Neff Warming drawer failures

Peter Perfect

Standard Member
Hello.

I have exactly the same issue with the flashing light on the Neff N17HH11N0B/02.
I tried to take it apart last night and managed to get so far with it, however, can someone please explain to me how to get access to the Control Module. I removed the whole chassis from the enclosure so that I could remove the right-hand side panel - and at least I can see the Control Module but I'm not sure how to proceed from there.
 
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Boiler10

Standard Member
On the Siemens model you just pull off the control knob and there are 2 screws behind it. So access is mainly from the front (inside the drawer). Make sure the power is off as the connectors and circuit have mains voltages.
 

kbfern

Distinguished Member

I use one of these and had it for a couple of years and works just fine.

I had a £14k new kitchen a year ago and nearly included a warming draw, I am glad I didn't bother reading about this fault it is really bad considering what they cost.
 

Nick0207

Standard Member
Well here's an interesting thing...

My ******* useless Neff warming drawer has gone wrong for the third time, first the drawer connector, second the drawer element and now, for the third time, with the dreaded flashing red light and the hotplate not heating up (the side heating element with the fan was working on position 2 of the switch) which I am assuming was the power control module. As I am getting a bit fed up with removing the oven above it to get the warming drawer out, I opened the drawer, gave the casing inside the unit just behind the rotary switch a thump with a wooden spoon several times and, bingo, the red light now stays on and the hot plate is working again!! This means that this fault is most likely to a sticky relay in the power control board for the drawer element, which, if you look at some of the other very useful posts above from others, is replaceable, but a bit of a job.

No idea how long it will last but at least, for the moment, it's working again. As I seem to have a lot of spare time at the moment I might think about replacing the relay eventually.
 

philip44

Standard Member
If and when you need to change the relays, an upgrade is possible with this 15A current contacts relay from Radio Spares - and maybe other outlets.

This is RS Stock 134-8400, a Relpol SPDT Non-Latching Relay PCB Mount, 12Vdc Coil, 15A current contacts - £3.05.

Dimensions are the same as the original relays.

From reading all the posts, no-one has rectified the flashing indicator problem by replacing the "kettle plug and socket". In all cases, it would look like the control module relay(s).
 

Nick0207

Standard Member
From reading all the posts, no-one has rectified the flashing indicator problem by replacing the "kettle plug and socket". In all cases, it would look like the control module relay(s).
Originally I thought I had as replacing the socket did cure the problem, but with hindsight it may have been me disturbing the relay enough to make it work again. After replacing the socket it did work for several months though. I'd agree though it probably isn't the main failure.
 

Niksles

Member
As I discussed in my previous post, I had some luck with removing the circuit board from the panel (very easy but make sure the drawer is isolated from the electricity supply), and giving the relays a couple of hard taps with a screwdriver handle.
This fix lasted approx 4 months or so (since my earlier post) and then the drawer temperature dropped. I know that the correct temp on level 4 is approx 80 degrees F or thereabouts (from a newly installed drawer) and mine was only reaching 50 or so.
Again I removed the board and wacked it, and it is now back to the correct temp.
How long this will continue to work I know not, but ultimately the board will need replacing, I’m sure.
Personally I consider the replacement of the relays a risky prospect; they are very close to other parts on the board and unless one is proficient with soldering circuit-boards I would steer clear.
I appreciate that a new board is over £100, (with no guarantee of long-term operation), but at least the board swop is very simple.
 

philip44

Standard Member
......the replacement of the relays a risky prospect; they are very close to other parts on the board
Being an electrician, I usually try to repair something before fitting a replacement. Mainly, because having been a marine electrician on deep sea ships, I had no alternative other than repair as a first instance. If that failed, I had to wait until the ship got to a port to be able to purchase new.

De-soldering, I used a hot setting on my Portasol gas soldering iron, and a solder sucker. Solder wick will do the same job. I used it very hot so as not to allow the heat to transfer to the other components.

You have nothing to lose in replacing the relays, if you are contemplating replacing the whole board. If you succeed, you are on a winner!

Recently, my Bosch SDS blew the suppressor capacitor - it makes a hell of a stink!! That was a good time to replace it, and also to renew the brushes. Success on both accounts.
 

Lennysham

Novice Member
Hi all
Ihave the 290mm warming drawer and the drawer won't close. I took out the latch which seems to be working fine its like the drawer pin isn't going in far enough to catch and stays open...any suggestions this latch is 35pound
 

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Boiler10

Standard Member
As I discussed in my previous post, I had some luck with removing the circuit board from the panel (very easy but make sure the drawer is isolated from the electricity supply), and giving the relays a couple of hard taps with a screwdriver handle.
This fix lasted approx 4 months or so (since my earlier post) and then the drawer temperature dropped. I know that the correct temp on level 4 is approx 80 degrees F or thereabouts (from a newly installed drawer) and mine was only reaching 50 or so.
Again I removed the board and wacked it, and it is now back to the correct temp.
How long this will continue to work I know not, but ultimately the board will need replacing, I’m sure.
Personally I consider the replacement of the relays a risky prospect; they are very close to other parts on the board and unless one is proficient with soldering circuit-boards I would steer clear.
I appreciate that a new board is over £100, (with no guarantee of long-term operation), but at least the board swop is very simple.
When I replaced the relay on my board I cut the top off the old one to see what was wrong with it. I expected to see burnt out contacts on the normally closed pair but there wasn't anything obvious, however the resistance across the closed contacts was much too high so this is clearly the fault. I'm therefore not surprised that tapping the relays buys you a few more weeks of operation. Using solder sucker can be tricky as you need to be quick and the nozel can hit the board and cause damage. Solder wick is easy to use (plenty of videos) and if you keep moving to a new piece of wick you can clear all the solder from the pins. It even gets the solder from deep in the hole from the wicking action so the relay can be prised out as there is no mechanical strength left in the tiny remaing solder. So For a few pounds you could get some wick and a relay. Nothing to lose? My relays, see earlier post were about £4 for 4 on eBay. By the way you only need to do one relay, it's the second one in so NOT the one in the corner of the board. Good luck Peter.
 

philip collins

Novice Member
Seems that the relay for the heater tray is failing on many units. The blower element and fan are a lower resistance (90R) so will be a similar switching current but does not appear to fail as much. These relays are switching quite often and I did not see any snubber connected to the contacts. I am replacing the relays but dont expect them to last without some contact protection. I have a theory that the tray heater is somewhat inductive and causes contacts to burn so I will fit 220R + 0.68uF across the contacts. Comment on this plan anyone?
 

philip collins

Novice Member
Additionally I see some circuitry near the relay hot side and I am wondering if this is 'sniffing' the voltage drop on the contacts and may disable the relay driver if it is too high. I will reverse - engineer the circuitry and report back. Does anyone have a circuit of this pcb ?
 

Nick0207

Standard Member
A quick but temporary fix to the relay problem, which works on my unit, is to open the drawer with the unit turned off and then give the metal casing to the side of the control switch a whack with a wooden spoon (to prevent scratches) a couple of times. The mechanical shock seems to resolve the problem and at least gets the drawer warming up! Not a substitute for a permanent fix but very handy! As I am able to plug a power monitor into the socket that feeds the drawer i can easily tell if it has started working by the power consumption (between 400-900 watts)
 
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philip collins

Novice Member
Got fed up with whacking the controller. The circuitry around the relay has both the 'Kettle' connector and the relay contacts in the series circuit so that explains why the relay and the connector failure present the same fault . I am going to put some silicon grease on the kettle connector to reduce the contact oxidation. Still waiting for the new relay and the snubber components. Lets hope that will give us a much longer lasting warming drawer. Lets hope this is the fix that we were all looking for ! Watch this space!
 

Peter Perfect

Standard Member
My Neff N17HH11N0B/02 seems to be still working (just) but only at the highest setting.
I tried getting access to the Control Module by pulling the control knob off from the front but it didn't want to budge. I thought that this might not be the correct way with this model. Can anyone confirm how I can get access to the Control Module please.
I gave the whole thing a whack a while back which stopped the light from flashing, but as I say, it only works at the highest setting now.
 

Nick0207

Standard Member
i'm afraid you have to remove the whole drawer unit from it's housing to get access. If you have an oven on top of the drawer you MUST remove the oven as well unless it is sitting on it's own shelf (not a usual fitment). Unfortunately it's a bit time consuming and you ideally need a table at oven base height to pull the oven onto.
 

philip collins

Novice Member
The Knob is a push fit and mine was a very tight fit. I had to lever it off. If your warmer only works on the highest setting , it suggests that the switch has failed(happens but unusual) . A more logical explanation is that the fan heater only is providing some heat and not the heated tray. The tray should be getting very hot.
 

Danwoods27

Novice Member
Hi guys.
New to this forum business but i have recently had a neff plate warmer installed (August this year) and only used it a handful of times. When i turn it on now the red light starts flashing and it fails to provide any heat.
Anyone else had this with a new product? Very frustrating!
Thanks in advance! :D
 

philip collins

Novice Member
The way forward is up to you but mine (like many others) failed inside 3 years . You should certainly be able to get Neff to fix it FOC since it is in warranty. For those whose drawer is outside warranty, the replacement parts which can ~ £120 , will only give further trouble again are not a permanent fix and Neff don't acknowledge that there is a problem so no modification will have been done to correct the design fault on the replacement parts. A few of us are working on a fix but this needs a modification to the power module and or the Heating tray connector by a competent engineer. I am in the process of modifying my Warming drawer power module . One tip (see previous post on here) you may want to try is to whack the control board that normally works by 'unsticking' one of the relays on the control PCB. It sometimes works by firmly hitting the metal enclosure that surrounds the Control board to the left of the Knob. . I will not buy another Neff warming drawer or any replacement parts since they are not a long term fix. Good luck!
 

philip44

Standard Member
Hi guys.
New to this forum business but i have recently had a neff plate warmer installed (August this year) and only used it a handful of times. When i turn it on now the red light starts flashing and it fails to provide any heat.
Anyone else had this with a new product? Very frustrating!
Thanks in advance! :D
I assume you mean August "last" year.
If so, it is still under makers guarantee, so touch nothing and contact the seller or maker for a service visit/repair.
Sounds like a hot-plate relay failure - once again/more. Alternatively (though less likely) a "kettle plug" problem.
Invoke the guarantee.
 

philip collins

Novice Member
Hell All,

Here is an update to my modified Power module for my Neff Warming drawer.
NeffWDrawerPowermod.jpg


Not the prettiest of mods but functional. The snubber network is connected across relay contacts that control the tray heater. The capacitor is a 275Vac 100nF and resistor 220R 5W. The resistor power rating is a bit over the top but what I had in the drawer. A further failure occurred in a 220R resistor (smt device marked 2200) and I replaced it with the same type of resistor that I used in the snubber. The modified Power module has been running for a few hours now on the bench so I will be rebuilding the warming drawer and putting it back in the kitchen tonight. The Tray heater control relay is rated at 10A so on paper it should be OK with the 2A load of the tray. My guess is that the contact life is being seriously degraded by the long leads to the tray and perhaps the heater itself presenting an inductive load to the relay. The relay is worked quite hard and cycles every 20 seconds when the drawer is powered up in switch positions 3 & 4. Should still be within its capability. The snubber should significantly reduce contact wear due to arcing. If this fails then I will replace and re-site the relay with a 20A capability and snubber of course. Oh, BTW If any of you are fed up with Neff and thinking to buying a Bosch or Siemens warming tray, note that they both use exactly the same power module as the Neff.
Happy days! All comments welcome.......
 

MM0ICM

Novice Member
Thank you all. I have had the same problem exactly. New relay due today, so that is hopefully the end of the problem.

Phillip, I can't see in your photo exactly where you have wired your snubber. It appears to be between NO and NC (pinout 12 and 14 on the Relpol data sheet). Have you a circuit diagram?

I cut the top off of the failed relay and the normally closed (NC) contacts were darkened and high resistance but the normally open (NO) were badly burned. I wonder if the NC circuit just senses 5V to know when the drawer is closed then closes the NO to power up. The NO maybe burning and sticking closed, thus the 5V is open and the controller believes the drawer is open. A good rap releases the burned contact. Perhaps a snubber circuit might be needed across both NC and NO?
 

philip collins

Novice Member
hello MM0ICM,
I screwed up! The snubber (now 100nF + 220R) was wired across the pins 12 & 14. I meant to connect across the N/O contact.
I have realised that in doing this, the snubber would be constantly live with 240V across it. It seems crazy that this PCB remains constantly powered up even with the switch off. (I might need to confirm this but I believe it to be true. What is even more bizarre is that the DC power supply 0v to the processor is also connected directly to the 240Vac line side!) Not a problem since the PSU relays isolate the load side but weird design practise nevertheless)
I don't believe that the NC contact is under any significant stress.
I have therefore decided to connect the snubber to the load connections (Heater tray) at a convenient place on the PCB. I have not tried this yet - waiting for 100nF caps to arrive. I will connect the snubber from pin 11 - RM50 and 240Vac live. Seems safer this way. I will take a photo when I have done this.
You are right about the 5V signal - its there as a test voltage for a comparator that tells the uC that the tray is present. The N/C connection applies 5VDC to the tray that collapses to ~2v when the tray is connected and triggers the comparator. I have got some sketches of the circuit that I have made. I will post them here. Its got to be the inductive load effect that is burning the contact since the load is only 2A steady state so the snubber will fix the problem. The designer has not tested this circuit for back emf on the relay contact.
 

MM0ICM

Novice Member
Looking forward to the photos.

The whole circuit seems over complicated, what is the problem with the drawer being heated all the time on a retracting cord and a simple stepless thyristor power circuit. All old school cheap and reliable.
 

philip collins

Novice Member
You are right about the control. Its too complicated. I will scrap the PCB and put in something like you suggest if this mod fails.
Cant power the drawer continuously since a spillage with the drawer open will be dangerous. These kettle connectors seem quite reliable. However there are two design faults with their implementation.
1. the connector should be mechanically floating as in a kettle.
2. the penetration of the connector pair is impaired by the drawer closing catch that requires the drawer to be not totally closed to permit correct operation of the toggle mechanism. Note that the drawer closure can be adjusted by an allen key inserted underneath the housing.
Thanks for your feedback. Interesting to read!
 

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