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04-18-2020, 04:35 AM
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#1
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Senior Member
Join Date: Apr 2019
Location: Henniker
Posts: 2,174
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AC Fan Speeds
Although we have 3” of fresh snow on the ground this morning, we are getting the itch to hit the road soon. Thoughts have turned to spring camper prep and maintenance. One item on the list is the AC unit; a 13.5 BTU Dometic Duo Therm Brisk II. There is no noticeable difference in fan speed between low and high regardless of the thermostat setting; it seems to run on high no matter what. It does cycle on and off on auto setting and will stay on all the time if set on low or high, but the fan speed is always the same. Any ideas?
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04-18-2020, 05:36 AM
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#2
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Senior Member
Join Date: Mar 2014
Location: Mountain Home, Idaho
Posts: 3,015
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Depending on what thermostat your RV is using you can enter diagnostic mode and turn on low speed or hi speed mode of fan...
Red wire to fan is for low speed operation. Black wire to fan is for hi speed operation..
If fan is running same speed from diagnostics mode ... Low and Hi speed are the same then I’d be looking at the air conditioner control module or six wire connector to the module.
__________________
2007 GMC Classic club cab 4x4 Duramax LBZ
2014 Alpine 3010 RE. 34 foot fifth wheel
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04-18-2020, 05:45 AM
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#3
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Senior Member
Join Date: Mar 2014
Location: Mountain Home, Idaho
Posts: 3,015
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Areas circled in Red are fan speed outputs to six wire connector on the control module.
I’d reseat the six point connector and try fan speed operation hi and lo... you can also measure output from control module points for proper voltage output to connector and to fan motor
__________________
2007 GMC Classic club cab 4x4 Duramax LBZ
2014 Alpine 3010 RE. 34 foot fifth wheel
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04-18-2020, 05:49 AM
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#4
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Senior Member
Join Date: Apr 2019
Location: Henniker
Posts: 2,174
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Quote:
Originally Posted by ChuckS
Depending on what thermostat your RV is using you can enter diagnostic mode and turn on low speed or hi speed mode of fan...
Red wire to fan is for low speed operation. Black wire to fan is for hi speed operation..
If fan is running same speed from diagnostics mode ... Low and Hi speed are the same then I’d be looking at the air conditioner control module or six wire connector to the module.
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Thanks Chuck, I will start diagnostics this weekend. I have the Dometic 3313192 capacitive touch single zone thermostat
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04-18-2020, 08:40 AM
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#5
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Site Team
Join Date: Feb 2014
Location: W. Texas
Posts: 17,695
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Keep in mind as you start diags on your system that the Dometic thermostat you have has had a history of malfunctions. I put 4 in my previous trailer. Looks like you have a 19 trailer. You might look at the actual construction date and see if it might have been in 18. Per Dometic, when I was dealing with them, they had some "bad batches" in 18. Whether your unit was made in 18 or you got a "left over" thermostat made in 18, it "might" be causing you an issue although your symptoms don't sound like any of the ones I encountered. Good luck.
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Danny and Susan, wife of 56 years
2019 Ram 3500 Laramie CC SWB SB 6.4 4x4 4.10
2020 Montana High Country 331RL
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04-18-2020, 09:00 AM
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#6
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Senior Member
Join Date: Apr 2019
Location: Henniker
Posts: 2,174
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Our build date was 8/22/18 and we purchased 4/27/19. I will do the diagnostics and see what I can find out, and then see if it might be the t-stat if nothing else shows up. I see the newer ones are Bluetooth now so maybe it might be another good excuse to replace. Thanks guys!
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Rob & Amy
2019 Passport 240BH SL (for sale)
2024 Cougar 29BHL (Taking delivery 5/11/24)
2022 Ford F250 7.3L Godzilla Crew Cab FX4
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05-03-2020, 03:39 AM
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#7
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Senior Member
Join Date: Apr 2019
Location: Henniker
Posts: 2,174
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No luck getting the t-stat into diagnostics mode. It might be because it’s a capacitive-touch single zone heat/cool. I found an old thread on a different subject and someone mentioned that theirs was the same, so maybe it’s intended that way.
__________________
Rob & Amy
2019 Passport 240BH SL (for sale)
2024 Cougar 29BHL (Taking delivery 5/11/24)
2022 Ford F250 7.3L Godzilla Crew Cab FX4
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05-03-2020, 03:48 AM
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#8
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Senior Member
Join Date: Dec 2018
Location: grand rapids
Posts: 596
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actually I've never notice a change in the speed on any of my RV a/c s unit.
The general rule of thumb is to just leave the setting on auto and go with that setting.
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05-03-2020, 05:55 AM
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#9
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Senior Member
Join Date: Apr 2015
Location: nm
Posts: 1,833
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Quote:
Originally Posted by Roscommon48
actually I've never notice a change in the speed on any of my RV a/c s unit.
The general rule of thumb is to just leave the setting on auto and go with that setting.
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I was thinking the same about fan speed low and high. Plugged into my 30 amp camper in the pole barn I can hear a slight difference in fan speed when switching from high to low .
__________________
2018 1 ton 4x4 c.c standard bed GMC Denali
Anderson ultimate hitch
2015 311 Impact Fusion toy hauler
2018 Milwaukee 8 FLRTU roadglide glide ultra
2018 800 Z force spot BUGGY.
500 watts of solar enough power for boon docking.
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05-03-2020, 06:19 AM
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#10
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Site Team
Join Date: Mar 2011
Location: Gaylord
Posts: 26,997
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With the OEM rooftop A/C and the Dometic digital thermostat, the way it's "supposed to work" is like this:
With the fan switch in LOW, the rooftop fan runs on low speed
With the fan switch in HIGH, the rooftop fan runs on high speed
With the fan switch in AUTO, the rooftop fan runs on high speed if the temperature differential (thermostat selected temperature and actual sensed temperature) is greater than 5degrees F. Once the temperature differential is below 5*F the fan shuts down, changes speed to LOW (compressor continues to run) until the thermostat temperature setting is reached. When reached, the compressor will shut down, fan will continue to run for 30-60 seconds then it will also shut down.
If the temperature (within 5*F) begins to rise after the fan speed changes to low, the fan will stop (compressor continues to run) and the fan speed will change back to high. It will continue to run on high speed until the differential temperature again falls to less than 5*F difference with the set temperature and the cycle will repeat (compressor on, fan stops, changes to low and starts again),
With the fan speed set to auto, the fan will start/stop based on A/C operation. With the fan speed on high or low, the fan will run continuously as long as 120 VAC power is applied to the circuit.
If it is cooler than the thermostat setting, the fan switch will not cause the fan to turn on until the thermostat setting is reached. So, in the winter, with the thermostat set to "furn" or "heat" and the fan set to "high or low" nothing will turn on until the first time the thermostat senses a need for heat. When that happens, the furnace fan AND the A/C fan will turn on. Once the heat setting is reached, the furnace will turn off but the A/C fan will continue to run until the fan setting on the thermostat is changed to "auto"....
__________________
John
2015 F250 6.7l 4x4
2014 Cougar X Lite 27RKS
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05-03-2020, 07:38 AM
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#11
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Site Team
Join Date: Oct 2011
Location: Joppa, MD
Posts: 11,758
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Opinions vary on the ac/fan settings. Coming from a retail/restaurant project management in construction and facilities management it's been the "norm" to leave the fan run constantly while in cooling mode. This was always the recommendation from all the major manufactures.
Having the fan run constantly distributes the air throughout the space for a more even distribution of tempered air, filters more air, and typically gives the thermostat or the remote sensor amore "representative measurement" of the air temp over the overall space. I know comparing a 4-10 sq. ft space isn't the same as a 300 sq. ft. space but the theories are the same, the distribution of air.
In our camper we leave the fan on for the above reasons and to help "drown out" outside noise while we are gone and leave the dog behind. On the rare occasion when watching TV I'll set it to auto so I don't turn the volume up to "stadium level" to hear it.
__________________
Marshall
2012 Laredo 303 TG
2010 F250 LT Super Cab, long bed, 4X4, 6.4 Turbo Diesel
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05-03-2020, 11:05 AM
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#12
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Senior Member
Join Date: Apr 2015
Location: nm
Posts: 1,833
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Quote:
Originally Posted by flybouy
Opinions vary on the ac/fan settings. Coming from a retail/restaurant project management in construction and facilities management it's been the "norm" to leave the fan run constantly while in cooling mode. This was always the recommendation from all the major manufactures.
Having the fan run constantly distributes the air throughout the space for a more even distribution of tempered air, filters more air, and typically gives the thermostat or the remote sensor amore "representative measurement" of the air temp over the overall space. I know comparing a 4-10 sq. ft space isn't the same as a 300 sq. ft. space but the theories are the same, the distribution of air.
In our camper we leave the fan on for the above reasons and to help "drown out" outside noise while we are gone and leave the dog behind. On the rare occasion when watching TV I'll set it to auto so I don't turn the volume up to "stadium level" to hear it.
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. Ok I get now after having let my lady reading the post and Five minute lecture from her. Ok your dog barks a lot when your gone and your AC is noisy.
__________________
2018 1 ton 4x4 c.c standard bed GMC Denali
Anderson ultimate hitch
2015 311 Impact Fusion toy hauler
2018 Milwaukee 8 FLRTU roadglide glide ultra
2018 800 Z force spot BUGGY.
500 watts of solar enough power for boon docking.
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05-03-2020, 11:09 AM
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#13
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Site Team
Join Date: Oct 2011
Location: Joppa, MD
Posts: 11,758
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Quote:
Originally Posted by roadglide
. Ok I get now after having let my lady reading the post and Five minute lecture from her. Ok your dog barks a lot when your gone and your AC is noisy.
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The dog doesn't bark while we are gone because we leave the noisy fan run.
__________________
Marshall
2012 Laredo 303 TG
2010 F250 LT Super Cab, long bed, 4X4, 6.4 Turbo Diesel
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05-03-2020, 11:30 AM
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#14
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Senior Member
Join Date: Apr 2019
Location: Henniker
Posts: 2,174
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So I was able to get the t-stat into diagnostics mode by taking the faceplate off and touching the terminals directly with my fingers. From there, I was able to get low speed fan and high speed fan. Although the difference in sound and speed is minimal, there was a difference between the two. I think the only way to tell is to toggle them back and forth in diagnostic mode, otherwise you will be challenged to tell the difference.
__________________
Rob & Amy
2019 Passport 240BH SL (for sale)
2024 Cougar 29BHL (Taking delivery 5/11/24)
2022 Ford F250 7.3L Godzilla Crew Cab FX4
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