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No De-Mist - Mondeo Mk1

2K views 13 replies 5 participants last post by  malmeida14 
#1 ·
Hello, I hope someone can help.

I've read several topics on this subject but I have the opposite problem to those I've read. My heater distribution works everywhere except on de-mist. There appears to be no difference between footwell/screen and screen only (these are next to each other on the control knob). Air blasts out of the footwell on both settings, There is a very slight breeze to the screen when fan is on no. 4.

I've taken the control panel off, checked that there is a vacuum, poked a straightened paper clip in the pipes to see if any gunk in there, seems clear.

Mine is the basic heater with no air-con. Any ideas what to try next please?

Many thanks.
 
#3 · (Edited by Moderator)
Sorry for not replying sooner. Any suggestions on how to check the flaps as they are inaccessible as far as I can see. There is no sound change when selecting between the screen/footwell modes on the control and air comes out the footwell in all three positions. When selecting between facia/footwell you can hear the flaps opening/closing.

Thanks for any help.
 
#4 · (Edited by Moderator)
Still got this problem, not good this time of year. Could it be the switch or is that wishful thinking? Don't know what else to try. There is vacuum if you put your finger over the pipe behind the controls, not a great deal but I'm not sure how powerful the suck should be.

Anyway, any other suggestions very welcome.
 
#5 ·
On the slim chance someone will be reading this;

I located the problem to the silver canister to the right of the glovebox that moves the yellow lever to direct flow. When you select windscreen, the pin that comes out of the top of the canister starts to rise but not very much. I pulled it up and down with my hand a few times but it was very stiff. I pulled it to the extreme and got air flowing to the windscreen again. Selecting footwell moved the lever right down but going back to screen only moved it a little. I sprayed WD-40 around the area as a desperate attempt to free it but it didn't work.

I assume this is unfixable without removing the dash which isn't going to happen. Please let me know if I'm wrong (if there's anyone there).
 
#7 · (Edited by Moderator)
Hello Steve, thanks for the reply. What do you mean, have a go at removing the silver thing?

Also, I checked the vacuum from the pipes near the clutch pedal. The one coming from the engine is quite strong and you can hear it sucking when you remove the pipe from the box. The one going to the dash is fairly weak in comparison, is that right? Not sure what happens in that box between in and out.

My vents always take a couple of seconds to open/close when you move the distribution knob, is that normal? I'm wondering if there isn't enough suction.
 
#9 ·
...my vents switch instantly so something isn't right with yours.
Thanks Steve. Yours is vacuum as well then, not motors? As I mentioned there is much less vacuum coming from the 'box' under the dash than going into it. Maybe there's something blocking it in there. Not sure what the box does, will have to see if it is able to be removed without stripping the dash.
 
#11 · (Edited by Moderator)
unfortunately, being as yours is LHD i'd imagine access to the "silver thing" as described above is going to be harder than just pulling the glovebox out, (as yours is on the wrong side) you may be able to get at it by removing the lower centre console trim (remove the little plastic covers to find the screws)

are you getting nothing at all, or very little air to the windscreen? if its a little, the silver thing might be blocked, there is some how-to's in this part of the mk1/2 mondeo forum, click "search" first and you can change where you "search" to "this forum" and use "vacuum" as your search word, and you'll only get results from this forum. :L
 
#12 ·
I had this with my 97 Mk2, no aircon. I found that the silver vacuum actuator for the screen demister flap has 3 positions: no vacuum = demist flap fully open, 1st stage vacuum (small pipe in the middle of the unit) = demist flap half-closed, 2nd stage vacuum (pipe on the end of the unit) = demist flap fully closed. There is a spring inside the unit that pushes the demist flap open when there is no vacuum, and in my case the spring was weak and it couldn't overcome the resistance of the flap and the rods. I think also the demist flap and rods had got stiff over time making it more difficult for the spring to push the flap open. I fitted a new actuator and gave the flap a good workout by hand, and so far it's solved the problem. It was a pig of a job to do on a RHD car, there was just about enough room to get a 1/4 drive ratchet in to move the nuts 1 click at a time.
 
#13 ·
Thank you for your quick replies. Today I tested again and some times work well, most of the times it blocks in to the windscreen, or only to footwell , or other position. Reading nigelrrb answer i think if the lack of use would be responsible for the stiff clasp and rods. Usually I only use in the windscreen position. My door handle of the left rear door is stiff needing some oil because of the lack of use (don't forget - left hand drive).

Well, I will try to see if changing the position frequently I can free the system, if not, by your answers it's a job for my mechanic.

Thanks again.
 
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