Hi everyone , I have a dometic Rmt 7655l, which is the oven freezer fridge tower and I have a conundrum that’s baffling everyone . Everything works ok on gas..if it’s switched to ‘gas’ or ‘auto‘mode On the selector knob. Everything also works ok on 12v when travelling , again if it’s it’s switched onto 12v or on the ‘auto’ slection .. but as soon as I plug ehu into the van both the freezer and fridge freeze. even if it’s all switched off on the tower itself. Someone said it might be the thermistor, but surely if it was it would put work ok on gas or 12v ? Whenever we go away I cannot know plug into ehu as the fridge freezes….any ideas as it’s driving us nuts ! Tia
Dometic fridge problem
- Thread starter Gemani2
- Start date
Could you plug into EHU for charging etc but turn off/unplug the separate fridge 230v supply which will be somewhere inside the Motorhome , and run the fridge on gas until the fault is found and fixed .( which may be a faulty power control board )
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Couldn't resist a quick (re-)"join" for this one.
I diagnosed and suggested a fix for an identical problem on a Tech Tower of a friend's 'van.
If he had EHU, and irrespective of any fridge settings, including "off", his fridge and freezer froze solid. Removal of all 12V made no difference. Not a good position to be in when wanting to leave the 'van hooked up whilst on an extended holiday elsewhere.
After much investigation and sucking of teeth I gave up diagnosis, but once back home started thinking again.
The 230V circuit on those fridges is very simple. The power goes in, it passes through a 230V/12V relay operated by the fridge control electronics, and straight out again to the 230V heater down the back. (This is the only 230V switching, and on the wiring diagram in the manual, it's 230V in at X101 through the relay and out at X102). There were only two possible causes, i) the control electronics being wrong, or ii) the 230V contacts in the relay welded closed. The former was very unlikely given the issue continued with no 12V available, the latter would cause permanent functioning regardless of fridge and thermostat settings, and was pretty much nailed on.
The PCB is removable with care; the screws for the switch panel removal can be accessed by pulling the control knobs off, and there's just about enough space to get the PCB out from the front.
Replacement PCBs can be difficult to source, and are expensive, but if you are lucky, as my friend was, the PCB will not be "potted" (components coated in resin) and the individual components can be replaced. If it is potted it's a new PCB! (Probably somewhat North of £200.
The relay is the obvious one between the two connectors noted above. On my friend's it was a Panasonic jw2sn-dc12v, though I've seen pictures of PCBs with others providing the same function. These are readily available at under £3 plus p&p (Google is your friend after you've read the number from the relay). The replacement is a fairly simple solder job, BUT, given that it has (ISTR) 8 legs/solder-points to the PCB, it needs someone who knows what they're doing, and preferably with a solder pump , to remove it.
Friend sourced the relay and got a local minor repair man to replace it for less than £10 all-in. (Friend is no electronic engineer, but he didn't have too much trouble with the removal/replacement of the PCB). That was almost 5 years ago, and it's still working! It was worth the risk, as it was only a tenner wasted if it finally did need a new PCB.
This may not be your issue, but it is/was identical, and from long pondering at the time, I couldn't come up with another cause.
I diagnosed and suggested a fix for an identical problem on a Tech Tower of a friend's 'van.
If he had EHU, and irrespective of any fridge settings, including "off", his fridge and freezer froze solid. Removal of all 12V made no difference. Not a good position to be in when wanting to leave the 'van hooked up whilst on an extended holiday elsewhere.
After much investigation and sucking of teeth I gave up diagnosis, but once back home started thinking again.
The 230V circuit on those fridges is very simple. The power goes in, it passes through a 230V/12V relay operated by the fridge control electronics, and straight out again to the 230V heater down the back. (This is the only 230V switching, and on the wiring diagram in the manual, it's 230V in at X101 through the relay and out at X102). There were only two possible causes, i) the control electronics being wrong, or ii) the 230V contacts in the relay welded closed. The former was very unlikely given the issue continued with no 12V available, the latter would cause permanent functioning regardless of fridge and thermostat settings, and was pretty much nailed on.
The PCB is removable with care; the screws for the switch panel removal can be accessed by pulling the control knobs off, and there's just about enough space to get the PCB out from the front.
Replacement PCBs can be difficult to source, and are expensive, but if you are lucky, as my friend was, the PCB will not be "potted" (components coated in resin) and the individual components can be replaced. If it is potted it's a new PCB! (Probably somewhat North of £200.
The relay is the obvious one between the two connectors noted above. On my friend's it was a Panasonic jw2sn-dc12v, though I've seen pictures of PCBs with others providing the same function. These are readily available at under £3 plus p&p (Google is your friend after you've read the number from the relay). The replacement is a fairly simple solder job, BUT, given that it has (ISTR) 8 legs/solder-points to the PCB, it needs someone who knows what they're doing, and preferably with a solder pump , to remove it.
Friend sourced the relay and got a local minor repair man to replace it for less than £10 all-in. (Friend is no electronic engineer, but he didn't have too much trouble with the removal/replacement of the PCB). That was almost 5 years ago, and it's still working! It was worth the risk, as it was only a tenner wasted if it finally did need a new PCB.
This may not be your issue, but it is/was identical, and from long pondering at the time, I couldn't come up with another cause.
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Hi, can’t thank you enough for this reply , you’ve nailed our problem exactly . We will take the pcb off tomorrow, nothing ventured nothing gained ! I’ll let you know how we get on but not sure which bit will need changing or how I’ll identify it ..but I’ll take a pic and let you know how we get on , thank you so much !
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The PCBs all differ in detail, but it will be something like this:
The 12/230V relay here is (if I recall properly) box under the barcoded label at the right and the in/out connections x101/x102 would be directly above. I think my friend said he had to remove the barcode label to get the part number. On some PCBs it is mounted in a similar position, but at right angles.
If you do remove the PCB, take copious pictures of the connections before detaching.
A Google check of the part number will indicate whether you've found a/the 12V/230V relay (there's only one). (and make sure you're not on hook-up whilst doing all this).
It was suggested above that the 230V fridge heater could be isolated at the back by temporarily removing the feed there and insulating the wires. We did this in the interim of the fix, which allowed the EHU to be installed "fridgeless" for the duration of the friend's holiday. It should still work on 12V/Gas.
I don't think I can add much more at this stage, and my free posts are disappearing, so that's it for now.
The 12/230V relay here is (if I recall properly) box under the barcoded label at the right and the in/out connections x101/x102 would be directly above. I think my friend said he had to remove the barcode label to get the part number. On some PCBs it is mounted in a similar position, but at right angles.
If you do remove the PCB, take copious pictures of the connections before detaching.
A Google check of the part number will indicate whether you've found a/the 12V/230V relay (there's only one). (and make sure you're not on hook-up whilst doing all this).It was suggested above that the 230V fridge heater could be isolated at the back by temporarily removing the feed there and insulating the wires. We did this in the interim of the fix, which allowed the EHU to be installed "fridgeless" for the duration of the friend's holiday. It should still work on 12V/Gas.
I don't think I can add much more at this stage, and my free posts are disappearing, so that's it for now.
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If you find that your pcb is potted or not repairable www.leisureshopdirect.com show one in stock ( £311 + delivery )
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Thank you so much, it is the same part number which I’ve ordered off eBay for about £5, hubby not confident enough to remove and put back on /solder…but we will definitely update you and let you know how we get on….The PCBs all differ in detail, but it will be something like this:
The 12/230V relay here is (if I recall properly) box under the barcoded label at the right and the in/out connections x101/x102 would be directly above. I think my friend said he had to remove the barcode label to get the part number. On some PCBs it is mounted in a similar position, but at right angles.
If you do remove the PCB, take copious pictures of the connections before detaching.
It was suggested above that the 230V fridge heater could be isolated at the back by temporarily removing the feed there and insulating the wires. We did this in the interim of the fix, which allowed the EHU to be installed "fridgeless" for the duration of the friend's holiday. It should still work on 12V/Gas.
I don't think I can add much more at this stage, and my free posts are disappearing, so that's it for now.
Upvote
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