Waeco Coolmatic compressor fridge re-gas?

Submitted: Sunday, Oct 06, 2019 at 20:46
ThreadID: 139160 Views:706 Replies:6 FollowUps:9
On recent trips across long stretches of corrugated dirt roads (e.g. Great Central Road), my caravan fridge (a Coolmatic 195 litre compressor type) has started to run almost continuosly, with a distinct low 'whooshing' sound (like small waves washing onto a flat shore), sometimes not turning off (i.e.cycling) for very long periods. Under these circumstances, the fridge seems to maintain its cooling ability, but obviously will consume more battery power, as it is running longer, rather than cycling on and off via its thermostat control. This issue seems to go away after we get back on smoother bitumen roads, and it is not evident when the fridge is used while the caravan is parked up after such trips.

The fridge is 10 years old now, but has had one re-gas (I believe) and a replacement thermostat several years ago. The unit is used for only a couple of months each year, and for irregular short periods while parked up at home to ensure the seals, etc, are maintained in reasonable condition.

The obvious assumption is that the cause of this condition is persistent vibration and bumping on the corrugated road surfaces, as it seems not to occur on good bitumen roads (the caravan suspension is a reasonably heavy duty Simplicity load-sharing type, with leaf springs). However, I wonder whether a re-gas might be advisable, if the 'rough travelling' causes the refrigerant to not behave as normal, perhaps because there is not enough of it?

Has anyone else observed the same condition with their compressor fridge, and if so what did you do about it?.
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Reply By: IvanTheTerrible - Sunday, Oct 06, 2019 at 21:02

Sunday, Oct 06, 2019 at 21:02
Most fridges dont have the ports to allow them to be re-gassed. I'd be checking the cooling fan to make sure it is running at full speed.
AnswerID: 628026

Follow Up By: Member - Helmick - Sunday, Oct 06, 2019 at 21:13

Sunday, Oct 06, 2019 at 21:13
Thanks Ivan, but I am not sure if there is a 'cooling fan' in my model, apart from a helper fan I installed in the outside vent to draw air up the condenser grid (?) at the back of the fridge.
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FollowupID: 902310

Reply By: HKB Electronics - Sunday, Oct 06, 2019 at 21:37

Sunday, Oct 06, 2019 at 21:37
If it is running normally in a park etc it is unlikely to be a gas issue, also if it had a leak it would soon loose all its gas.

There is very little refrigerant in a typical fridge so movement of the fridge with regards the refrigerant is unlikely to be an issue I would have thought also.

The thermostats tend to have a toggling action to give them a hysteresis affect, possibly the thermostate has worn and the vibration is causing it to switch on before it normally would?
HKB Electronics

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AnswerID: 628028

Follow Up By: Member - Helmick - Monday, Oct 07, 2019 at 12:20

Monday, Oct 07, 2019 at 12:20
Thanks HKB. As the thermostat has been replaced once already (although some 8 years ago), it would not be a surprise to me if indeed this is a cause of the current issue, somehow. Are thermostats in RV fridges sensitive to vibration and bumping over extended periods?
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FollowupID: 902319

Follow Up By: HKB Electronics - Monday, Oct 07, 2019 at 13:51

Monday, Oct 07, 2019 at 13:51
Most cheapish thermostats are a mechanical device, they have a small bellows filled with refrigerant, when the refrigerant in the thermostate cools the pressure in the bellows reduces and a spring in the thermostate closes a switch, the mechanism is setup so that it is over center meaning the pressuring has to be higher for the switch to open then it is for it to close so you get a hysteresis of a couple of degrees or so to prevent switching on and off to rapidly.

If the fridge has worked ok in the past under similar environmental conditions but playing up now it would seem something has changed, possibly the thermostate but then maybe be not. Try putting a thermometer in the freezer and see if it is running colder than it is set for when playing up, this would tend to imply the thermostate is the issue.
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FollowupID: 902322

Reply By: RMD - Sunday, Oct 06, 2019 at 22:28

Sunday, Oct 06, 2019 at 22:28
Helmick
As it is a sealed unit there are no seals to be preserved by running it purely for that reason. As HBK mentioned, if it lost gas, it is losing gas, and will have none soon after. Running normally later can't be possible if no gas. Maybe two fans wired in series so one supplies cool air below the condenser and one to remove it at the top of the condenser will assist. Wired in series, 12v computer fans are quiet and draw very little current.
The issue might be with the hotter ambient temp and the fridge is working to remain cool. The fans will help. I have fitted twin fans to a few, both compressor and 3 way and they then use less power and gas respectively.
Does your fridge cabinet have the sides and top insulated so there is no hot air transfer re absorbtion from condenser to sides and top. If hot air is there it is largely circulating the heat from within back through the walls and top. It makes fridges run long time. Driving in hotter temps means the airflow of hot getting to the sides and top is continually heating the fridge outer as the air is changing rapidly taking any cool away.
AnswerID: 628032

Follow Up By: Member - Helmick - Monday, Oct 07, 2019 at 12:33

Monday, Oct 07, 2019 at 12:33
Good points, well made, RMD. In fact, I have installed two small computer fans at the back of the fridge in the air vents, which can operate when the fridge is on. The lower one pulls air in through the lower vent behind the fridge, with the other one pushing (warm) air out through the top vent. I have a manual switch which allows me to choose when I want the fans to work, usually only in hot conditions. The latest episode on the GCR was in late May, and the ambient air temps during the day were in the low to mid 20's only, so I had not operated the fans - perhaps I should have.

I have insulated the side and rear walls of the fridge recess with 25 mm thick polystyrene sheeting, but there was insufficient clearance to do this on top of the fridge.
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Follow Up By: Member - David M (SA) - Monday, Oct 07, 2019 at 14:07

Monday, Oct 07, 2019 at 14:07
You might just have to put it down to Global Warming as the cause Helmick. :)
Dave.
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FollowupID: 902324

Follow Up By: RMD - Monday, Oct 07, 2019 at 16:13

Monday, Oct 07, 2019 at 16:13
Helmick
If you know it is only happening on rough roads, is it possible the catch on the door, presumably near the top, is allowing the door to flap open an little and shut again over rough roads. That will let the cool out and the compressor to run a lot more. Also the TX valve within the fridge gas stream, the thermostatic expansion valve, might then be passing the maximum compressor delivery and causing the whoosh sound. ie, similar to when the fridge is started at initial switch on and cool down.

Do you run lower tyre pressures while on rough roads?
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FollowupID: 902329

Follow Up By: Al-one - Monday, Oct 07, 2019 at 20:56

Monday, Oct 07, 2019 at 20:56
Helmick,
I just want to clarfy something. You said you have a Coolmatic fridge. The one that I saw had no external condenser cooled by a fan. This fridge'e condenser was in the side walls of the fridge. This means that the side walls of the fridge can't have extra insulation installed against them. The walls containing the condenser need to be cooled by air circulation. You said that you have insulated the side and rear walls with 25mm polystyrene sheeting. Did you maintain enough clearance between this sheeting and the fridge wall containing the condenser? If not this may be your problem.
Cheers,
Al-one
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FollowupID: 902334

Follow Up By: Member - Helmick - Monday, Oct 07, 2019 at 23:36

Monday, Oct 07, 2019 at 23:36
RMD: whenever we travel, be it on bitumen or dirt, we secure both the freezer door and main fridge door with stretchy nylon straps (basically, child-proof devices, available from that great big DIY store that starts with a "B"). The fridge's standard magnetic door seals are in good condition as well, so I cannot see there has been any movement or opening of the doors. And I do always reduce tyre pressures to 27-30 psi for extended travel on dirt roads.

By the way, my fridge's condenser is exposed across the whole back of the unit, not in the sides.

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FollowupID: 902338

Reply By: Tony F8 - Monday, Oct 07, 2019 at 17:43

Monday, Oct 07, 2019 at 17:43
This may sound silly, but check to see if there is a fuse, could be a blade fuse located on the 12 volt inlet to the fridge, my Engel did the same when corrosion built up on it
AnswerID: 628043

Reply By: swampy - Thursday, Oct 10, 2019 at 11:47

Thursday, Oct 10, 2019 at 11:47
hi
Many of the small fridges have a capillary line which is a tube of fixed orifice size . A T/x valve does the same but is variable orifice size.

Fridge charge by weight
evacuating charging has a lot of pitfalls . Lazy frigies often stuff this up suprisingly
thermostat working
evap and condenser clean
compressor and piping secure
Have a hard wired monitor with only sensor in fridge and head unit on dash --check .
AnswerID: 628100

Follow Up By: Member - Helmick - Thursday, Oct 10, 2019 at 19:50

Thursday, Oct 10, 2019 at 19:50
Hello Swampy. Obviously, you know a heck of a lot more about fridge mechanics than I do, so you might understand some of your 'shorthand' is a bit confusing to me. However, I can state that the thermostat works (but maybe not so well after days of rough corrugations); the evaporator and condenser are difficult to access, as the vent in the caravan wall at the lower back of the fridge allows only a very small area of the fridge to be touched - and even that requires a small arm and hand and a degree of contortion! I do try to blow out accumulated dust on the unit after dirt road trips, but the limited access means this is never going to be perfect. I can also state that the compressor and piping appear reasonably firm (i.e.very limited play), and I do use an Engel battery powered wireless remote sensor unit in the caravan to keep tabs on the inside fridge temp. This has been reasonably consistent in performance over 8 years of ownership, but of course is subject to ambient temps, the number of door openings, the loading in the fridge, the placement of the sender unit in the fridge, etc.
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FollowupID: 902387

Reply By: Dave B18 - Saturday, Oct 12, 2019 at 18:57

Saturday, Oct 12, 2019 at 18:57
What you describe is a common problem with that model. If my memory serves me correctly the condenser fails. Waeco Qld would be able to tell you if they have any competent staff left. They are irreparable and will need to be replaced. There is no direct fitment and Vitrifrigio DP150I is the closet you can get. Not to many of those Coolmatic 190L models are still going.
AnswerID: 628137

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