WilleyB
Snip..
Hi John, while reviewing the thread there's little doubt in my mind that the culprit is two fold. I do believe between Dometic's recall paper, only fridges with the underrated element (354w???),Tim's post about the common factors to the failures was the underrated heating element and that it failed at the first weld above the elbow, plus Chris' post on the effect of stress from heating the weld.
Willis, I agree this is a multi part problem where the right conditions have to add up. And I can see a cyclic thermal expansion problem adds up with the higher wattage element. Without a real good picture of how the element is placed in relation to the crack and the metal thickness around it, I can't add much more science to this. If we do not come up with a pic soon, I may find out on my own.
A big question in my mind "Why such a low failure rate?"
There's also no doubt in my mind that a lot of failures happened but for reasons unknown (not reported)are not included in the statistics. Yet there's much reason to believe the failure rate is still low.
Yes I agree with this too. Unless someone knows of the problem, this could be just written off for road vibrations, or a weak unit. Tim, helped make it clear that his failures where not even on the road.
Now here it gets kind of iffy, Chris most likely could explain this better.
Those who have welding experience will understand there is a quality of weld depending on the penetration (mix of new metal to the pieces being welded)when heated the stress characteristics of this welded joint are quite different to the surrounding metals. It's easy to believe that a lower number units might have a much deeper weld penetration than the rest (new or novice welder)and when overworked by an excessive expansion and contraction, the weld will break from from one of the metals that were joined leaving a very weak structure.
Yes, there is merit in this as well. Running mostly on propane would create a different situation than those running mainly on electric. And then there is weld quality
No matter which parts list you look at the parameters for a 325 watt element is 44 ohms +/- 10% if your fridge has that it's not on the recall list. There is a reason for this, an absorption refrigerator must have the correct heat to operate. The low end tolerance is 39.6 ohms, so it is safe to assume this would generate the hottest allowable temperature and the expansion and contraction factor does not overwork the weld.
Well there are different ratings.
Look at this RM 2620 it is listed as 48 ohms and 295 watts. See page 2
And here is a RM2663 with 41 ohms and 325 watts. See page 2 RM 2663
If that 41 ohms is right, 10% less is 36.9 ohms.
I can't figure out how they get 41 ohms, 325 watts, 120 volts and 2.7 amps. Would they have a typo on 2 product sheets?
The Dometic modification to the best of my knowledge, from what is posted on this thread, consists of a fix so that the unit does not catch fire when the cooling unit fails while operation on LP gas.
So What to do. I don't know about anyone else but here's my reaction.
1 Replace the heating element with a new one of correct specifications (preventative, why push one's luck)
2 When the Dometic fix is ready, have that done (Safety, it's free why take a chance)
3 When we have enough information I will install the thermal cutoff. (more safety, it's easy to do so why not)
Because of the thread I believe we have a better understanding of the problem and remedial actions we might take. At least now when we go out for a run I'll feel a lot better about it all than when the thread first started.
Cheers Willis
