Siemens Bosch Washer Dryer Faults and Repairs

Do you have a Siemens / Bosch iQ series washing machine or washer dryer like the iQ500 WD15G421GB that’s faulty? If so you may be able to repair it yourself without the high cost of BSH service engineers.

Warning: Disconnect all electrical appliances before attempting any repairs and take care when moving heavy appliances.

Faults covered in this post:

1. Tumble dryer won’t dry
2. Drain pump filter jammed
3. Detergent residue on clothes after washing
4. RCB circuit breaker tripping

There are many excellent Youtube videos that can also help you repair and fix your Siemens / Bosch appliances but they do take time to watch and omit some details that you may need.

This post is for the Siemens iQ500 WD15G421GB but there are many similar models so you may find it useful even if your appliance is a different model. See the the links below to Youtube and spare parts finder.

1. Tumble dryer won’t dry

Our machine was over 7 years old – well out of warranty, so the cost of a BSH engineer callout plus parts would have exceeded its value. So I thought it’s worth trying to diagnose what’s wrong and source replacement components directly. Clothes were wetter after running the dryer programme and so I guessed the tumble dryer was refusing blow hot air. All fluff cleaning programmes had been run.

The iQ500 beast weighs a ton (150kG) and difficult to move in our small utility room so I ordered some replacement parts from the excellent Ransom Spares here in the UK. I’m not affiliated with Ransom Spares or have any payback if you decide to buy from them. Ransom are very helpful, stock many parts and are cheaper than direct from BSH Spares Parts UK. The BSH site is useful to identify the part number from the appliance diagrams and see what’s inside – see the links at the end of this post.

As the tumble dryer was not heating but the washing machine seemed okay I ordered some thermal cutouts and a NTC temperature sensor using the BSH diagrams and numbers as a guide. I guessed, as it turned out wrongly, the dryer heater was not switching on due to a cutout. If I’d struggled to pull the appliance out and open it to check first I’d have saved the cost. Braun won over brain!

With the top removed the dryer fan and heat channel assembly along with the cutouts and sensors are accessible. Pull the connectors off and use a multimeter to check continuity. The cutouts should be closed at normal temperature so a high resistance reading on a multimeter will indicate if faulty or tripped. Press the central button to reset the cutout if tripped and the breaker should close (low resistance < 1Ω). If it remains open circuit replace the cutout.

The NTC temperature sensors are used in several places to monitor dryer air temperature before the fan and after the heater along with water temperature for the main heating element (more later). It should read around 4k ohms at room temperature. If you find it’s higher than 20kΩ replace the sensor. remember to reconnect all the push on leads. They are held in a loom so it’s difficult to get them mixed up.

I found nothing unusual with either cutouts or sensors so I turned attention to the dryer heating element. Cost around £25 for spares that I will keep incase of problems later.

A reading of around 30 ohms found the tumble dryer heating element was also okay. So why did the tumble dryer not heat? I’d set the tumble dryer programme to the minimum 15 minutes setting to check if it worked and found it started by opening the cold water valve to let in some water. This seemed odd but the iQ500 uses a condensing dryer and needs some water to condense I thought. But it did not heat and the drum remained wet at the end of the cycle. Could the programmer be faulty? Or was the pump blocked?

Google searches returned many rabbit holes to explore. Many report a blocked fan that reduces air flow and overheating which triggers the cutouts. The fan housing is held by several torx bolts that can be unscrewed to check inside. However our iQ500 designers had placed one bolt under the top chassis – impossible to remove – see below – go figure why? So I cut away a small section of the chassis.

iQ500 Chassis cut away to access fan bolt

Dryer fan bolt hidden under chassis top right.

Dryer fan housing opened to remove dust

I discovered some dust in the fan but nothing serious that could affect flow. I reassembled the fan, replaced the top to try again. The problem must be due to the pump so I had to find a way to remove the fluff filter.

2. Drain pump fluff filter

Our Siemens washer dryer had featured in an earlier rant post about the jammed filter and I found the drain pump fluff filter had indeed jammed again. The post is critical of BSH’s design which allows debris to jamb in the filter preventing it unscrewing. It seems a deliberately bad design that’s set up to fail requiring a service engineer.

Even a wrench would not open the plastic filter this time, it would need to be accessed internally. I’d found a Youtube video showing how to remove the front panel if you could lift up the front side, to access the pump.

Removing the back cover it’s possible to see the drum hose and pump but it’s near impossible to reach in and release the hose clip. You have to access via the front.

Pump and hose clip from rear

As the video shows the BSH designers have set a few more obstacle traps. You must first remove the top panel taking care not to break any connecting wires. Then you need to remove the rubber door seal – don’t worry about the door – this comes away, together with the front panel. And don’t forget to remove the manual door release from the lower filter pump housing. There are two hex head screws underneath that hold the front panel so you need a 8mm flat spanner and lots of patience or a way to tilt 150kg without severe injury!

Front panel removed to access pump drum hose

With the front panel removed it’s easy to unclip the drum hose leading to the pump and fish out whatever’s stopping the fluff filter from turning. In our case it was an allen key, 9 plastic shirt stiffeners and unmentionable gunk. It beggars belief how any engineer could have dreamt up such a filter design. It’s set up to fail.

Debris blocking pump hose

iQ500 drain pump fluff filter

With a clean filter and hose simply reverse your steps to put it back together. It helps to have a hook tool to replace the door seal. And don’t forget to relocate the emergency door release or you will curse when you find you can’t open the door.

Running the short dry programme after clearing the pump still resulted in no heat but at least the drum was not soaking wet. More google searching found a helpful mention that the last 15 minutes of any drying programme is to cool down. It turned out those ever clever BSH designers had designed a 15 minute tumble dry programme that does not actually heat! Really, I did not expect that.

When selecting a 1h dry programme the tumble dryer lived up to its name again – problem solved.

So if your tumble dryer no longer dries open the little flap at the bottom and check if the filter is blocked. And keep checking the filter regularly!

3. Detergent residue to clothes

Check if the drain pump filter is blocked. This prevents the drum from fully draining and an effective rinse cycle. In our case this was linked to the tumble dryer not drying as the drum was too wet and the condenser failed.

If you can’t remove the filter see Drain pump fluff filter above.

4. RCB circuit breaker tripping

If you find the lights go out or other devices don’t switch on, the culprit could be your washing machine / washer dryer. Most homes now feature RCBs which detect potentially dangerous earth leakage conditions. The RCB trips when a small current flows from live or neutral to earth. This occurs when a washing machine heating element’s insulation fails and allows current to flow from mains to the element’s casing which is earthed. Similar faults are found in dishwashers and kettles, toasters, ovens, electric hobs, etc.

You can identify which appliance is causing the RCB to trip by unplugging each one and reseting the RCB to see which trips it. Built in appliances should have a double pole isolation switch that effectively ‘unplugs’ it.

A simple ohmmeter to check resistance between earth and live / neutral at the plug may not show the problem as the appliance only switches on its heating element when it runs. You need to check the heating element continuity directly – and that means opening up and disconnecting the terminals.

Location of heater element fixing

Check the element engages with the internal clip

There are many videos showing how to replace heating elements in washing machines and washer dryers (see links below) such as our Siemens iQ500 WD15G421GB. Here are some tips to help you try. Remember always unplug your appliance before carrying out any work inside.

1. To check if the element is faulty remove both live and neural push on connectors and measure the resistance between the element’s earth terminal and live / neutral. Use the meters highest resistance range – any reading indicates a leakage. If you’ve drained the water from the drum you may not see a reading.
2. Genuine replacement heating elements for Siemens / Bosch cost around £50. There are many alternatives available but unless you know the OEM part number it’s best to buy a genuine part.
3. Drain the drum using the small hose in the drain pump filter accessed via the flap on the front of the machine.
4. The element is held in place by a rubber compression seal which is released using the single nut – see below. First remove all three push on connectors and the temperature sensor plug. Then unscrew the nut using a 10mm socket. Use a manual socket spinner so you can judge the torque needed to undo. Impact drivers can be too fierce.  The nut does not need to be fully removed. The element should pull out but may need prizing out of limescale has built up. Have a tray / sponge beneath to catch any residual water and deposits.
5. The element is held in place by a clip inside the drum housing. After removal, use a torch to look inside to see where the clip is located and how the element slides into place – as below. Failure to do so could result in the element touching the drum leading to early failure as it rubs though or melting the plastic drum housing.
6. Note the alignment and remove the temperature sensor from the old element to insert into the new one. Make sure the nut is undone in the new element to ease insertion.
7. Failure of the heating element will likely show as black marks where the metal casing has corroded.
8. After inserting the new element and locating the internal clip, rotate the drum via the real belt to check it’s not hitting the element. If there’s any ratting noise remove the element and try again.
9. Tighten the nut using the same torque needed to undo. Do not over tighten – the seal is rubber it does not require too much force. Check you can’t pull the element out or the temperature sensor.
10. Replace all terminals and the sensor plug – double check you have the earth terminal in place. If the earth terminal is not connected your RCB may not trip if the element fails again and this could be dangerous.

Links

• How to access a Bosch drain pump filter – Youtube video showing how to remove the front panel to access the drain pump hose and clear a jammed filter.
• How to replace a Bosch heater element – Useful Youtube video showing how to access and what’s inside. I suggest you don’t use a power impact driver to undo the element fixing as mentioned above.
• Heating element from BSH – this is for the iQ500 but you can select your model from its E-Nr number found on the appliance door. Once you have the BSH part number you can search for alternative suppliers such as Ransom Spares that may stock at a better price.
• Siemens iQ500 Service mode – Youtube video showing how to access the service mode to check for error codes. Something your BSH engineer can do and you can too.

It took a couple of hours in total to clear the drain pump and replace the heater element. The beast is working well again with a post-it reminder to check the filter monthly and note to self – don’t leave allen keys in pockets!