UK-POLOS.NET - THE VW Polo Forum

Hi Guys
I love my 2020 Polo (at least until the last week.)
The winter has arrived, and the car (kept outside) has front screen totally fogged up when car is entered.
The demist system is totally non effective - even after 10 minutes there is no sign of demisting taking place. This with the heater motor going full tilt. Obviously with the postion set to front screen and the AC turned on.
Are there any obvious areas I can check - never had any demist problems with previous polos.
Ideas and suggestions welcome. For example could the rotary postion control become diconnected? Could the vents be blocked?
Thanks in advance for your guidance. Trying to avoid visit to VW dealer (costs a fortune to just get a diagnosis!)
Colin

Is this the first winter where you’ve had this issue or has this always been a problem at this time of year?

Are you getting any directional airflow to the windscreen at all. If not, that does suggest there may be an issue with the cables and flaps that control the direction of air flow to the screen. Sorry, don’t know what’s involved to fix them but with your car now being between around five years old, I don’t think I’d be paying VW main dealer prices for investigative work, repairs and servicing; a good independent VW specialist will probably be a little cheaper than a VW dealer and you’re likely to get much better service too and probably shorter wait times for an appointment.

If you have good airflow to the screen but it’s cold rather than hot, that might indicate a blocked heater matrix - not uncommon on some models of VAG cars that have a silacate pouch in the cooling system expansion tank - not all do; I think it depends on the version of coolant used. The expansion tank should be marked ‘mit silikat’ if it contains a silicate pouch. The silicate pouch is added to prolong the life of the coolant and to provide corrosion protection to aluminium components but the pouch can degrade with age and split; if this happens, the contents are released into the cooling system which then usually block - or partially block - the heater matrix.

A totally fogged up screen could be the result of inadvertently leaving some wet outdoor clothing in the car. Assuming this isn’t the cause, then another possibility of fogged up windows might be water ingress into the car’s cabin as a result of rubber seals around doors, windows, rear light clusters etc. perishing and failing with age. Over the years, there’s been quite a few instances of water ingress reported on Golf forums with the mk7 / mk7.5 Golf. Hopefully this isn’t your issue as it can be very difficult (and costly in labour charges if using a garage) to track down the source of the issue. A quick check to hopefully eliminate water ingress as reason for your fogged up windows is to check the carpets, spare wheel well and rear seats for signs of water or dampness and check the roof lining at the rear of the cabin for water staining. I’ve included a list below of known water ingress points on the mk7 / mk7.5 Golf that have been mentioned on forums over the years, some - but not necessarily all - of which might also be relevant to the Polo.

Good luck in getting this issue sorted. Please update this discussion topic with progress and the outcome for the benefit of other forum members.

Water ingress issues with the mk7 / mk7.5 Golf reported on various forums - there maybe others but these are the ones I can remember reading about over the years;

1. Blocked pollen filter.
2. Cars with sunroof - blocked sunroof drain pipes.
3. Damaged / broken speaker seals in rear doors, resulting in water draining into the foot wells (water can also ‘travel’ from the rear to the front footwells, so check the front footwells too).
4. Damaged / poor fitting door or window seals.
5. Damaged / perished grommet on the bottom of the drain pipe from the hatch release handle, allowing water to drain into the tailgate and then run into the boot.
6. Damaged / cracked rubber sleeving covering the wiring from the car into the tailgate.
7. Poor seal between the tailgate hinges and where they’re attached to the body shell above the tailgate opening.
8. Damaged / perished washer / gasket between the roof and roof mounted aerial.
9. Damaged or perished seal(s) between the rear light clusters and the car body.
10. A/C drain tube becoming detached from the evaporator, draining into car interior rather than on the ground outside the car
11. Water ingress via air equalisation vents in the lower rear quarter panels either side of the boot behind rear bumper cover (rear bumper cover needs to be removed to access these).
12. Replacement windscreen not bonded correctly to car body shell.
13. Drainage holes in windscreen scuttle panel blocked with leaves and other items.

Also check that the air flow is set to fresh air rather than recirculate, my daughter did that and was annoyed that she always steamed up even on a warm ish day and had to keep the a/c on all the time.