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Open Roads Forum  >  Tech Issues

 > Is this a bad circuit board? (fridge)

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wopachop

Who run bartertown

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Posted: 06/18/21 11:12pm Link  |  Quote  |  Print  |  Notify Moderator

Its the type that uses the resistance probe. Which is all fine and dandy. I have not measured the ohms but assume its measuring accurately.

Lets pretend the temp probe was hanging off the fins. Resistance to the circuit board is way out of spec so the fridge goes into a protective mode. Why the heck didnt it cycle all day? Man i just got home. Nothing i could do. Havnt opened it yet. I dont understand how it could go so long without attempting a cycle.

I have my probe attached to the fins. Its not hanging. Im just trying to present the topic as if the probe is set anywhere. Cut the thing in half with diagonal cutters. Can the fridge really go that long and not try to cycle? Makes me think maybe the circuit board is not working properly.

Its been overly hot. I left my front bedroom AC running. Which feeds cold air to the back of my fridge. I checked my phone this afternoon and saw the bedroom temp was 90F. Which meant the AC was not running. Got home and sure enough the dial AC was set to LOW. But it was not blowing cold air. That is another failure i need to figure out. Will ask if the shore power went out today.


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agwill

enosburg falls, vt

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Posted: 06/19/21 08:01am Link  |  Quote  |  Print  |  Notify Moderator

What are you asking? Is the fridge getting warm when the outside warms up? Is the side of the trailer the refer is on in the sun? Do you have a fan to keep the air moving in the back of the fridge? We need more information as to what is your problem.


al

Old-Biscuit

Verde Valley

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Posted: 06/19/21 09:21am Link  |  Quote  |  Print  |  Notify Moderator

Lot of 'data' that really doesn't get to the question

Brand/Model of Fridge??

Many fridge use a BOS (Backup Operating System) that ALLOWS for continuous operation (cooling) upon loss of temp sensing so food doesn't SPOIL

Thermistor is the temp sensor for the fridge thermostat. It measures FIN temp in food compartment...which is roughly 10*F lower then the food compartment
Thermostat is calibrated for temp range (approximately 34*F----44*F) based on each temp setting

Thermistor Bad.....usually results in overcooling condition

Circuit Board Bad....issues with heat source functions (short cycle)


Repeat/ask your question..........
*BRAND/MODEL for specific info on that fridge
*In AUTO Mode
*Any Error Codes
*fridge did get cold or didn't


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
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Gdetrailer

PA

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Posted: 06/19/21 11:31am Link  |  Quote  |  Print  |  Notify Moderator

Over thinking things.

Dump the 24/7/365 monitoring and don't obsess.

Your A/C and inside trailer temps has zero to do with the fridge temps.
RV fridges are exposed to the outdoor temps and seeing short 45F spikes on overly hot days is pretty much the normal range of a RV fridge. While 45F is sort of above my comfort zone for refrigerated foods it isn't going to kill you, it just means your foods will not last as long as possible.

You mention "overly hot" which I take as the daily outdoor temps and what you see for the fridge is a direct result of the outdoor temps.

Some RV manufacturers will include a couple of small fans on the back of the fridge to help with the high outdoor temps, perhaps you might wish to look into that but I doubt your going to see a big improvement.

Camping off level also does affect RV fridge efficiency, RV fridges use gravity to move the coolant inside the tubes, off level operation slows the coolant circulation (yes, I know, there are folks who claim the fridges were redesigned to work off level, but reality is off level operation should be avoided for best efficiency).

Consider yourself lucky, one of the RV fridges I dealt with would peak at 55F for several hrs with outdoor temps over 95F and then would freeze everything solid in the fridge when night time temps dropped to 70F.

dougrainer

Carrolton, Texas

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Posted: 06/19/21 11:45am Link  |  Quote  |  Print  |  Notify Moderator

Are you an Engineer??? I ask because you have given a lot of DATA, but have given NO IDEA what your problem is. Your main problem is the old chestnut----A Man with a Watch knows the time. A Man with 2 or more watches is never sure what the correct time is. I have never heard of a dangling Thermister causing a Refer circuit board to go to Protective mode whatever that is. The usual response to a dangling Thermister is to run all the time. Now, some refers(Norcold) DO go to a "protective" type response for a parameter out of spec. It is called BOS mode. This is just one of a few Norcold BOS parameters. Doug

Backup Operating System ("BOS")Your refrigerator features a Back-Up Operating System which provides a means for the refrigerator to cool in the event ofa failure within the refrigerator's operating controls. In the event this failure occurs, the refrigerator will display DiagnosticCode C5 and will switch automatically to the "BOS" mode. This mode provides refrigeration until the refrigerator is serviced.The fresh food and freezer compartment temperatures should be monitored to prevent over-freezing or thawing of refrigeratorcontents when operating in the "BOS" mode. If the refrigerator temperature is too cold, adjust the thermostat up (warmer) inone bar increments. If the refrigerator temperature is too warm, adjust the thermostat down (colder) in one bar increments.Allow the refrigerator to operate at the new setting for one hour before rechecking the freezer and fresh food compartmenttemperatures (frequent door opening prevents the temperatures from stabilizing). While the refrigerator can operate in thismode, Norcold recommends that you seek service as soon as practical to restore normal operation

ernie1

Sacramento,California,USA

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Posted: 06/19/21 11:48am Link  |  Quote  |  Print  |  Notify Moderator

45deg F is 5deg above the temperature that its is safe to keep potentially hazardous foods at. Yes that temperature and anything above 40deg F can cause foods to grow bacteria that is harmful to the body. Foods don't have to appear or smell spoiled to be harmful nor does "spoiled" foods always make you sick. Keep in mind that the longer the time at the wrong temperature will cause the bacteria to grow more and probably make you sick or worse.

wopachop

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Posted: 06/19/21 12:21pm Link  |  Quote  |  Print  |  Notify Moderator

wopachop wrote:


Lets pretend the temp probe was hanging off the fins. Resistance to the circuit board is way out of spec so the fridge goes into a protective mode. Why the heck didnt it cycle all day?


What causes a fridge to go 10 hours without cycling?

Bad probe = continuous cooling?
Bad board = short cycling?

What causes 10 hours of not attempting a cooling cycle? (with fridge temp well above 40F)

Gdetrailer

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Posted: 06/19/21 12:23pm Link  |  Quote  |  Print  |  Notify Moderator

ernie1 wrote:

45deg F is 5deg above the temperature that its is safe to keep potentially hazardous foods at. Yes that temperature and anything above 40deg F can cause foods to grow bacteria that is harmful to the body. Foods don't have to appear or smell spoiled to be harmful nor does "spoiled" foods always make you sick. Keep in mind that the longer the time at the wrong temperature will cause the bacteria to grow more and probably make you sick or worse.


You have forgot about "time".

Takes time and temperature to ruin food otherwise you would not be able to buy food at a store, transport it 5 minutes-30 minutes in 90F+ temps to your fridge.

But, one of the major flaws of DIY refridgeration temp monitoring is folks stick a probe into thin air inside a fridge, doing so you are simply monitoring the air temp in the location of that probe which may not be an accurate assessment of the fridge operation.

That does not tell the complete story.

RV fridges do not have fans inside to move the cold air from near the fins, overcrowding the fridge can block air movement and can result in warm and cold spots inside the fridge and false readings at the temp probe.

Ideal way to monitor the fridge operation is to place probe in say a water bottle and monitor the temps of that bottle of water.

Alternately but may not be as accurate as the water method is to thermally fix the temp probe to one of the metal shelves, but thin air is least effective for monitoring fridge operation.

ernie1

Sacramento,California,USA

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Posted: 06/19/21 12:30pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer-Please reread my post concerning "time".

Gdetrailer

PA

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Posted: 06/19/21 12:39pm Link  |  Quote  |  Print  |  Notify Moderator

wopachop wrote:

wopachop wrote:


Lets pretend the temp probe was hanging off the fins. Resistance to the circuit board is way out of spec so the fridge goes into a protective mode. Why the heck didnt it cycle all day?


What causes a fridge to go 10 hours without cycling?

Bad probe = continuous cooling?
Bad board = short cycling?

What causes 10 hours of not attempting a cooling cycle? (with fridge temp well above 40F)


Depends on what you are calling a "cycle".

RV fridges do not work in the same manor as compressor fridges.

They do not "cycle" on/off like or as fast as a compressor fridge.

RV fridge uses gravity to do it's magic, if you have ever been around any heating system that uses gravity then you would fully understand what is happening with your RV fridge.

A great example of this is a Lava Lamp.

To get the lava to move up in the lamp one must apply a lot of heat at the bottom of the lamp base (think of this as the RV fridge boiler).

The heated lava the rises to the top where it is cooler.

The lava at the top cools down and then sinks back down to the bottom.

The cycle the repeats.

In order to get the coolant to move through a RV fridge, you have to apply heat, a lot of heat. The heated coolant rises from the boiler then creates circulation in the tubing.

As such, it takes a long time for a RV fridge to cool to the desired temp. It also takes a long time to recover and stabilize after the fridge door has been opened. It can take several hrs for the fridge to recover and stabilize.

A more accurate way to describe "cycle" is to verify and measure how long the fridge burner (or electric heating element) is on compared to off..

But, with a RV fridge, the hotter it is with ambient outside temps the longer the burner must run. High ambient outdoor temps will considerably reduce the efficiency of gravity type circulation. So, it is not unusual to have a RV fridge burner run at max all day in extreme high ambient outside temps.

Your inside RV temps really do not affect a RV fridge all that much, it is the outdoor temps that can cause difficulty.

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