Dometic RMDT8505 fridge problem

OldAgeTravellers

OldAgeTravellers

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I know there are many threads on here but I have not found an answer.
we have been full timing in our Hymer B614SL for four months now so the fridge has been on constantly. 230-volt, gas & 12-volt
when motoring and solar when sunny. It is a Tech Tower RMDT8505.
yesterday after motoring for about two hours we found that although the blue light was on it did not appear to be cooling. Now this model has always cooled just as well regardless of the power source, unlike many earlier versions.
The blue light was on but none of the panel buttons appeared to do anything and the light didn’t come on when opening the door.
I had read about the problem of condensation in the lock/light assembly so dismantled it and it didn’t seem damp but dried it carefully from any condensation. I couldn’t find a fuse for it so disconnected the 12volt feed on the rear. Left it for half an hour but the panel didn’t restart.
I am sure if I take it to a service place if I can find one near Telford where we are if, they will immediately replace the board £1,000 thank you then “oh dear that didn’t work”. I actually can’t immediately see how to get to the board. That may have condensation on it causing the problem.
So, if anybody has any ideas or knows of a service place they can recommend I would be grateful.
Steve
 
OldAgeTravellers said:
I couldn’t find a fuse for it so disconnected the 12volt feed on the rear.
Click to expand...
Which EBL model is it? Probably the fuse 'Spare 4A' or 'Spare 4B' will be the fridge low current supply, because it is a permanent 12V, not switched off by the panel 12V switch. It might power other things too.

To get at the control board, on many of these fridges the control knobs simply pull off, and they hide some screws for the front panel.
 
Try d
David newel leasure services Telford
 
Waiting for DMS. to look into my 8505. Works on gas but not on 12v or hook up. No slots until mid September.

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autorouter said:
Which EBL model is it? Probably the fuse 'Spare 4A' or 'Spare 4B' will be the fridge low current supply, because it is a permanent 12V, not switched off by the panel 12V switch. It might power other things too.

To get at the control board, on many of these fridges the control knobs simply pull off, and they hide some screws for the front panel.
Click to expand...
Thanks it was 4B but only a 2 amp fuse rather than the 10 in the EBL101 diagram
 
Thanks for the suggestions.

Been looking at it this afternoon, drying out the lock and very slight dampness in the front electronics and a few times when reconnecting the 12 volt it has lit up then gone off again so possibly a dry joint or a component failing. Discovered a bit of play in the ribbon cable from the control box at the rear so may be able to look closer at the electronics tomorrow.
Steve
 
Another vote for Dave Newell, he's in Telford.

Terry
 
OldAgeTravellers said:
I know there are many threads on here but I have not found an answer.
we have been full timing in our Hymer B614SL for four months now so the fridge has been on constantly. 230-volt, gas & 12-volt
when motoring and solar when sunny. It is a Tech Tower RMDT8505.
yesterday after motoring for about two hours we found that although the blue light was on it did not appear to be cooling. Now this model has always cooled just as well regardless of the power source, unlike many earlier versions.
The blue light was on but none of the panel buttons appeared to do anything and the light didn’t come on when opening the door.
I had read about the problem of condensation in the lock/light assembly so dismantled it and it didn’t seem damp but dried it carefully from any condensation. I couldn’t find a fuse for it so disconnected the 12volt feed on the rear. Left it for half an hour but the panel didn’t restart.
I am sure if I take it to a service place if I can find one near Telford where we are if, they will immediately replace the board £1,000 thank you then “oh dear that didn’t work”. I actually can’t immediately see how to get to the board. That may have condensation on it causing the problem.
So, if anybody has any ideas or knows of a service place they can recommend I would be grateful.
Steve
Click to expand...

Hi Steve,

You mention using solar when it is sunny. Is this through an inverter? The specs on these type of fridges are about 4kw per 24h, so would be using 166w per hour, so probably about 200w after conversions and inefficiencies. Is that how you calculate power requirements?

Thanks
BigDean
 
BigDean said:
Hi Steve,

You mention using solar when it is sunny. Is this through an inverter? The specs on these type of fridges are about 4kw per 24h, so would be using 166w per hour, so probably about 200w after conversions and inefficiencies. Is that how you calculate power requirements?

Thanks
BigDean
Click to expand...
Hi BigDean,
No inverters here. My Fridge has an ”S” input to switch over to 12-volt when the sun is shining as well as a “D” input to switch over to 12-volt when the engine is running. This is controlled by a Votronic MPPT solar controller which switches the fridge to 12-volt when there is enough solar input and the batteries are at about 95%. On a sunny day in the UK my fridge will be powered from the sun from about midday till about 4pm a significant saving on gas. In Morocco it is on solar for most of the day.
I did the same with my previous Motorhome with a standard fridge using a bit of simple electronics to switch to battery using the ”D” input.
Hope this helps.
Steve
p.s. On a sunny day in the UK I get about 10-amps from the panels and of course if it isn’t opened the fridge does not need power all the time.

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OldAgeTravellers said:
Hi BigDean,
No inverters here. My Fridge has an ”S” input to switch over to 12-volt when the sun is shining as well as a “D” input to switch over to 12-volt when the engine is running. This is controlled by a Votronic MPPT solar controller which switches the fridge to 12-volt when there is enough solar input and the batteries are at about 95%. On a sunny day in the UK my fridge will be powered from the sun from about midday till about 4pm a significant saving on gas. In Morocco it is on solar for most of the day.
I did the same with my previous Motorhome with a standard fridge using a bit of simple electronics to switch to battery using the ”D” input.
Hope this helps.
Steve
p.s. On a sunny day in the UK I get about 10-amps from the panels and of course if it isn’t opened the fridge does not need power all the time.
Click to expand...
Thanks Steve,

Very interesting. I don’t think the Thetford we have has an S, so would have to tap into the D.

Sorry to be a pain, but did you use a manual switch or an automatic one? Any details appreciated.

I have a Victron system so should be able to take a signal from the CerboGX to only switch when certain criteria are met.

Thanks again.
 
BigDean said:
Thanks Steve,

Very interesting. I don’t think the Thetford we have has an S, so would have to tap into the D.

Sorry to be a pain, but did you use a manual switch or an automatic one? Any details appreciated.

I have a Victron system so should be able to take a signal from the CerboGX to only switch when certain criteria are met.

Thanks again.
Click to expand...
Hi,
If you can get a signal from your solar controller then all you need is two diodes into the “D” input on the fridge to stop feedback. One connected to the alternator feed and one to the solar controller.
Obviously I don’t know your system so check suitability first and don’t do it if you are not confident.
Could be worth a switch in the “S” feed to switch it off also. I have also put a relay in activated by the 230-volt so it doesn’t go on to solar when on hookup.
Hope this helps.
Steve
 
OldAgeTravellers said:
Hi,
If you can get a signal from your solar controller then all you need is two diodes into the “D” input on the fridge to stop feedback. One connected to the alternator feed and one to the solar controller.
Obviously I don’t know your system so check suitability first and don’t do it if you are not confident.
Could be worth a switch in the “S” feed to switch it off also. I have also put a relay in activated by the 230-volt so it doesn’t go on to solar when on hookup.
Hope this helps.
Steve
Click to expand...
Thanks again. Will research more…..
 
Hope this helps you and possibly save you money
I had the same problem a few weeks ago when the temp at the top vent was 53° that’s with using 2 fans to vent the hot air out. The control panel just shut down. I checked everything and eventually solved the problem by pulling the 2 wires (brown and black) out of the black box at the back of the fridge on the schematic it is described as INput heating element 12v dc. This seamed to reset the whole system and the fridge started working again

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Poutie57 said:
Hope this helps you and possibly save you money
I had the same problem a few weeks ago when the temp at the top vent was 53° that’s with using 2 fans to vent the hot air out. The control panel just shut down. I checked everything and eventually solved the problem by pulling the 2 wires (brown and black) out of the black box at the back of the fridge on the schematic it is described as INput heating element 12v dc. This seamed to reset the whole system and the fridge started working again
Click to expand...
Sounds interesting Poutie57 , I don’t have a schematic unfortunately will have to search a bit harder. So unfortunately I am just dealing with a “black box” literally.
How did you stumble on or work out this solution?
I have been checking for moisture in the lock and display as this is reported as a problem And checking for good contacts. Today I was going to check for dry joints on the display module.
Did you just pull the wires with the power on or power off, disconnect, power on, then reconnect with power off?
Just trying to work out some logic to the process.
Thanks for the input.
Steve
 
Here you go I hope it opens up ok as how I solved it put luck I’m afraid I tried all the connections on the rear with a multi meter and all seemed ok fuses were also good so I just started to pull wires out and as I pulled these there was a click and started working again.
I might just say that an electronics mastermind friend of mine did tell me that above 47° Some resistors shut down and since we left the provonce in France it’s all worked ok
 
Sorry I don’t think it uploaded so I took a screenshot
F40BDAC0-55CE-4D6D-A64D-9986CE7AC967.png
 
Poutie57 said:
Here you go I hope it opens up ok as how I solved it put luck I’m afraid I tried all the connections on the rear with a multi meter and all seemed ok fuses were also good so I just started to pull wires out and as I pulled these there was a click and started working again.
I might just say that an electronics mastermind friend of mine did tell me that above 47° Some resistors shut down and since we left the provonce in France it’s all worked ok
Click to expand...
Screenshot fine thanks. My black box is a long thin one so a different unit to yours. But gives me something to try.
I was in Wales at the time so I don’t think it was a heat issue! :giggle:
Thanks.
 
We too have a problem with our RMDT 8505 -- door swings open whilst travelling - beeping from fridge letting us know the fridge door not holding. Had a look, to me seems as if the catch on the door not retaining. Supposed to push down two buttons to release and open the door - but seems to be not moving when buttons pushed. Freezer door works fine
Any ideas guys ... is there an easy fix ??

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Yorkshire blood myself, so guess I will be shocked. Wonder if I can take the door off and get inside to look
what's wrong :unsure:
 
Great news ..... I have fixed it (y)
Took the catch off the door and there was a spring inside which had broken. Replaced with a spring from inside a pen , works perfectly. Put the broken spring inside the pen and it to works to ---
Happy Days ::bigsmile:::bigsmile:::bigsmile:::bigsmile:
 

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