Delta Brake Warning System

[Neil Lewis]

Hi Fellas

My Integrale has the "check panel" with a brake wear warning facility.  The car has not had the factory pads on it for all the time I've owned it and the warning light is always on.

The system relies on a resistor in the front brake pads so that it can tell if the brakes are worn down (no resistance) or the wire is broken (full resistance).  So, in order to extinguish the warning light I need to add a resistor to the wiring but which one?  I have looked in the detailed specification pages of teh big workshop manual and hunted on the web to no avail.

Does anyone have a set of this style of brake pad and can measure the resistances?  I'll need the resistance between the two wires and the resistance between each wire and the little spring on the pad itself.  That's three resistance measurements.

Please help
Neil

[Neil Lewis]

It used to be true that, if someone posted a query on this forum, there'd be loads of replies in a short time.  Recently I've noticed that far fewer people write anything at all nowadays.  Is that a sad reflection on the people or on the forum; I don't know.

So do I take that no-one wants to help me with this little problem or have I just not left it long enough yet?

If you have a check panel car (and it's fitted with the "correct" brake pads), all I need is a few resistances measured.  Once I have that I can devise a way of fitting resistors to the system so that uprated and other after-market brake pads can be fitted without the confounded dashboard light being on all the time.  And of course I'll tell you all what I've done so you can do the same.

Now isn't that what a forum like this is for...

Neil

PS
Don't respond with why I'm getting no replies!!!

[stuwilson128]

I can't help with giving resistances, but have you considered getting some variable resistors?  Once connected to the wires, it should allow you to adjust the resistance until the indicator goes out.

[Chris5090]

Now i've had a think about this, and this will sound like a silly question, but are you sure of how the system works? I've no experience of the check panel on a Delta, but most modern systems work in one of two ways

 1. They have two wires to the pad wear sensor and rely on the disc slowly cutting through the sensor
     to break the wire, when this happens the light is illuminated. The easy way around it is to just join the
     wires at the plug for the sensor. Most modern cars work this way (BMW etc), it's more reliable.

 2. They have a single wire to the pad, and as the pad gets worn it earths the wire on the disc, making
     the earth and putting on the light.

I would assume that the system on the Delta check panel is something similar to the first example, as the light is on all the time, so maybe just bridge the wires? I unfortunately don't have a Delta with a check panel or i'd be happy to have a look.

Hope this helps.

Chris

[Neil Lewis]

Thanks for the responses.

Unfortunately Chris, according to the workshop manual, Lancia (or Marelli?) decided to do this in a complicated way.  So they fitted a resistor inside the pad and linked the two wires through that and  I'd expect any two wire system to work the same way.  When the pad wears down the wires are shorted through the disc so the resistance goes to zero and when the wires break (or are worn down too far and are cut) the resistance goes very high (probably not an open circuit cos the other side is still there).  So the check panel looks for the resistance and, if it goes out of range either way, the LED lights up.  I've already linked the two wires together and the LED is illuminated at the time.  My guess that in a 21 year old Italian car there may be so much resistance in the wiring by now that I may not be able to fix it.

Stu I think you might have the answer so I'll "borrow" a variable resistor from work and see how that goes.  Of course, if as I suspect both sides work in parallel, I'll have to adjust both sides at the same time (and I don't see how they could NOT do that; nothing if not awkward those Italian electronics people).  I could just pinch a load of resistors from work and try them one at a time...

Knowing the proper resistances is still the easy way though,
Neil

[fay66]

Hi Neil,
not sure if this is of any use, or even what you're looking for; but this is the wiring diagram for the Delta HF Turbo with the check panel and pad wear warning light.Items 41 and 38 being the pad wear sensors.
colour code= M= Brown,SN = Pink-Black,S = Pink,VG for some strange reason isn't listed. Item 60 is obviously the check panel.

Brian 8227

[stuwilson128]

colour code= M= Brown,SN = Pink-Black,S = Pink,VG for some strange reason isn't listed.

Assuming that the standard (fir Fiat/Lancia) colour codes are used, then VG = Green-Yellow

[stuwilson128]

Of course, if as I suspect both sides work in parallel, I'll have to adjust both sides at the same time

Neil,

If it is that case that both sides need adjusted at the same time, I would suggest using a dual gang potentiometer.  These are basically 2 pots in one, and alter the resistance by exactly the same amount.  You can use fly leads to connect the pot in to the wires at the pads.  Once the indcation goes out, measure the pot resistance and then connect some fixed resistors of the same value (rather than leave the variable resistor connected which could be accidentally altered).

Hope this helps a little!

[Chris5090]

Another silly question, but i dont know the answer!

Are the pads with wear indicators not available anymore? I though i'd read on Brakes International's site that they could supply them? Just thought it may be the simplest option?

[Neil Lewis]

Not a silly question.  Most of the pads for the 8/16 valve Integrale have wires into them but, in my experience, they all just run to earth, ie, they have a single wire and don't have the resistors.  Those are fine for the usual brake warning light on the dashboard but are not suitable for the Check Panel cars.  The resistor pads have two wires going to them and a soft rubber plug to connect to the car's harness.

After going through many makes and types of brake pad I've settled on Ferodo DS2500 which seem to have the best compromise between acting quickly during normal driving and not overheating when driving spiritedly.  The standard pads overheat too quickly and I don't want to buy a pair (probably only available from a Lancia dealer - remember them) to measure the resistances.

By the way Brian, my Integrale workshop manual also shows that diagram but the description of the check panel specifically mentions the resistance but gives no details except how it works in practice.

Anyway thanks everyone who's contributed.  I think I'll try the variable resistor route.  I'll let you know what I find.

Neil

[ben]

Hi Neil
            Just read your thread so looked in my box of useless bits and found an old pad with twin wires and a sensor that was still intact.The resistance between the wires was negligable and from wires to pad base infinite.I dug out the sensor and it simply comprised a loop of the wire.
            It occurs to me that when the pad wear reaches this wire it will make a connection to earth via the disc when the brakes are applied without cutting the wire initially.It may well then take several hundreds of miles before wearing through the wire.Thus the state of the circuit when the wear indication first appears is distinguishable from a broken wire situation without any need for a specific built-in resistance in the pad.Clearly with a twin wire system there must be a resistor in the circuit to limit the current but I would not have thought it would be in the pads.Sadly however this doesn't explain why your warning light is on if you have short circuited the wires at the plugs.
            It would be interesting to check for voltage at the plugs.If my theory was correct there should be 12v on one side. If you felt brave you could try applying a 12v feed if it wasn't already there to see if that might put out the light!
            Incidentally neither of my cars have the check panel and I dont know the source or history of the pad I checked so the above is all quesswork really.Best of luck
                                               Ben

[Neil Lewis]

Thanks for that Ben, that's really interesting.  Now I'm completely baffled.  As you say, if I've shorted out the two wires and just connected in the single wire from the Ferodo pad I shouldn't be seeing the light on the dashboard.   Depending on the weather this weekend I shall have to have a play around to see what is going on.

Cheers
Neil

[Chris5090]

I've done a bit more research on this, mainly because i'd like to know!

An extract from the manual i have just bought:

Front brake pad wear
When the conductor on the brake pad insert is earthed becuase it touches the brake disc, during braking, the check system indicates the fault.
When the pedal is released, the fault ceases to be displayed.
If wear continues until the insert conductor is "cut", the fault is indicated CONTINUOUSLY and not only during braking.

So, in theory, if you join the wires at the plugs in the wheel arches, then the light should go out. If it doesn't there must be a break in a wire somewhere in the system.

With reference to a wiring diagram i think the checks should be as follows
- Check panel connector F wire 2 to Nearside connector in arch (pink - black wire) - Zero Resistance
- Pink wire in left pad connector to pink wire in right pad connector - Zero Resistance
- Check panel connector F wire 3 to Offside connector in arch (Green - yellow wire(it's colour isn't listed 
   in the key)) Zero Resistance

So with the connectors bridged you should see Zero resistance between wires 2 & 3 of connector F at the check panel, if you do but it's still on then it must have a short to Earth. If you do have a short to Earth and don't want to spend hours looking for it you could just join the wires behind the check panel.

I hope this helps.

Chris