PTC (Auxiliary) Heater for Quicker Heating in Winter

[dieselV6]

One idea I entertained for a while was to run all 3 sections in parallel using efficient PWM modulator dc-dc converter, Nowadays you can find ones intended for high power LED and motor applications, even with 100A output. The voltage to control the pulse width would then simply be battery / alternator voltage minus a fixed offset (zener diode), plus of course a relay to switch the whole thing off. PWM modulator would then effectively increase power output as alternator voltage goes up, and decrease it as it goes down. What stopped me other than the heater matrix housing was that at the time suitable PWM drivers were only available in China in quantities of 10-25 minimum. 

[piggoy]

Success!! I managed to fit the PTC heater into the hot air assembly over the weekend. After unbolting the airbag ECU the lower cover just about slid out and removed. This was possible without having to disconnect the heater matrix plumbing :-) thanks DieselV6. I then had to modify the enclosure by cutting a slot using a Stanley knife. Don't do as I did and split the plastic by being careless - I had to repair it with fibreglass which was annoying to say the least! Upon fitting I connected the GND cable to E3 grounding point just in front of the gearstick. From this point I was able to power the heater using a jump lead direct from the battery and I got instant hot air! Really pleased. Now for the electrics.

 

[piggoy]

A slot needs to be cut in the top to allow the PTC heater to slide in. I managed to break the enclosure when doing this and had to repair it using glass fibre.

 

Powering the heater using a jump lead direct from the battery. Instant hot air!

[Breezy_Pete]

:clap: Nice one.

[georgef]

This is a fascinating project. Well done. I admire your skills and ingenuity and co-operative working.

[Phil-E]

So I've now started looking to install one in my Octavia.

 

It seems it's a bit easier.

 

It literally slides in, live wire to battery with 100amp fuse, earth point on passenger side and then tap into the can high and low cables going to the back of the headunit. Then just code the car for aux heating. Done!

 

I'm so doing it!

[tamiyaandy]

Guys, Maybe its just time to "MAN UP" !! :p

[Phil-E]

Guys, Maybe its just time to "MAN UP" !! :p

 

Says he with the Touran... didn't they come as standard with the aux diesel heater at the back?  

 

Phil

[SkUG]

Sorry to thread jack - do you have a picture of the space below the radio with the "console" upper removed? Trying to work out where best place to mount additional cig lighters without taking everything out in the dark! 

Cheers 

[tamiyaandy]

@ Phil-E, if mine does have an aux heater, I havent a clue were it is or how to use it!.. At 6am my 7 mile, 20 Min drive to work along the seafront roads of the South coast it still is just shy of the norm 90 deg operating temp!!

[Phil-E]

@ Phil-E, if mine does have an aux heater, I havent a clue were it is or how to use it!.. At 6am my 7 mile, 20 Min drive to work along the seafront roads of the South coast it still is just shy of the norm 90 deg operating temp!!

 

I'm almost 100% sure it came standard on all the diesel Tourans and Sharans. My dad's old 1.9 Sharan had it. It should work automatically. If you have climate control make sure "Econ" is switched off.

 

If it doesn't seem to be working then there may be a problem with it that some diagnostics will show up.

 

One way to check if you have it is to look for it's exhaust:

 

 

If it's slightly newer the exhaust will be further back.

 

Phil

[trundlenut]

I'm almost 100% sure it came standard on all the diesel Tourans and Sharans. My dad's old 1.9 Sharan had it. It should work automatically. If you have climate control make sure "Econ" is switched off.

If it doesn't seem to be working then there may be a problem with it that some diagnostics will show up.

One way to check if you have it is to look for it's exhaust:

If it's slightly newer the exhaust will be further back.

Phil

Bloke at work has just bought an 53 plate touran, that has one, but it's broke.

Sent from my Nexus 4 using Tapatalk

[trundlenut]

So I've now started looking to install one in my Octavia.

It seems it's a bit easier.

It literally slides in, live wire to battery with 100amp fuse, earth point on passenger side and then tap into the can high and low cables going to the back of the headunit. Then just code the car for aux heating. Done!

I'm so doing it!

Ooooooo.

Do it, I'm interested in doing this and it sounds quite simple.

Sent from my Nexus 4 using Tapatalk

[Phil-E]

Ok enough talk of Octavia PTCs and Tourans in here. Sorry guys!

 

I fully intend on fitting the heater to my Octavia. They are about £70 on ebay and the other bits are cheap.

 

Looks like a fairly straight forward job for a competent car DIY-er like myself.

 

Once I've started I will be starting a thread in the Octy MK2 section.

 

Phil

[tamiyaandy]

Sorry Phil, mine def does not have one and it's an SE spec car, I have checked the manuals. :-(

[softscoop]

I'll be very interested to see how you get on Phil

[Breezy_Pete]

I've just been doing some measurements on one of these heaters, same part number as piggoy's 6Q0963235A.  I'm using a 100A-capable server PSU that is nominally 12V, but I'm measuring 12.6V at the element connections when powered up.  I think this is close enough to what it will see in service to be representative enough, but I will repeat the measurements in the near future with the same stuff wired direct to a car battery with engine running.

 

I wanted to see what the highest, and steady-state currents were, for each element individually; with and without airflow through. I've got a 0.005Ω shunt resistance that will handle a 25A continuous current without getting too hot, which I thought would be adequate for this testing, enabling me to measure the (small) voltage across this resistance to give me a fairly accurate current reading, without the resistance of the shunt affecting the circuit significantly.  As it turns out, I could probably have done the measurements directly with my multimeter which has a 20A dc range, but it would have been borderline.

 

Here's a graph showing the resistance versus temperature characteristic for a generic PTC heater:

 

You can see that the minimum resistance Rmin occurs somewhere above normal ambient temperatures, and then the resistance climbs steeply once a little hotter than that.

 

Correspondingly, the maximum current doesn't occur when the things are stone cold, but after a short time of being powered on. Steady-state current also varies strongly with how much heat is removed from the element by airflow. Staying higher if the heat is extracted by airflow, dropping away if it isn't.

 

I was hoping to capture some nice graphs with a PC-based oscilloscope I have, but I couldn't get it to do what I wanted, so I ended up with just some numbers on a piece of paper; sorry!

 

Anyway; as per piggoy's resistance measurements, the central element fed by the red wire is different from the others, taking the most juice.

 

From room temperature, around 18°C, with no airflow, current flows at about 20-22A initially, rising to about 27A peak after about 2 seconds, before dropping off again to about 20A again over the next 10 seconds or so, and continuing to drop steadily to about 10A after 30 seconds and 8A after a minute.

With a two-speed desk fan running right up against it, the figures are different, as expected:

Low speed, we see roughly the same during the first 10 seconds, but now the current stabilises at about 18A and sits there unvarying.

At high fan speed, it settles at around 19A.

 

The other two elements are similar to each other, but a little less powerful. Both showed a switch-on current in the high teens, maximum current of around 22A a couple of seconds after switch-on, and steady-state current of around 16A with fan on high speed.

 

I do have some 0.001Ω 70A-capable shunt resistors that could potentially be used to measure all three elements together judging by the above numbers, and could even potentially be used 'in service' to monitor power usage, but I haven't wired them up yet, and I'm not sure they're really necessary. I doubt that switching on all three elements at once is a good strategy.

 

To my mind, this suggests that for minimum 'surge impact' the three elements should probably be switched on sequentially, a few seconds apart, before the cabin fan is switched on. Pragmatically; switching the two lower-power elements on together, after the first one, possibly as per OEM set-up, will give more hot air sooner - which is kinda the whole point!

A total steady-state fan blown current in the region of 51A  (19+16+16)  doesn't sound too scary (to me) in terms of impact on the overall electrical system, but I still think that battery voltage should be an input/inhibit to the control system, and I believe piggoy is working towards this.

 

Now that I've cobbled a measurement system together, I'm happy to make any further measurements that anyone thinks would be useful. I'll try to get some graphs of current against time too, once I've got a clue about how to make the 'scope do what I want.

[piggoy]

Many thanks Wino. That's excellent work! I am now a more confident about using the cheap ebay relays -

 

http://www.ebay.co.uk/itm/2x-High-Quality-12v-CAR-AUTO-30A-AMP-On-Off-4-Pin-Fused-Relay-/181404927631?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item2a3c93868f

These are 30A rated and fused. If I connect one of these to each element, 3 in total, then then current rating for each relay should not be exceeded in all situations. I may still consider installing 40A relays instead although these come without fuse holders so adding extra complexity in the wiring.

 

The micro code for the control board is nearly complete. We just need agreement on the switching sequence and times. This should be based on Wino's measurements.

[Rob.]

E...

P...

I...

C...

 

I'm so made up this project finally got off the ground! It's like coming back to a seed I planted a few years ago to find someones been taking care of it and now it's a big aux heater tree!

[piggoy]

Hi guys,

 

An update on this project. Wino and myself have been working in the background to make this happen. We've now successfully designed and implemented the control electronics and we are pleased to announce we now have a working auxilary heater system in a Fabia vRS! The result is instant hot air at the touch of a button on a cold and frosty morning :-)

 

The three elements in the auxilary heater assembly are switched using three 30A rated fused relays like the ones in the post above. These relays are controlled by the electronics which monitors the system voltage and switches the elements on and off in response. The whole shebang is controlled from the heated rear window switch for that OEM feel :-)

 

In the new year we will post a definitive pdf guide showing briskodians how to implement the system for themselves. For now I have some pics. The relays bolt to the chassis on the central console upright. The supply cables connect to the Terminal30 junction next to the interior fuse box - so no need to run cables into the engine bay :-)

 

[hockeylad72]

Well done guys, all this electronics is WAY over my head!

[MattCutts]

Looking forward to the guide, great work!

Sent from my iPhone using Tapatalk

[Phil-E]

Wow. Very impressive guys.

 

Very clever making your own controller.

 

I've been given the go ahead by the other half to buy the auxilary heater so will be buying and fitting hopefully early in the new year.

 

How quick does the air become warm? And how warm is it? Enough to demist a windscreen straight away?

 

Phil

[Breezy_Pete]

Rather late in the proceedings, I came across some useful information yesterday, after the turkey.

It's from a self-study programme (SSP218) about the Lupo 3L, but the system sounds the same as what's in a Fabia when it's factory installed.  Some technical details that I didn't know before, and may be useful.  I've made one correction, on the last page, where a sentence makes much more sense ending with the word "on" instead of "off".  Here are some snapshots of the relevant pages:

 

1st page

 

2nd page

 

3rd page

 

I found myself wondering last night if the ECU wiring (1 input and 2 outputs) specific to this heater might be present by default in all (diesel) engine bay looms, which may provide an easier alternative to our own dedicated controller, possibly just requiring activation of the function in VCDS (plus wiring the heater  into the system via some relays and fuses).  Unfortunately, in the cold light of day when I look at partscats.info for part numbers of engine ECU looms, I see at least two different versions, one of which is referred to as being for "vehicle use in cold climates" -  the suffix AT one here. I can't help thinking that'll be the one with the necessary wires we would need already in place, and likely not the one fitted in UK Fabias unless specced at build time.  Confirmation from any diesel Fabia owner of whether they have any wires going to pins 15, 21 & 22 of connector T81a on the engine ECU would be useful in relation to this. ( I found those pin numbers relating to a 1999> SDI Fab, engine code ASY; really not sure whether they generalise to any other Fabia diesels) 

 

Also, in connection with the references on the third page above to the alternator load factor (info the ECU gets from the DFM output of the alternator); does anyone know what form this signal takes? One reference I found to it (not specific to a Fabia) suggested it might be a simple square wave, with mark/space ratio related to alternator output level. That might be something we could work with in piggoy's circuit, to make it even more like the factory install, at the price of one more wire and a bit more thought and programming. 

[jacissmiling]

Hi Guys,

 

Might be a little bit late to the party with this, but have recently been thinking about this and found the current flow diagrams showing the oem setup, more for reference than anything else of course...as to be honest I prefer the idea of being able to control it using the rear window defrost button haha!

 

It shows relays 8 & 9 are the low and high (or preheat / staging relays) used to supply the ptc heaters.

Additionally it shows that in relay slot 10, 3 fuses (40A each) are used to protect each heater and associated cabling.

 

Ive not had a chance to check (and with the weather just now - unlikely to get a chance to check until the temp improves) but if relays 8 and 9, as well as the 3 fuse carrier in relay slot 10 are already installed, it might be possible to just get away with buying the ptc heater...

 

Has anyone had any luck and seen if relays 8 and 9 are there? And if 3 slots for 3 fuses are in relay slot 10?

 

Also, link to the place where I found the current flow diagrams and lots more - http://www.mediafire.com/?32vct1hmvx1rz

Taken from this thread - http://www.briskoda.net/forums/topic/117337-excellent-free-service-manuals/

 

Jac.