I would like to add two 90mm fans behind the service vent (side of trailer). This is the lower vent where most of the electrical connections are located. MY current unit Dometic DM2652LBX with one fan near top that is thermostatically controlled.The current installation appears the best/correct I have ever seen in my last 4 trailers/motorhomes (Jayco, ORV, Monaco, MPV Toyhauler). By correct I mean...proper space all around refer (especially behind refer), and a fan near top that sucks hot air through coils and out of top vent. All other units had twice the all around space of this one and no fan near top. I have added fans on other trailers (mid area behind refer) but I want to do something a little different this time to perhaps increase cooling efficiency.Current temps:Direct sun, ambient temps 77F-83F, refer emptyWireless thermometerRefer/Freezer: 38F/7F (77F-11:20am); 42F/8F (81F-2:00PM); 45F/9F (83F-3:00pm)MY Plan:Add two 90mm fans behind lower side vent. My thoughts are to add these two fans directed to blow air upwards(sucking fresh air from outside vent)and having the upper fan suck it out at same time. I would like for all three fans to work synchronously (all three on at same time). I can not see where the current fan thermostat is located.My questions:1. How can the three fans be wired together?2. Can all three fans be controlled from the one thermostat to ensure they are all three activated at the same time. How can I accomplish this?3. I would also like all three to be controlled manually in addition to thermostat. I am thinking a three way toggle switch (SPDT, DPDT, ?) How can I best accomplish this?I am unable to access upper fan, thermostat, and wiring as I do not want to remove the refer.Thanks!

Baja Man wrote:I would like to add two 90mm fans behind the service vent (side of trailer). This is the lower vent where most of the electrical connections are located. MY current unit Dometic DM2652LBX with one fan near top that is thermostatically controlled.The current installation appears the best/correct I have ever seen in my last 4 trailers/motorhomes (Jayco, ORV, Monaco, MPV Toyhauler). By correct I mean...proper space all around refer (especially behind refer), and a fan near top that sucks hot air through coils and out of top vent. All other units had twice the all around space of this one and no fan near top. I have added fans on other trailers (mid area behind refer) but I want to do something a little different this time to perhaps increase cooling efficiency.Current temps:Direct sun, ambient temps 77F-83F, refer emptyWireless thermometerRefer/Freezer: 38F/7F (77F-11:20am); 42F/8F (81F-2:00PM); 45F/9F (83F-3:00pm)MY Plan:Add two 90mm fans behind lower side vent. My thoughts are to add these two fans directed to blow air upwards(sucking fresh air from outside vent)and having the upper fan suck it out at same time. I would like for all three fans to work synchronously (all three on at same time). I can not see where the current fan thermostat is located.My questions:1. How can the three fans be wired together?2. Can all three fans be controlled from the one thermostat to ensure they are all three activated at the same time. How can I accomplish this?3. I would also like all three to be controlled manually in addition to thermostat. I am thinking a three way toggle switch (SPDT, DPDT, ?) How can I best accomplish this?I am unable to access upper fan, thermostat, and wiring as I do not want to remove the refer.Thanks!in response to your questions1) wire the fans in parallel, each of them connected to +12V and ground2) yes all three can connect to the same thermostat. Just connect the thermostat in and out to each fan just like you would do if you only have one fan3) Do you want to just turn all three on or all three off at the same time? Do you also want to bypass the thermostat? Or do you want to turn all three on independently? Need more info on how best to accomplish (3)

Baja Man wrote: MY current unit Dometic DM2652LBX with one fan near top that is thermostatically controlled.Current temps:Direct sun, ambient temps 77F-83F, refer emptyWireless thermometerRefer/Freezer: 38F/7F (77F-11:20am); 42F/8F (81F-2:00PM); 45F/9F (83F-3:00pm)Hi,If you already have a factory install fan with a T stat at the top area and you are getting that bad of cooling as described above, the bell goes off in my head something else is not right.A question, Is your fridge installed in a slide or other place where the top air vent is in a side wall and not up at the roof line?I have seen some real bad wall side vent setups that rob the efficiency of the fridge. The OEM of the camper did not follow the instructions Dometic states on how to create the air path/ductwork out a side wall vented fridge setup. The air flow gets all bogged down trying to get out of a improper damper/duct setup above the fridge. Just putting a fan up top to help for a bad duct install, does not always fix the root problem.By chance, if yours is in a side wall, can you post pics with the top vent removed so we can see the top of the fridge and how the directed the air to get out of the cabinet?Hope this helps,John

I wouldn't install them at the bottom. take a look inside and see how much room there is from the cooling fins to the baffel or compartment wall. there should only be a small hap. if there isn't you would benifit more by installing a baffel and putting the fans up top so the air flow is directed across the fins.

Refer is not in a slide.Fridge vent is on roof.It appears to be properly installed per installation guidelines. There is little space between refer and trailer side wall. My thinking is to add fans at bottom so there is a push (of lower fans I will add) and a pull by the upper OEM fan.How best to wire so all three are on at same time?Is there a reason to not have them all on at same time?Thoughts?

I found the wiring diagram. Can someone explain the small box to the left side of diagram? The fan (part V) is show wired differently in both diagrams. One shows that one wire (negative) from goes straight to ground and in the other diagram it shows one wire (negative) goes to (R, K, J2, G, J10, Ground) switch, heating cable, lamp, J2, J10, and ground.Thanks

Adding Fans to Rear of RV Absorption Refer - How to Wire?

15 Replies

Baja_Man
Explorer
Oct 15, 2022
I found the wiring diagram.

Can someone explain the small box to the left side of diagram?
The fan (part V) is show wired differently in both diagrams. One shows that one wire (negative) from goes straight to ground and in the other diagram it shows one wire (negative) goes to (R, K, J2, G, J10, Ground) switch, heating cable, lamp, J2, J10, and ground.

Thanks
Baja_Man
Explorer
Oct 15, 2022
Refer is not in a slide.

Fridge vent is on roof.

It appears to be properly installed per installation guidelines. There is little space between refer and trailer side wall.

My thinking is to add fans at bottom so there is a push (of lower fans I will add) and a pull by the upper OEM fan.

How best to wire so all three are on at same time?
Is there a reason to not have them all on at same time?

Thoughts?
StirCrazy
Moderator
Oct 15, 2022
I wouldn't install them at the bottom. take a look inside and see how much room there is from the cooling fins to the baffel or compartment wall. there should only be a small hap. if there isn't you would benifit more by installing a baffel and putting the fans up top so the air flow is directed across the fins.
JBarca
Nomad II
Oct 14, 2022
Baja Man wrote:

MY current unit Dometic DM2652LBX with one fan near top that is thermostatically controlled.

Current temps:
Direct sun, ambient temps 77F-83F, refer empty
Wireless thermometer

Refer/Freezer: 38F/7F (77F-11:20am); 42F/8F (81F-2:00PM); 45F/9F (83F-3:00pm)

Hi,

If you already have a factory install fan with a T stat at the top area and you are getting that bad of cooling as described above, the bell goes off in my head something else is not right.

A question,

Is your fridge installed in a slide or other place where the top air vent is in a side wall and not up at the roof line?

I have seen some real bad wall side vent setups that rob the efficiency of the fridge. The OEM of the camper did not follow the instructions Dometic states on how to create the air path/ductwork out a side wall vented fridge setup. The air flow gets all bogged down trying to get out of a improper damper/duct setup above the fridge. Just putting a fan up top to help for a bad duct install, does not always fix the root problem.

By chance, if yours is in a side wall, can you post pics with the top vent removed so we can see the top of the fridge and how the directed the air to get out of the cabinet?

Hope this helps,

John
ktmrfs
Explorer II
Oct 14, 2022
Baja Man wrote:
I would like to add two 90mm fans behind the service vent (side of trailer). This is the lower vent where most of the electrical connections are located.

MY current unit Dometic DM2652LBX with one fan near top that is thermostatically controlled.

The current installation appears the best/correct I have ever seen in my last 4 trailers/motorhomes (Jayco, ORV, Monaco, MPV Toyhauler). By correct I mean...proper space all around refer (especially behind refer), and a fan near top that sucks hot air through coils and out of top vent. All other units had twice the all around space of this one and no fan near top.

I have added fans on other trailers (mid area behind refer) but I want to do something a little different this time to perhaps increase cooling efficiency.

Current temps:
Direct sun, ambient temps 77F-83F, refer empty
Wireless thermometer

Refer/Freezer: 38F/7F (77F-11:20am); 42F/8F (81F-2:00PM); 45F/9F (83F-3:00pm)

MY Plan:

Add two 90mm fans behind lower side vent. My thoughts are to add these two fans directed to blow air upwards(sucking fresh air from outside vent)and having the upper fan suck it out at same time. I would like for all three fans to work synchronously (all three on at same time).

I can not see where the current fan thermostat is located.

My questions:

1. How can the three fans be wired together?

2. Can all three fans be controlled from the one thermostat to ensure they are all three activated at the same time. How can I accomplish this?

3. I would also like all three to be controlled manually in addition to thermostat. I am thinking a three way toggle switch (SPDT, DPDT, ?) How can I best accomplish this?

I am unable to access upper fan, thermostat, and wiring as I do not want to remove the refer.

Thanks!

in response to your questions
1) wire the fans in parallel, each of them connected to +12V and ground
2) yes all three can connect to the same thermostat. Just connect the thermostat in and out to each fan just like you would do if you only have one fan
3) Do you want to just turn all three on or all three off at the same time? Do you also want to bypass the thermostat? Or do you want to turn all three on independently?

Need more info on how best to accomplish (3)

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Adding Fans to Rear of RV Absorption Refer - How to Wire?

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