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Old 19-06-2018, 06:42   #1
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Question Fridge working intermittently (Dometic VD-15)

Hi,
We installed a new cooling unit, a Dometic/Waeco VD-15 to replace the old VD-15.

The problem now is that the cooling is working intermittently. Sometimes it's cooling OK, sometimes a bit and sometimes not at all.
It doesn't matter if we are under engine, on shore power or just on the batteries.

The compressor is connected directly to one of the house batteries and the batteries are good.

The guys that installed the cooling unit (to be honest, a bunch of cowboys, but the only fridge guys around in Leros, Greece), stated that there is nothing wrong with the compressor (but is 15 yrs old) so that it must be the thermostat in the VD-15.
The tech guys at Dometic stated that it's a possibility, but unlikely because it's an intermittent problem.

So Im kinda stuck and not on the boat right now to troubleshoot further.

I'm thinking to ask the Marina electrician to check the wiring to see if that's OK. maybe a small break or oxidation? If I look at Dometic/Waecom compressors compatible with the VD-15 they all state a rated input power of 45 Watt.
What else should I tell the electrician?

However, if that's ok I need someone to check the compressor itself. Problem is that I forgot to look in the docs what compressor it is . I know it's compatible with the VD-15 because we had one before.

Long story, but my question is: How can I perform a diagnosis on the compressor? what to look for and how to look for it?

I know, pretty vague story, but I'm hoping that the sailing hive mind can give me some clues..
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Old 19-06-2018, 08:19   #2
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Re: Fridge working intermittently (Dometic VD-15)

Quote:
Originally Posted by De.windhoos View Post
Hi,
We installed a new cooling unit, a Dometic/Waeco VD-15 to replace the old VD-15.

The problem now is that the cooling is working intermittently. Sometimes it's cooling OK, sometimes a bit and sometimes not at all.
It doesn't matter if we are under engine, on shore power or just on the batteries.

The compressor is connected directly to one of the house batteries and the batteries are good.

The guys that installed the cooling unit (to be honest, a bunch of cowboys, but the only fridge guys around in Leros, Greece), stated that there is nothing wrong with the compressor (but is 15 yrs old) so that it must be the thermostat in the VD-15.

The tech guys at Dometic stated that it's a possibility, but unlikely because it's an intermittent problem.

So Im kinda stuck and not on the boat right now to troubleshoot further.

I'm thinking to ask the Marina electrician to check the wiring to see if that's OK. maybe a small break or oxidation? If I look at Dometic/Waecom compressors compatible with the VD-15 they all state a rated input power of 45 Watt.
What else should I tell the electrician?

However, if that's ok I need someone to check the compressor itself. Problem is that I forgot to look in the docs what compressor it is . I know it's compatible with the VD-15 because we had one before.

Long story, but my question is: How can I perform a diagnosis on the compressor? what to look for and how to look for it?

I know, pretty vague story, but I'm hoping that the sailing hive mind can give me some clues..
It is very unlikely that the problem is compressor.
1. Why was the evaporator VD15 replaced?
2. Is the compressor running when the cooling Stops?
3. When compressor is running is the VD15 fan still running?
4. If your WAECO condensing unit has fan is it running when compressor has stopped running?
5. When you look through the VD15 fan do you see frost on evaporator coil?

Intermittent cooling after an an evaporator change could be a refrigerant problem but it is more likely an electrical problem. Answers to the above questions should help determine where to look.
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Old 19-06-2018, 09:56   #3
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Re: Fridge working intermittently (Dometic VD-15)

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Originally Posted by Richard Kollmann View Post
It is very unlikely that the problem is compressor.
1. Why was the evaporator VD15 replaced?
2. Is the compressor running when the cooling Stops?
3. When compressor is running is the VD15 fan still running?
4. If your WAECO condensing unit has fan is it running when compressor has stopped running?
5. When you look through the VD15 fan do you see frost on evaporator coil?

Intermittent cooling after an an evaporator change could be a refrigerant problem but it is more likely an electrical problem. Answers to the above questions should help determine where to look.
  1. Because on the old one the fan kept running, the dial knob was broken, and it was almost impossible to set the temp and the casing was cracked in several places.
  2. It's very difficult to determine because the compressor is build under the bed in the aft cabin and you can't hear it.
  3. See 2
  4. See 2
  5. Didn't check

However these questions give me a good indication what I need to do to troubleshoot if it's not the electricity and when I'm back on board.
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Old 19-06-2018, 11:39   #4
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Re: Fridge working intermittently (Dometic VD-15)

The Questions asked were to eliminate the expense of guessing what is causing the performance problem.

First it is important to know if the person who changed evaporator correctly. Was the test pressure removed and complete system evacuated sufficiently before installing pure R134a the recommended refrigerant.

Someone with basis electrical experience need to see if thermostat and wiring to both fans is correct.
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Old 19-06-2018, 12:03   #5
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Re: Fridge working intermittently (Dometic VD-15)

Quote:
Originally Posted by Richard Kollmann View Post
The Questions asked were to eliminate the expense of guessing what is causing the performance problem.

First it is important to know if the person who changed evaporator correctly. Was the test pressure removed and complete system evacuated sufficiently before installing pure R134a the recommended refrigerant.

Someone with basis electrical experience need to see if thermostat and wiring to both fans is correct.
This really helps, itís extremely frustrating to try to troubleshoot something that is essentially black magic to me AND from a loong distance

I did check the wiring from the evaporator to the compressor based on the wiring diagram included with the VD-15 and that was correct.
I know that they also filled the system with gas, I do not know if they removed the old gas.
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Old 19-06-2018, 14:11   #6
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Re: Fridge working intermittently (Dometic VD-15)

There are two simple tests you can make one is to test and eliminate thermostat's control over refrigerator cooling. Locate the Danfoss Control module attached to compressor. Near the bottom of this module there are two wires connected to terminals C and T. If wires on C and T are Disconnected and replaced with a jumper wire across C and T compressor and both fans will run all the time. After an hour and again after 4 hours describe box cooling and if fans keep running.

Some boats have an amp meter and see if when cooling conditions change there is a difference in current draw.

I usually find a solution to these problems by asking questions that require only a visual look see. I do not think we are going to get anywhere playing 20 questions. The worst case is always when someone tampers with refrigerant like changing an evaporator knowing that only one in 20 technicians will get it done right.

You are lucky you have a simple system for any one that can operate a boat can understand except maybe when there is a refrigerant problem. There are refrigeration system sold today that are not repairable by anyone but the people that build them. I do not know how this unit is going to be repaired but access under the bed is required.
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Old 22-06-2018, 00:03   #7
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Re: Fridge working intermittently (Dometic VD-15)

Quote:
Originally Posted by Richard Kollmann View Post
There are two simple tests you can make one is to test and eliminate thermostat's control over refrigerator cooling. Locate the Danfoss Control module attached to compressor. Near the bottom of this module there are two wires connected to terminals C and T. If wires on C and T are Disconnected and replaced with a jumper wire across C and T compressor and both fans will run all the time. After an hour and again after 4 hours describe box cooling and if fans keep running.

Some boats have an amp meter and see if when cooling conditions change there is a difference in current draw.

I usually find a solution to these problems by asking questions that require only a visual look see. I do not think we are going to get anywhere playing 20 questions. The worst case is always when someone tampers with refrigerant like changing an evaporator knowing that only one in 20 technicians will get it done right.

You are lucky you have a simple system for any one that can operate a boat can understand except maybe when there is a refrigerant problem. There are refrigeration system sold today that are not repairable by anyone but the people that build them. I do not know how this unit is going to be repaired but access under the bed is required.
Hi Richard,
Iíve asked the marina electrician to check the wiring. If thatís still good Iíve decided to fly to the boat (found some cheap tickets ) and use your questionlist and tips to troubleshoot. So you might expect some more questions in the next week or so

Again, thank you for your input.
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Old 22-06-2018, 01:28   #8
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Re: Fridge working intermittently (Dometic VD-15)

Quote:
Originally Posted by De.windhoos View Post
  1. [*]Because on the old one the fan kept running, the dial knob was broken, and it was almost impossible to set the temp and the casing was cracked in several places.
  2. It's very difficult to determine because the compressor is build under the bed in the aft cabin and you can't hear it.
  3. See 2
  4. See 2
  5. Didn't check

However these questions give me a good indication what I need to do to troubleshoot if it's not the electricity and when I'm back on board.
You may find it best to have the VD15's fan running continuously. That would help prevent its evaporator fins from frosting over and restricting / preventing cooling. Having this fan only cycle on with the thermostat is a possible cause of your intermittent cooling.

If when you run the fridge after it has been off (and warm) and it works ok for several hours, then that would confirm that the fan needs to run 24/7

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 22-06-2018, 05:37   #9
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Re: Fridge working intermittently (Dometic VD-15)

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Originally Posted by OzePete View Post
You may find it best to have the VD15's fan running continuously. That would help prevent its evaporator fins from frosting over and restricting / preventing cooling. Having this fan only cycle on with the thermostat is a possible cause of your intermittent cooling.

If when you run the fridge after it has been off (and warm) and it works ok for several hours, then that would confirm that the fan needs to run 24/7

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
Pete? what information do you have that indicates that evaporator frost is a problem on this installation. It is more important to find out if both fans and compressor are running before modifying the design.

It is true the VD15 and VD16 convection evaporators are not self defrosting. I would think it is best to confirm first what the actual problem is before modifying what may be an energy efficient installation.
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Old 22-06-2018, 06:34   #10
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Re: Fridge working intermittently (Dometic VD-15)

OP stated it was 15 yrs old, assumption is that it has been running for 15 years OK until it developed an issue requiring the evaporator to be changed.
Assuming it was the same as the original evaporator, I wouldnít change the design.
However I see what I think Peteís point is, if itís icing up, then no airflow of course, and that could be the problem, but it ought to be very easy to check for an icing evaporator, both by checking airflow and by just looking at the evaporator.
If itís icing up, wouldnít the first step be to verify refrigerant level?
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Old 22-06-2018, 07:03   #11
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Re: Fridge working intermittently (Dometic VD-15)

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Originally Posted by a64pilot View Post
OP stated it was 15 yrs old, assumption is that it has been running for 15 years OK until it developed an issue requiring the evaporator to be changed.
Assuming it was the same as the original evaporator, I wouldnít change the design.
However I see what I think Peteís point is, if itís icing up, then no airflow of course, and that could be the problem, but it ought to be very easy to check for an icing evaporator, both by checking airflow and by just looking at the evaporator.
If itís icing up, wouldnít the first step be to verify refrigerant level?
a64pilot, My point is always to take a non destructive professional trouble shooting approach, False direction guessing is not helpful in most cases.
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Old 22-06-2018, 07:06   #12
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Re: Fridge working intermittently (Dometic VD-15)

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Originally Posted by a64pilot View Post
OP stated it was 15 yrs old, assumption is that it has been running for 15 years OK until it developed an issue requiring the evaporator to be changed.
Assuming it was the same as the original evaporator, I wouldnít change the design.
However I see what I think Peteís point is, if itís icing up, then no airflow of course, and that could be the problem, but it ought to be very easy to check for an icing evaporator, both by checking airflow and by just looking at the evaporator.
If itís icing up, wouldnít the first step be to verify refrigerant level?
I think some here missed where the user said previously the fan was running continuously with the old FDC (VD15) but is now cycling on and off!
Refrigeration systems using forced draft cooling without any auxiliary defrost method, rely on air movement across the cooling fins during the compressor off cycle to defrost the coil. It is called 'Cyclic defrost' . If the FDC is not relieved of frost during off cycles the frost builds up until the air flow is restricted or blocked.

The description the user gave indicates to me that this is a possible cause of his problem, besides it will work far better if the fan runs continuously.
There are many other possibilities also including as others here indicate, including poor practices when the FDC was changed.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
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Old 22-06-2018, 07:23   #13
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Re: Fridge working intermittently (Dometic VD-15)

Quote:
Originally Posted by OzePete View Post
I think some here missed where the user said previously the fan was running continuously with the old FDC (VD15) but is now cycling on and off!
Refrigeration systems using forced draft cooling without any auxiliary defrost method, rely on air movement across the cooling fins during the compressor off cycle to defrost the coil. It is called 'Cyclic defrost' . If the FDC is not relieved of frost during off cycles the frost builds up until the air flow is restricted or blocked.

The description the user gave indicates to me that this is a possible cause of his problem, besides it will work far better if the fan runs continuously.
There are many other possibilities also including as others here indicate, including poor practices when the FDC was changed.

Cheers OzePete Ozefridge | 12 Volt Refrigeration Systems
Nothing missing the original plastic cover was damaged and thermostat,was defective. Many owners of these fan convection units in non freezer boxes are pleased with there performance.
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Old 22-06-2018, 07:30   #14
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Re: Fridge working intermittently (Dometic VD-15)

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Nothing missing the original plastic cover was damaged and thermostat,was defective. Many owners of these fan convection units in non freezer boxes are pleased with there performance.
I think you missed it! Check post 3! OP's QUOTE: "on the old one the fan kept running",

Aren't the fans on these things supposed to run continuously? If not what prevents them icing up?

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Old 22-06-2018, 07:33   #15
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Fridge working intermittently (Dometic VD-15)

I did miss him sayin that the old ran continuously,
However reading it again, Iím not sure he meant evaporator fan or condenser?
I guess he will tell us
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