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09-08-2019, 04:25 PM #1
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Dometic Thermal Fuse Thermocoupler
Dometic Thermocoupler, Thermal Fuse
We lost power to our Dometic 2862 refrigerator. The first clue was the eyebrow lights (3 of them) were all off. Nothing would bring the reefer back online, not 120vac nor propane. That's because they both require 12vdc to power the circuit board which controls the fridge. The resettable overheat thermal fuse, that's what Dometic calls it, on the chimney was not tripped. It also passed the continuity test. Turns out there is another thermal fuse, though I was told years ago that the device is called a thermocoupler. Either way, it will open the circuit when the heat gets to the rated temp. In this case its 152 degrees Celsius. That's about 305 degrees Fahrenheit. This thermal fuse, or thermocoupler, was not mentioned in the manuals I read. The terminal block provides 12v, then it runs to this thermal fuse, then to the over-heat resettable thermal fuse on the chimney and then finally to the circuit board.
I have a hard time believing that the temp in this location got over 305 degrees Fahrenheit, but it blew so it had to be replaced. I found 5 of them for $7 on Amazon, but it would take two weeks to get them and we were moving on in a few days. So, I now own 50 of them for about $14 because they could arrive in two days. I guess I'll have spares in case there really is a problem I'll have to diagnose. But I think it’s a simply a failed part. I had to bypass it for 3 days. I kept a constant eye on the area, checking it for overheating. But there was never any excess heat in that area.
This is a one-time use device. Once it overheats and cuts the circuit, its done for life. It is located in a black insulated sleeve, folded in half, and gently crimped onto the back of the fridge about 5 inches from the chimney. Bend up the two fingers holding it in place, slide down the insulation tube and expose the thermal fuse. You'll have to cut it free. Cut as close to it's leads as you can so you will still have enough wire length when you replace it. I thought I'd be clever and use bullet connectors on the replacement, but the insulation on them was too big in diameter to fit inside the black insulation sleeve. I could not solder it in that location and I didn’t have any small crimps, like you can see in the picture, that GD used. So I used the bullet connectors by cutting off their insulation and relying on the black insulation sleeve.
I'll look for some small crimps like the OEM connection. Since I have 49 more of them, I can always install another one if I do find the small crimps.
It may take a couple posts to get all the pictures uploaded…
Hope this info helps someone with a similar problem.
Mike
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09-08-2019, 05:57 PM #2
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I do recall seeing these in small appliances I've opened up, like https://en.m.wikipedia.org/wiki/Thermal_cutoff
Didn't expect for you to find one on the frig.
Small uninsulated butt or parallel crimp splices might work:
Non-Insulated Butt Connectors
Morris Products 12152 Parallel Connector, Non Insulated, 22-16- Gene
Kim & Gene
2015 Reflection 317RST
2017 Ram 3500 CC LB 4x2 6.7 CTD AISIN 3.73 DRW Auto Level Rear Air, BD3, Prodigy P3, Aux Tank
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09-08-2019, 06:06 PM #3
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09-08-2019, 06:09 PM #4
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By the way... I don't know if it's important, but I made sure to orient the replacement in the same direction. As I recall, the tapered end goes to the resettable over heat switch on the chimney.
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09-08-2019, 07:54 PM #5
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Depends on the crimp tool. I have an old T&B that's like this Gardener Bender GS-388 for non-insulated splices, it puts a dimple in it.
- Gene
Kim & Gene
2015 Reflection 317RST
2017 Ram 3500 CC LB 4x2 6.7 CTD AISIN 3.73 DRW Auto Level Rear Air, BD3, Prodigy P3, Aux Tank
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09-08-2019, 08:00 PM #6
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09-24-2019, 03:33 PM #7
Mike, Thank you so for your post. I just experienced the same problem on Saturday. We stopped for lunch after traveling for 3 hours only to find the fridge dead. I quickly checked the usual fuses and all were good. I couldn't do much else on the road. I just started troubleshooting the problem and looked at the forum before starting. You saved me some valuable time. I just got back from the electronics store and bought a thermal fuse for $2. They only had one in stock and several more on order. I plan to pick up at least one spare when they come in. I would like to know how it got over 300 degrees F (152 degrees C) to blow that fuse. At any rate, Thank you again for saving me some time. Again, this shows how helpful these forums are because of the people who participate.
Jim & Kathy
Gracie, our 14 year old Rescued Beagle, waiting at the Rainbow Bridge with her big sister Bailey
Suzy our 8 year old rescued Beagle
2019 2500RL
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09-25-2019, 08:06 PM #8
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You're very welcome.
On a side note, I think fishermen may use a small wire crimp for some of their homemade lures. I'm guessing I'll find smaller crimps instead of the bullet connectors, and a crimping tool, in a good sized sporting goods store. Maybe Bass Pro Shop or Cabelas. Next time we're by one I'm going to go look.
Mike
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09-12-2021, 11:35 AM #9
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Mike, thank you so much for this post! Our fridge had the same failure after driving with it turned on for 8 hours through California's central valley with temps nearing 110F. Fridge starting to defrost, no lights on the display, but other 12V and gas systems in the trailer working fine.
We had already scheduled service when I decided to open the fridge maintenance door on the rear of our Imagine XLS 17MKE and take a look. All obvious fuses read closed, but I had no idea where fuse "3" on the included diagram was. I have some basic hobby experience with electronics; I had no idea the black thing against the wall was a thermofuse!
Your post gave me all the information I needed to dig out the thermofuse, buy some new ones, and replace the blown one.
I also verified the fuse was the problem by making a short wire with a blade connector to bypass the fuse, just for diagnosis.
I used some Molex circular connectors (02-09-1119 and 02-09-2118) to replace the crimp connectors around the fuse since they fit inside the black insulating sleeve and I had them handy.
I made one spare fuse with Molex connectors and have put that in our trailer utility drawer. I still have the bladed jumper wire just in case both the replacement and spare fuses blow on a future trip, but Kris and I have agreed to only use that jumper wire to save a camping trip, and not drive with it installed.
I'm a little astonished like you were that the temperature in there exceeded 305F. We probably won't drive with the fridge operating on gas again because that kind of scared us. We may in the future upgrade to solar panels, LiFePO4 batteries and an inverter, and then we may drive with the fridge on AC, especially during the daytime with plenty of power. In the meantime, we plan to put blue ice packs in the fridge and dry ice in the freezer for long drives.
-Brad
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09-12-2021, 12:43 PM #10
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You're welcome Brad. I wouldn't be afraid to drive with the fridge on propane. We full timed for a little less than 2yrs. Fridge was always on. Propane while driving and overnight boondock, 120vac when at the campsite. This was the one and only time that fuse failed.
Glad it helped you out. Now I'm going to go look for your molex connectors.
By the way, we have 200Ah lithium (Battleborn), 320 watts of solar, and a 1000 watt pure sine wave inverter. I think the fridge on AC would put a sizable dent in the battery bank. Next time I have the camper at the house I'll put my kill-a-watt meter on the fridge and see what it draws.
Industry Looking for Lithium...
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