Refrigerator Fan Running when Refrigerator Off

[DCPAS]

I searched and found a few old threads discussing this but nothing recent. We have a side vent refrigerator in our FC 25RBT. The vent fan in the upper side refrigerator compartment runs even after the refrigerator has been off for a day. We are in Houston in July so it is hot, of course. I assume that is why it is running. Is that correct? It is not a huge problem because we store our trailer with power, but is there a way to make the fan not run when the refrigerator is off?

[RivetED]

The thermistor mounted on the fins in the upper outside vent compartment is possibly shorted (stuck closed). Nothing to get overly worried about except to preserve battery charge but you said there is power to the trailer. Not great for fan MTBF numbers and when using the refer the temp inside will be more erratic.

To confirm, disconnect one of the wires on the 'silver button looking thing' (AKA: Klickson/Clickson Thermal switch) and if the fan stops that is your issue. If you have a DVM you can check the resistance, it's a switch so it's either 0 or infinity.

There is the possibility that it is operating correctly because it is an 'F40-15C' which means it 'closes, switches on' at 40C (~104F) and in Houston it's possible for it to be that hot.

I'm looking at your thread because of the same issue, with the same 25' (RBT) trailer. floorplan. I have been able to confirm mine is shorted, it's in my house and still is 'closed'. I just called Jackson Center and they told me to call Dometic because it's still a warranty issue. Nothing but fun!

[pmclemore]

Are you sure the fan is connected to the refrigerator at all? Many are add-ons that have a separate switch.

When your rig is not in use, and the fridge is turned off, will the fan keep running then? If so, then it is likely that there is a separate switch.

Pat

[RivetED]

Originally Posted by pmclemore

Are you sure the fan is connected to the refrigerator at all? Many are add-ons that have a separate switch.

When your rig is not in use, and the fridge is turned off, will the fan keep running then? If so, then it is likely that there is a separate switch.

Pat

Thanks Pat, but we both have the same year, model, and floorplan. Unless Airstream redesigned the refer compartment in mid-production it's unlikely, however not impossible, they are different.

I am building a 3-fan plate to install in the exhaust (upper) vent and would like at least one of the fans to be connected to the thermistor, same CFM as the OEM fan. The other 2 will be manually switched.

I also live in Texas and I will not know just how much air movement will work under changing situations. This will be a work in progress experiment.

[DCPAS]

Originally Posted by RivetED

I'm looking at your thread because of the same issue, with the same 25' (RBT) trailer. floorplan. I have been able to confirm mine is shorted, it's in my house and still is 'closed'. I just called Jackson Center and they told me to call Dometic because it's still a warranty issue. Nothing but fun!

Sorry for your issue, but at least I know I am not alone. I have a service appointment next week so I don't think I will go testing prior to that (trailer is stored away from home). I'll post here if they tell me what the issue was. I store the trailer indoors where it is not 40C so I am pretty sure something is amiss - just didn't know how the fans are controlled. Thanks for the explanation.

[uraljohn]

We had a 2017 Int. Serenity 23D with the 2 side vents refrig cabinet. The small fan supplied with the refrig would only run when refrig was switched on. No power to the little dime size thermoswitch when refrig was off.

On our 2019 FC 25 RBT the factory supplied fan (which I replaced with a twin fan setup to move more air thru the back cabinet of the refrig) has power going to the little dime size thermoswitch all the time. So even if the refrig is turned to the off position if it is hot enough outside to warm up the refrig cabinet the fans will come on and move some air until temp drops below thermoswitch cut off temp.

I discovered this by accident. We keep our AS at our home plugged in all the time as we use it often. Noticed the fridge fans running one day so I checked out the wiring. Low and behold, constant power to the thermoswitch. Why is it wired this way? I don't know. If I were to store the AS someplace without power I would manually unplug the fan thermoswitch.

[DCPAS]

Originally Posted by uraljohn

We had a 2017 Int. Serenity 23D with the 2 side vents refrig cabinet. The small fan supplied with the refrig would only run when refrig was switched on. No power to the little dime size thermoswitch when refrig was off.

On our 2019 FC 25 RBT the factory supplied fan (which I replaced with a twin fan setup to move more air thru the back cabinet of the refrig) has power going to the little dime size thermoswitch all the time. So even if the refrig is turned to the off position if it is hot enough outside to warm up the refrig cabinet the fans will come on and move some air until temp drops below thermoswitch cut off temp.

I discovered this by accident. We keep our AS at our home plugged in all the time as we use it often. Noticed the fridge fans running one day so I checked out the wiring. Low and behold, constant power to the thermoswitch. Why is it wired this way? I don't know. If I were to store the AS someplace without power I would manually unplug the fan thermoswitch.

So it's not a bug, its a feature? We only got our trailer in March and I thought that the fan did not do this then, but I am not certain.

[RivetED]

Originally Posted by DCPAS

Sorry for your issue, but at least I know I am not alone. I have a service appointment next week so I don't think I will go testing prior to that (trailer is stored away from home). I'll post here if they tell me what the issue was. I store the trailer indoors where it is not 40C so I am pretty sure something is amiss - just didn't know how the fans are controlled. Thanks for the explanation.

It took me over an hour to get through to Dometic. They told me they would need to have the issue verified by an authorized Dometic repair center and not send out 'warranty' parts to an owner directly. Good thing you are going to a service dept.

I got the Dometic part #3104133.016 and if I want to buy from them it was around $40.- + $25.- shipping, Amazon Prime was ~$42.-.

Since I'm redoing the whole system I bought a 12vdc 'Ink Bird' digital thermostat (Amazon) with a remote probe, <$15.-. I'll experiment using the 3 fans with the thermostat and manual switches and see what works best.

Nothing like another design modification to help me pass the time!!

[DCPAS]

Originally Posted by RivetED

It took me over an hour to get through to Dometic. They told me they would need to have the issue verified by an authorized Dometic repair center and not send out 'warranty' parts to an owner directly. Good thing you are going to a service dept.

I got the Dometic part #3104133.016 and if I want to buy from them it was around $40.- + $25.- shipping, Amazon Prime was ~$42.-.

Since I'm redoing the whole system I bought a 12vdc 'Ink Bird' digital thermostat (Amazon) with a remote probe, <$15.-. I'll experiment using the 3 fans with the thermostat and manual switches and see what works best.

Nothing like another design modification to help me pass the time!!

Excellent info. Thank you.

[CharlieZoner]

We bought our first Airstream (2015 FC 25RBT) earlier this year and while we love most things about it we found the refrigerator performance to be pathetic, even at moderate outside temperatures. After much research on this site I realized that the side vent configuration on this (and other) AS models is poorly engineered with regard to the convective airflow necessary for absorption refrigerators to perform well. As you can see in the "before" picture, the optional cooling fan is located below the upper fins and only serves to draw the rising air away from the fins and out the vent before it can do its job and leave the fins trapped in the upper section full of hot, dead air. In addition, the vent screens are too fine and add additional restriction to the airflow.

With no evidence of leaking refrigerant I decided to try to improve the airflow before considering a replacement fridge or cooling unit. The process consisted of four steps: 1) Create a baffle under the upper condenser fins to direct the rising air through the fins rather than out the upper vent. 2) Replace the (very noisy) factory fan with quieter units mounted to a custom bracket. I bought Noctua NF-F12 iPPC-2000 fans from Amazon for $22.49 each. 3) Replace the thermostat with a lower cut-in temperature part. I used the NTC-DTC120 thermostat from Digikey.com for $2.74 each. At this price by several since they seem to be a common failure item. 4) Remove and replace the insect screen with a larger mesh. I used SS wire cloth from McMaster Carr PN 9211T402 (mcmaster.com) and attached it with clear silicone.

The difference in performance was incredible. What took 48 hours to cool from 85F to <40F (if at all) now happens in <8 hours. Opening the fridge or freezer or adding warm food no longer sends it in to the 50s. I can easily maintain 40C at the middle setting (3) and get down to <37 at the coldest setting.

Hopefully this helps others that are experiencing the same problem. Feel free to send me a PM if you have questions. Berfore and after pics of the install are attached. Feel free to PM me if you have any questions.