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Unusual Air Conditioner issue
We have something unusual happening with our just over 2 year old air conditioner - Dometic brisk air II. I have been working with JonS slowly as I have had time, but nothing is showing up as problem.  I have time to work on it again, so I am putting this out here in case someone else ran into this unusual situation.

The air conditioner is running fine, then the fan stops.  It is like a bike wheel slowly stopping spinning.
There is a low hum (very quiet).
This happens in the warmest part of the afternoon and I believe something is getting overheated and shutting off the fan, we just can't find what.

I believe the condenser is still running when this happens.  We usually have the temperature setting set close to the warmest setting (or it gets too cold).  So our condenser goes off and on over the day, even in our hot weather.  One of the times the fan quit running, the hum was significantly louder, so I think that was when the condenser was on - because about 10 minutes later I turned on just the fan and again it worked for a bit then came to a stop and the  hum was again pretty quiet.

The fan turns easily - both the blades by the evap coils and the "hamster wheel" looking blower wheel by the condenser coils.

It is not a freeze condition (e.g. putting a hand up to touch the evap coils shows they are room temperature - not even cool and not warm). 

Voltage into the rig and into the lower part of the unit is fine (just over 120V).  We have not yet used the voltmeter on components on top of the rig.

The capacitor shows no sign of wear/bloating - it looks pristine and all connections are tight.

At Jon's suggestion I took apart the electrical box that holds the wires for the fan switch and thermostat switch - again everything looks pristine with tight connections.

I used my thermal camera when the air conditioner was running, but from the roof side the only "hot spots" were the fan motor and an area where the fan motor wires running thru the housing are exposed (about a fist sized "cup" they are resting in). 

I used my thermal (Flir) camera at the inside of the air conditioner.  It showed hot where the thermostat and fan controls were, but I think that was a fluke (the Flir takes a bit to see what you are seeing and why) because when I opened the box up and ran the fan for about 45 minutes everything was room temperature to the touch - and the Flir was still showing "heat", so I think the Flir was just showing that compared to the other areas that were colder that box area was warmer.

I am hoping to connect with Dometic tech support tomorrow (long hold times are the norm now and they are back east and quit their day early).  But I thought I would post this in case someone happened to have the same issue.

Ok, any ideas?
Jane

P.S. for anyone looking to reproduce some of these tests, please respect electricity and don't stick your hands into an air conditioner unless you know all power is off (and I double check with a volt meter).  When I am doing a test where I need live electricity I turn off the electricity, then position the wires where they can easily be tested with the volt meter without touching other parts, then the electricity on for the test - turning it off afterwards to close up the appliance.
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Unusual Air Conditioner issue
Reply #1 –
Following... Thinking of replacing our our air conditioner soon and the Dometic Brisk Air II is on the list as a possible replacement.

Charles
Harvest Hosts + Boondockers Welcome #23975
Escapees SKP #138195
2007 23.5' Twin King
Re: Unusual Air Conditioner issue
Reply #2 –
Hi Charles: is your A/C unit not working?   RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Unusual Air Conditioner issue
Reply #3 –
Hi Ron. Nope, last week I ran the generator for it's monthly run and I always run the air conditioner to present a load to it. The air conditioner would not start. So far I have confirmed it has 12V and 120V at it's entry wiring harness. It does not display any fault codes. Gone through all the Atwood trouble shooting steps with no success in isolating the problem. Every 120V outlet has power. I won't go on the roof at my age so I will have the shop that installed it take a look as soon as they have an opening. It's an Atwood AC-1351, a big ugly unit. It was there when we bought the LD and I have not been impressed with it but it worked fine when it did run. It's only three years old. Am now researching what to replace it with.

Charles
Harvest Hosts + Boondockers Welcome #23975
Escapees SKP #138195
2007 23.5' Twin King
Re: Unusual Air Conditioner issue
Reply #4 –
"The air conditioner is running fine, then the fan stops.  It is like a bike wheel slowly stopping spinning. There is a low hum (very quiet).  This happens in the warmest part of the afternoon and I believe something is getting overheated and shutting off the fan, we just can't find what."

PSC (permanent split capacitor) motors are the type of motor in our AC units.  PSC motors are thermally protected internally.  Many, if not most light duty PSC motors are 'air over' motors, which means they rely on air over the motor windings to keep them cool. They have vent holes in the end bells of the motor to allow free flow of air through them.  If the vents become plugged due to dirt, or some other object coming loose and blocking air flow, or high inlet air temperature, this could cause the motor to overheat and trip on its thermal protection.  Once the overload cools, it will reset, and try again... 

Bill
Bill
2003 -- 23' FL
Re: Unusual Air Conditioner issue
Reply #5 –
Bill, thanks lots.  That makes sense.  We will go look for those vent holes.
Jane
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Unusual Air Conditioner issue
Reply #6 –
Charles, 3 years is way too short! - IMO.  But if you are paying someone else to debug, a handful of hours of debugging can equal the cost of a new air conditioner installed.  Our original one - a Dometic, lasted almost 30 years before it gave out (would not turn off, we had to turn it off with the breaker).  I don't know how heavily it was used, but I am sure it was used some.

I was not impressed when we researched things. I liked the Atwood but dometic now sells it and I could get very little info.
This couple used a Furrion air conditioner and liked it above the other typical ones used.  I have not heard of that one but it sounds very different in many ways (good ways).  Note:  The sound... our new Brisk Air Dometic (just over 2 years old) has a very very quiet condenser - It took me weeks to figure out how to tell when it goes on/off, I pay attention to a slight vibration sound rather than the whomp you usually hear from an air conditioner condenser going on.

See this video - there are links in the text below that will take you right to the air conditioner review = starting at about 25 minutes in  furion air conditioner review

Here is their full video of installing the Furrion.

Here is the Furrion web page.

If you get one of these I want to hear how it works for you.
Jane
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Unusual Air Conditioner issue
Reply #7 –
Jane, yes three years is not acceptable. I'm not going to pay for hours of debugging. The business I am taking it to is local and owned by a man and wife. I've met both and negotiated with and bought our LD from the husband. They are RV owners. They own four businesses; a new and used RV sales operation, an RV rental business, an RV storage facility, and the RV service and repair facility. I've met and spoken with the manager of the repair and service facility; he has considerable experience.

I will probably just replace the Atwood, who needs a three year lifespan appliance. I've seen a few reviews of the Furrion and will continue the research and seek advice and recommendations.

Charles









Harvest Hosts + Boondockers Welcome #23975
Escapees SKP #138195
2007 23.5' Twin King
Re: Unusual Air Conditioner issue
Reply #8 –
Hi Charles:  I'm sure this Atwood A/C is not a 'three year' appliance. When you say "it has 12V and 120V at it's entry wiring harness"  I'm not sure what that means?  There is no 12 vdc at the wire harness. It has it's own built in 12v. supply.  The circuit breaker in your power distribution panel is only for the A/C. The fact that you have 120V AC at other outlets only means that the LD is plugged in.  This is a standard 13,500 btuh model. (edited because I got the wrong A/C in my first post.
    The fact that nothing lights up (most A/C's don't have a built in control panel), I'd suspect that the circuit breaker has tripped. A tripped handle, in your power distribution center, half way between on and off, isn't always easy to spot. The handle has to be turned off all the way, then turned back on to reset it.  The .pdf manual I looked at says that the internal connector to the control panel at the roof (inside grille) can become disconnected. This would give you the same symptoms.
 Vibration, and/or (originally) not quite properly connected, it can work loose over time. I'd check there first for the presence of power.  The manual also mentioned a 3 minute wait before start up of the compressor. This built in wait is to let compressed freon dissipate from inside the compressor, before it tries to restart the compressor.   The Manual, odd there aren't page numbers, but figure 13 shows that control panel plug. https://www.gulfstreamcoach.com/media/uploads/1/11450_Atwood-Roof-Air-Conditioner-AC1351-and-AC1501-Manual.pdf         Fixed this link, thanks Charles.
   You, or your RV repair person should check that, and the main circuit breaker first.    RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Unusual Air Conditioner issue
Reply #9 –
Hey Ron. Thanks for your response. However, this unit is not the one you are talking about. Please give me some credit here, the very first thing I checked was the dedicated circuit breaker. When it is on there is 120V at the unit's coach to unit connection; when the breaker if off there in no voltage. It's very simple, everything I can check has power but the unit does not start.

If the failure cause is not found and corrected within 15 minutes I will have the unit replaced. I have zero tolerance for sub-par hardware. This unit has been on my list to replace since the day we took possession, it performed OK but I knew it was not what I wanted.

Charles

Harvest Hosts + Boondockers Welcome #23975
Escapees SKP #138195
2007 23.5' Twin King
Re: Unusual Air Conditioner issue
Reply #10 –
Hi Charles. Sorry I got the wrong model, I was just a zero off. I went back and fixed it.   If you bought it from your fix-it person, maybe he put this unit in?  I don't think Lazy Daze used this unit.  Depending on where you camp, you might want to upgrade to a 15,000 Btuh unit.  I'm having a start/run capacitor issue right now on mine. (but its 21 years old)
     Let me know what was wrong if you find out. Just the technician curiousity in me.    RonB
RonB (Bostick) living in San Diego
Original owner of "Bluebelle" a '99 TKB
Re: Unusual Air Conditioner issue
Reply #11 –
Hi Ron. Again, thanks for your support. Yes, this A/C unit is not the unit installed by LD and was installed by the company I bought the LD from. I was told the original A/C did not work. The estate of the original owner consigned it to this business. When I replace this unit I will go to a 15,000 BTUH unit since we do travel to high-temp regions.

Sure, I'll let you know what we find out is wrong.

Charles

Harvest Hosts + Boondockers Welcome #23975
Escapees SKP #138195
2007 23.5' Twin King
Re: Unusual Air Conditioner issue
Reply #12 –
When my original a/c gave out last year,  I knew that I wanted a larger unit as the 12.5k original unit was no where close to cooling the coach.  I was planning on putting a 15k Dometic briskaire unit in because I could use the same interior panel.  But both my mobile RV mechanic and the independent RV shop that I use recommended a Coleman unit.  They both said the units were fairly equal but the customer service at dometic was terrible.  Pricing was about the same.
Re: Unusual Air Conditioner issue
Reply #13 –
FYI - parts are hard to get right now - if it is a Dometic (and other brand) parts it could take months (dealers and distributors are out).  I am guessing because of supply line and possible manufacturing issue caused by the pandemic.

Update:  We checked out the vent holes of the motor And they seemed fine - can’t get to them to blow them out real well until we get one of those tiny straws to direct air and bend it into the narrow space.

We went ahead and swapped in the new capacitor just in case (the old one looked pristine as did all it’s electrical connections).
We had not done the “push the fans with a stick - while not losing fingers etc test” because both dans turned so easily.  Also this test usually catches when your start capacitor has failed but your run capacitor is working - so it “starts” the fan and the run capacitor keeps it going.  We have a dual capacitor (one capacitor does starts and runs).

But we decided to do the stick test anyway.  The fan ran for 2-3 seconds than stopped, like the motor stuck on something or got resistance and couldn’t turn.   We knew the fans spun freely, so we have ordered a motor (maybe the last one in the U.S.).  Not from a company I know or trust but the only one around and yup I looked hard for replacement units and found none that worked with our air conditioner (Brisk air II).

It will take a week or two to get here before we can test if it is the fan.

Jane

Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
 
Re: Unusual Air Conditioner issue
Reply #14 –
Paul, I was interested in the Coleman, but none of our local service guys knew that unit or how to work on it and said they got better support from Dometic.  (Yes a surprise and a disappointment but it is what it is).  We knew we would be here in Phoenix for a few years. 

We did decide to get a taller model (not the lower one) because it is easier to work on and we figured the person who would buy our older rig from us would be more likely to do the work themselves.

I also was interested in the Atwood as it has a small but strong following.
Charles I would be interested in hearing what you didn’t like about it.

Jane
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Unusual Air Conditioner issue
Reply #15 –
Quote from: Jane and Scott  - 
I also was interested in the Atwood as it has a small but strong following.
Charles I would be interested in hearing what you didn’t like about it.

Jane
Jane, I'd be glad to comment on the Atwood Air Command AC-1351 non-ducted unit on our LD.

First, after a little more than three years of ownership with minimal use it now doesn't function.

Second, although it is compact at ~27" wide and ~39" long it is 13" high. It looks out of place on the LD and is aesthetically ugly, IMO.

Third, it has a flip-down control panel that I must avoid when lowered and is difficult to use. The panel is also awkward to deploy from it's retracted position. The unit has a remote control that is small, easily lost, and has a short battery life.

This unit was designed, I assume manufactured, and sold by Atwood Mobile Products LLC based in Elkhart, Indiana. The Atwood AC brand has been acquired by the Dometic Group, which is an international business. I suspect the Atwood unit we have has little in common with the "Atwood" AC products now made and sold by Dometic.

Right now I am interested in the newer Coleman-Mach low-profile units made by Airxcel, which are built in their factory in Wichita, Kansas. But it seems inventory is slim, if any. Dometic also seems to be having the same issue. In addition to Coleman AC the Airxcel RV Group consists of Dicor, Suburban, MCD Shades, Maxxair, and Aqua-Hot. As an aside, Dometic Corp has not responded to my request for Country of Origin details for all Dometic Corp AC brands/units.

Charles


Harvest Hosts + Boondockers Welcome #23975
Escapees SKP #138195
2007 23.5' Twin King
Re: Unusual Air Conditioner issue
Reply #16 –
Ok, I think we got the air conditioner going again.
It was the fan motor.  Interestingly, the symptoms didn't clearly the fan was the problem, the symptoms pointed much more to a capacitor or overheating problem.  So while we did our fan spin test, it was not so bad that this popped out as an issue.  

You can see in this video, at the 2 minutes mark, a fan that does not spin freely. 
And you can see at the 10:30 mark that is spins freely.
We didn't spin ours as hard as this guy did, but ours spun about 1/2 as long as the video at spot 10:30.
Way more than his initial non-spinning fan.
RV air conditioner repair video
Note also the dirk caked on the motor (brown cylinder between the squirrel cage and the fan blades), it should be black (not brown).  You can also see the dirt on the fan blade and the squirrel cage.  Our old motor had about a 1" strip of brown at one end and the squirrel cage and fan blades were maybe 25% as dirty as the ones in this video.  Yes we cleaned off the fan and the squirrel cage and both got a nice dirt bath for our efforts. :D

Here is another video, this again shows a very long spin at the 12:05 mark, to me this one looks like it spins longer than the first video.
Another rv air conditioning repair video

Our new fan does have a significantly longer spin.  The air conditioner has been running for about 18 hours now with no troubles, including thru the heat of the afternoon.

I am disappointed (as is Charles) that these air conditioners don't last that long.  The guy in the second link above talked about working on a lot of Dometic air conditioners in Phoenix that failed early.  Now in our hot summers,  most people (including us) are likely run their air conditioner fan 24/7 for 4-5 months of the year (depending how hot it is in May & Sept).  But I sure would expect a fan motor to last more than 2 years and a couple weeks (when ours failed) - I would expect 4 years in heavy use like we use it and much longer for people who don't use theirs nearly that much.

The nice thing is the newer models have much quieter condensers - we have to really listen to ours, it is sounds equivalent to dropping a smart phone onto a bed from 6" higher than the bed and 6' away.  I hear the vibrations more than the actual sound. 

I would be interested if anyone else has run their fairly new air conditioner at that heavier usage and how long it lasted till it needed a new motor.
Jane
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Unusual Air Conditioner issue
Reply #17 –
Jane, if they would put oil ports on either end of the fan motor they would last longer but not everyone would oil them anyhow.
Glad you found your problem, motor cycling on it's motor overload. Now you have an excuse to buy an amp probe...

Jon
1994 MB
Re: Unusual Air Conditioner issue
Reply #18 –
Jon, Scott also thought there was some wobble in the shafts - Seen when we did the stick push test.
As if the bearings were going out and when it got torqued it might have been wobbling the shafts which shut it down.  The new one doesn’t have that wobble.

Ok since I am tool freak but I limit myself to ones I really “need”, how would you use an amp probe in this situation?  I worked with someone who used a flick clamp meter (same kind of tool?) but he used it for testing electrical lines in a sticks  and bricks structure (to see if the line was live or not) and over time I didn’t see much need for it since most times an end of the wire was available to test.

Also, neither Scott nor I were sure what you meant by  “motor cycling on it's motor overload”.  The concept seems right I just can’t figure out the specifics.
The motor went from shutting down for a couple hours when we were over 110 degrees, to shitting off when we were just over 100 (for about 5 hours till we cooled down) to shutting off after 3 hours in the middle of the night (around 85).  So it was degrading over a week or two (being shut off most of the time).

Jane
 
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.
Re: Unusual Air Conditioner issue
Reply #19 –
Quote from: Jane and Scott  - 

Ok since I am tool freak but I limit myself to ones I really “need”, how would you use an amp probe in this situation? I worked with someone who used a flick clamp meter (same kind of tool?) but he used it for testing electrical lines in a sticks  and bricks structure (to see if the line was live or not) and over time I didn’t see much need for it since most times an end of the wire was available to test.

The answer here is that the clamp probe will measure AC current (not voltage). So, IF you measure current in a line, then the circuit is "live" (ie, don't touch the bare wires!). How would this be used to diagnose a bad motor? You can think of it this way: the harder the motor works, the more current it pulls. If you measured the current of a running motor at, say, 1 amp, then tightened a clamp around the motor shaft (like putting on the brakes of a car), you would see the current rise above the 1 amp. Now you know something is "wrong" with the motor. The clamp meter is just a device to help quickly isolate a problem like a motor going bad (in this case).

Also, neither Scott nor I were sure what you meant by  “motor cycling on it's motor overload”.  The concept seems right I just can’t figure out the specifics.

All AC motors used in air conditioning (that I'm aware of, and I think all AC motors generally) have a thermal overload "switch". You can think of this similar to a thermostat for the furnace. When the room is cold, the contacts on the thermostat close and the furnace comes on. When the room reaches the set temperature, the contacts open and the furnace turns off. In a similar way, the AC motor is considered "cold" until it reaches the temperature that would cause damage to the motor if it kept running, so the overload switch opens and the motor turns off. Actually, it disconnects the motor windings, so no current can flow through the motor. Depending on the motor, most overload switches will reset when the motor cools. So, the motor can/will turn back on. Obviously, this is not the way the motor is designed to normally operate. The thermal switch is a safety device. If it were not there, the motor could overheat and possibly start a fire.
 

Ken
Former 2009 MB owner
Re: Unusual Air Conditioner issue
Reply #20 –
Jane, exactly what Ken said and one more thing, most motors have an attached tag which will  give voltage, RPM, direction and full load amps. When a normal motor is running with the two fan blades attached it will pull something less than Full load amps. As the bearings begin to seize, this FLA will go up to the point of overheat of the winding and the internal overload will open.
An amprobe is a very handy tool, I wont leave home with out mine. Many different MFG's all do the same thing.

Jon
1994 MB
Re: Unusual Air Conditioner issue
Reply #21 –
Ken thanks.
Jon, you answered my question after reading Ken's reply (what the amps should be in a good working motor).

I will put this on my tool wish list.
Jane
Jane & Scott
Currently have a 1989 TK  LD we did a lot of upgrades on.
Bigfoot 25RQ Twin on order with early summer 2024 ETA

Our smartphone autocorrects into very poor English.
 We disclaim the illusion of ignorance this creates as we have enough ignorance we rightly claim.