I've purchased and fitted a set of LED replacement bulbs for the front running lights on the Panda. They look great; but I have one question.

After I shut the car off, the LEDs stay on, although very very dim for approx. 30 seconds.

They don't seem to correspond with the interior dome light, either. Because, if you wait for them to go out, and then press the door-lock button on the key they turn on (again very dim) for another 30 seconds and then go out.

Has anyone else experienced this?

I have led bulbs on my interior courtesy lights (Panda Cross) they are permanently on although when they "shouldn't" be on they are very dim. I have been told that the reason is that led bulbs are so much more efficient that they will light up when there is a mere hint of a current. If incandescent bulbs were sensitive enough they too would shine permanently on the courtesy light circuit as it always has some residual current going through it.

As my led's have been on since December and my battery is still as fit as a fiddle It seems my source is right. Maybe the DRL's have some residual current for 30 secs after shutdown? If so I would not worry about it, the Led's are merely using the current that an incandescent can't.

Possibly.....?

Yup mine do the same

Yup I had the same problem, it's not a problem anymore as I dont look at the lights after Ive turn them off

Carl05 said:

Yup I had the same problem, it's not a problem anymore as I dont look at the lights after Ive turn them off

Click to expand...

Lad!

There shouldn't be any current going through any 'off' circuit.

This would definitively apply here if the mechanical switch(es) controlling each circuit were to be directly connected to the load of that specific circuit, in this case the light bulbs / LEDs.

However, almost all modern cars employ some kind of signal multiplexing technology in order to save on copper wire length / cost. This means that multiple electrical signals, originating from multiple mechanical / electronic switches are multiplexed and transferred around the car using only one wire, then a de-multiplexer separates the signals and controls each respective circuit load, such as light bulbs / LEDs.

The problem arises when someone replaces the load / type of load of some de-multiplexed circuit, then the electronic control of that circuit, specifically the power semiconductor used to turn on / off that load is no longer operating within design specification, thus when there should be zero current supplied to the load, some current exists because the load itself has different electronic characteristics, such as changing from a simple resistor (old style light bulb) to a diode (LED).


Just my 2c.

asxetos said:

There shouldn't be any current going through any 'off' circuit.

This would definitively apply here if the mechanical switch(es) controlling each circuit were to be directly connected to the load of that specific circuit, in this case the light bulbs / LEDs.

However, almost all modern cars employ some kind of signal multiplexing technology in order to save on copper wire length / cost. This means that multiple electrical signals, originating from multiple mechanical / electronic switches are multiplexed and transferred around the car using only one wire, then a de-multiplexer separates the signals and controls each respective circuit load, such as light bulbs / LEDs.

The problem arises when someone replaces the load / type of load of some de-multiplexed circuit, then the electronic control of that circuit, specifically the power semiconductor used to turn on / off that load is no longer operating within design specification, thus when there should be zero current supplied to the load, some current exists because the load itself has different electronic characteristics, such as changing from a simple resistor (old style light bulb) to a diode (LED).


Just my 2c.

Click to expand...

Thanks for the explanation - very interesting. Does that mean there are any reliability implications for components operating outside their normal regime?

No, there are no reliability implications since LEDs are using less power, so the circuit is working less to power them on.

It is just that the circuit can not operate properly as it was designed to use a resistor for load whereas a diode behaves very differently in a power semiconductor circuit.


As for the gradual dimming of the LEDs after power down, this is just a capacitor discharging, this will take longer through LEDs so it is noticeable.


But the constant (very low) light emitted by LEDs, when they are supposed to be off, this is another issue altogether and personally I would not be happy at all if it was happening in my car.

For interior lights I switched from plain simple led bulbs to canbus error free and the problem was solved. They are a bit dimmer because of the built in resistor but still very bright.

These are the ones I ordered

http://www.ebay.com/itm/171675397091

I always think that the addition of a resistor to an LED bulb kinda defeats the object, but it will make it work correctly of course!

asxetos said:

No, there are no reliability implications since LEDs are using less power, so the circuit is working less to power them on.

It is just that the circuit can not operate properly as it was designed to use a resistor for load whereas a diode behaves very differently in a power semiconductor circuit.


As for the gradual dimming of the LEDs after power down, this is just a capacitor discharging, this will take longer through LEDs so it is noticeable.


But the constant (very low) light emitted by LEDs, when they are supposed to be off, this is another issue altogether and personally I would not be happy at all if it was happening in my car.

Click to expand...

This issue may be due to the fact that modern cars monitor the lamps for failed filaments and other faults. They can do this by monitoring the current drawn when on and th resistance when off. Low on current can give what is commonly known as a CANBUS error. the bodge fix for this is to connect a resistor in parallel with the LED so it draws more current. This defeats the energy saving of the LED. To monitor the resistance when off the electronics pass a small current through the lamp. This will not light a conventional lamp but may cause a dim glow from a LED. Adding a parallel resistor diverts this current stopping the glow. The electronics may turn this circuit off after the car has been off for a while.
The LED being on dim is not going to flatten the battery any more than a standard lamp would in the same circuit. The standard lamp will pass the same current, but just does not glow.

Robert G8RPI.

It could be some kind of control current and if such current was the case then it could actually be measured when the circuit is off, but what I was saying is something different.


Lets assume that a power transistor controls the load switching it on and off. It could be some other kind of semiconductor like a MosFET etc, same principles would apply.


These components operate by creating precise voltages (or voltage ranges) between their pins (namely Base, Emitter and Collector for a transistor) using resistors. Then, an external low voltage signal going to the Base pin would shift these voltages in a way that current flows between Emitter and Collector pins, where the load is placed in series, so in essence the low voltage signal applied at the Base pin switches the load on or off.

What I am saying is that these precise voltages (or voltage ranges) between the pins, could be shifted out of specification (range) when ANY resistive component in that circuit significantly changes its value, even more so when a resistive component is replaced with a semiconductor (a LED), this happens because the resistance of the load itself is calculated in the design of the circuit.


On the other hand, if that specific circuit was designed to operate using a LED for load in the first place, then that LED would be completely off when turned off, no control current or whatever would make it glow, it is just a matter of circuit designed for such semiconductor load or for resistive load like an old style light bulb.

Just my 2c.

Hi,
While what you say is generally correct, changing a filament lamp to an LED in a typical lighting circuit will not affect the circuit operation. The lamp will draw more current than the LED and has a very low resistance when cold (off) so any small current flowing through it when "off" will develop little voltage and no light will be emitted. An LED has a (fairly) constant minimum voltage across it regardless of the current and will emit some light (even below what we can see) at even tiny currents. The voltage varies depending on the type an colour of the LED and is typically around 2-3V. There are typically 2 or 3 LEDs in series (and parallel for bigger lights) in a LED LAMP so the voltage is 4-9V and it's this that can cause CANBUS errors. Lekage currents due to dirt across connector can be enough to light an LED, but a lamp in the same circuit will draw the same current (probably more due to lower resistance). Just beause you can't see it glow does not mean there is no current flowing. With simple mains (household) LED lamps I've seen them glow dimly due to the capacitance between conductors allowing enough current flow. This was in a two way switching circuit were the 1.5mm twin cable does not have an earth conductor between them. I actually measured the capacitance and calculated the current and the measured value matched the calculation. This proved it wasn't leakage due to water etc. It passed an insulation test OK.
This sort of stuff is my day job, but on aircraft rather than cars.

Hi there!

Some real life measurements taken with a cheap Multimeter would probably clear this up a bit.

If I could, I would measure DC current in milliampere range, during power off, in line with the old style bulb. Would expect to find zero current but...

Then repeat DC current measurement, in line with LED bulb replacement, during power off. Also measure voltage drop across LED bulb during power off.

Then also measure resistance of cold bulb and LED bulb (both polarities).


Since I have no real knowledge of what kind of electronic circuit is connected to the bulb, especially the monitoring / feedback that checks for load continuity, as this could influence the power circuit behavior if there are dependencies between them, or it could be an independent measurement circuit altogether without any kind of feedback to influence the power circuit, so this is pure speculation on my part.


Having said that, maybe here is an answer to the question why car factories seem to be so slow to convert to LEDs at least for some of the lights in a car where the conversion seems to be so easy and obvious, well it looks like the conversion needs a lot more than a new LED bulb, since it involves changes in expensive proprietary car parts like combo electronic units of de-multiplexers / power circuits / monitoring circuits and such. While the in-circuit change itself is minor, still the old expensive combo parts would be rendered obsolete, new parts designed, tested, ordered etc, all this costs way more than we would care to believe.

hi guys

anyone have tried using LED drl bulbs for our panda and there is no error and blinking issue?

care to post the sellers link ebay maybe?

thanks

These are recommended from several Panda drivers and they work without any problems.

http://www.hids-direct.co.uk/canbus-380-p21-5w-27-white-smd-led-bulbs/

Here you can see comparison between stock and led bulb

https://www.fiatforum.com/members-motors/306548-my-panda-pop.html?p=3071622

Or these cheaper made by HSUN factory

http://www.auto-lighting.co.uk/prod...-27x-SMD-5050-P21-5W-BAY15d-CanBus-WHITE.html

Or you can buy some really cheap ones from ebay like these for less than 3 AUD for a pair and they will work great and are even more white than above mentioned but you will probably experience this tiny annoyance. It is not a big deal.

I've purchased and fitted a set of LED replacement bulbs for the front running lights on the Panda. They look great; but I have one question.

After I shut the car off, the LEDs stay on, although very very dim for approx. 30 seconds.

They don't seem to correspond with the interior dome light, either. Because, if you wait for them to go out, and then press the door-lock button on the key they turn on (again very dim) for another 30 seconds and then go out.

Has anyone else experienced this?

Click to expand...

http://www.ebay.com/itm/1157-BAY15D..._DefaultDomain_15&hash=item5b10f7a6cd&vxp=mtr

There are many different factories in China so I guess it is a lottery.