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Old 05-21-2018, 04:30 PM   #1
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Nova Kool Frig Wiring Problem?

Working out the kinks in our 2017 AI GT. After our first long weekend we found the refrigerator to cut in and out. Had to pull food and beer down to the freezer section after the first day. Frig would get down to 44 degrees, then 5 hours later it was 70, then back down to 40s the next day. I do not know if it was tied to shore power vs. dc only (driving time). The lower freezer unit (two separate units in the GT model) worked perfectly for 4 straight days.

Called NovaKool tech support number and they are ready to help troubleshoot. Two calls to them so far and they answered right away - I give them 5 stars for answering the phone and wanting to help.

I removed the refrigerator from the cabinet this afternoon. It was a simple 10 minute, 1 beer project. Unlike other posts on this removal there was plenty of loose AC and DC cable to remove and unplug. On the AC side I am getting 118V. On DC it looks like I am getting 1.233v. ??? House and main batteries were fine at 12.8V. But here is the stranger part. Now that I have disconnected the DC connectors from the frig unit I no longer get any readout of Axillary batteries on the tank level panel. Main batteries still reads normal but Aux batteries is completely blank. No numbers at all.

Not sure if this is a sign of a wiring problem. Will put calls into NovaKool and Airstream tech support tomorrow. Thoughts are welcome. Mainly documenting this with future conclusions for others to learn and help with future searches.
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Old 05-21-2018, 05:32 PM   #2
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I have the lounge, but I find that my fridge works much better if I simply unplug the 120v line and run it on 12v all of the time. When running on 120v, I would have 35 degrees most of the time, then it would go up to 42 or 43 degrees for a time, then drop back to 35 degrees. Never higher. I have no idea why.

Once I unplugged the 120v, it reliably stays in the 30s; 35 +/- 2 degrees.
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Old 05-21-2018, 06:50 PM   #3
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I don't see anything in the schematics that would tie the fridge into the house battery monitor, but my guess is you may have a bad compressor (or controller). If you can take it to an authorized NovaKool shop vs. your RV dealer you may get faster/better service. Check with AS Cust Serv first to make sure they'll authorize it:

Airstream Customer Service and Technical Support
1 (877) 596-6111, option 2.
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Old 05-21-2018, 07:26 PM   #4
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I have not had time yet to understand the EMS (PCS) heirarchy, so might be useless banter here - but could it be getting shed when high demand, higher pri 120v systems are being used; though on 2nd thought shouldn't the fridge be a hi-pri above others?
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Old 05-21-2018, 08:13 PM   #5
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Originally Posted by Alex AVI View Post
I have not had time yet to understand the EMS (PCS) heirarchy, so might be useless banter here - but could it be getting shed when high demand, higher pri 120v systems are being used; though on 2nd thought shouldn't the fridge be a hi-pri above others?
On my 2014.5, the 120v breaker is shared between the electric side of the water heater and the 120v outlet for the refrigerator. If there is load shedding, that could turn off the 120v input, but the fridge should simply revert to running on 12v and not stop cooling.

If the 12v fuse is blown or there is a problem with 12v wiring, then load shedding could affect the refrigerator.
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Old 05-21-2018, 08:14 PM   #6
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Quote:
Originally Posted by Alex AVI View Post
I have not had time yet to understand the EMS (PCS) heirarchy, so might be useless banter here - but could it be getting shed when high demand, higher pri 120v systems are being used; though on 2nd thought shouldn't the fridge be a hi-pri above others?
The OP has a '17, which only sheds between 4 loads: A/C, W/H (water heater), Coffee (AC outlet over the galley), and Microwave. The Refer/Freezer doesn't play into that hierarchy.
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Old 05-21-2018, 08:16 PM   #7
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Originally Posted by Pahaska View Post
If the 12v fuse is blown or there is a problem with 12v wiring, then load shedding could affect the refrigerator.
The refrig and freezer are on the same 12v fuse (ckt 6 of the 12v distrib panel), and the OP said his freezer is working fine. Given that, I don't think it's a fuse.....
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Old 05-22-2018, 05:51 AM   #8
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Here are my thoughts, comments, and observations. Afraid that I am as baffled as you as far as where the problem lies.

Where are you recording the 1.233V?
Is this an open circuit voltage drop across the + and - DC wires feeding the fridge (fridge disconnected)? If so, something is wrong.
Or is this the voltage drop across the wires at some point in the circuit with the fridge running? If so, that voltage may not signify a problem.

One post says the fridge and freezer are fed by the same 12V DC fuse. That would suggest that the power TO the fridge is not the problem if/since the freezer works fine.

On our single-unit (combined freezer/fridge) the compressor runs on 12V DC. If AC power is available the 120 V AC is converted to 12 V DC. But when running on DC it runs 'directly' from the 12 V wires.
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Old 05-22-2018, 03:57 PM   #9
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Frig troubleshooting part II - Making progress.

First, the 1.2V was measured off the DC spade connectors after pulling them off the frig unit. Simple answer - I popped a 15 amp fuse. Must have let the spades touch at some point and I guess the fuse was still letting a little V through. Replaced the fuse and got 12.8V to the frig. Also the battery indicator started working again for the Aux batteries (on the tank level panel). So either this was running off the same fuse or maybe breaking any of the fuses cuts of the battery V readout on the panel? Guess I could pull a few other fuses as an experiment.

Called back Nova Kool to take the next troubleshooting step. The frig is now on the galley counter over the sink. Thankfully the AC cord it long enough to reach across the isle. Per his instructions I plug in the AC only (DC cables not long enough to stretch across) and turned it on. He then went straight to the source - there is a stack of spade connections going to the control panel in the back of the frig. The bottom one is modified with an extra component with heat shrink wrapped around it almost like a jumper. Just the slightest little jiggle and the cooling fan/compressor cuts in and out. I removed the component and connected the spade directly to the control panel eliminating this component.


The frig is now running and I have a wireless frig sensor that monitors temps and min/max so I will know over the next 12/24 hours if it is holding steady. The Nova Kool rep said the component was a "speed" sensor or regulator? Don't recall exactly. I will call him again tomorrow evening to report results.
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Old 05-22-2018, 04:06 PM   #10
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Quote:
Originally Posted by Land Stitchy View Post
Frig troubleshooting part II - Making progress.

First, the 1.2V was measured off the DC spade connectors after pulling them off the frig unit. Simple answer - I popped a 15 amp fuse. Must have let the spades touch at some point and I guess the fuse was still letting a little V through.
Interesting. I've not seen a fuse "partially blow" in about 20 years. Maybe that reading was a red herring and was some parasitic from somewhere else?

What I really don't get is why was your freezer working? Unless the schematics are tragically wrong (again), the fridge and freezer are on the same circuit (ckt #6, red wire). If the fuse blew, how was the freezer on?

Best luck with the rest of your triage. Sounds like you've got it on the run!
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Old 05-22-2018, 04:35 PM   #11
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Timing difference on my freezer report. I was originally reporting the freezer working during the weekend trip while the frig was intermittent. Once I got home I shut both frig and freezer off as my normal procedure when not in use.

When I started the troubleshooting and removed the frig last night the freezer was already turned off and warm. I understand that they are both on the same fuse along with the propane detector so presumably they were all cut off at the same time but would not have known.
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Old 05-22-2018, 04:38 PM   #12
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On my fridge there is a resistor that can be used to adjust the compressor speed. Slow speed minimizes the power draw. It is more efficient to run nearly continuously but this limits how fast you can cool your warm beer. I'd guess that is the 'jumper' that he called the speed regulator. In removing the resister you have set it to the slowest speed. Here is an excerpt from the manual.

All Nova Kool units are supplied with the silent and efficient BD series variable speed compressors from Danfoss. Nova Kool has supplied your unit preset at the optimum speed for most “normal” applications. The speed is controlled by a resistor in the thermostat circuit. 0 ohms (no resistor) runs the compressor on its slowest speed, a 1523 ohm resistor will provide you with the fastest speed. The slower the speed, the lower the amp draw, and the lower the capacity. The chart provides four examples; the resistance must be between 0 ohms and 1523ohms.
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Old 05-22-2018, 04:47 PM   #13
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That was it. Thanks for the clarification. The second paragraph is way over my head. Should have paid more attention to my college engineering courses.

I will send a picture of the component tomorrow.

If this works I do not know if Nova Kool will suggest a replacement or eliminate it. Will update with Round III tomorrow evening.
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Old 05-22-2018, 04:49 PM   #14
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I think the replace or eliminate will be totally up to you. If you are satisfied with how fast (or not) it cools off the warm stuff, then you can leave it out.
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Old 05-22-2018, 05:27 PM   #15
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Not sure I understand the technical benefits enough to make the call (actually I am sure I don't understand..).

The coach is stored in my driveway and I shut down the frig/freeze in between trips. Using it about once a month for a tailgate or longer trip. Two days before a trip I turn on the frig/freezer and get it down to temp. Loading food and life-sustaining beverages the night before leaving. Typically driving to a full hook-up destination - no boondocking or leaving the coach unplugged for more than 24 hours so aux batteries not a big concern.

Based on this application would you say I need it?
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Old 05-22-2018, 06:12 PM   #16
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I have a 1k potentiometer on my desk that will be installed on the fridge the next time I pull the refrigerator for any reason. That will allow me to boost the cooling a bit in our 100-degree Texas summers and dial it back a bit in cooler weather. It should help in keeping food in the safe range in century temperatures.
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Old 05-22-2018, 07:08 PM   #17
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If the food/beverages are cold when you put them in a fridge that is already cold, then you should be OK at the slowest compressor speed (no resistor). I think the slowest speed should keep things cold in all but the hottest ambient conditions. The real problem is if you add a lot of food/beverages to the fridge that are warm. If you do this it will take a long time to get that stuff cold. It would be good to know what size of resister you removed. There are color-coded stripes on it that tell you the size. Google 'resister color code' for the secret decoder ring that you need to determine size. The four sizes that mine has are 0, 277, 692, and 1523 ohms corresponding to compressor speeds of 2000, 2500, 3000, and 3500 rpm. If you removed the 1523 ohm you would see a big (unsatisfactory?) difference. You would not notice much if you only took out a 277 ohm (280 = red, grey, brown stripes, with the 4th stripe color not important in this application). Was the resistor bad or just loosely installed?
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Old 05-22-2018, 07:12 PM   #18
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PS
A VOM (volt ohm meter) will let you measure the resistance. I have a cheapie from Harbor Freight that I keep in Titus to help me diagnose problems on the road.

The 1k pot that Pahaska refers to is an adjustable resistor (0 to 1000 ohms) that lets him dial a speed. I have not seen a need for it, but I don't live in Texas either.
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Old 05-23-2018, 04:12 AM   #19
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Frig held steady all night at 36 degrees. Of course the coach is static in the driveway. This is a pic of the factory unit that I removed. Tried to read it with my tester but I think the short is giving me inconsistent readings - maybe something in the 500 range?
Will post again this evening after my next call with Nova Kool.
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Old 05-23-2018, 06:48 AM   #20
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The Lounge comes with no resistance on that pin. The Lounge has the smallest refrigerator and that runs the compressor at the slowest speed which is OK for the small box. It also minimizes current draw to allow the Lounge to overnight on the batteries.

The GT has a much larger refrigerator, thus the resistor in the circuit to make the compressor run faster.

You apparently have a defective resistor. That is not uncommon. Bypassing the resistor will make the compressor run at the slowest speed which may or may not cool well enough for high summer temperatures in your area. It almost surely would not run fast enough for our Texas summer in a GT. The lowest speed is just enough for my Lounge with improved insulation and venting.
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