degrees without any fans. The fans were functional at noon and at 5:00 PM the inside temp had gone up to only 48 degrees. The outside temp here was 103 at 5:00 PM and over 100 degrees all day long. On previous days with similar outdoor temps the fridge got up to over 60 degrees by 5:00 PM.

I am still going to install the proper baffles. I was going to use sheet metal but after careful inspection sheet metal baffles would be very hard to attach to the wall. I found a local source of flame retardant foam that is fabricating the baffles for me. The high density foam is very light weight, has a melting temperature of 180 degrees and is self extinguishing. I will pick up the baffles next week and don't know what they will cost. I will report any additional improvements once they are installed. I anticipate at least as much improvement with the baffles that I observed with the fans.

Re: Refrigerator not Cooling ???

Reply #46 – June 24, 2011, 11:30:22 pm

Quote from: Kent Speers – June 24, 2011, 11:20:38 pm

The fridge stayed cool all day with both fans installed. I had the remote thermometer on the bottom shelf near the door, the warmest place in the fridge. At 7:00 AM the temp was 46 degrees without any fans. The fans were functional at noon and at 5:00 PM the inside temp had gone up to only 48 degrees.

I am still going to install the proper baffles.

Kent,

As Steve will tell you, I tend to be the "food safety police" in our family. The safety zone for food storage is below 40 F or above 140 F if it's over 4 hours. And that's cumulative hours.

So target a few degrees below 40 as your sustained temperature.

Michelle

Re: Refrigerator not Cooling ???

Reply #47 – June 25, 2011, 01:15:30 am

Kent,

I was getting the exact situation in a newly-installed Dometic this week. Sub-zero freezer, up to 68 refrigerator box, hot cooling unit.

Don't know how he did it, but the tech at the authorized Dometic dealer hard-wired the refrigerator to bypass thermister and all other controls. Coach plugged in to shoreline power. Ran it this way for 24 hours. No improvement. Diagnosis: blockage in cooling unit. A functioning cooling unit would have brought temps in bottom of refrigerator box to sub-freezing in just a few hours. New cooling unit on the way for installation next week.

Re: Refrigerator not Cooling ???

Reply #48 – June 25, 2011, 08:53:12 am

Bob, thanks for the input but that's not what I wanted to hear. Please let us know if this is correct after you get the new cooling unit installed.

I spoke with David Force, the owner of RV Cooling Unit Warehouse for over 30 minutes. I have never talked with a more knowledgeable person on absorption refrigerators. He has been at this for over 40 years. After explaining the situation, rather than try to sell me a new cooling unit, he felt certain that by correcting the installation with baffling and adding the fans the problem would be corrected. He said when the outside temps are over 100, these types of refrigerators are hard pressed to maintain acceptable fridge temps even when everything is installed correctly and working properly. It is imperative that the back of the fridge gets maximum air flow.

By your description I think what the tech did was unplug the thermister causing the unit to run full out constantly. I did the same thing on mine but got the same result as when the thermister was plugged in and the unit set of the highest cooling level.

I will be very interested to hear if the new cooling unit makes a difference in your case. Please indicate what kind outside temperatures you are dealing with?

Re: Refrigerator not Cooling ???

Reply #49 – June 25, 2011, 12:11:37 pm

New refrigerator installed last day of March, when outside temp range was 35-40 nights, 45-50 days. Everything happy, with freezer sub-zero and refrigerator at 40 on the 4 setting. As daytime temps rose, so did internal temps of refrigerator, not by much, but enough to notice. Experimenting with auto/gas settings, thermistor positioning, and 3-4-5 settings had no detectible consequence, even when each adjustment had 12-24 hours to work.

As outside daytime temps rose, so did refrigerator internal temps. 70 degree days produced internal of around 50. 85 degree days produced internal of 60-65. Freezer remained subzero throughout.

When I took it to place where it was installed (Cummins Coach Care), tech was in touch with Dometic techs on line and by phone. One test was to remove thermistor, place it in ice-water, measure ohms. It was OK. Just for giggles, got another thermister, tested it OK, installed it. No impact on refregerator behavior.

Because of warrantee issues with new unit, needed to move to Dometic dealer for hard-wire test. Hard-wire test was more than simply pulling thermistor. Working from the outside, tech pulled some connections loose and made some new connections working with what looked like a small double-wire jumper cable, with connectors on all four ends. Bypassed everything. Control panel disabled. Plugged in refrigerator, run it wide open. Should have dropped internal temps big-time, pronto. No such result, even after 24 hours.

I'll let you know the rest of the story next week. And I will pursue the insulation question with them at that time.

Bob

Affiliate Notice