We have a Dometic NDA1402 refrigerator in our RV. It is not cooling. We get error message 17, air temperature sensor in

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Customer: We have a Dometic NDA1402 refrigerator in our RV. It is not cooling. We get error message 17, air temperature sensor in fresh food compartment faulty. Walking through the service mode series we find 03 ("--" = sensor fault, air temperature sensors, freezer + fridge) and 04 ("--" = sensor fault, surface temperature sensors, freezer and fridge) are the only "errors" shown. Back of the heater unit that should be hot is cold. We did turn off power to coach when we moved it a couple of days ago but otherwise it's been on AC power continuously and working until this problem.
Answered by Randall in 10 hours 11 years ago
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Hi: Thank you for coming to Just Answer with your question. Sorry for the delay in someone getting to your question. I was out all day and just got home. My name is XXXXX XXXXX perhaps I can assist you with this issue if you still need help.

Most of the time this is due to a bad connection on the plugs where these thermistors plug into the main control board. Is some cases it can be the board itself. These connect to the main control board on the top once you remove the cover. They are labeled "P3" and "P4" and you can unplug them and do a quick test with an multimeter. If you take them loose inside the fridge you can submerge the tip into some ice water for about 10 minutes. On the plug side you take an ohms reading between pins 1 and 2 and then pins 3 and 4. These should read about 5500 ohms. When the connection on these goes open or they go bad you can get that Error 17 message. These are what control the cooling in the fridge. If they all test out good and you plug them back into the board and still get no cooling the board is most likely the cause. If you don't have a meter they can be found at most automotive or hardware stores for about $15 to $35 for a digital readout version. These are easy to use and come with instructions. Please get back to me with the results and we can go from there. Another thing to check is the DC voltage to the fridge to be sure it isn't too low. You want to see at least 11 VDC on the DC scale. R.J.

Hi, Randall

The unit is still not working. Now the error messages are gone, the power is still on, still turned on to AC on the display, now simply reading Hi-Hi on the readout, the parts on the back that should be very warm are cold, no refridgeration at all. Turns out the error messages were related to the things you suggested but unknown to us the RV technician that had been out here had disconnected those leads in order to "allow the fridge to run wide-open" in an attempt to see if the fridge/freezer would run at all. It had previously stopped cooling without any error messages appearing and this was a last-ditch attempt at their part to gain other information. Now the technician says that it is obvious that the whole unit is just not working (he's also tried banging on the pipes to get the ammonia moving if blocked) and says that we will have to replace the entire cooling unit or replace this unit with a residential fridge. (Note on that...we have replaced Dometic units with residentials in a Class A we owned with good sucess, plus this fifth wheel (a Teton) will not be moved from this spot so it should always be hooked into shore power with no necessity for it to operate on gas, so a residential is a good option.) However, this is an expensive way to go (maybe $2K to replace all the guts, that much or more to do a residential swap out), is bound to be messy (taking fridges in and out windows isn't much fun) and I'm not pleased that we don't have any other information as to why it isn't working. Taking it through its diagnostic routine, btw, only showed up the error messages we were working on above. Let me know if you think there are any other interim steps we could explore before we go to the next step.

The first thing is to find out if the cooling unit is good or not.............that is the real expensive part of this as you know. That is easy to do and I am surprised that the technician who looked at this didn't do it. Unplugging the thermistors only works IF the board is working. I always hook up the heating elements directly to a good AC source to bypass ALL the controls. Make sure the elements are good first. If either one is bad you won't get the correct heat. Once you know you have good elements the back area and boiler will get hot whether or not it cools. I don't see it getting hot even..........unless I just didn't get what you related correctly. The elements can be disconnected from the board and wired up to an old lamp cord and then plugged in. You should see cooling in about 4 hours in most cases. At this point I suspect the main control board, but testing will prove this out. R.J.
Thanks for the quick response, Randall. I talked again with our technician (who I have worked with for several years on different rigs) and he indicates that, if the board was working, the sheet metal tube to the left of the cooling unit would be warm, which it was when he was working with it. I just checked it and it's only slightly warm. He said we should switch it over to LP for a few hours to see if it will work in that mode, which I have done. It previously had been in LP when we checked it at one point but I'm not sure that was for any length of time.
It will be more than warm..............it will be too hot to touch. Both elements should be tested first to be sure they are good. If the board is bad it can effect any cooling efforts. It may be a bad solder joint that keeps opening up or a bad relay. Hooking the elements up directly will eliminate the cooling unit without a doubt or prove it bad and then you can decide what direction to take. R.J.
OK, I will try that and get back. Thanks!
O.K...............the ohms reading on EACH element after you disconnect them should be 34 ohms plus or minus 10%. Then take each lead and test them for shorting against the ground on the back. It either one is starting to go to ground you will get a reading here. You don't want to see one. Then hook them up to an old electrical cord..........tape the leads so you don't have any danger or shorts and plug it in. No polarity to be concerned about on the elements. Get back to me with the results. R.J.
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