By adding moisture you're adding resistance to the airflow or to a seal... You probably just have a bad O-Ring somewhere which is why it isn't sucking properly... The filter comes into contact / or fills the area at the back, from what I've seen of all guns, where the o-ring is supposed to seal.. By adding fluid, with the filter material you're clogging the leak, essentially.... So if you just fix that area by adding a bigger washer / o-ring, or something around that area then you'll likely resolve the issues...
As for me - I'm thinking of buying just a gun and using an air blower motor I have and wiring it up to my current rework station... It really doesn't look all complicated... I could wire it up in a way that it uses either the heat-gun area ( especially as that means I can use the dial to control the power of the motor ) but I'd probably need to add an extra circuit and a switch to switch the dial from sucking motor control / power to the different motor - or I wonder.... it may be possible to build a simple attachment to the heat-gun motor to disable the heat, and reverse the leads on the motor with a switch so it sucks - then it'll be cool area being sucked and that could act as the vacuum... Then I wouldn't need to use a secondary motor, I'd have control over the amount is sucks - and I'd wire up a trigger to enable / disable it... so I'd have to set up a relay probably so it's closed by default except when the gun is plugged in - and I'll likely need a second connection for that....
I'm going to look up mods to see what others have done - because if I can simply add the feature to my existent rework station ( ZENY 853D - which I already modified in the past so be able to remove the heat-gun just like the soldering iron / want ) then I'll be more likely to actually use it because it'll be there.......
It's probably better if I have a 3rd plug to connect the gun into, then I'd need the nipple, filter area for the motor and it is probably best to have a separate motor inside the unit..
Is there an electrical circuit which can remember the potentiometer state, or whatever the dial does in my unit ( does anyone have a wiring diagram for it? ) so I can keep the heat gun plugged in, and flick a switch so if I want to use the desoldering gun and the heat gun at the same time, I can adjust the dial then flick a switch and it'll then be used for the vacuum motor instead.....
Looks like I have some work to do... but it could be a fun project and I'll see about documenting my progress if I end up doing it so others with the same, or similar unit can get away with spending $40 or so on a gun, and $5 or so for a motor, give or take up to $5, and a few extra for connectors, wire, etc.. dial, etc.. although I'm sure there are already motor controllers incredibly inexpensively..
I just need to see how much power my unit can currently provide so see if I have to add to the board a separate power circuit or if I can piggyback...
Any advice would be appreciated - and if anyone has a wiring diagram for the Zeny 853D it'd be greatly appreciated...
Oh - I am open to the idea of buying the ZD-985 but someone said there was a huge flaw in the design which could lead to a fire or other issue ( ended up discoloring their tip after it went to 800 or 900 degrees??? )... and I don't want to spend $200 on something with a flaw that big...
I'd prefer to only spend $100...