3 year old Dometic doesn't work

[lewster]

Originally Posted by KJRitchie

I've been reading this thread with interest because my 2008 Classic 25fb we just bought about a month ago experienced this on our first extended trip. Our fridge is the Dometic 3762 2 way. I'm having issues with my converter not charging the batteries at 13 v while on shore power but I used a charger to keep the batteries topped up on this trip.

I had the fridge on Gas during the time at camp to test out the LP system. The freezer compartment seems to be level with the floor adjacent to the fridge. At setting 4 (1 through 5) the temperature displayed on the fridge was 38F. The weather had been cool in Missouri but on Sunday the weather had cleared and the temperatures got into the high 70s low 80s. The fridge seemed to maintain temperatures or maybe it got up to 40 deg. The trailer was in the full sun. We even ran the AC inside to learn and test it out. (Unfortunately we have that dreaded problem with water leaking inside the interior from the AC, another story for other threads)
We broke camp on Monday around 11am to start the 350 mile drive home from Missouri to Dallas, TX. The wind was blowing strong out of the south so most of the time it was a headwind. For a period of about an hour on I40 its a crosswind with the street side of the trailer getting the wind and that is where the fridge is located. We stopped for lunch at a rest stop and my wife made lunch. I didn't notice the temperature reading because I didn't know there was going to be a problem. The wife knows not to keep the door open long when getting food out the fridge.

When we arrived home and the trailer was in storage I checked the fridge and it was at 54F. It was about 80 degrees. I checked the LP flame and it was hot and the flue part was too hot to touch.

Earlier you mentioned touching parts A and B and they should feel about the same hot to touch. I'd like to try that too. Can you post a link to the Dometic document that shows this troubleshooting test. My fridge documents down show that procedure.

When I had the Dometic recall performed this week, I talked to the RV tech about this issue and he said traveling shouldn't be a problem with the movement. He did mention that air coming across the top vent can cause flame outs and exhaust issues and my AS has a fence between the AC and the fridge vent on the roof. Here is the interesting thing he said about RV fridges. He says that a certain percentage of them have an issue with cooling while traveling. He couldn't explain the cause.

I'm admire your tenacity with this problem but by now I would've bit the bullet and bought a new fridge. I may be forced to go this route and if the if it still doesn't work while traveling I'd be forced to sell my AS with this disclaimer and take a big loss.

Kelvin

Kelvin,

I would try adding several fans under your roof vent for the fridge before doing anything so drastic as selling your trailer. There are also other work-arounds for your problem to keep your fridge cold and you and yours happy.

[HowieE]

Lewster

Yes a bit of over kill but as one that suffers from "terminal tinkeritis" I tend to over engineer my projects.

I installed a Synder some time ago with no noticeable improvement. My problem with it was the fan had no means of spreading the air flow over the covered area of the coils.

I like the idea of evacuation of the heat, per your suggestion, rather than movement behind the frig.

[lewster]

Originally Posted by HowieE

Lewster

Yes a bit of over kill but as one that suffers from "terminal tinkeritis" I tend to over engineer my projects.

I installed a Synder some time ago with no noticeable improvement. My problem with it was the fan had no means of spreading the air flow over the covered area of the coils.

I like the idea of evacuation of the heat, per your suggestion, rather than movement behind the frig.

GO FOR IT!

Let us know how it turns out............

[Buttercup]

I ran a bypass test (thermistor disconnected from the control board) last night on electric and damned if the fridge didn't cool down to something like 7 degrees in less time than it took to get it to 15 degrees on Gas. Electric works better than gas on this trailer and to me at least shows that in a bypass situation, works. None of this explains why it STOPS working once we get on the road.
One of the diagnostic manuals I found is HERE. It is somewhat dated, but still valuable information as the cooling units themselves have not changed much at all in the way that they work. You put heat into them and away you go. If the absorber is about the same temperature as the boiler, you have good circulation.
BTW, this morning, my boiler was warm and the absorber coils were actually cool. I suspect that is because the fridge temp was so low that the ammonia was simply not evaporating much all the way through. Perhaps it was staying liquid all the way down the absorber.
I'll post pictures of my unloaded and loaded electric bypass tests later.

One thing I am going to do is install a removable fan with a motor speed controller directly on the lower compartment door to force air up and across the absorber (not needed) and cooling fins (necessary for hot weather) and I will show how I did that later. I just ordered the parts, should arrive in a week or two.

[richinny]

lewster has mentioned in the past that the fridge drain tube can cause a draft while traveling. i think he mentioned that a screen should be on the end of that tube.

[KJRitchie]

What about the thermistor wire coming out the back. Speaking of thermistor where does everyone have theirs located on the fins? With my 7 cu/ft the fins run vertical and then curve at the bottom. I want the coldest performance so I've set my thermistor has high on the fins as possible.

Kelvin

[Buttercup]

I tested the old Drain Tube by plugging it with a tissue, didn't help in my case.

Originally Posted by richinny

lewster has mentioned in the past that the fridge drain tube can cause a draft while traveling. i think he mentioned that a screen should be on the end of that tube.

[Buttercup]

Here is my latest test (and probably last test of this cooling unit). This test is a bypass test on Electric only. These graphs show 2 tests actually, the first dip represents an empty fridge and freezer and the second dip is all of my water jugs and bottles loaded in.
One thing you can see is that the fridge can cool down quite well on electric. Unloaded, the fridge would pull down to a really low temperature. Loaded, after 12 hours it still had not got down to 40 degrees BUT the water that went in the fridge was not pre-cooled so it is impressive that it did get as cold as it did.
Of course, none of this shows why it quits working when we get on the road.

[HowieE]

Tim

Back to richinny's question. The hole under my frig to allow the water to drain is all the way across the back of the frig from the flame. If yours is closer could the air currents be blowing out the flame at road speeds only to reignite at ever slow down or stop. Do you have a way to graph the duty cycle of the flame while traveling? Would your thermistor withstand being a fixed to the side of the chimney as a recorder?

[perryg114]

Put your thermocouple data logger thingy close to the firebox and it will tell you if it is getting blown out or not. Does your fridge have a 12V option?

Perry

[lewster]

Originally Posted by richinny

lewster has mentioned in the past that the fridge drain tube can cause a draft while traveling. i think he mentioned that a screen should be on the end of that tube.

Hard to believe....but true! The drain tube that comes from the drain pan located under the fins of the refer will allow the cold air of the fridge to leak out......unless it has the proper plug in it.

These plugs have small holes in them to allow the water to drip out slowly while keeping a majority of the cold air in the fridge.

[Buttercup]

I am pretty sure it is not getting blown out because at each stop, the boiler column is HOT! If the flame was blowing out, for a few moments then it would not appreciably impact boiler temperature. If it was blowing out enough to impact operation then I would expect the CHECK light to come on from failure to ignite OR the boiler would be cool. Neither happen so I suspect that the flame is lit the whole time based on the hot boiler temperature alone.
My drain tube is plugged with a tissue so I do not believe that a draft from there is an issue.

[KJRitchie]

Looking at post 29 where you show the fridge pulled out I can see the vent in the roof and the vent access on the trailer side wall. There isn't any baffling on the wall to channel hot air up to the roof vent. Is there baffling now between the fridge and the outside wall?

It appears you have done everything that you can do. The only resolution is a new fridge or cooling coil replacement.

Kelvin

[Buttercup]

Yes, the vent is covered to keep the outsize air from passing into the cabin. Standard issue Airstream '70s refrigerator install. The vent cover seals over the top of the cabinet opening where the condenser heat exchanger is and ports the air over to the final roof vent.
That picture was from when we were doing a bunch of work and had everything ripped out.

Originally Posted by KJRitchie

Looking at post 29 where you show the fridge pulled out I can see the vent in the roof and the vent access on the trailer side wall. There isn't any baffling on the wall to channel hot air up to the roof vent. Is there baffling now between the fridge and the outside wall?

It appears you have done everything that you can do. The only resolution is a new fridge or cooling coil replacement.

Kelvin

[Buttercup]

When I do get the fridge removed and re-installed with the new cooling unit, I am also going to add some little features to help it cool better. I am doing this mostly because we do camp a lot in the desert. I plan on adding the following:

• Power Fan
• Fan Speed Controller
• AC Unit baffle

First things first, I am going to mount a 12 volt radiator fan on the access door with a shroud that will ensure positive air flow through the back of the cabinet. I will include an interior baffle to prevent the fan from blowing out the flame should it be run on higher speeds. The fan is a 9" radiator fan that can move up to 850 C.F.M. if run on full speed. It will be a temporary mounting that I can remove as needed. It will just slip in the door.





Next I will run the fan at a lower, quieter speed by using a PWM DC Motor speed controller. With this controller I should be able to maintain a speed enough for cooling at a low current draw when in use.

Lastly, I had made a baffle that I will place between the air conditioner and refrigerator vent. Last year at the International Rally in Sadelia, MO, we had the fortune of being parked next to someone who had a baffle between their AC unit and fridge vent. The problem apparently is that the hot exhaust air blows on the fridge vent and stops it from venting properly. However, I am going to mount my baffle with a slight offset on the rear end such that as we are driving down the road it will help to pull some of the heat from the fridge vent like a wing - sort of.


I can say that when we are parked and the fridge is on, the upper cabinet tends to get toasty warm. It will be interesting to see if these changes help that.

Now - to order the new cooling unit. I am leaning towards a new Amish unit listed HERE. I looked around and found plenty of people who got one installed but only one complaint of it not working.

[Aage]

Regarding the Amish site: I find the owner of that site to be very forthcoming with helpful advice and information. You might try bouncing your problem off of him before doing anything. He isn't going to simply push a new kit for you if it isn't needed, IMHO and experience.

[Buttercup]

I wrote to him about it, but honestly, I am not expecting or looking for help anymore, I am jut looking to replace the unit. I am also looking for some thermocouple wire to throw on a few places and monitor temperatures...hehehe.
I ordered a new unit from him but he came back that they had no new ones in stock - would be 2-3 weeks before they made some. I can't wait that long so I ordered a rebuilt. I just want to get it swapped out before we depart for International and other places. I swear if that fridge don't work on this trip 100% my marriage may end.

[KJRitchie]

Good luck with the installation of the replacement cooling unit. I hope it fits without modifications, goes in easy and and you have no further issues. Are you going to stay with the Dometic controller board? I see that site offers the Dinosaur replacement boards but i'm not sure if you fridge has one.

I watched a youTube video of someone replacing their cooling unit for a Norcold double door in a motorhome with one of these 'Amish' units. He built a an elevated framed plaform the same height of the fridge base and slide the fridge out onto it and then screwed it down onto the platform. He replaced the cooling unit inside the motorhome and after the installation leveled the platform and ran a test using AC to test it before installing the fridge back into its hole.

I hope you can take some photos of the process to share with us

Kelvin

[lewster]

Originally Posted by KJRitchie

Good luck with the installation of the replacement cooling unit. I hope it fits without modifications, goes in easy and and you have no further issues. Are you going to stay with the Dometic controller board? I see that site offers the Dinosaur replacement boards but i'm not sure if you fridge has one.

I watched a youTube video of someone replacing their cooling unit for a Norcold double door in a motorhome with one of these 'Amish' units. He built a an elevated framed plaform the same height of the fridge base and slide the fridge out onto it and then screwed it down onto the platform. He replaced the cooling unit inside the motorhome and after the installation leveled the platform and ran a test using AC to test it before installing the fridge back into its hole.

I hope you can take some photos of the process to share with us

Kelvin

From what I have seen, the 'Amish' units are nothing but another re-built replacement cooling unit done to the original OEM unit. They are not a magic bullet and are prone to failure just like any of the others...... including newly manufactured units purchased directly from Dometic or Norcold. As a factory authorized service center for both Norcold and Dometic, I only use new factory cooling units as I have encountered warranty and replacement problems with aftermarket units.

I also use a hydraulic table to remove and replace a fridge after I R&R the cooling unit. Allows me to do it single handed. I have never had to remove a fridge from an RV for a cooling unit replacement.

I use Dinosaur boards exclusively as replacements for the OEM boards, which are usually made in China. Enough said!

[KJRitchie]

After browsing the recoilingunit site for my fridge, Dometic 3762, they only offer a new unit which is a redesign of the Dometic unit. It would be interesting if someone performed a face off to see if the Amish unit redesign and ammonia formula gives better warm weather performance. With only two manufacturers left in the marketplace there isn't much incentive to innovate. Atwood is offering a fridge with helium but isn't helium in very short supply?

Do the Dinosaur boards allow you to tweak the fridge performance better than the OEM boards? Unfortunately, they don't seem to offer a replacement board for my Dometic 3762 board 3851005011.

Kelvin