Fridge not cold enough - Page 5

rollingrock · 08-11-2011, 08:13 AM

well here is something...a small front blew through, dropped the outside temp to 95 and lo and behold my fridge dropped to 36 degrees.

avvidclif · 08-11-2011, 10:45 AM

Mine does fine as long as it's below 95-100. It's this extreme heat we've been having.

AND all they can say is "It meets spec's" No acknowledgement of a problem in out of "norm" temperatures.

rollingrock · 08-11-2011, 03:58 PM

wow, showed up after the Cowboys game and the temp inside is 35

Stan · 08-12-2011, 02:31 AM

Sounds like it is working better. I think just about everyone has some issues when the outside temp goes real high. Maybe you could install a small fan that blows onto the rear fins?

rollingrock · 08-12-2011, 06:01 AM

Quote:

Originally Posted by Stan

Sounds like it is working better. I think just about everyone has some issues when the outside temp goes real high. Maybe you could install a small fan that blows onto the rear fins?

Ok, new baseline low. 32 this morning and holding. Time is 2 pm CST...

I just plugged in the Thermistor on the back of the board. Repositioned the therminstor inside to where "Dometic" says it goes. Going to monitor the temps. If it goes to to 38 in a hurry, I am going to unplug the thermistor again.

More later.

Stan · 08-12-2011, 06:21 AM

When you unplug it again check the resistance of it. It should be about 3-4K ohms (or less) when the sensor is placed into 65 or so degree water and 8-10K ohms (mine was about 9.2K) when placed in ice water.

rollingrock · 08-12-2011, 06:42 AM

Quote:

Originally Posted by Stan

When you unplug it again check the resistance of it. It should be about 3-4K ohms (or less) when the sensor is placed into 65 or so degree water and 8-10K ohms (mine was about 9.2K) when placed in ice water.

Just so I am clear, what am I testing? The board or the thermistor leads "after" I pull it off?

avvidclif · 08-12-2011, 08:23 AM

I have a problem I can't resolve.

On the thermistor;

When the temperature goes up the resistance goes down.

As the temperature goes down the resistance goes up.

Unplugging the thermistor takes the resistance on the control board to infinite which should shut down the cooling, but it doesn't. Even Dometic says to unplug the thermistor.

FWIW at about 45 deg my thermistor was 6.9k.~ Best I remember.

??????

Stan · 08-12-2011, 08:53 AM

RR - your are testing the plug end of the Thermister AFTER you unplug it (not the board). The sensor end either is at room temp or in a glass of ice water. The resistance of the thermister changes as the temperature of the sensor changes. (see readings in earlier post).

Clif - your are correct - but it is not necessarily a problem. Unplugging the Thermister tells the computer to go "max cold" (IE: run all the time). As the temperature of the sensor goes up the resistance goes down and vice versa. 45 deg with 6.9K sounds about right.

avvidclif · 08-12-2011, 09:47 AM

Think about it again. Zero resistance is high temp and controller to max cold. High resistance is low temperature and no cold. No thermistor is infinite resistance, NO cold. But that's not the way it works????

shoe2728 · 08-12-2011, 11:20 AM

Why not just take out the thermistor and try a variable pot that has about the same range as the thermistor and set it at different settings and see what happens.

Stan · 08-12-2011, 11:21 AM

Not sure where you got term "infinite resistance", but to me that is confusing and not really relevant. Think of it this way, as the Thermister approaches 0 ohms (sensor is really warm), the computer thinks it needs to turn on the cooling system. When you pull out the thermister plug, the computer sees 0 resistance so it thinks "hey, the sensor is really warm" and so it decides that the fridge needs to be cooled down.

fixit5561 · 08-12-2011, 11:23 AM

Here is a link on how to test a thermistor. http://www.ehow.com/how_5398454_test-thermistor.html

And another that is in more laymen terms on the airstream forum http://www.airforums.com/forums/f425...tors-3110.htmlEdited by: fixit5561

Stan · 08-12-2011, 11:24 AM

Shoe2728....See my earlier post. That won't work because it is the thermister that varies resistance with temp. A potentiometer holds the same resistance regardless of temp.

fixit5561 · 08-12-2011, 11:28 AM

Quote:

Originally Posted by Stan

Shoe2728....See my earlier post. That won't work because it is the thermister that varies resistance with temp. A potentiometer holds the same resistance regardless of temp.

As stan said if you just had the pot. in the line, you would have to constantly be changing the position of the pot in relation to the outside temp. So you would be messing with it more than you would want to and wouldnt have good control over thefridge cycling

avvidclif · 08-14-2011, 08:29 AM

What's hard to understand? A short is zero resistance. An open is infinite resistance. Unplugging the thermistor is the same as an open.

avvidclif · 08-17-2011, 01:38 PM

Ok, looking for suggestions and or help. This refrigerator has been at 46 deg for 2 days. Hasn't been opened, I don't want to think about what it might be if I had been using it.

This trailer/refrigerator was purchased new 7/1/2011. It has already been back to the dealer and the thermistor replaced. I have contacted Dometic and the answer is it meets spec's (The spec's are written at an ambient outside temperature of 90 deg) and it does meet that spec. But my ambient temperatures here are not to spec...

Crossroads said they warranty the trailer and Dometic warranty's the refrigerator. See above.

I don't want to do the mods listed for obvious reasons, warranty voided. This is a new refrigerator not one in a used trailer I bought. If I bought it used I would mod it/replace it and go on. Lesson learned.

Thoughts???? What next? Crossroads points to Dometic, Dometic is saying it meets spec's, and the dealer can't do anything without Dometic approval.

Stan · 08-17-2011, 01:49 PM

Clif...I looked back through the posts and I did not see one where you

unplugged the thermistor to see if the cooling system would cool down.

Have you done that? If it cooled properly then my personal opinion

would be to do the mod and see what happens. Another option would be to

talk directly with Randy (unless he is the one you have been talking

to), and explain how you are caught in the middle with an unusable

fridge.

fixit5561 · 08-17-2011, 05:49 PM

Maybe get a new thermistor, do the mod to the thermistor currently on your fridge. Then if something does happen to the fridge, replace the thermistor with the new one you have and there is now no signs of a mod being done. Have your warranty work done on the fridge and then return the moded thermistor to the fridge again.

rollingrock · 08-18-2011, 01:12 AM

Ok, i love to piddle now....picked up one of these <a href="http://cgi.ebay.com/ebaymotors/Dometic-Thermistor-3851059042-RM3662-63-2852-62-3862-3-_W0QQcmdZViewItemQQ_trkparmsZalgoQ3dLVIQ26ituQ3dUC IQ26otnQ3d4Q26poQ3dLVIQ26psQ3d63Q26clkidQ3d2149263 806607053975QQ_trksidZp5197Q2em7QQitemZ27069129892 4" target="_blank">http://cgi.ebay.com/ebaymotors/Domet...mZ270691298924

After talking with them, this isn't a pot so for me, its worth a shot! </a>

Edited by: rollingrock

You may also like: