Temperature gauge reads 90 driving along, car interior warms up a bit - but not much

I'd like to do a bit of diagnoses to find what might be wrong (I don't have VCDS)

To my mind it's either a water problem (the matrix isn't getting the hot water it needs), or it's an air problem with the motorised mixer flap people talk about or something.

The first thing I'd like to check is does the heater matrix get hot.

I've got the Haynes book and it shows pictures of parts of the heater matrix - but doesn't make it clear where it is on the car.

Is the matrix behind the dash or under the hood - if so where about briefly where is it and how can you get to see / touch it.

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Assuming the matrix does get hot - where is the motorised flap?

for test purposes is it possible to manually put it into a fixed open / closed position to see if it makes a difference?

Thanks in advance for anyone who can help by answering these simple questions

I might have found part of my own answer by reference to http://skoda.worksho...dex.php?id=3264

- the matrix is on the passenger compartment side of the front bulkhead so will be a so-and-so to get to, but the water tubes connect to it in the engine compartment.

so the next thing to do would probably check the temperature of the rubber tubes - if both are cold there's a big blockage, if one is cold then there's some flow but not much

The matrix is about 8" square and in the middle of the car, will the tubes connecting it be accessible if the big plastic cover on the top of the engine is removed?

Thoughts anyone?

Edited 13 December, 201213 yr by peterhr

My money would be on a failed mixer flap motor or similar. VCDS would reveal a stored fault code if that was the case.

You can probably get your hand on the matrix pipes down the back of the engine to check for hot water. But with modern anti freeze mixes, you don't really hear of heater matrix blocking up/corroding like in the old days.

If after a drive, I sit in the car with the engine running and blower off for a couple of minutes, then turn the blower on - with other hand on the passenger foot well - it seems to blow warm for a while, then cool off after about 30s (but it ould be me getting used to the warmer air)

Do you reckon the Torque android app + ELM327 bluetooth adaptor would show the fault?

(I'll try it - its only about £15 for both bits)

As that is an OBD2 scanner, it probably won't show up codes related to mixer flap motors.

On VAG vehicles (and actually a lot of marques), OBD2 scanners only show codes related to emission control systems on the car......it's a legal requirement that allows mechanics to diagnose faults that may effect emissions, without having to have expensive VAG diagnostic equipment.

I'm also getting a USB cable for the shareware version of VCDS (wonder if it'll work on my netbook with a 1024 * 600 screen?)

- I'm aware that this will probably gradually suck me into getting the full version by way of register the shareware version, then after finding it's limitations move on up

Aha: A really useful post - but it's offsite

http://www.justanswer.com/uk-car/670mx-skoda-octavia-skoda-octavia-tdi-estate-car.html

OK, the pipes to the heater matrix are hot.

So that leaves the heater flap motor - where on the scale of difficulty is replacing it - one hammer (+ throbbing thumb having hit it) to 5 hammer (the car was built around the unit to be replaced).

How much time would it take a beginner?

Well I've never done it, but I have read that although access to the motor is difficult, it is a doable DIY job.

Have a look here:- http://www.briskoda.net/forums/topic/137932-has-anyone-replaced-a-flap-motor/

in order of events

Indy has verified hoses are hot (infrared laser guided missile temperature - so probably not matrix)

Plugged into dealers version of diagnostic software - flap motor and all temperature sensors show up as good.

Thinking flap motor might be working but flap disengaged - did some dis-assembly - flap etc is OK - visually it can be seen to flap.

Has noticed that if blower is turned off - then turned on, you get hot air for 10 - 15 seconds

Present thinking is the matrix is almost completely blocked (remember I had the system drained flushed, refilled in April because it was full of carp pictures/story > http://www.briskoda.net/forums/topic/234849-after-4-year-service-how-important-are-these-items/ ) - so the matrix is coming out tomorrow.

This car is becoming a money pit!

(it didn't help that the people [not a dealer] doing the front track rod in the earlier story adjusted the rear camber and the rear tyres got saw toothed - had to buy new tyres and get the geometry put right in central France 2 weeks later - had a nice tour of Amboise east of Le Mans while they did it ... nice place worth a visit)

I just read your previous thread about rusty coolant.

That certainly changes my above comments re modern coolant inhibiting corrosion. Having ruled out the flap, I'd say your theory is sound.

Is there a stream of air hot or cold from the vents? Or just stops after the initial burst of enthusiasm?Have you checked the pollen filter? Have you checked the pollen filter?

OK, Matrix has been replaced - total bill 500 notes - There's a lot of labour involved in the job.

The indy who did the job said they shook the old one out and it almost filled the sink with rust flakes.

I bought the car at a year old from a skoda dealer - it had been the service managers company car - It was indicating 47mpg - at the time the best I could get was 53 on a long run, so I doubt if the thrashed it or put anything nasty in the cooling system (get 64mpg now after a dealer dit the 4 yr service & cambelt - think it must have had an official Skoda remap *shrug)

I'd love to know where the rust flakes came from - I get no appreciable coolent loss - as far as I know it's always had the correct additive in the water.

Any ideas?

System has been flushed again and refilled with G12 + water

Tomorrow I need to see if the coolant level has dropped as any air lock bubbles find their way out (I keep a bottle of G12 in the boot to resist the temptation to top up with water if a top up is required)

(hope I don't get the same problem with the rad.)