PTC heater burning smell

[SuperV8]

I have recently noticed a burning smell coming from behind my dash (2014 2.0TDI 184 FR ST) -
At first I thought aha my PTC heater is working (it was cold outside; 3 deg), and its just some dust on there being burnt off (like the smell you get on an electric bar heater that hasn't been used for a while); but the next day the burning smell was worse, no smoke - but enough for me to open my windows and turn off the PTC heater!
Following cleaning out my heater matrix (for the second time) I had a look at the PTC heater and can definitely see the thick brown wire looking like it's part melted where it bolts onto the PTC matrix and can smell the burnt plastic smell up close.

Anyone else had similar issue? or know of a fix?

Thanks,
Tom.

 

[SuperV8]

Bump;
Nobody had this issue?

 

[BillyCool]

Bump;
Nobody had this issue?

Hi Tom,

I've never heard of it before. I have exactly the same car as you, also 2014.

Sounds like a bad earth and/or worn wire? Is something rubbing/touching bodywork? Could be a resistance issue (bad earth) as something is overheating and melting. Have you nudged a wire that is now touching the PTC?

Can you do some resistance type tests, check earth etc?

 

[SuperV8]

Thanks for the comments,
When I checked the large brown ring terminal - I presume earth - I noticed the terminal post on the PTC heater moved a little.
Well looking at some pictures of the PTC heater the terminal post looks like it is just a spring contact on the PTC! so i'm thinking if there is movement there then there is a slack contact which could be high resistance and so the terminal post and ring terminal will get hot and melt the wire where it crimps.
Is the PTC easy to remove? When I cleaned my heater matrix (twice now) It looks like the PTC heater is behind some dash structure so a lot more involved to remove and check? I could check the resistance between the earth post and the three positive spade terminals but I don't know what a correct value is supposed to be?

Tom.

 

[BillyCool]

No idea! You've exceeded my knowledge level.

I guess that if you test a few other circuits, you'll soon know what a bad value looks like?

 

[RUM4MO]

@SuperV8 your location flag shows as UK, but I'd think that very few Leon TDI were supplied with PTC heater into UK unless it was spec'd as an optional extra, mainly it will be "cold climate" areas that get a PTC heater fitted to a TDI engined car, although one or two british made/used cars got that, maybe Rover 75 - I'm sure that I read that they had them, also so Audi TDI's but bigger models.

Edit:- I'm guessing, just guessing - that a brown wire is a supply wire, ie +12V. Spring contact when running quite a few amps sounds a bit silly, maybe that post has been riveted to the board and that rivet is now slack.

 

[SuperV8]

@SuperV8 your location flag shows as UK, but I'd think that very few Leon TDI were supplied with PTC heater into UK unless it was spec'd as an optional extra, mainly it will be "cold climate" areas that get a PTC heater fitted to a TDI engined car, although one or two British made/used cars got that, maybe Rover 75 - I'm sure that I read that they had them, also so Audi TDI's but bigger models.

Edit:- I'm guessing, just guessing - that a brown wire is a supply wire, ie +12V. Spring contact when running quite a few amps sounds a bit silly, maybe that post has been riveted to the board and that rivet is now slack.

Yes, I live in the UK - and the car is British.
It has FR trim - don't know if PTC heaters were standard with 184 Diesel's? and yes I was surprised to see it when I was fixing my heater matrix - but it definitely has one! Trouble is the dash frame looks like it is in the way to simply pull it out so I think it will be much more involved that taking out the heater matrix. When the heater matrix isn't blocked the heater gets warm really quickly so I don't really think it needs a separate electric heater - and looking through the EPC it doesn't list a part number for 2017+ Leon's so looks like its no longer available?

My initial thought was that the big brown wire was 12+ but then a VW tech I know suggested to me that VAG's often brown is earth and also the fact there is no shielding on the big ring terminal would be very easy to touch a spanner on it!

When I have a minute i'll have a poke about with my DVM to see if anything looks strange. I found some resistance curves for some PTC heaters (they all work with the same technology - positive temperature coefficient resistor) so I know roughly within an order of magnitude the resistance to look for.

This is a side view of the terminal and can't see any rivit/solder? Looks a bit sketchy to me!
PTC heater terminal by Tom Cranmer, on Flickr

 

[RUM4MO]

If that is a spring and not a threaded post, then seeing is believing!

I sort of thought about buying the correct one for my wife's 2015 Polo 1.2TSI and make it help to boost the cold start consumption instead of stealing so much heat from the engine coolant while the engine is warming up - though probably taking more out of the alternator so using more fuel!

Maybe the aux heater is part of the Tech extras?

Edit:- ah, re-reading your posting it sounds like it is a threaded post, though I'd expect that the "tail" of the end of the PTC is welded/rivetted to that/these terminal post(s).

 

[matt_s]

The heater is only on diesels because they take so long to warm up

 

[RUM4MO]

The heater is only on diesels because they take so long to warm up

Yes, I'm sure that we all knew that, or most of us did, diesels are more thermally efficient than petrol engines, so the cabin heaters tend to be less effective - which is why some manufacturers fitted PTC auxiliary heaters to the heater boxes.

 

[MATT RILEY]

Can't you just take the fuse out and not worry about it?

 

[RUM4MO]

I think that he wants to sort this out, having an aux heater in a TDI will be quite useful.

 

[MATT RILEY]

I think that he wants to sort this out, having an aux heater in a TDI will be quite useful.

I'm sure he does, but for safety sake remove the fuse if the wiring is going to catch fire!

 

[RUM4MO]

I'm sure he does, but for safety sake remove the fuse if the wiring is going to catch fire!

I think that the picture proved that it is currently not a fire risk as it is out of the car!

 

[Smilerr]

Hi , did you sort out the problem with this smell
Thanks
Vinny

 

[SuperV8]

Hi , did you sort out the problem with this smell
Thanks
Vinny

Hi, no not sorted yet.
I turned it off in the climate settings - so it won't set on fire!
I had another look and do believe it would be a right pain to remove - I can get the heater matrix out easily in 30mins, but this PTC heater even though it is next to the heater matrix is just behind the dash support frame, so I think that means centre tunnel and more out.
I didn't see earlier replies to this thread - with all the Pandemic got in the way!!
I find my EA288 Diesel does get warm really quick (within a few miles) so I don't really have need for this PTC heater. The heater matrix is in a mirco coolant circuit with the EGR valve and I don't believe the later cars even had one.

No - I didn't get mine out - that was just a picture from google to have a look at the connection. I did undo the big ring terminal and it was tight, so I think something internal has failed.

Why do you ask - Can you smell burning?

 

[Smilerr]

Hi,thanks
Yes smells a lot when start car early in morning but only in cold weather and only if heater is on. I will check the fan tomorrow if I have time. But this happened last winter few times and than till now I don't smell it at all but is not been cold ,but last few days is every morning because is around 2 celsius must be something with water or freezing don't know . But I think when the car warm up there is no smell not sure yet . If the heater is off when start car and leave it off for 15 -20 min and switch it on there is no smell.

 

[Woody_72]

I've got the exact same car and I'm pretty sure I don't have a ptc heater. The EA288 engine has two coolant circuits in the cylinder head specifically designed for faster cabin warm up. I know mine starts to chuck out warm air by the time I get a couple miles up the village bypass on my way to work. Maybe just the first few months of cars had them ??

 

[Smilerr]

Not sure about main , I will open to check must be something cable or fun

 

[SuperV8]

Hi,thanks
Yes smells a lot when start car early in morning but only in cold weather and only if heater is on. I will check the fan tomorrow if I have time. But this happened last winter few times and than till now I don't smell it at all but is not been cold ,but last few days is every morning because is around 2 celsius must be something with water or freezing don't know . But I think when the car warm up there is no smell not sure yet . If the heater is off when start car and leave it off for 15 -20 min and switch it on there is no smell.

If the PTC heater is switched on in the AC settings it still needs certain criteria to be met to activate - something like,
outside temp below a limit;
request for heating above a certain limit,
battery voltage above a certain limit,
engine coolant below a certain limit etc...

This is my heater matrix (with the large aluminium pipe) and PTC above with the thick brown wire it connected to the PTC. You can see the dash frame blocking the PTC removal.

You can see the wire insulation starting to melt arround the ring terminal: this is what's smelling burnt!
I'm presuming this is the earth - as there is no protection on the nut.