General Dashboard vents (the large ones in the centre and sides)

[Marsamakanik]

I have been searching and found that the vents on the dash are only fresh air vents. Now k have an issue where the side ones with the blower motor on will suck air and the the centre ones blow air through em. (We tested this with my father putting a lit cigarette near it and seeing that the side one where sucking the smoke into the dash on both sides and the centre ones actually blow the air into the cabin. Any ideas on why it's doing this? I also know that the small vents on the side above the fresh air vents are for hot air to defrost or demist the side windows.

Thanks for any info given.

 

[the green vanper]

Hello,

The ventilation system includes some flaps behind the dashboard, they are operated with the levers on the dash (cold/hot, feet/face/windscreen, sometimes also internal circulation on/off - but can't remember if it was available in the 90' Uno).

The flaps are operated mechanically with cables, they have small hooks and the end. I'll start by checking if those are in place, not blocked (the cables can rust in such old vehicles) and that the flaps are operating properly.

The system seems complicated, but it isn't if you get to understand how it works.

 

[Marsamakanik]

So i have confirmed that all cables are good without rust everything works (haven't tested thee heating yet but will try it today), i have also figured out why the side vents don't blow air and suck air out, they were designed that when you open them it will suck out the air while the car is moving.
This is achieved with the design of the front cowling (that hides the wiper motor), under it there are two openings which both side vents are connected to. While the aerodynamics of the car while moving (with the side vents open), it will suck out the cabin air inside and release it outside, allowing for the air to circulate while the windows are closed. Only the centre vents and footwell vents actually blow air.

(Adding some pics with illustrations and showing a pipe passing through the opening under the cowling passing through the side vent)

Red : air being sucked out
Blue : air being blown in or the aerodynamics representation

 

[Marsamakanik]

So i have confirmed that all cables are good without rust everything works (haven't tested thee heating yet but will try it today), i have also figured out why the side vents don't blow air and suck air out, they were designed that when you open them it will suck out the air while the car is moving.
This is achieved with the design of the front cowling (that hides the wiper motor), under it there are two openings which both side vents are connected to. While the aerodynamics of the car while moving (with the side vents open), it will suck out the cabin air inside and release it outside, allowing for the air to circulate while the windows are closed. Only the centre vents and footwell vents actually blow air.

(Adding some pics with illustrations and showing a pipe passing through the opening under the cowling passing through the side vent)

Red : air being sucked out
Blue : air being blown in or the aerodynamics representation

I would like to know if anyone else's mk2 Uno's also do the same thing as I'm not 100% sure if that is intended or not

 

[worcestersource]

I always thought my Mk II Uno I had *coughs* 28 years ago fed cold and warm air from the central vents and cold air from the side vents. However, memories distort with time.

The Mk II Uno I have today only supplies fresh air from the central vent and nothing from the side vents, stationary or moving, dial set to max air or off. As you state here, I suspect the side vents suck warm air in and vent it outside. I only get warm air on the windscreen or directed to the footwells out the heater, so I don’t think the rods and wires inside are faulty.

Even better, the matrix is good and it gets nice and warm.

 

[Marsamakanik]

I always thought my Mk II Uno I had *coughs* 28 years ago fed cold and warm air from the central vents and cold air from the side vents. However, memories distort with time.

The Mk II Uno I have today only supplies fresh air from the central vent and nothing from the side vents, stationary or moving, dial set to max air or off. As you state here, I suspect the side vents suck warm air in and vent it outside. I only get warm air on the windscreen or directed to the footwells out the heater, so I don’t think the rods and wires inside are faulty.

Even better, the matrix is good and it gets nice and warm.

Cool ok so i might be getting closer to this discovery of mine that was most probably a feature they did. Next I'll try it on my father's uno (which came to my mind today honestly to try it out). I also discovered that my heater matric valve is good and so it the cable but the plastic piece that turn the valve open amd closed had snapped. But got the pieces (2 of em only thankfully) and used some araldite and hopefully by tomorrow it should have bonded well and will last a bit longer if it breaks again I'll just ask a buddy of mine to 3d print me one.

Hopefully we get more people to confirm this theory of mine of the side vents.
If anything else pops up (even picks of an owner manual to prove my theory) do not hesitate to add to this thread.

Pic of the plastic piece that broke

 

[the green vanper]

Here are the four pages from the 1989's Uno user manual in brasilian portuguese that explains its the ventilation system.

As I cannot download the whole document, I'm adding the link under which it is available: https://www.instrukcjaobslugipdf.pl/fiat/uno-1989/instrukcja

I've also just uploaded the service and repair manual in English here: https://www.fiatforum.com/downloads/fiat-uno-gasoline-service-and-repair-manual-from-1996.510/
It should be available soon.

It covers only the gasoline models, but the interior ventilation system is the same.

Cooling and ventilation section 2-5 and 2-6.

 

[Marsamakanik]

the dashboard on the pics are from the mk1 Uno, mine's the mk2 and is like this that i got from eper,
https://eper.fiatforum.com/en/Drawings/Detail/F/F/UNO/MR/705/2/0/0/SubSubGroup
we know the airflow of the mk1 dash as it's shown even in the Haynes manual, but sadly the mk2 dash (the more common one where i live) has barely any info given about it. I've been trying to find the proper workshop manuals given to agents by fiat themselves, but are all behind a paywall/physical copies only. If by some miracle someone can scan it even if it's in Italian, i just need to find an air flow diagram of the mk2.
Still thanks for the pics and link for one from 1989. Also the link you sent of the other manual it isn't loading.

I've also just uploaded the service and repair manual in English here: https://www.fiatforum.com/downloads/fiat-uno-gasoline-service-and-repair-manual-from-1996.510/
It should be available soon.

 

[the green vanper]

Knowing how automotive industry works I doubt that they changed the ventilation system with a facelifting. Especially that it was almost 35 years ago, when engineering was much more time consuming (= expensive).

So, I assume that the system is the same in the 1989's and 1990's Uno and they only changed the part of the steering for a less problematic one. And perhaps some visible parts to make it look fresh. Of course there is a possibility they also could have change some parts of the system, but again - not everything, including the air ducts etc.

The document from the other link is being checked... That's why I've wrote that it should be available shortly. It's the Haynes repair manual, edition 96', but couldn't tell which models years it covers. I've never owned an Uno (but I was very close to buying one in 1996/97 )

 

[Marsamakanik]

hmm fair enough on that part. To me, the only thing that might be effecting the side vents is how the cowl went from just the bonnet with slits in it, to a separate plastic cowl which when you look at it, looks like something that uses Bernoulli's effect which sucks out the air from the inside could be an error in design or made on purpose to exhaust the old air inside. Would be great for any other mk2 owners who are willing to test this out, and maybe even some mk1 owners so i can try to wrap this around my head. Also i own a manual that goes to 1993 (physical) and the one you find everywhere online which goes to 1996 but has chapters 5-7 missing, which is kind of annoying to me but not much you can do about that.

 

[the green vanper]

And one more thing. I've owned / been driving for longer periods around 15 - 20 cars (from which around 1/3 were older FIATs or similar ones) and never saw a ventilation system in which the side vents were sucking the air out. They can be moved around, when you direct them to the side windows, they are ment to demist / defrost them.

Is there an internal circulation switch?

EDIT: Just got an idea. None of the cars (except the now owned Ducato) was in the Southern European specification. Perhaps that could be the factor which makes the difference in how the ventilation system works... If so, the British specs are most likely same as on the Central / Northern / Eastern Europe. We are trying to keep the warm air inside, not to suck it out

 

[Marsamakanik]

And one more thing. I've owned / been driving for longer periods around 15 - 20 cars (from which around 1/3 were older FIATs or similar ones) and never saw a ventilation system in which the side vents were sucking the air out. They can be moved around, when you direct them to the side windows, they are ment to demist / defrost them.

Is there an internal circulation switch?

There isn't an internal circulation switch and the two small vents about the side vents are the ones that demist/ defrost the side windows as they let out warm air but the normal adjustable side vents are meant to be fresh air, but for me and @worcestersource they don't even blow air with the all the settings on (with the heater off) and still doing nothing be it while moving or while stationary. I'm also finding it weird why it's like this as i've been in quite a few cars and the sides usually blow air out of them so idk what's up with the Uno. so this is the reason why I made this thread and why I'm asking for other Uno owners to test and send results to study this case.

 

[Marsamakanik]

So i have confirmed that all cables are good without rust everything works (haven't tested thee heating yet but will try it today), i have also figured out why the side vents don't blow air and suck air out, they were designed that when you open them it will suck out the air while the car is moving.
This is achieved with the design of the front cowling (that hides the wiper motor), under it there are two openings which both side vents are connected to. While the aerodynamics of the car while moving (with the side vents open), it will suck out the cabin air inside and release it outside, allowing for the air to circulate while the windows are closed. Only the centre vents and footwell vents actually blow air.

(Adding some pics with illustrations and showing a pipe passing through the opening under the cowling passing through the side vent)

Red : air being sucked out
Blue : air being blown in or the aerodynamics representation

in the fourth image there is the small vent above the adjustable side vent that i mentioned which is used to demist the side windows

 

[the green vanper]

in the fourth image there is the small vent above the adjustable side vent that i mentioned

Yes, I know which vents are you talking about.

Looking at the diagram (3rd image posted earlier) and making the translation from Portuguese the white arrow is for 'cold air only' (which I assume is fresh, coming from outside, ommiting the heat exchanger), the darker one is for both cold and hot air. But definitely those problematic ones should be blowing the air (or at least letting it) in.

Again, in theory there could be a difference in the ventilation system for cold / hot regions. And Brasil seems to be rather the hot one... So it should be the same as in Italy / Malta.

 

[Marsamakanik]

Looking at the diagram (3rd image posted earlier) and making the translation from Portuguese the white arrow is for 'cold air only' (which I assume is fresh, coming from outside, ommiting the heat exchanger), the darker one is for both cold and hot air. But definitely those problematic ones should be blowing the air (or at least letting it) in.

i agree with you here that they should at least be letting air in. Either way i'm going to check out my father's 97 uno tomorrow to see what it does on it's side vents. For now i bid you a good day/night as it's 1am here.

 

[the green vanper]

From the Haynes manual:

11 Heating and ventilation system - description
1 The heater is centrally mounted under the facia and is of fresh air type.
2 Air is drawn in through the grille at the base of the windscreen. It then passes through the coolant heated matrix when it can then be distributed through selective outlets according to the setting of the control levers.
3 A booster fan is provided for use when the car is stationary or is travelling too slowly to provide sufficient air ram effect.
4 Fresh air outlets are provided at each end and centrally on the facia panel.

So, it is the same as in the FIAT owners' manual. The diagram with the arrows is shows the same air temperatures.
Another diagram shows the control panel with sliding controls only, so I assume it's the mk1.

As the fan is located in the round element on the left hand side, perhaps the positionning of the two flaps is messing with the direction of the air flow?

EDIT: it doesn't make sense, as the side vents are not connected to the heater... sorry

 

[Marsamakanik]

So driving my uno today i found out my issue is that when the blower motor is on, the side vents suck air into them and the centre ones blow air out. But when the blower motor is off and the side vents are open you feel air coming from them. So it creates a circulation with the side vents when the blower motor is on.

 

[the green vanper]

So driving my uno today i found out my issue is that when the blower motor is on, the side vents suck air into them and the centre ones blow air out. But when the blower motor is off and the side vents are open you feel air coming from them. So it creates a circulation with the side vents when the blower motor is on.

Assuming the Haynes drawing is correct, it really doesn't make any sense. It looks like the fan / blower + heater unit is not connected to side vents. What are the two flaps for? Can you get it from the cables / levers position? I assume one of them is 100% cold / hot air. The other should be probably up / down. But who knows... perhaps it changes the function of the side vents

Have you checked if changing the temperature during driving changed everything?

 

[Marsamakanik]

Assuming the Haynes drawing is correct, it really doesn't make any sense. It looks like the fan / blower + heater unit is not connected to side vents. What are the two flaps for? Can you get it from the cables / levers position? I assume one of them is 100% cold / hot air. The other should be probably up / down. But who knows... perhaps it changes the function of the side vents

Have you checked if changing the temperature during driving changed everything?

Haven't tried it yet as i had part of the heater valve break but maybe today I'll be able to try it but ye the side vents aren't connected whatsoever as they're a single unit with one passage (as both side vents are independent of each other and the blower motor). Now the thing is that the drawing is the mk1, sadly the mk2 doesn't seem to have it's own drawing showing the flow of air coming from the vents. Now i think it might be due to the fact that all three fresh air holes are all where the window wiper is hidden under the plastic cowl so it could be that the fan is creating a suction strong enough to make it to the side vents are sucking air out instead of just air from the car moving.

 

[worcestersource]

I was out in my Uno today and noticed fresh air coming from the side vents after all - well, whilst moving at traffic pace anyway. If I remember, I’ll be more scientific in my observations of heat, air and speed of the car to see what happens with them.