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Old 05-24-2018, 06:51 PM   #1
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Dometic 3962 refrigerator

I’ve searched the forum looking for a similar situation and so far found nothing.

I have a new 2018 Rockwood Windjammer 3008W with a Dometic 3962 refrigerator, 120V / LP operation. I’m new to RV’ing so I don’t know if my issue is an issue or not.

We have noticed when traveling with the refrigerator on “gas” operation it cools very poorly. Starting the day with air temperatures 75/77 degF ambient finishing the day with 85/87 degF. The refrigerator (by the front panel gauge) starts the day 36/37 degF and finishes the 5 to 6 hour journey around 43/47 degF. Cooling setting is set at 4 (1 - 5 is the available temp setting range, 5 is the coolest). No error codes are shown and the fridge indicates gas operation when 120V shore power is disconnected.

The fridge works fine on 120V shore power. Moreover, it works fine on LP when stationary in the campground. I’ve run it on both for 24 hours and both have maintained temperatures in the 36/37 degF range, even when the door is being opened/closed while cooking.

All this indicates to me that the cooling unit and control circuitry are working properly. On the last couple of travel days I’ve listened at the exterior vent door and can hear the roar of the burner when stopped at rest stops. I’ve also disconnected all the fans that I wired to the 12V supply in case these were drawing down the 12V supply - this step did not result in any improvement. I have not removed all the tin heat shielding so I have not yet assessed the “quality” of the flame. I can see it is blue, but I can’t see anymore than that without some more dismantling.

So I’m at a loss. Is a temperature gain like this normal while traveling?
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Old 05-25-2018, 06:44 AM   #2
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Reconnect your fans they keep the air moving up over the coils if you didn't have enough 12V the frig wouldn't run on gas at all. Air movement may be the problem here. If the frig works fine while parked but not when in motion I would think you may be getting a positive pressure in the frig chimney. A test if you could do it would be to run your frig on 120V with your generator while traveling if it does the same thing then it is air flow. Now how to fix it if air flow is the problem, I would make a faring for the front of the chimney that would cause the air to move up and over creating a low pressure area drawing air across the coils and see if that solves the problem. Good luck let the forum know what you do to fix the problem
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Old 05-25-2018, 06:57 AM   #3
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We have the same refrigerator in our Wildcat and had similar problems. After numerous attempts by the dealer to repair it, they finally changed out the circuit board and it seems to work fine now. He said that our problem was that the board was bad and kept telling the fridge that it was at the correct temperature even when it wasn't. This made it shut off. Because it was under warranty they had to change the thermistor first, then something else, and so on. Not saying that this is your problem but that was ours with the same fridge. Good luck because I know how frustrating it is.
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Old 05-25-2018, 07:54 AM   #4
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Your fridge is in the sidewall, and it's in the worse place possible for updraft airflow when moving.

How many fans did you add and how are they positioned?

I think the negative pressure generated by the airflow from the nose when moving right at the fridge lower grate is causing a reverse draft across the fridge cooling unit and therefore causing it not to cool properly.

You can install enough fans to overcome that effect.

If you want to test my theory, you can temporarily add a "scoop" to the back of the lower fridge vent to force air into it when moving and see if that improves the cooling when moving.

You could use a piece of cardboard and some gorilla tape to make one if you wanted to. It'd only need to be 3" or 4" wide and as long as the grate is tall to work. I think the front edge would only need to stick out a couple of inches. Imagine the vent hood exhaust cap turned vertical facing into the wind to see what it should look like.
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Old 05-25-2018, 08:18 AM   #5
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We both agree its airflow I assumed it was a standard installation should have looked it up good call BR
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Old 05-25-2018, 02:17 PM   #6
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Thanks for the replies - I never thought about an aerodynamic issue - good point both of you. I reconnected the fans once I found disconnecting them had no effect.

However, my fridge is not a sidewall installation any more than any other fridge. It has a lower intake on the side and the upper vent exit in the roof, (see picture). It is near the front of the trailer roof at the beginning of the V so it is entirely plausible that the aerodynamics are different from usual.

I installed 4 low speed fans, 46 ft3/min, so with all 4 running I’m pulling nominally 184 ft3/min through the vent stack. They are installed at the roof vent, see pic.

Based on the replies, I think my next steps will be:
1. Use a fridge thermometer to verify internal temperature vs the built in meter on the fridge. The freezer definitely keeps ice cream frozen so I believed the meter - but it makes sense to verify. I’m on the road right now and have been unable to find the kind of thermometer I want and Amazon doesn’t deliver to a moving target LOL!
2. If the meter checks out. Build and try various “fairings” in front of the roof vent to create low pressure area.
3. Source high speed fans and/or temporarily install some fans at the wall vent to push air up from below and see if that improves the moving situation.

It is all still under warranty so if “1” doesn’t check out my dealer will definitely be doing some work. He’s definitely going to be asked about it regardless.
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Old 05-25-2018, 02:42 PM   #7
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Originally Posted by Bama Rambler View Post
...If you want to test my theory, you can temporarily add a "scoop" to the back of the lower fridge vent to force air into it...

...It'd only need to be 3" or 4" wide and as long as the grate is tall to work. I think the front edge would only need to stick out a couple of inches. Imagine the vent hood exhaust cap turned vertical facing into the wind to see what it should look like.
Being a Porsche guy, I’m thinking GT4 intakes. It’d be the sexiest looking Windjammer ever. . More seriously though I would think other 3008W Windjammer owners would be having the similar issues if it was aero dynamics alone.
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Old 05-28-2018, 03:33 PM   #8
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Other 3008 owners may be having the same problem. Maybe they're not driving as much as you do or maybe they're tow vehicle isn't the same and therefore affecting the aerodynamics differently.

I like the GT4 intakes. You may start a trend if you put something like that on your unit!
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Old 05-31-2018, 09:59 AM   #9
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Considering aerodynamics further what thoughts does anyone have about this theory...

My condensate hose sticks out 3” or so from the lower wall vent (in the picture above). I sometimes see water on the wall of the trailer after we’ve been in motion for a couple of hours. Could the air flow across the end of the tube (Bernoulli Principle) be causing sufficient low pressure to pull the cold air out of the refrigerator over time. We would never feel a vacuum in the fridge because as soon as the air flow past the tube stopped, air flow in the tube would reverse until the pressure gradient is equalized.

It’s crazy I know... I could cap the tube for travel and test the theory quite easily.
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Old 05-31-2018, 05:06 PM   #10
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Further update: Sitting in the driveway the additional refrigerator thermometer is within 1 degF of the Dometic panel gauge, so I believe the fridge really was heating up during travel.

I have higher speed fans in hand and will be installing them this weekend. Approx 71 CFM, I’ll wire them in pairs so I can pull 142 or 284 CFM across the coils.
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Old 06-11-2018, 04:24 PM   #11
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Considering aerodynamics further what thoughts does anyone have about this theory...

My condensate hose sticks out 3” or so from the lower wall vent (in the picture above). I sometimes see water on the wall of the trailer after we’ve been in motion for a couple of hours. Could the air flow across the end of the tube (Bernoulli Principle) be causing sufficient low pressure to pull the cold air out of the refrigerator over time. We would never feel a vacuum in the fridge because as soon as the air flow past the tube stopped, air flow in the tube would reverse until the pressure gradient is equalized.

It’s crazy I know... I could cap the tube for travel and test the theory quite easily.
I tested this hypothesis taking the trailer to storage and the dealership. I taped up the end of the hose and took a long way round to the storage lot. Over 1 1/2 hours of towin gon mixed roads (interstate and 2 lane) the fridge gained about 3 degF or 1deg every 30 min. This roughly correlates with the 10 - 12 degF gains over 5 - 6 hours observed while on our trip. Thus loss of cold air via the condensate hose does not appear to be an issue.

It is under warranty and at the dealership right now. They’re going to run checks on all the control circuitry and sensors. They initially felt that this was “normal” operation however when I expressed skepticism based on the amount and rate of gain they agreed to investigate further.
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Old 06-11-2018, 04:31 PM   #12
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The condensate drain hose should have a perforated cap or screen on it to prevent critters entering it. In order for a vacuum created by moving to warm up the fridge, there would need to a way for warm outside air to enter the fridge in some volume. The vacuum created by moving may lower the pressure in the fridge slightly, but not enough to pull warm air in past the fridge seals.
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Old 06-30-2018, 07:21 PM   #13
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I tested this hypothesis taking the trailer to storage and the dealership. I taped up the end of the hose and took a long way round to the storage lot. Over 1 1/2 hours of towin gon mixed roads (interstate and 2 lane) the fridge gained about 3 degF or 1deg every 30 min. This roughly correlates with the 10 - 12 degF gains over 5 - 6 hours observed while on our trip. Thus loss of cold air via the condensate hose does not appear to be an issue.

It is under warranty and at the dealership right now. They’re going to run checks on all the control circuitry and sensors. They initially felt that this was “normal” operation however when I expressed skepticism based on the amount and rate of gain they agreed to investigate further.
Your experience is similar to our 3008w but we have even more issues... Our first year with the trailer, we didnt have any issues. This year, we've gone through 3 thermal fuses (all replaced under warranty) and an ignitor (wire insulation was burned or worn away near the hard insulation mount point). In our case, the thermal fuse has only blown during travel (the 3rd one just today after the ignitor was replaced).

Like you noticed, our fridge temp. rose during travel (before the latest fuse went out) to about 55 ( from 36).

On a side note regarding your fans, I spoke to an authorized Dometic tech that said if I added fans, make sure to connect them to the 12v circuit on the Dometic panel that cuts power if the thermal fuses blow due to a fire. The last thing you want is fans feeding a fire in the fridge chamber.

At this point, I have told our dealer to reach out to Forest River and Dometic since not running the fridge during travel is not an option and the temperature rise is an issue.

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Old 07-01-2018, 09:45 AM   #14
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Thanks for the reply, sorry to hear of your thermal fuse problems.

Reading your post am I right in understanding you too observed temperature rises when traveling before this years fuse issues? Or did the temperature rises only begin this year when the fuse issues began.

If the latter, then your data point indicates a potential impending electrical issue in my case. If the former, then it appears that air flow as suggested by Seadog and Bamarambler is the likely culprit.

I’m still awaiting a call from my dealer regarding the electrical troubleshooting they are supposed to do... The longer it goes without me hearing anything from them the less faith I have that they’ll actually do anything.

I also purchased one of these to be mounted on my lower vent cover before my next trip. It’s just the right size to fit on the vent cover which is 13+ inches tall. I’m contemplating how to strengthen the vent cover mounting though to withstand the additional wind drag. Wouldn’t do to have it fly off going down the road.
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Old 07-01-2018, 10:32 AM   #15
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Thanks for the reply, sorry to hear of your thermal fuse problems.

Reading your post am I right in understanding you too observed temperature rises when traveling before this years fuse issues? Or did the temperature rises only begin this year when the fuse issues began.

If the latter, then your data point indicates a potential impending electrical issue in my case. If the former, then it appears that air flow as suggested by Seadog and Bamarambler is the likely culprit.

I’m still awaiting a call from my dealer regarding the electrical troubleshooting they are supposed to do... The longer it goes without me hearing anything from them the less faith I have that they’ll actually do anything.

I also purchased one of these to be mounted on my lower vent cover before my next trip. It’s just the right size to fit on the vent cover which is 13+ inches tall. I’m contemplating how to strengthen the vent cover mounting though to withstand the additional wind drag. Wouldn’t do to have it fly off going down the road.
Honestly, I probably wasn't really paying attention to the temperature after arriving at a destination prior to this year's issues.

If all else fails, I may install an inverter to power the AC side while traveling so the gas doesn't blow the thermal fuse. I realize that a 425w element will probably draw 30+amps @ 14v while driving but may be the safer option. I would just have a switch to turn on the inverter once hitched and engine on.

Another plus is the AC only powers the heating element so a cheap modified sine inverter would be enough.

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Old 07-01-2018, 10:47 AM   #16
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Honestly, I probably wasn't really paying attention to the temperature after arriving at a destination prior to this year's issues.

If all else fails, I may install an inverter to power the AC side while traveling so the gas doesn't blow the thermal fuse. I realize that a 425w element will probably draw 30+amps @ 14v while driving but may be the safer option. I would just have a switch to turn on the inverter once hitched and engine on.

Another plus is the AC only powers the heating element so a cheap modified sine inverter would be enough.

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thermal fuses blowing all the time suggests a problem . i would service the burner tube make sure no obstructions exists, seems you also burned the wire to the igniter. more things are going on then just bad fuses . I've traveled across the country and thousands of miles with out issues while running fridge on gas while traveling . something is causing it to over heat .
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Old 07-04-2018, 01:38 PM   #17
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thermal fuses blowing all the time suggests a problem . i would service the burner tube make sure no obstructions exists, seems you also burned the wire to the igniter. more things are going on then just bad fuses . I've traveled across the country and thousands of miles with out issues while running fridge on gas while traveling . something is causing it to over heat .
The burner tube was checked before the last trip as well as the chimney. We still had the thermal fuse go (granted it was on the second driving day).

We had the dealer check the fridge again and we noticed the insulation on the ignitor wire was melting again which he speculated was from continuous attempts to reignite the flame that gets blown out from either turbulent air or vacuum generated by eddy currents.

I think I am going to plan b and install an inverter with ats to power the electric side of the fridge during travel.

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Old 07-04-2018, 08:32 PM   #18
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The burner tube was checked before the last trip as well as the chimney. We still had the thermal fuse go (granted it was on the second driving day).

We had the dealer check the fridge again and we noticed the insulation on the ignitor wire was melting again which he speculated was from continuous attempts to reignite the flame that gets blown out from either turbulent air or vacuum generated by eddy currents.

I think I am going to plan b and install an inverter with ats to power the electric side of the fridge during travel.

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Something still does not sound right . if the igniter wire is burnt or melted imo i don't think it's from wind or turbulent air while driving . if that was that case it would be a common thing , which it is not . I wouyld just for the sake of it check your gas pressure . it wouldn't be the first time q regulator went bad and allowed way more pressure by then should be . no more the 11 to 14" of wc . had one the other day reading 35" he had the same symptoms as you
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Old 07-04-2018, 08:34 PM   #19
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Something still does not sound right . if the igniter wire is burnt or melted imo i don't think it's from wind or turbulent air while driving . if that was that case it would be a common thing , which it is not . I wouyld just for the sake of it check your gas pressure . it wouldn't be the first time q regulator went bad and allowed way more pressure by then should be . no more the 11 to 14" of wc . had one the other day reading 35" he had the same symptoms as you
Funny that you mention the regulator. I was having it replaced under warranty since it wasn't showing RED when it switched over in one direction....


But when the last technician checked it out and lit it after checking the burner tube, etc., the flame looked normal.
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Old 07-05-2018, 06:03 PM   #20
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Funny that you mention the regulator. I was having it replaced under warranty since it wasn't showing RED when it switched over in one direction....


But when the last technician checked it out and lit it after checking the burner tube, etc., the flame looked normal.
Looks can be deceiving, let us know if anything changes with the new regulator / by the way did the tech do a test of the gas pressure ?
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