PTC (Auxiliary) Heater for Quicker Heating in Winter

[AaronMountford1990]

Did anyone manage to make a guide for this yet?

[piggoy]

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.

 

The guide is not ready yet. Sorry guys, been very busy.

 

@jacissmiling - Unfortunately it isn't as simple as plugging in the heater to the existing wiring loom. The two relays (J359 and J360) and the 3x fuse carrier are not installed in cars that do not have the heater fitted - so naturally there exists no OEM way of connecting the heater element. If you want to dismantle your dashboard to try find them they won't be there. The whole goal of this project has been to provide that very connectivity be retrofitting relays. The relays themselves have to be controlled by a custom control board that myself and Wino have designed. They cannot be controlled by the ECU without knowledge of the interface and how to activate it.

[jacissmiling]

Ah ok, I wondered as much from reading earlier posts in the thread - that unless it came out the factory that way...none of the required bits will be there :(

 

Last time I was looking at the relay holder for the glow plug relay I cant remember if they were there...but as above....doesn't seem likely :(

 

From the current flow diagrams, it shows that the relays connect to points 60 and 61...

...had a quick look through earlier and couldn't find it...but if those points could be found then a full on OEM style solution could be done...

...subject to the coding being present on the ECU to allow it right enough...but again as before...im not sure how likely that would be :(

 

Like your solution you guys came up with though!  It more or less mimics the OEM setup with the hold off on low voltage instead of alternator load factor.

And as before, I prefer the idea of it being button controlled rather than it being dependant upon coolant temp and heater temp control knob posn.

 

 

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. 

 

In reference to the above, have attached another diagram showing the current flow diagram for the alternator.

As Wino said, It would appear that 'D' is just a start permissive signal, with 'DFM' being the voltage regulator output signal. 

 

Will try do some digging, but id guess if a small switched mode DC/DC convertor were present, it may output a square wave with the duty cycle being related to the alternator load factor (i.e. high amps - high duty cycle as the smps tries to keep the terminal voltage at nominal) - or if the alternator were of the non permanent magnet type, this may be a signal taken off of the voltage regulator which controls the alternator rotor excitation - in which case I imagine the signal will be just a varying DC voltage (i.e. high amps, higher signal voltage from the higher rotor excitation current).

 

As I said before, bit cold outside and I don't have a garage so I wont be going hunting for relays that most likely arnt there...and im afraid I cant get my 70's relic of an oscilloscope outside lol, but will have a look through the current flow diagrams tonight and try find the 60, 61 and 41 cable continuation references to see where they end up too!

Edited 4 February, 2015 by jacissmiling

[Breezy_Pete]

@jacissmiling: Are those wiring diagrams from the very last link in that mediafire page, the .rar file? I daren't try to download that at work. The 'diagram flux curent' document further up the list stops in late 2002 as far as I remember, limiting its usefulness.

 

In your last picture, there are two wires that finish in rectangular boxes labelled 60 and 61. This means those connections continue at current tracks 60 & 61, which are the numbers along the bottom of each diagram. Can you have a look at which (ASZ) ECU pins those wires go to, on the page that has current tracks 60 & 61 on it, please?

 

It  would be nice to have someone eyeball their ECU wiring to see if the wires for this heater are even in that loom, as per my comments in post 99 above.

 

As piggoy says, no suitable cabin loom, no relays, no fuseholders in UK cars without the heater option, as far as we can tell. All that could be retrofitted, but at some considerable expense compared to piggoy's implementation. 

 

Whether the ECU can just be 'enabled' with VCDS for this function is another matter that I/we have no idea about just now, but I suspect so.

 

Edit: thanks for your input BTW. :sun:

[Breezy_Pete]

Oh, forgot to mention: DFM is a 5V 150Hz square wave, with on-time inversely proportional to alternator load, I found the other day on my Polo that is wired the same. Could be useful. I'm also pretty sure that this tells the ECU what's happening, rather than it being a signal from ECU to alternator, telling it what to do.

 

The voltage regulator (alone) is what governs the alternator's current output.

[jacissmiling]

@Wino - Yeah its from the very last link with the .rar file.  Another good one is the electrica.pdf that there too, quite useful to say the least!

Not actually sure whos mediafire page it is...but big thanks to them!  Hence why I linked the original briskoda thread that I found them in lol.

 

I think my car must have been an experimental model where they let the lads from lambo have a go at wiring it...had more electrical faults than you can shake a stick at haha!

...turns out being an electrical engineer isn't glamorous...but it does save a fortune in garage bills and saves me having to call an auto electrician every time something else goes wrong haha!

 

Havnt found where 60, 61 or 41 end up yet (im at work too) but when I do will post it up (unless someone beats me to it lol).

 

EDIT:

 

Ah that's interesting as to DFM!

Maybe not an smps as 150Hz seems rather low for a switching frequency...not strictly relevant...but wonder how it derives its duty cycle in relation to load current...something to investigate when its warmer I think!

 

EDIT 2:

 

http://www.motoplat.nl/Tech%20Info/DFM%20Explanation.pdf

 

Next time I post il make sure its strictly on topic!  Turns out the DFM signal is just based on pwm of the rotor excitation current!

The above seems to fit nicely with what you found Wino with your Polo.  ECU then just looks at this signal and can infer the load factor of the alternator.

Thought 150Hz was a bit low for a switching frequency...but that said the required output of the alternator is DC...so I don't suppose AC generated power quality actually matters so long as the alternator holds its output at a reasonably clean 14.5V(DC) (or whatever the nominal voltage of the car is).  

Edited 4 February, 2015 by jacissmiling

[Breezy_Pete]

Yep, I found a much clearer picture of DFM versus load level somewhere, and I think I have it saved on a computer at home somewhere. It's basically the case that the field winding is powered by a FET(?) that switches on when its input is low, and off when its input is high; leading to that inverse relationship I observed. DFM is just the ECU looking at this control signal within the voltage regulator.

 

I think the battery acts like a huge capacitor to smooth the alternator output.

 

Edit: here you go, a Hella pdf on the subject of voltage regulator function, including DFM signal; last paragraph and associated pic.

 

Snapshot:

[jacissmiling]

@Wino - Nice one, that's interesting!  Cheers for that!  Been thinking about it all afternoon, now got plans to build one out of nosiness lol.

Triangle oscillator, op amp comparator, switching device of some sort (likely a MOSFET for ease) and I think its quite doable

 

Back on topic though, did some more digging through the current flow diagrams, not sure how I kept missing it this afternoon but found the full current path now

 

Have attached a rough sketch (via paint) from the current flow diagrams.  Matches the links you provided in post #99, with the F268 switch essentially being the start of the chain.

 

Once that switch is closed and the other conditions (monitored by J248 - engine speed, alternator load, coolant temp and external temp) are all met, then the far side of the relays see 0V and they close allowing power to the ptc heaters.

 

The wiring between each 'shouldnt' be too taxing...BUT...im not sure if the ECU will allow such without some coding mods...

 

'shouldnt' as anyone who has ever looked im sure will agree that trying to start wiring up a car with mods / attachments to the original loom can at best be time consuming...and at worst mega ballache!!!

 

Pages (for further reference) from the current flow diagrams are: 53/22, 10/7 and 10/10.

 

EDIT:

But as I said before, to be honest I actually much prefer the idea of it being controlled via the rear window heat button with a low volt hold off!

As I cant help but imagine really the only time Id get proper use out of it would be cold mornings to help warm the car up to a comfortable state and help defrost it...i.e the sort of times you need to use the rear window heat button!

Edited 4 February, 2015 by jacissmiling

[mattbvRS]

Good work people! Very interesting read, I don't know why most cars don't come with these as standard, especially modern ones!
Same with the heated front windscreens too (though I believe Ford own the rights to them).

[Coco76]

As you can see, I'm new to the Forum and Skoda in general. On looking through the site I found this thread.

 

As you might also see I am in Spain, however,my Fabia was originally a German registered car and out of interest this morning I started her and put the heater on full - immediate warm air soon followed by hot. If there is anything I can do to help progress then just ask - but bear in mind I'm no use with electronics !

[FinnVrs]

Hello my car is that the PTC resistor.
The ECU adjusts the operation .

Water temperature must be within a certain area

Alternator load should not exceed a certain level.

And of course, the heater must be turned on and the fan also  .

If I have yet to understand correctly then the resistance would be the 2 -level , ie 700w and 1000w max power , depending on the need for the ECU determines .

I do not remember whether this all the terms which the ECU needs to know before  put that resistance to heat

 

[piggoy]

@Wino - Nice one, that's interesting!  Cheers for that!  Been thinking about it all afternoon, now got plans to build one out of nosiness lol.

Triangle oscillator, op amp comparator, switching device of some sort (likely a MOSFET for ease) and I think its quite doable

 

Back on topic though, did some more digging through the current flow diagrams, not sure how I kept missing it this afternoon but found the full current path now

 

Have attached a rough sketch (via paint) from the current flow diagrams.  Matches the links you provided in post #99, with the F268 switch essentially being the start of the chain.

 

Once that switch is closed and the other conditions (monitored by J248 - engine speed, alternator load, coolant temp and external temp) are all met, then the far side of the relays see 0V and they close allowing power to the ptc heaters.

 

The wiring between each 'shouldnt' be too taxing...BUT...im not sure if the ECU will allow such without some coding mods...

 

'shouldnt' as anyone who has ever looked im sure will agree that trying to start wiring up a car with mods / attachments to the original loom can at best be time consuming...and at worst mega ballache!!!

 

Pages (for further reference) from the current flow diagrams are: 53/22, 10/7 and 10/10.

 

EDIT:

But as I said before, to be honest I actually much prefer the idea of it being controlled via the rear window heat button with a low volt hold off!

As I cant help but imagine really the only time Id get proper use out of it would be cold mornings to help warm the car up to a comfortable state and help defrost it...i.e the sort of times you need to use the rear window heat button!

 

Thanks for the info jacissmiling, great detective work there! It really would be fantastic if we could install the heater as a proper OEM setup by making use of all the control functionality that already exists in the ECU. However, I like you like the idea of controlling the PTC elements via the heated rear window switch. The control board solution Wino and I have been working on works quite well here. One additional advantage of the control board solution is it allows you to use three cheaper 30A relays with integrated fuse holders (post #93), rather than 1x40A and 1x70A rated and expensive relays with separate fuse holders. This simplifies the setup and makes it cheaper. The cheap 30A relays with integrated fuses are available on ebay for less that £3 each! 

 

Since our original posts I have been working on some changes to the control scheme. The original plan as you are aware is to have a microcontroller monitor the system voltage from the point of view of the control board's power supply. One of the difficulties we have is that the board's power supply voltage is quite strongly affected by the system load, and you see quite erratic swings in voltage depending on what accessories and perphericals are activated. Using voltage to monitor the battery health is also fraught with difficulty since lead acid batteries only begin to show appreciable voltage drops when they are on their last legs - hardly an ideal method for a system that is supposed to prevent that from happening! We could measure the battery voltage directly by running a sense wire into the engine bay, but if we do that then we can just as easily hook up to the alternator DFM. That's what I'm coding up at the moment on the microcontroller - a program that measures the alternator loading via the DFM PWM signal and switches the relays on and off in response. The scheme will follow the VW Lupo recommendations in Wino's post #99.

Edited 10 February, 2015 by piggoy

[jacissmiling]

With previous things Ive built for the bike (shift lights, rev counter and quick shifter) Ive had pretty good success using discrete voltage regulators.

 

They are fairly cheap and can take a fairly large input voltage range and output a reasonably clean 5V.

Shunt capacitors and or a series inductor can help with noise rejection on the 5V supply rail too - but in all but the rev counter circuit, I never had any real trouble with 5V rail noise.

I havnt even had to bother with a heatsink with them either as the current draw for the control circuitry is way down in the couple of mA region.

 

Not sure what the closing / holding current of the relays is, but if 5V isn't enough then as you had suggested before, using mosfets or similar to switch the v+ of the car, but with the control circuitry supplied by the 5V rail, might be an option.

 

Only way Id guess to monitor the battery voltage would be to have again another fixed voltage source (quite a few discrete components or IC's available for such) and an op-amp comparator circuit.  i.e. comparing supply voltage (the terminal 30 connection straight onto the circuit board would be ok id guess) as well as that fixed voltage generated from the fixed voltage source.

 

As you say though, I guess the battery voltage isn't the best solution for monitoring load.  Getting the microcontroller to monitor the DFM duty cycle would defo be good! 

Il be keeping an eye on this thread excited for when Wino and yourself have it all sorted!

[piggoy]

Only way Id guess to monitor the battery voltage would be to have again another fixed voltage source (quite a few discrete components or IC's available for such) and an op-amp comparator circuit.  i.e. comparing supply voltage (the terminal 30 connection straight onto the circuit board would be ok id guess) as well as that fixed voltage generated from the fixed voltage source.

 

 

The best thing about using  microcontroller is that it has all that functionality built in (voltage regs, comparators, ADCs, timers). It makes for much simpler circuitry and a huge reduction in component count. We've been able to construct this circuit on veroboard smaller than a matchbox. I'll keep you posted.

Cheers.

[jacissmiling]

Ah that's good! Have never played about too much with microcontrollers or C, didn't know that functionality could come already in place!

Everything I done before was either old school analogue, quasi modern analogue IC's or via an atmega chip coded on an arduino lol (spot the idiot who codes like a monkey lol) :p

As I say excited to see this complete as every morning I drive to work whilst cursing the cost of having a diesel rather than petrol hot hatch lol.

[AaronMountford1990]

So did this work out in the end? Interested in the mod! 

[Breezy_Pete]

22 hours ago, AaronMountford1990 said:

So did this work out in the end? Interested in the mod! 

No, or we would have documented our success.

 

I gave up when, after fully installing our homebrew system, I tried it one frosty morning and could barely tell that it was on. It didn't give hot air, or even warm air, just slightly less cold air.

Was having a bit of battery trouble at the time and it seemed crazy to add a big electrical load to a system that was already seemingly struggling, for minimal benefit. New battery fixed the trouble, but I never bothered trying the system again. It was/is in the missus's car and she wasn't that keen on me tinkering with it unnecessarily.

 

The other fella had trouble with a relay that stuck on after it was supposed to be off, flattening his battery, I seem to remember.

 

 

[BilTechnik]

Apologies for the terrible thread revival, but I've just ordered all the parts to make this work as an OEM system. Is there still enough intrested for it to be worth me making a guide?

[Breezy_Pete]

Go for it, please. 

I ended up fitting a manually controlled system in my Polo, just a couple of rocker switches on the coils of the two relays. Never got round to making it inhibited by the cabin fan being off or any such niceties. Works well though. 

[BilTechnik]

Will do  I think the wiring diagrams were the misleading bit last time, Fabia’s, at least with air con, come pre wired on the engine bay side for it. They also the HVAC control system from a Polo 6R ( or I guess the Polo 6R using the controls from the Fabia) so the control is CAN based, rather than using that F248 wire.

 

Glad it worked out on yours, was a bit worried when I saw the posts about the heat output being very low

[Breezy_Pete]

19 minutes ago, BilTechnik said:

rather than using that F248 wire.

That's not ringing any bells, what page is that on?

 

Ah, maybe J248, the engine ECU on diesels? I think the system that piggoy and I came with up was independent of that, more self-contained, from memory. 

I'll have another look at the circuits, but I think it's only the diesel engined Fabias that have that wire in the engine bay loom?

 

Edited 23 August, 2022 by Breezy_Pete

[BilTechnik]

12 minutes ago, Breezy_Pete said:

Ah, maybe J248, the engine ECU on diesels?

Ahh whoops sorry I meant F268. The PTC enable switch/line in the heater controls

[Breezy_Pete]

Ah, I see, yes, just seen the * not valid for vehicles with air conditioning system 

bit in the WD.

Good info.

 

[BilTechnik]

Yeah I was confused by that a first, it’s deceiving because non of the wires on that diagram exist in that way on my car, at the end of the wiring diagram document there actually a page which shows the correct wires, and that matches the polo setup. Surprised me that the Polo uses an “old” Skoda system, though it was normally the other way/equivalent 

[Breezy_Pete]

Which car/year/engine will you be working with?