I decided to add two fans at the top refer vent. They are thermostatically controlled as well as manual override. 3 amp inline fuse.
It is currently 89F in the shade. The two added fans have turned on to level 3/6 (auto mode). This means fans are turning at half speed. The hotter it gets, the faster the fans will spin. I can feel the warm air exiting the refer vent cover....good sign!
The single OEM fan has yet to turn on. If trailer/refer were in the direct sun, it would have turned on by now (last testing I did).
I'll do some testing over the next several days and see what I find. It's supposed to cool off into the low 70s by Saturday, so testing in the heat may not happen until next summer.
It is currently 89F in the shade. The two added fans have turned on to level 3/6 (auto mode). This means fans are turning at half speed. The hotter it gets, the faster the fans will spin. I can feel the warm air exiting the refer vent cover....good sign!
The single OEM fan has yet to turn on. If trailer/refer were in the direct sun, it would have turned on by now (last testing I did).
I'll do some testing over the next several days and see what I find. It's supposed to cool off into the low 70s by Saturday, so testing in the heat may not happen until next summer.
UPDATE:
1. Found that my thermistor adjustment slide clip (inside refer) was in the UP (colder) position. However, the actual temp prob was in the middle of the plastic slide. I had moved it up, but the probe stayed put. It appears that there was no clack in the wire to allow it to slide up with the plastic slide clip.
I checked the wire inside access vent and sure enough the excess wire had been zip tied together to keep things nice and tidy. I removed zip ties and pulled a few inches of slack inside refer. I also tape the wire nd of the probe so it would not slide on plastic slider and the used a clip to hold slide in place. I moved the probe to the top of the fins.
2. I removed roof top refer vent. I wanted to inspect what was inside above refer. I did find that there is a cavity at the very top of refer between refer and roof. This cavity is approx. 24" wide by 8" tall x 8" deep. I will leave cavity alone for now and test my refer with new probe position. If needed, I can fabricate a piece of sheet metal flashing to remove cavity from upward flow of air. Not sure if I can make it fit by just cutting back wire mesh.
3. Fans....How well with they sucking air up and out of vent if mounted above wire mesh? I don't want to cut into the wire mesh to mount them just underneath wire mesh if fans will work as well above mesh. I wonder if these fans will work well enough to make up for the cavity above refer? I guess only testing will tell.
Thoughts?
1. Found that my thermistor adjustment slide clip (inside refer) was in the UP (colder) position. However, the actual temp prob was in the middle of the plastic slide. I had moved it up, but the probe stayed put. It appears that there was no clack in the wire to allow it to slide up with the plastic slide clip.
I checked the wire inside access vent and sure enough the excess wire had been zip tied together to keep things nice and tidy. I removed zip ties and pulled a few inches of slack inside refer. I also tape the wire nd of the probe so it would not slide on plastic slider and the used a clip to hold slide in place. I moved the probe to the top of the fins.
2. I removed roof top refer vent. I wanted to inspect what was inside above refer. I did find that there is a cavity at the very top of refer between refer and roof. This cavity is approx. 24" wide by 8" tall x 8" deep. I will leave cavity alone for now and test my refer with new probe position. If needed, I can fabricate a piece of sheet metal flashing to remove cavity from upward flow of air. Not sure if I can make it fit by just cutting back wire mesh.
3. Fans....How well with they sucking air up and out of vent if mounted above wire mesh? I don't want to cut into the wire mesh to mount them just underneath wire mesh if fans will work as well above mesh. I wonder if these fans will work well enough to make up for the cavity above refer? I guess only testing will tell.
Thoughts?
Baja Man wrote:
Thanks John. I added pics.
Is there a reason you placed thermal switch at bottom of refer on absorber pipes instead of up top closer to fan on the upper tubes? I thought the upper areas were the hottest?
You may be thinking into this more then is practically going on as far as the fan disk switch location. My work on these fridges deals with restoring older campers and servicing the appliances on them. I know the RM2652 very well, I looked up your DM2652 and the basic operation is the same although the upper coils are arranged differently.
This is the only Dometic I have seen in person that had factory installed fans. The pic date is correct. That is a more special fridge then a standard RV fridge, they were advertising their fridge as the Elkhart Hall of Fame.
I'm glad to hear Dometic finally is installing factory fans to help the situation, they should of done it a long time ago, I suspect cost was a factor in the RV world.
This U tube shows at least one of the DM2652's fan location, not sure if yours is like this, but this one has the disk switch almost on top of the fan, but yes up high. It is a sad looking OEM install if it was truly a OEM/Dometic install.
https://www.youtube.com/watch?v=dGBG1Jyx5SU
The reason I mounted my thermal disk switch at the bottom was of ease to get to it. The intent of the switch was, as the fridge is working, turn on the fan as it heats and off when it cools down. The location is different then what Dometic picked, not sure if it matters, it fits the fan need.
As FYI, I have tested the different temps all over the RM2652 coiling coil and the "hottest" pipe (location 2 below) is just after the tube that comes out of the burner stack, from there, the pipes are all colder then that location. But, they are all warmer then when the unit is not cooling. (locations 9 - 12 below are the next warmest) See here
When bench testing the fridge the temp locations measured.
The test data
Baja Man wrote:
Since I have the OEM fan which is about 1'-2' below yours, which is at roof vent, I will add the two fans down below just inside the bottom vent just below absorber tubes, horizontally mounted, pointing upwards. These fans (similar to Titan 90mm fans) have a wire probe as a thermostat. Where should this probe be mounted?
The fans have a wired remote that controls speed and also has auto/manual modes so speed can be reduced if fans are working too good and refer temps are too low. I live and camp in SoCal (where it can get HOT and mostly camp in warm areas, so having refer temps too low may be a pipe dream, but definitely welcomed!!
Since with the above mentioned wiring method, what would be the efficiency/advantage or disadvantage of having two lower fans NOT in thermostat synch with the solo upper fan?
It seems your new fans no longer has a need to get power from the Dometic fan switch. They have their own T stat. OK, as long as you can locate their T stat to turn on the fans when the system heats and off when it cools, they should work. Not sure where you are mounting the T stats for those fans, if they do not work out for you, then add a separate thermal disk switch like I did to power them.
As for not having the bottom fans in snyc with the top fan, while there may be a small amount of inefficiency if you can measure it, I'm not sure it really matters. The fans are to help create a better draft up the back of the fridge.
I would be cautious about a fan next to the LP burner area, when I started doing fan testing, I jury rigged one fan on the bottom on the opposite side of the burner blowing up. It for sure helped as opposed to no fan, however the fan up on the roof vent, worked better as if forced more air up the entire back of the fridge versus a single one sided location.
You may want to try just one fan below and leave space for two. Test it and see if you need the second one.
I'm still not convinced something is not right with your factory installed fan setup. Or you have other issues going on creating the temp swings you are seeing. One good working fan in the right location should solve the problem, granted I am on the east coast and you are on the west in a hotter area, that may aggravate a poor fan install or the real issue with the fridge.
Have to checked the thermistor inside the fridge compartment? I just replaced one 2 weeks ago as hers was doing what yours is. Hers is 18 years old, not sure it matters, just mentioning.
Hope this helps,
Let us know how you make out.
John
Baja Man wrote:
I added a few pics, perhaps these are easier to read.
There are no pics extra pics showing up, did you miss posting the,?
I will pass this along to consider, I used a 3 speed fan installed in the roof vent. I started with the fan on high thinking that was a good thing. And I had a fan in the lower compartment blowing upward that was on wire plugs that I could unhook it.
I found out it was not a good thing to over fan the system. The fridge then worked too well, the compartment went to 30 F or slightly below and freezing things inside. I ended up putting the top fan on slow, unhooking the bottom fan and the fridge settled into 33 to 34F consistent.
See here, this may help you. I installed a thermal disk switch just for the upper fan so it turns on and off as needed. You may consider this for your new fans.
This is a double bearing fan made to run in the horizonal direction. The small black cube is the 3 speed switch
3M 33 taped the motor and the speed switch to help make it more dust and water protected. The speed switch is outside the grill, just unscrew the roof vent cover and adjust switch.
Folded screen back down and Dicor no sag caulked it shut
The thermal disk switch
I have done this on several campers. I also created a better bracket for the disk switch if you want to see it. I have to upload the pic, it is not on my file server.
If you put all 3 fans wired at once, you may have too much fan. Suggest running wires on the new fans down to the open compartment area where you can unwire (or unplug, use plug type connectors) them as needed. Make sure you fuse this. Those tiny fan wires will be the fuse if a short ever happens.
Once I see your diagram, I can answer your questions better if they will still be needed after reviewing this reply.
John
Yes, thank you all for the assistance. I added a few pics, perhaps these are easier to read.
What I'd like to do is, wire all three off of the one thermostat and also have a manual option. Ex. A toggle switch with Auto-Off-manual.
Can the wires to the OEM fan and T-stat all be accessed at bottom? It appears I need to access the wire (part 3) from the thermal fuse (part U) to fan, but I believe that wire is near top of refer making access difficult. It would make wiring all this much easier if I could access at bottom of refer.
If not able to access those wires, I would then need to determine "where" to the mount t-stat sensor wire (it is not thermal fuse as is OEM) from new two fans? Fans would be mounted pulling fresh in from lower vent and pushing air UP towards roof vent. Is the T-stat wire taped to lower absorber tubes, to absorber vessel, or ?
Thanks
What I'd like to do is, wire all three off of the one thermostat and also have a manual option. Ex. A toggle switch with Auto-Off-manual.
Can the wires to the OEM fan and T-stat all be accessed at bottom? It appears I need to access the wire (part 3) from the thermal fuse (part U) to fan, but I believe that wire is near top of refer making access difficult. It would make wiring all this much easier if I could access at bottom of refer.
If not able to access those wires, I would then need to determine "where" to the mount t-stat sensor wire (it is not thermal fuse as is OEM) from new two fans? Fans would be mounted pulling fresh in from lower vent and pushing air UP towards roof vent. Is the T-stat wire taped to lower absorber tubes, to absorber vessel, or ?
Thanks
Baja Man wrote:
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
Your diagram is fuzzy and hard to read. But the fan appears to be wired the same in both diagrams. What looks different is the boxed area on the lower left shows other ground connections that can maybe be confusing.
If the fuzzy words on the top right of the boxed area says, GROUND, then both diagrams show the same thing. A +12 VDC hot wire feeds what looks like a fuse. Then the fuse feeds a thermal disk switch which then feeds the fan. The other wire on the fan goes to ground. Both drawings show that, it just looks different as the boxed area has other grounds connected to the same ground coming off the fan motor.
Hope this helps. If what I said above it not clear, please create a pic zoomed in we can see all the words etc.
John
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
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
