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=dGBG1Jyx5SUThe 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
