Technical Punto 176 (mk1) 1.7 TD cabin heater resistor pack by Valeo

[shutterfreak]

A couple weeks ago the cabin fan from my 1999 Punto 1.7 TD died. Whatever position I selected from the central console switch (0-1-2-3) didn't bring the fan to live. First I checked the fuses, but they were all okay. Then I called my garage to see if they could have a look.

To make a long story short, it was the heater resistor pack that died. That's basically a set of fixed value resistors that are put in series with the cabin fan to control its speed. Pretty simple and not very energy efficient since the resistors dissipate heat when current flows through them. That heat can be lethal to the resistor, which must have happened with mine.

Okay, I should be able to source a new one in aftermarket channels I thought. Apparently not - neither in the new nor in the used parts markets I could find a replacement.

It appears that Punto cars like mine had 3 different makes of internal heater fan / resistor pack units. Mine, a Valeo brand, can apparently no longer be sourced, not even in scrapyards (so far no luck).

The part is still listed on the Valeo online catalog (part number 508869, EAN 3276425088696 ) but alas, I can't source it over here. Even on the 'bay I couldn't find one. I added a couple images to show which part I mean (I hope this is okay):

So, for the time being, I "bridged" the heater resistor pack by means of a wire bridge in the connector normally attached to the heater resistor pack, and connected the thick wire going to the motor with the closest wire (blue), which is linked to the 1st speed setting on the fan speed selector in the central console. At least I have heat again, be it at full fan speed for now.

Since I know how to handle a soldering iron I'd consider either repairing the current defective resistor pack, or "upgrading" it with a DC/DC converter.

Sadly, disassembling the resistor pack does not seem to be working, unless I go ahead and try to unsolder the 4 lips of the PCB with the as of yet invisible electronics (I expect to find 3 resistors, maybe one diode).

The DC-DC track would be much more energy efficient, requiring much less heat to dissipate... if I know for sure that the fan motor will like being fed with a switched DC power source (it's basically a PWM circuit which I'd lock in 3 different PWM settings available through the speed selector in the central console).

Any opinions on the track(s) to pursuit?

Best regards,

Olivier

 

[fingers99]

The DC/DC idea has great technical merit, but, at the end of the day, is it worth the effort?

Can you not simply get hold of one of the alternative units and fit it?

 

[shutterfreak]

I don't know if a compatible alternative unit albeit exists.

Knowing the electronic circuit of the broken part and knowing the resistor values could help a lot already I think. I should measure the current drawn by the fan motor at full speed to get an indication on the power consumption of that fan, as this will help me in dimensioning/rating the required parts, be it for a passive, resistive solution (as is the case today) or with an active DC/DC circuit.

Also, I do not know if in my case it's a broken component or if it's PCB delamination that's the culprit. If you look at the 4th image, you'll see a "floating" metal tab under the heat sink (thermal radiator). I think it was intended to be soldered to the printed circuit board, but that's not the case in mine.

 

[s and b]

Pretty simple and not very energy efficient since the resistors dissipate heat when current flows through them. That heat can be lethal to the resistor, which must have happened with mine.

if you think about it this resister pack runs in the cold air created by the fan so its a cheap and effective way of reducing fan air throughput

you want to be able to reduce the speed of the fan so its just a matter of designing a small circuit with a completely variable output and able to withstand the amperage,whilst its above my realm to be able to design this
im sure a quick trawl of google woulds bring something up or even a complete article for the build of
i also bet someone in ebay sells one made in china with flashing lights and lucky charm included for under 10 dolla delivered
heres my last letter from gud celler

Dear friend
when you receive the item if it is damaged or it cant work,pls get in touch with me,i must resolve it, , please remember,i am in china, we are not in the same time because of the Equation but i am sure i will replyto you within 24 hours, Of course except sunday. Pls pls pls don’t leave your negative feedback or 1,2,3,4 stars to me easily.
I am honest ebay seller.Ilove my ebay store.I love my customer.
Please do not rashly give in the commentary as well as the poor commentary! Those in poor commentary harsh assessement of the buyer, We do not Welcome. Pls pls get in touch with ebay message.The email always lost it.
Thanks for your time to read this message
Best wishes!

of course as said just modifying one of the standard green ones would be simpler

good luckas

 

[PuntoHowTo]

I think you are over estimating how complex a heater blower resistor pack is.

3 fan speeds most likely means 2 resistors speed 1 resistor 1 speed 2 resistor 2 speed 3 both resistors.
High power diodes are expensive so why would they put one in?
Usually you have a large gauge coil of single core wire as your resistor, they are such low values that they don't need to be anything more than that, only a few ohms at most. Looking at yours it looks as if there is maybe a couple of ceramic coated resistors directly butted up to the aluminium heat sink but i cant see in the pics they are not great quality but looks like the legs of one of the resistors in pic2

Finger99 hit the nail on the head why not just use one out of another punto that isn't a Valeo model, do they not fit the whole? Or does the electrical plug not fit? Building fancy modules it very over the top to replace what is essentially 2 resistors and a lump of aluminium

 

[shutterfreak]

I think you are over estimating how complex a heater blower resistor pack is.

3 fan speeds most likely means 2 resistors speed 1 resistor 1 speed 2 resistor 2 speed 3 both resistors.
High power diodes are expensive so why would they put one in?
Usually you have a large gauge coil of single core wire as your resistor, they are such low values that they don't need to be anything more than that, only a few ohms at most. Looking at yours it looks as if there is maybe a couple of ceramic coated resistors directly butted up to the aluminium heat sink but i cant see in the pics they are not great quality but looks like the legs of one of the resistors in pic2

You're most likely correct, that's probably the most likely way things are wired in that component. Regarding the diode, I remember having seen electric circuit schematics of such resistor pack one day, featuring a diode. I suppose to avoid negative voltage spikes due to the inductive load (fan motor).

I still need to pry open the heater resistor pack to be able to identify its constituents (if at all possible). If somebody has the right values from a functional unit, it would be very helpful of course

Finger99 hit the nail on the head why not just use one out of another punto that isn't a Valeo model, do they not fit the whole? Or does the electrical plug not fit? Building fancy modules it very over the top to replace what is essentially 2 resistors and a lump of aluminium

I am not sure the components are connector compatible or even pin compatible, nor do I know whether the fan motor differs in the Punto units that use the other heater resistor packs (e.g., the green ones depicted in Punto Mk2). If the fan motor is more powerful in my Punto, I'll burn through the resistor pack in no time. If it has other pin wirings, I don't have to explain the hazard I guess

Since it's barely possible to find an aftermarket version, I'd like to know how the pack should be so I can see which way to move forward.

Best,

Olivier