The Craftmans Shop > New from Old
Steam Cleaner. Re-Birth of a Karcher MPDS
awemawson:
Things have gone rather quiet on this repair until recently.
The pressure switch that I ordered failed to arrive. Tracking information said that it had been 'damaged in transit' but I didn't receive that information for a very long time. The seller did the decent thing and posted me a replacement that arrived in the New Year. But I found that unlike the description it was NOT a normally closed contact that opens on pressure rise (thus disengaging the electric clutch) but a normally open one.
Searching the web I failed to find an adjustable pressure switch centred on 60 BAR / 900 psi, suitable for water and at a reasonable price, so I decided that the obvious thing to do is insert a relay to reverse the sense of the switch.
To this end I ordered up a standard 12 volt car type relay and socket.
Meanwhile I had already made up an adaptor for the plumbing that actually proved to be far simpler than I'd imagined. The hose fittings on the Karcher are threaded 18 mm x 1.5 mm pitch (spark plug thread!!) and eBay provided me with male to male 1/2" BSP to 18 mm x 1.5 mm male adaptor fittings with a 60 degree cone. This allowed me to assemble a 1/2" BSP brass Tee fitting with the adaptors in the straight through positions and the branch on the Tee adapted with a 1/2" Hex blanking plug that I drilled and taped 1/8" BSPT to suit the pressure switch. I've sealed all the threads with Loctite hydraulic thread sealant.
Yesterday the relay and it's socket arrived so time to get serious, but frankly it's so bally cold outside it's really not sensible to be playing with water so it's going to have to wait a bit longer !
vtsteam:
Yes the cold.......! Gettiing a relay to reverse the pressure switch's NO to NC is just the sort of cob I would do! :thumbup:
WeldingRod:
At least you resisted the urge to open it up and change the internals ;-)
Sent from my SM-G715A using Tapatalk
awemawson:
I’ve fitted the new pressure switch and managed to house the relay in the main control box AND by carefully pulling the cable from the original switch through the corrugated trunking and coiling it up in the box have left it so that reverting to the original configuration is pretty easy should someone want to do so.
It turned out that it was not possible to fit the new switch where I had intended. The Tee fitting needed to be rotated to screw into the original casting and there wasn’t room so I’ve relocated it to the pressure manifold on the pump itself.
Switch and relay work just as they should, and adjusting the set point is just a case of twiddling an Allen key in the switch.
So it’s all back together and working. For what I need it’s rather overkill and I have my eye open for what may turn up. Sadly most steam cleaners seem to be very plastic and not very durable.
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