If the heating element is 9 ohms but you read 40 ohms at the connector, you have found the trouble.

 

At least 9Ω is reasonable. Have you check to make sure it is providing 24V? And, if it is, unloaded, what is the current when the iron is connected?

 

@MisterBill2 I measured again at the connector... that 40 Ohm was a dodgy measurement. My bad.
Also that 9 Ohm now shows abt 7 Ohm. Those alligator clips in the picture probably added a few Ohms as well.

@Yaakov I will have to continue later.. it is getting pretty late here in Belgium. But now I slowly get a baseline and I have some ideas of what to measure
Thank you so much for your guidance !

 

I have a WSP81 and the graph is for a WSP80

Further inspection is required.

the back of my PU81 says: PU81 + WS81. I assumed WS81 was the model number of my soldering iron.
Now that I have everything disassembled, I noticed an inscription in the plastic molding of the soldering iron saying "wsp80" (see picture). I now assume WS81 is the model number of the soldering holder with standby switch when the iron is at rest

I was just trying to help.

What am I missing?

A crystal ball! But it helps when you have the same unit .

 

My apologies for the confusing model numbers.
I was confused myself and posted wrong model numbers in earlier posts.
Because I value your help, the least I can do is provide some clarification. Here are some pictures that should clarify
(not relevant to the discussion, but part of the confusion: what is "WS81" as indicated in the picture with the IDtags? )

 

PU81 is the part number for just the power supply

WS81 is for the set which includes the soldering iron and holder

these are EU versions for 230 VAC

 

@Wolframore That is exactly what I was thinking as well, but the label at the bottom of the holder for the soldering iron says WDH 11T (see photo above).
Not super important, but a bit confusing
/c

 

The set includes the iron and the holder which have their own part numbers. Little confusing but I’m sure it was done to make it easier when you have to order just a replacement part.