The Craftmans Shop > New from Old
Steam Cleaner. Re-Birth of a Karcher MPDS
awemawson:
So now I turned my attention to the ignition side of things. There are two 'spark plug like' electrodes protruding into the flame chamber close to the fuel jet. These are fed by screened EHT leads (military remember so EVERYTHING is screened) emanating from an EHT transformer whose primary is 240v mains. No mains in this device so another unit described on the circuit diagram as a 'transformer' but infact a transformer driven by a transistorised inverter, takes in 12v DC and outputs 240v. Initially I was convinced that the screened leads were 'leaky' as measuring to frame I was getting only about 50 kOhms - then it dawned on me that the EHT transformer secondary was 'centre tap earthed' so I was measuring half the secondary winding resistance :bang:
So a quick test: I rigged up a lab power supply to the inverter and sure enough nice crisp discharge crackling could be heard (10 kV at 20 mA). I re-terminated the EHT ends as they were rather frayed and put it all back together.
awemawson:
For the CDS control box to fire up the boiler a few other conditions need to be correct. One is a 'flow switch' needs activating by pulling the trigger on the lance.
The flow switch is mounted in a dual purpose housing (it has the main pressure switch in it as well) but this flow switch has a magnetic shuttle that is pressed 'left' by a weak bronze spring, and 'right' by the water impinging on it. The magnet operates a reed switch in an external brass tube.
I had tried operating it by pressing it 'right' - there is a filter plug that can be removed and an allen key would just reach round the corner and press it - sure enough operated according to my meter. However measuring is real operating conditions it didn't work - all very odd :scratch:
Next I made a bit of an error :bang:
I decided to unscrew the plug that gives access to the bronze spring and magnetic shuttle. It went ok until, having difficulty getting the shuttle out, I turned the water on. Of course - obvious realy- the shuttle shot out like a bullet from a gun :(
I eventually found it after a bit of searching, but now I didn't know which way it was supposed to face.
awemawson:
Now initially I had though that the large end should face the incoming water, but then I noticed the 'screwdriver slot' in that end - this could only be accessed from the right. Both ends of the shuttle had turned down sections that nicely matched the spring diameter so no help there :bang:
I put it in 'screw driver slot right' - tested it with the allen key trick through the filter plug - which worked - and then tried it under operating conditions. No go, still not closing the reed switch.
Well - nothing to lose I pulled it apart again this time putting a rag over the opening to catch the shuttle :ddb: then re-assembled it 'screwdriver slot left'.
:clap: :clap: Hey it now works :bugeye: :bugeye:
Now the magnet is very weak and various descriptions of other Karcher pressure washers say to change the magnet annually. So I've ordered another one. BUT - it begs the question - was it in wrong to begin with. The only other explanation I can come up with is that I did ease a few slight burrs on the shuttle - was it perhaps jamming. Anyway at this stage she fires up on demand.
Just two more issues to resolve:
Firstly there is a two way fuse box that seems to be described as a 'continental type' holding the style of car fuses that are pointed and sit between springy brass leafs with location holes. One way was weak in the springyness department and I'd temporarily wired it out. Someone had packed the other way with a screw to give it more oomph but it needs changing. (The holder on the left is an 'indicating' ie has a neon across it - 2A mains fuse for the inverter circuit)
Secondly there is a persistent diesel leak with diesel running out of the vortex chamber of the main blower fan - not healthy :bugeye:
awemawson:
After much searching I managed to locate an exact replica of the two way fuse box - at one point I'd thought I'd have to use 'in line' fuse holders as space is very tight, but this turned up.
Joy when it arrived - EXACTLY the same size even down to hole mountings - joy was soon dashed when I took it off the vacuum packing and found it cracked :bang:
awemawson:
Never mind - the seller seems to have loads and is posting another one, having first unpacked it to check it hasn't suffered the same fate !
So on to the diesel leak:
Close examination revealed that the diesel was coming out of the rear of the injector pump so I rather expected major mechanical issues with the pump itself. It looks almost identical to a standard oil boiler injector pump, just not quite the same :(
Then is occurred to me - in the book of words for this machine I have a parts list where all the parts have NATO stock numbers - Google the NSN ! This not only told me it was a SUNTEC pump, but one was for sale in the USA on eBay !
However it also allowed me to identify the model and get the makers literature. This showed me that there was an oil seal on the drive shaft, that is in a chamber that is filled by the oil retuning to the tank. Hence not huge pressure. It also allowed me to locate the very same exact seal on eBay in Germany - it's a bit of an odd size - 8mm shaft but 26mm outer diameter.
Seal duly ordered and arrived this morning
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