OLD FRIDGE- Now not cooling.

[Stanski]

Need to confirm my understanding of working please folks.
3 way, 24 Yr old, 40L capacity with freezer compartment.
OPERATION- my understanding
Refrigerant is a liquid, stored in a reservoir that feeds a heating pipe.
This liquid gets heated by gas burner, or heating element, so becomes a gas that will rise to the freezer matrix.
As it passes through matrix the gas absorbs heat in fridge, then moves on to a cooling condenser (pipe with fins along it), so then gas cools and returns to liquid, falling back into the reservoir at bottom of system.

QUESTIONS
Outside temp is typically 18degrees in daytime.

1. How hot should the lower heating pipe/burner be?
My burner was replaced 3 yrs ago, ( by me) removed and seen to work fine, settings on all 3 different levels of gas change.
2.The cooling condenser with fins I would expect to be warm. (No warmth in it).
3. How critical is the positioning of the heater spiral in the heater/ burner transfer?
4. Have been parked at odd angles over past week, but have found fridge worked adequately before when in similar conditions.
5. If I get a fan, I would place it to cool the Condensor pipe with fins. Do you agree?
6. Have parked with cool breeze blowing into fridge, should bottom vent be covered so heater works more effectively?

Over to you clever lot to advise.

Cheers.

 

[n brown]

most important question is - does it work on any of the heat sources ?

 

[BigAldo]

Absorption fridges rely on a flow of cool air, so the bottom vent needs to be open. It works by convection, so as the back of the fridge warms up, it heats the air around it, The warm air rises and goes out the top vent, which in turn draws cool air in the bottom vent. A small fan can assist the flow of cooling air.

First check, as already suggested, is to establish if cooling is achieved using 12volts or 240 volts. If neither of these work, (The flue pipe should still get warm) then it's likely the coolant circulation which is the problem. My understanding is that a bubble can form in the wrong place in the system which then prevents the coolant from circulating (a bit like an air lock in a heating system) In this case the usual solution is to take the fridge out and leave it upside down overnight. Then reinstall it and leave it to settle for a few hours before switching it on.

The spiral in the flue pipe is designed to slow down the rise of hot gas from the pilot light, ensuring maximum heat transfer to the cooling system. The position of the spiral is not critical, but should reach from the top, to almost the bottom of the flue pipe for best effect.
Hope this helps.
Aldo

 

[Stanski]

most important question is - does it work on any of the heat sources ?

Yes, just not as strong when on gas at the moment.
Found that levelling has improved situation, but still not cooling/freezing as it was when in UK.

I shall now admit, DC when engine running has recently (2 month ago) failed, found charging V is at controller, have not yet gone further with investigation, waiting for this journey to do it.
As this is electrical, can resolve, feel the vehicle charge controller that manages fridge has a relay with contacts possibly burnt, or a loss of earth.

Oddity with symptoms was a false illumination of Fridge ON led indicator when switched on, with no engine running. Did look at panel controls, and proved wiring was intact. Time did not allow more investigation.
Need Circuit diagram of charge controller to make life easy.

Will seek opportunity to prove AC when it appears.

 

[Stanski]

Absorption fridges rely on a flow of cool air, so the bottom vent needs to be open. It works by convection, so as the back of the fridge warms up, it heats the air around it, The warm air rises and goes out the top vent, which in turn draws cool air in the bottom vent. A small fan can assist the flow of cooling air.

First check, as already suggested, is to establish if cooling is achieved using 12volts or 240 volts. If neither of these work, (The flue pipe should still get warm) then it's likely the coolant circulation which is the problem. My understanding is that a bubble can form in the wrong place in the system which then prevents the coolant from circulating (a bit like an air lock in a heating system) In this case the usual solution is to take the fridge out and leave it upside down overnight. Then reinstall it and leave it to settle for a few hours before switching it on.

The spiral in the flue pipe is designed to slow down the rise of hot gas from the pilot light, ensuring maximum heat transfer to the cooling system. The position of the spiral is not critical, but should reach from the top, to almost the bottom of the flue pipe for best effect.
Hope this helps.
Aldo

Many thanks BigAldo for this info. Very informative, Confirms my understanding.
Had not heard of the 'bubble lock' before.
Main pipe from heater is warm at top of heater flue, can touch with hand comfortably, I was expecting it to be very hot, near burning to touch.
How hot should it be?
The pipe then bends and rises to the left, it joins/ attached to top of the cooling condensing matrix (pipe with fins).
This is cool, which in my mind is OK, as the coolant gas is lowered in temp by the condensing matrix.
Do you agree with this?

Am considering removing the fridge for inspection, just not immediately.

 

[n brown]

generally ,these fridges work best on gas ,not as well on 240v ,and even less on 12v . but the fact that it's cooling on 240v shows that the fridge is working and points to the gas side being at fault .
you probably know all this , but the flame must be clean and blue
the fridge must be no more than 3 or 4 degrees out of plumb
the flue must be clean and unobstructed
if all these are ok then it's time for the upside down treatment !

 

[Stanski]

..... then it's time for the upside down treatment !

Bugger - if its the way forward then so be it.
Bloody started raining here in ARTA, Majorca.
Bugger x2.
Have to cuddle up to keep warm - Bugger x3.

ARTA Caves were really truelly excellent.

 

[BigAldo]

Many thanks BigAldo for this info. Very informative, Confirms my understanding.
Had not heard of the 'bubble lock' before.
Main pipe from heater is warm at top of heater flue, can touch with hand comfortably, I was expecting it to be very hot, near burning to touch.
How hot should it be?
The pipe then bends and rises to the left, it joins/ attached to top of the cooling condensing matrix (pipe with fins).
This is cool, which in my mind is OK, as the coolant gas is lowered in temp by the condensing matrix.
Do you agree with this?

Am considering removing the fridge for inspection, just not immediately.

The heat exchanger, immediately above the pilot light, is designed to pass as much heat as possible to the cooling system. This creates the circulation of the coolant within the system. The flue above the heat exchanger should get quite hot, so if its cool enough to touch there may be a problem with the flame or the flue may be partially blocked. You asked about the spiral...?
Ideally you need to work through each of the system components individually:
1 Is the burner producing enough effective heat. (good flame, clear heat exchanger and flue)
2 Is the heat exchanger sufficiently insulated to enable good heat transfer to the cooling system.
3 Is the fridge sufficiently level to allow coolant to circulate.
If all of the above are ok, then either there is a bubble in the coolant, or a possible loss of coolant (which for old absorption fridges is game over...))

 

[Stanski]

The heat exchanger, immediately above the pilot light, is designed to pass as much heat as possible to the cooling system. This creates the circulation of the coolant within the system. The flue above the heat exchanger should get quite hot, so if its cool enough to touch there may be a problem with the flame or the flue may be partially blocked. You asked about the spiral...?
Ideally you need to work through each of the system components individually:
1 Is the burner producing enough effective heat. (good flame, clear heat exchanger and flue)
2 Is the heat exchanger sufficiently insulated to enable good heat transfer to the cooling system.
3 Is the fridge sufficiently level to allow coolant to circulate.
If all of the above are ok, then either there is a bubble in the coolant, or a possible loss of coolant (which for old absorption fridges is game over...))

Agree with you, BigAldo,
I suspect heat exchanger is possibly rusty, so poor heat transfer as found lots of dust&rust flakes in lower cover shield, will investigate again and seek to clean flue with wire scourer.
Did discover that better cooling is achieved when level is offset a little L to R across the vehicle.
Will persevere for a while, also investigate research of newer absorption coolers.
Many Thanks again for support.

 

[Stanski]

GOOD NEWS, - Fridge working on Gas.
BAD NEWS - DC heating element is broken.

STORY of Repair.
After stripping away all seen fixings, securing screws and removing doors bloody thing would not move. Seems a secondary external wooden frame is fitted around the fridge, and secured within kitchen frame. Requires full dismantling of kitchen woodwork - no easy job.

Reviewed options, took off cooker hob, PITA job as one (always one) of 3 securing screws were seized, after 24 yrs not surprising really.
Needed 14 & 16mm spanners to disconnect gas connections.
Good decision as allowed full access to fridge wiring, all controls, switches and improved access to rear.
So - cleaned out heat exchanger flue, by pulling up an down and rotating the swirl plate.
Repositioned swirl plate to be lower down in heater. ( have attached wire coat hanger to it to allow better positioning).
Checked resistances of heating elements,
6.7k ohms for AC, Markings indicate 125W power required.
Open circuit for DC, Markings indicate 120W required. Looked to replace it within heating flue surround but cannot easily dismantle as restricted access in situ.

Cleaned the heater burner, found build up of rust on inside of pipe, also loose rust particles in near jet.
Tested gas flame on all 3 setting, all OK, possibly better heat output it felt(burning palm in test).
Rebuilt everthing and voila, superb freezing within an hour.
Heat at lower supply pipe (feeds liquid to heat exchanger) is now effing hot - before just warm.

CONCLUSION.
Probability that rust dust was partially blocking jet, So better heating, also repositioning swirl plate along with derusting of inner flue allowing better heat transfer.

Overall took 3.5hrs, so not too bad a job.

ADVICE sought
How hot should the lower heat exchange pipe be?

 

[Stanski]

Fridge working best ever possibly too good.
Q - Should main compartment metal fins be frozen?
Trying to judge what is best gas setting.

 

[Fisherman]

Fridge working best ever possibly too good.
Q - Should main compartment metal fins be frozen?
Trying to judge what is best gas setting.

Water in the atmosphere can condense onto metal surfaces and then freeze.
If there is excessive freezing that would suggest that the door is not sealing properly alowing air to enter the fridge or it’s been left open whilst operating.

 

[BigAldo]

I rarely need to turn the gas up more than 1.5. The metal cooling fins inside will frost over, but not form ice.
Remember that in the cooler weather you need a smaller flame, as the cooling system becomes more efficient with cooler external air.
In warm weather you may need to turn the flame up a bit. One of the disadvantages of not being thermostatically controlled.

 

[Stanski]

1 week Update - apart from a giddy foolish schoolboy error of switching off igniter, and changing gas position so no cooling for a day and half before realising, the fridge is super effective.
Freezing and cooling all good on the top/high setting.
Now to change gas position again to middle option to reduce heating and ascertain effectiveness.