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Old 09-25-2016, 06:06 AM   #11
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A/C cycles.....

Glad i came upon this thread. My Dometic is doing this exact thing and i took it in to have it looked at. I guess i wont be perplexed when the shop calls and says there's nothing wrong.
I will also say, however, seems as though this is a poor design. On a really hot day, slowing the fan down at a 4-deg difference just means it has to run much longer, and probably will never catch up to the correct temp. Its much easier on the unit, and cheaper, to run a fan on high than to run the compressor longer.
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Old 09-26-2016, 12:24 PM   #12
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One of my complaints about this control is that you can only select auto mode to have the fan shut off when the temp has reached it's setting. In both Hi and Lo it runs constantly.
How about a setting that let's the fan run on Hi, or Lo, only when the AC compressor is running.
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Old 09-26-2016, 01:07 PM   #13
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We have had a coupe of occasions where the outside temp is increasing, the coach gets within 4-5 degrees of the thermostat setting and the fan switches from hi to low. With the outside temp increasing it go back to hi within a couple of minutes then cycles back to low after catching up. Pain in the butt. We just switch to hi and leave it there until the evening and go back to auto.

This only happened a couple of times while camping for weeks in Mississippi this August.
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Old 09-26-2016, 03:23 PM   #14
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You could management it manually but it is possible disconnect the low speed wire to the inside fan and strap the low and high from the relay to the high speed wire of the fan and "lock" it to high now and forever, amen. Personally I like to switch to Hi fan while the rig cools down, then after cool, switch to auto.
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Old 09-26-2016, 05:16 PM   #15
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A/C cycles.....

Quote:
Originally Posted by WolfWhistle View Post
You could management it manually but it is possible disconnect the low speed wire to the inside fan and strap the low and high from the relay to the high speed wire of the fan and "lock" it to high now and forever, amen. Personally I like to switch to Hi fan while the rig cools down, then after cool, switch to auto.
WW

Sorry. But i didn't follow your post. So it can be rigged to run one speed even when on "auto," or it can only be changed to run one speed when on permanent "high" (or low, if you wanted)? We always use "auto" through the day... then continuously run the fan on "high" at night.
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Old 09-26-2016, 06:54 PM   #16
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Quote:
Originally Posted by KDHfan View Post
Sorry. But i didn't follow your post. So it can be rigged to run one speed even when on "auto," or it can only be changed to run one speed when on permanent "high" (or low, if you wanted)? We always use "auto" through the day... then continuously run the fan on "high" at night.
I want to be clear on what model AC you have, whether it is a heat pump and if you have more than one zone. Let me know.

I don't think making the fan run on one speed (high) is difficult, but am not looking at a schematic. I also don't want you to do anything to harm your unit. Keep in mind you could void your warranty if you don't know what you are doing ... and you don't know how to undo it, undetected..

I would also like to test this theory, myself. An unknown to me, is since these little units only have one fan (common shaft to the outdoor fan) what does that do to the functionality of the unit since the outdoor will also turn all the time on high. It certainly uses more energy, but should work better; certainly will be noisier.

I think in the wiring harness coming down via 6 pin, to the control board the leads in question are black and red; on pins 2 and 4; they stay on color to the control board ... I also think K1 is the controlling relay. It seems reasonable that you could remove the low speed lead to the 6 pin, red I think, and tape it up. Then make a strap connecting that terminal to the terminal that the black is running to. That way if K1 turns on red or black the fan runs on high. You cannot run on both speeds simutaneously (will generate smoke and not the good kind)
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Old 09-26-2016, 07:00 PM   #17
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OK, this conversation reminded me that I need to get going on my solution. My Cool Cat is located directly below the bed in my A-Frame, and the crazy switching of fan speed really make it hard to get to sleep.

I am going to install a LUX WIN 100 programmable thermostat. I am quite sure that it will do what I want - i.e. eliminate the female mode (Can't make its mind up) that is built into the Dometic Digital Thermostat.

The Lux is a line voltage control. It switches the 120 volt power. By setting the Dometic thermostat at the minimum temperature and fixing the fan speed at either high or low, the Lux with a higher cut-off temperature set-point will take over control of the system. This is theory, but I am 95% sure it will work as I want. I will do some testing later this week when the new thermostat arrives, and post my findings.
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Old 09-26-2016, 07:31 PM   #18
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Originally Posted by Bluepill View Post
OK, this conversation reminded me that I need to get going on my solution. My Cool Cat is located directly below the bed in my A-Frame, and the crazy switching of fan speed really make it hard to get to sleep.

I am going to install a LUX WIN 100 programmable thermostat. I am quite sure that it will do what I want - i.e. eliminate the female mode (Can't make its mind up) that is built into the Dometic Digital Thermostat.

The Lux is a line voltage control. It switches the 120 volt power. By setting the Dometic thermostat at the minimum temperature and fixing the fan speed at either high or low, the Lux with a higher cut-off temperature set-point will take over control of the system. This is theory, but I am 95% sure it will work as I want. I will do some testing later this week when the new thermostat arrives, and post my findings.
Let us know. BP, I think the thermostat's drop to low speed and go back to high speed is the real issue. It is like both are set to the same temperature point. I wonder if there is a better t-stat? Slightly off the subject, but I have a Haier portable set up in my garage (toy hauler) and the fan runs all the time (3 speed) so the additional sound when the compressor comes on is barely noticeable(love it); unlike these 13.5 15.0 roof top units that could wake the dead. I am going to try manually setting the fan to low at night and see if it is better. Why have I not thought of this?
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Old 10-04-2016, 11:27 PM   #19
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Quote:
Originally Posted by Bluepill View Post
OK, this conversation reminded me that I need to get going on my solution. My Cool Cat is located directly below the bed in my A-Frame, and the crazy switching of fan speed really make it hard to get to sleep.

I am going to install a LUX WIN 100 programmable thermostat. I am quite sure that it will do what I want - i.e. eliminate the female mode (Can't make its mind up) that is built into the Dometic Digital Thermostat.

The Lux is a line voltage control. It switches the 120 volt power. By setting the Dometic thermostat at the minimum temperature and fixing the fan speed at either high or low, the Lux with a higher cut-off temperature set-point will take over control of the system. This is theory, but I am 95% sure it will work as I want. I will do some testing later this week when the new thermostat arrives, and post my findings.
OK. The testing is complete. The plug-in thermostat works just as I had hoped.




Installation.

Cut the 120 volt wiring that goes from the circuit breaker panel to the A/C unit. Attach an outlet to the side that is connected to the CB panel, and a matching plug to the side going to the A/C. Plug the new thermostat into both.

Operation:

Choose either High or Low fan speed at the original thermostat. Set that 'stat to 55 degrees. When the new thermostat calls for cooling, both the compressor and the chosen fan speed come on together. The original delay between the fan coming on and then the compressor coming on a few seconds later is gone.

When the new thermostat is satisfied, it turns off both the compressor and the fan. This is unlike the original design that will run the fan constantly when High or Low speed are chosen. The constant "Hunting" for fan speeds when in the "Auto" mode is eliminated.

If you want to revert to original operation with the fan running constantly, either unplug the new thermostat and plug the line to the A/C directly into the outlet, or set the new 'stat to 55 degrees and the old one to your desired temperature. This is a nice option if you want some constant fan noise to mask a noisy environment like a truck stop or a Walmart lot.

Another bonus: The new thermostat has an adjustable differential (they call it "Swing") That is the difference between turn on and turn off. I set it at "7" (it has a range of 1 to 9.) That is just an arbitrary scale, not directly related to temperature. With the new 'stat set to 70 degrees, it would come on at 72 degrees and turn off at 68 degrees. That is a larger "Swing" than the original 'stat, and means fewer start-ups. For me, that means better sleep due to fewer start/stop cycles.

But wait - there's more. The new 'stat is also programmable by time. That means you can leave the temp higher when you are out, and have it come down before you return, just like a house programmable 'stat.
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