Fridge WOES......Again

[joe_blow]

Hi all,

2008 WW CR3705 with the Dometic RM3862 fridge. I have been balls deep into this fridge several times. The first was the ciruit board. I bought one from dinosaur electronics and it worked well for a year. The same board had an ignitor issue and the board was warrantied. Long story short this current board is the third in a series of "warranty" boards.

So I plugged my trailer in on Tuesday (flat ground). The freezer and fridge are perfect by the 24 hr mark. Come Friday I went to load a bag of ice into the freezer and the thing was warmer than it should be. I checked all lights, fuses and it was all in check. No "CHECK" light on.....nothing.

Needless to say I transferred over to propane (bled the lines and all was good...fridge burner/pilot on). I got to my destination and it was 68*

I am so sick and tired of this unpredictable fridge and/or the dinosaur board.

I am going to get into to it tomorrow and check the obvious but at this point I am at a loss.

Any ideas on what might be the issue?

Is the fridge done?


Thank you
Joe

[Old-Biscuit]

joe blow wrote:
Thank you for all the help old biscuit. You definitely had me thinking on this one with the AC ripple:p
The good thing about it all is I will have a **** near new fridge after I'm done for less than 750.00.

As far as swapping in a household fridge. I cannot do it since I dry camp

Lots of folks have residential fridges and dry camp.......batteries, solar, inverter----good to go

[joe_blow]

Thank you for all the help old biscuit. You definitely had me thinking on this one with the AC ripple:p
The good thing about it all is I will have a **** near new fridge after I'm done for less than 750.00.

As far as swapping in a household fridge. I cannot do it since I dry camp

[htwheelz67]

I have the same fridge, no problems yet but after reading this and other threads like it I'm swapping in a residential fridge.

[Old-Biscuit]

Snip the tip thermistor is a good option when one needs to replace faulty OEM thermistor and not wanting to run leads down to board.
But if fridge out..OEM thermistor is better

Dometic fan/t-stat install


Fan thermostat switch

[joe_blow]

Old-Biscuit wrote:
Inverter supplies 120V AC...it is a draw off batteries

Do you not have a converter?

If batteries only supply DC System then you will not have issue with AC Ripple.
AC Ripple is a result of Converter using 120V AC to supply DC

No converter.....no AC Ripple

Only mentioned AC Ripple due to the number of circuit boards you have changed out.

The boards were a problem on their end. They told me they had a bad batch. The current one is the newest format and programming.

No sir....I have a xantrex freedom 458 inverter/charger that controls two outlets in the trailer and charges the house 12V DC and gives me 110V from 12V DC to power some items in the trailer when the ONAN 5500 is not running

I am in the process of isolating the coils. So far the heating element is hot as hades and the heat stops right at the top of the coils before the condenser.....will go no further. It has been 3 hours so far. Not a hint of temp change in the freezer or fridge. By this time I would have felt a temp change in the freezer given past performance

I did confirm the 60 cfm fan and therm switch work. I am going to install one 200cfm fan instead of two 60cfm fans since the room is limited and I don't want it melting next to the flue.


Old biscuit....questions for you sir.

Any ideas on the:

-thermistor modification I posted earlier in the thread? I tested the thermistor and it is within Ohms range but its out on the floor why not change it or modify it. What are your thoughts on the mod? http://www.snip-the-tip.com/cgi-bin/articca.cgi

-where I can get a new two prong therm heat switch for the fan (its way up there and I'd rather change it now that its out and in my garage.)

Thank you very much for the help!

Joe

[Old-Biscuit]

Inverter supplies 120V AC...it is a draw off batteries

Do you not have a converter?

If batteries only supply DC System then you will not have issue with AC Ripple.
AC Ripple is a result of Converter using 120V AC to supply DC

No converter.....no AC Ripple

Only mentioned AC Ripple due to the number of circuit boards you have changed out.

[joe_blow]

Old-Biscuit wrote:
Guess you didn't pull electric heat element leads off of circuit board and plug the ends directly into 120V AC outlet like I suggested? I have not purchased any thing yet. This test is tomorrow morning.

Running element directly bypasses the board and would determine if cooling unit worked or not..........Correct.....tomorrow

Hope it wasn't just the thermistor, the board or even poor ventilation/air flow :H

I tested ohms on the thermistor and it was within ranges, I went through the board with the help of the dinosaur electronics tech and it appears to be working....as far as airflow I highly doubt it since nothing has changed and everything is pretty clean and clear in there


Didn't test for AC Ripple either.......
Multimeter set to AC Voltage but leads connected to 12V DC connection

This didn't yield any results for me. I tried it a few times and it never gave me anything near a readable value. Which leads me to my question.

My inverter has two pieces of romex coming from the output side. Where in the trailer is my fridge tied into the inverter? I have never run the inverter to use my fridge while dry camping just to watch TV....that's it. I am still trying to grasp how the inverter ties into the fridge operation on the 12V side.

I have constant battery voltage at the fridge distribution block....nothing less or more.

Thanks
Joe

[Old-Biscuit]

Guess you didn't pull electric heat element leads off of circuit board and plug the ends directly into 120V AC outlet like I suggested?

Running element directly bypasses the board and would determine if cooling unit worked or not..........

Hope it wasn't just the thermistor, the board or even poor ventilation/air flow :H


Didn't test for AC Ripple either.......
Multimeter set to AC Voltage but leads connected to 12V DC connection

[joe_blow]

Thank you for the advice. I had plans to add two fans since it was out for preventative maintenance purposes. You mentioned the thermistor. I was considering buying one of these http://www.ebay.com/itm/Dometic-Thermistor-3851059042-RM3662-63-2852-62-3862-3-/282094933120?hash=it...

Any feedback on this unit?

thanks

mudmaker wrote:
If there is a fan it should be attached to a thermostat on the cooling fins directing the fan to come on at 130 degrees or at least around there. If it's not then the heat can't rise and escape so the freezer will work but not the fridge. Thermistor should read between 8-10000 ohms after about ten minutes in the ice. To make sure the board works just unplug the the thermistor from the circuit board and over about a day at most the fridge should become a freezer. That will prove the circuit board is functioning.
Just went through this on my parents fridge last month. These instruction were in the dometic book and online for troubleshooting. There are checks for the heating elements but I never got that far. Replaced the fan with two, (the factory bracket will accommodate two in my parents) and works really good now.
Oh and double check the door gaskets too. Unbelievable how much cold air you lose when the door opens.

[joe_blow]

Well after diagnosing for most of the day it appears that my cooling coils are the issue. I contacted this company http://www.arcticoldstore.com/dometic-rm3862-brand-new-manufactured-cooling-units/ and the guy was really helpful. In a nutshell the fridge had two ways to heat the ammonia and neither was doing anything. I pulled the fridge out today and didn't notice any major yellowing indicative of a leak but the tech said that at times the coils get plugged.

After describing all the diagnostics/findings I went through and explaining what symptoms I am experiencing the guy stopped me mid sentence and guaranteed to me the coils are the issue. Pretty bold statement but he knew quite a bit about the fridges and their operation so I am going with it.

I will post once I install the new coil assembly. Looks like a really nice self contained, fully enclosed unit. Not to mention it has a lifetime warranty to boot.

Thank you for the help

Joe

[mudmaker]

If there is a fan it should be attached to a thermostat on the cooling fins directing the fan to come on at 130 degrees or at least around there. If it's not then the heat can't rise and escape so the freezer will work but not the fridge. Thermistor should read between 8-10000 ohms after about ten minutes in the ice. To make sure the board works just unplug the the thermistor from the circuit board and over about a day at most the fridge should become a freezer. That will prove the circuit board is functioning.
Just went through this on my parents fridge last month. These instruction were in the dometic book and online for troubleshooting. There are checks for the heating elements but I never got that far. Replaced the fan with two, (the factory bracket will accommodate two in my parents) and works really good now.
Oh and double check the door gaskets too. Unbelievable how much cold air you lose when the door opens.

[joe_blow]

YC 1 wrote:
Is it in a slide?

Is the drain tube cracked?

Has the drain tube been moved?

Not in a slide

If you are referring to the water drain tube it has not been moved and I'll go look to see if it is cracked.

[joe_blow]

SO I have been messing with this all morning and here is what I found.

I called dinosaur electronics and talked to their tech guy. He ran me through some tests and determined the board to be functioning fine. The board does two things (according to the tech) it basically switches between LP and 110v to either heat the ammonia using LPG or the heating element. After determining this I decided to move on.

I checked some of what old-biscuit suggested but I am stumped because I am getting constant battery voltage (12.5-12.7v) at the back of the fridge and don't understand if this is normal or what he suggested only had to do with 3-way fridges? I tried with the inverter on (which I RARELY run when I am dry camping and it has always worked fine for years)The 12V power block next to the circuit board is wired into the RV system but not regulated by the inverter as far as I can tell.

I tested the thermistor ohms and at 80* ambient it gave me 2500 ohms. I put it in a glass of ice cold water, waited 5 minutes. It went to 6500-6600 ohms. I have read that it has to reach a minimum of 9000 ohms to be considered ok.....but I am not sure.


I called dometic's troubleshooting line and they were as stupid as could be.....directed me to a repair shop.


I looked up in the cavity where the fridge sits and it looks pretty filthy. I considering taking it out and cleaning the back of it just to make sure. By the way there is a fan way up there and to be honest I have never heard it come on.

[YC_1]

Is it in a slide?

Is the drain tube cracked?

Has the drain tube been moved?

[joe_blow]

As far as I can see it does not, atleast not in the vented area when the access panel is removed. The fridge was perfect for three days and gradually both freezer and fridge came to warm temperatures.

mudmaker wrote:
Does it have assist fan or fans in the back outside of the fridge to move air? If they burn out it can breathe and while freezer will be cold the fridge will not.
Just a thought.