Domestic RMDT8505 fridge v freezer (1 Viewer)

[Zacshoomans]

I invested recently in a temp data logger - so we’ve done a couple of tests so far and I have some questions that I hope that someone can help with.

On the mains elec - both fridge and freezer work fine. The freezer goes between -5 and -15, and the fridge between 3 and 5deg. This is however at ambient of 6 to 8 degrees (uk in December)....

We’ve now done a couple of day trips out to check 12v and gas.

Driving on 12v the freezer has chilled down to -10 from about -1, on one trip it went down to -18 with a max of -4 - which seems fine, however the fridge didn’t cool at all and warmed up at the same rate as no 12v at all ie 2deg an hour.

On gas though - the fridge also didn’t cool, but again the freezer was fine - apart from it takes 30mins to kick in. Gas took it from -4 to -11 in the hour it was on (parked up on Weston -s-mare beach eating fish n chips!).

So i’m glad that I’ve got the data to now argue with the dealer - but has anyone got any suggestions?

In summary - freezer works on mains elec, 12v and gas - but fridge only works on mains elec..... (with ambient being around 8deg).

We put gaslow in for the fridge - really would like to use it!
Sian

 

[Lenny HB]

In theory it can't happen, there is only a single refrigerant circuit, the freezer only gets colder than the because the same size cooling unit is used in both the fridge & freezer but the freezer is only 20% the size of the fridge. The only thing that could affect it is if the aluminium fins are not fully in contact with the coolant pipe.

The aluminum fins are screwed to the back of the fridge making contact with this pipe, exactly the same in the freezer. Some funsters have found the fridge performance can be improved by renewing the heat sink compound between the pipe & fins. The pipe you see just carries on up to the freezer.

When taking internal measurement the temperature can vary a lot dpending on how the fridge is loaded.

 

[Zacshoomans]

Hi Lenny - thank you for responding - it’s really not the news that I wanted to hear!

If the fridge and freezer only have one circuit - then it should be consistent - which it is on main elec - but not on the others!

The fridge is pretty empty (I’ve got a couple of large bottles of water in there) but I’m not opening the door to check temp as I’ve got an external temp logger with sensors inside the fridge. And the sensor is in the same place (just below the top shelf).

I thought that having cold objects in the fridge means that the fridge keeps its temp when the door opens (as it’s like having ice blocks in there to help chill) - or am I missing something?

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[Richard n Ann]

I would remove the aluminium fins in the fridge and run it. The pipe behind should get very cold and frost up as there is not much heat load on it. If not the system could be short of refrigerant (unlikely) or the heat source driving the system isn't very hot which could be due to the cold ambient temperature.

 

[Richard n Ann]

PS if the pipe does frost up it's the heat transfer paste dried out, it's surprising what difference it makes..

Our 3 way fridge saga

My story just might help someone with 3 way fridge trouble so here goes; We've had our motorhome 3 years now and the fridge was always ok even in Spain's high ambient temperatures, until suddenly about a year ago we were in Spain, temperatures were the usual high twenties and I noticed the...

www.motorhomefun.co.uk

 

[tonyidle]

The differences between using lpg, mains electric, and 12v need to be sorted out first. All three heat sources heat the same part of the cooling circuit and assuming each is working correctly should produce the same cooling performance. 12v performance is, or should be, the only variable - but only because due to the wiring run / wire size used a full 12v is often unavailable at the fridge

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[Zacshoomans]

thanks for the responses - just tried to remove the fins for another test today - but we don't have a screwdriver slim enough to get between the fins - doh!

in the meantime i'll try to share my data - but i've not shared a picture before - so it may not work....

 

[Zacshoomans]

and it didn't work - so i'll try again... this is the first test - on EHU sat on drive - with set to max (5)

 

[Zacshoomans]

this is the 2nd test - a couple of journeys so on 12V - and changed the setting to 3 - but it wasn't on EHU before the trip

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[Zacshoomans]

3rd test - a day out on sunday so a mix of driving and parked up on gas

 

[Lenny HB]

Hi Lenny - thank you for responding - it’s really not the news that I wanted to hear!

If the fridge and freezer only have one circuit - then it should be consistent - which it is on main elec - but not on the others!

The fridge is pretty empty (I’ve got a couple of large bottles of water in there) but I’m not opening the door to check temp as I’ve got an external temp logger with sensors inside the fridge. And the sensor is in the same place (just below the top shelf).

I thought that having cold objects in the fridge means that the fridge keeps its temp when the door opens (as it’s like having ice blocks in there to help chill) - or am I missing something?

Here is the results I did of a temperature check when installing an internal fan, since then I have found mixed results in normal use.
generally it runs quite a bit warmer than those results often between 7 to 9 deg but on one occasion it started to freeze stuff near the door catch. It appears to vary a lot depending on how it's load but it could be the position of my sensor against the back wall I am going to move it more central and see what the results are.

Lenny's Modding the new Gin Palace

@Lenny HB how's the fridge fan modification performing, especially inconsideration of the higher French temps your are currently experiencing? Sorry missed your post, when we were in France it was 31, with the fans ruinning performance was just about acceptable, 8 deg at the bottom 4 at the top...

www.motorhomefun.co.uk

 

[Lenny HB]

this is the 2nd test - a couple of journeys so on 12V - and changed the setting to 3 - but it wasn't on EHU before the tripView attachment 352391

3rd test - a day out on sunday so a mix of driving and parked up on gasView attachment 352392

Can't see the results very well, I assume the lower blue line is the freezer.

You don't say what your van is but judging by the temp increase when driving I would guess a Brit van where they always use undersized wiring.

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[Googlebot]

My fridge is exactly the same, its currently in Travelworld for the 4th time to investigate why it won't cool down past 10 degrees on gas. On electric it is absolutely fine.

If they ever get to the bottom of it, I will update the thread.

 

[Zacshoomans]

The van is a 2013 Burstner.

We've just managed to get the screws out of the fins - but the fins are really stuck on solid. No movement at all. Really nervous about forcing it!

I really don't understand all this - so apologies for silly questions.

Can anyone suggest other tests that I need to do?

Just realised that the first EHU test that I showed was set to max - whereas I took it back down to 3 as it was getting too cold. I'll try the EHU on 3 now to see if it drastically changes the fridge pattern

 

[Zacshoomans]

My fridge is exactly the same, its currently in Travelworld for the 4th time to investigate why it won't cool down past 10 degrees on gas. On electric it is absolutely fine.

If they ever get to the bottom of it, I will update the thread.

Does the freezer still perform - but not the fridge? It really is frustrating isn't it

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[Zacshoomans]

Can't see the results very well, I assume the lower blue line is the freezer.

You don't say what your van is but judging by the temp increase when driving I would guess a Brit van where they always use undersized wiring.

apologies - its really difficult to get the graphs on the same page - yes freezer is the bottom line

its a german van - burster 2013

 

[Richard n Ann]

but the fins are really stuck on solid. No movement at all.

Can only be frost holding it on if all the screws are out ?

 

[Googlebot]

Does the freezer still perform - but not the fridge? It really is frustrating isn't it

Not really, as soon as you load it, it gets too warm and unfreezes.

It is indeed extremely irritating.

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[jockaneezer]

They sometimes perform better on gas if you have the stat set to the midpoint.

 

[Lenny HB]

We've just managed to get the screws out of the fins - but the fins are really stuck on solid. No movement at all. Really nervous about forcing it!

I really don't understand all this - so apologies for silly questions.

Can anyone suggest other tests that I need to do?

Just realised that the first EHU test that I showed was set to max - whereas I took it back down to 3 as it was getting too cold. I'll try the EHU on 3 now to see if it drastically changes the fridge pattern

If it's running OK on mains it can't be the cooler unit as there is only one just different ways of heating it.

The van is a 2013 Burstner.

Should work fine on 12 v unless a faulty element or control circuit.

 

[Lenny HB]

My last van with the 8505 fridge from new it didn't cool that well on gas and the burner sounded like a furnace, had the burner replaced and it was quieter and ran cooler. While in Greece the ignition started playing up, the ignitor wire had tracked out, as easy repair with self-amalgamating tape, while repairing it I had the burner out. After refitting the fridge worked better than it ever had.

Although the burner position isn't adjustable (unless you bend the mounting lugs) the position of it does appear to be critical, so it maybe worth playing around with it.

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[Googlebot]

Travelworld have replied, they think it’s a problem with the cooling unit which they have ordered. I did point out it was working on electric but they didn’t seem to think as well as it should be.

Part will arrive in next 10 days so I will update then.

 

[autorouter]

I notice that the cooling does not start on the first drive period, but starts (like you would expect) on the second and subsequent drive periods. Is this normal, or is it a control board fault? Or a sticking relay?

 

[Lenny HB]

I notice that the cooling does not start on the first drive period, but starts (like you would expect) on the second and subsequent drive periods. Is this normal, or is it a control board fault? Or a sticking relay?

That must be a fault, if it was a sticking relay I wouldn't expect the behaviour to be consistent, but for the price of a relay compared to a PCB probably worth changing.
What happens if you out a 12v signal on the S + terminal, it should switch straight to 12v. The S+ terminal is where you wire the AES output from the solar regulator if you ones that has it. It's how mines wired.

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[tonyidle]

My fridge is exactly the same, its currently in Travelworld for the 4th time to investigate why it won't cool down past 10 degrees on gas. On electric it is absolutely fine.

If they ever get to the bottom of it, I will update the thread.

I spent (wasted) a lot of time trying to sort the same issue on my last van. Eventually I decided to change the burner assembly. That cured it but only because the wrong burner had been fitted before I bought the van. Fitting the correct part solved the problem - unsurprisingly.

 

[Googlebot]

I spent (wasted) a lot of time trying to sort the same issue on my last van. Eventually I decided to change the burner assembly. That cured it but only because the wrong burner had been fitted before I bought the van. Fitting the correct part solved the problem - unsurprisingly.

It wouldn’t surprise me, they don’t make it easy to find the part numbers.

I couldn’t find a cooling unit for it online, they all said discontinued so I wouldn’t be surprised if it means a new fridge.

 

[Googlebot]

Well, it’s back and surprisingly working at the moment.

The cooling unit is new, also the burner. Not sure if the burner assembly was changed this time or last time (it has took them 6 attempts), so as it was working on electric my hunch would be the burner assembly.

The flame roar certainly seems louder now as well.

So in summary, if this happens to yours, spend £70 on the burner assembly then over a £1000 on the cooling unit.

John

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[Zacshoomans]

Glad to hear yours is working now.
We are still collecting data - this weeks job is to write it all up to try to get dealer to accept that there is an issue.

 

[Googlebot]

If it makes you feel better, I was told all sorts of piffle. The best one was that these fridges aren’t designed to get colder than 10 degrees Celsius. How I laughed at that one!

I wish you luck, it took me 4 months, 6 visits to the workshop and one failed attempt for them to turn up at my house.

The industry is alas, rife with poor service and outright scandalous behaviour.

 

[Zacshoomans]

We had an interesting conversation with gaslow last week. We used to get a really bad gas smell as well as the poor performance of the fridge.

Gaslow suggested that the tanks had been overfilled when they were initially filled by the the dealer - which causes the smell and the burner not working properly (as too much compressed oxygen in the mix). And then when burstner ‘cleaned’ the burner they might have also damaged it.

Since we first refilled the tanks (carefully stopping at 80%) the gas smell is hugely better - although the fridge performance on gas (and 12v) hasn’t changed.

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