Technical Headlight switch failures??

[petel]

Good morning all.
Yes, I know this subject has been covered before and I make no apologies for raising it again for the benefit of all Panda owners.

I am still waiting to see any definative answer to the question of why these switches burn out and what can be done to prevent this happening.

Comments such as " I always carry a spare one " or " We fitted a switch from a Golf " are all very well, but they do not address the question asked. The question was recently posed on the forum of the FMC(GB) but again, despite a number of contributions, the actual question was not addressed.

I would therefore ask, if anyone has looked into this question and can provide any relevent feedback or, if anyone on this forum is or has access to, a vehicle electrician, with whom this question could be raised?

Thank you.

 

[Pandaki]

Good morning all.
Yes, I know this subject has been covered before and I make no apologies for raising it again for the benefit of all Panda owners.

I am still waiting to see any definative answer to the question of why these switches burn out and what can be done to prevent this happening.

Comments such as " I always carry a spare one " or " We fitted a switch from a Golf " are all very well, but they do not address the question asked. The question was recently posed on the forum of the FMC(GB) but again, despite a number of contributions, the actual question was not addressed.

I would therefore ask, if anyone has looked into this question and can provide any relevent feedback or, if anyone on this forum is or has access to, a vehicle electrician, with whom this question could be raised?

Thank you.

If you post a link to the initial question that you are refering to so I can have a look

 

[petel]

Hello Pandaki and thank you for your reply.

I do not refer to any specific thread, this matter having come up numerous times, often within other threads.

I am hoping that by starting this thread, I can focus attention on the actual question asked and avoid the slide " off-topic " which has happened in the past.

Best regards. Petel

 

[Most Easterly Pandas]

Hello Pandaki and thank you for your reply.

I do not refer to any specific thread, this matter having come up numerous times, often within other threads.

I am hoping that by starting this thread, I can focus attention on the actual question asked and avoid the slide " off-topic " which has happened in the past.

Best regards. Petel

It is either due to the following I think. Either a current stonger than what the switch is capable of taking as a load is going through the switch, leading it to burn out. Or the switch contacts are melting due to the electrical current and the heat from the heater unit. Its unlikely to be the latter but you never know.

I can think of why it would be the first though because the headlight do run through a relay. What Panda model are you having the problems on, because out of our three it's only the 750L we have which likes to burn out switches. Also have you got any aftermarket lights wired through the switch?

Jon.

 

[petel]

Hello Jon and thank you for your reply.

I am not having a problem with any of my Panda,s and I do not have any extra lights on any of them.

It is obvious that this is an electrical problem and as you rightly say, there is a relay through which the lights operate so this problem should not occur in the first place.

However, as you know from your own 750, the problem does still occur. It is for this reason that I raise this thread and invite relevent comment.

Best regards. Petel

 

[Most Easterly Pandas]

Hello Jon and thank you for your reply.

I am not having a problem with any of my Panda,s and I do not have any extra lights on any of them.

It is obvious that this is an electrical problem and as you rightly say, there is a relay through which the lights operate so this problem should not occur in the first place.

However, as you know from your own 750, the problem does still occur. It is for this reason that I raise this thread and invite relevent comment.

Best regards. Petel

One thing that might help with the 'investigation' into the problem is that fact that the failiure only occours when the switch is being used for switching the light on and off.

Let me explain. Last year when the 750L was my main run about I always left the headlights on, not because of the switch problems, but because I always drive with some sort of lights on. Now have LED DRLs on the Selecta so don't have to do the same. But during this time of the switch always being left in the on possition, I never had any problems, but when it came to MOT day, the examiner turned them off, and went to turn back on and nothing. So almost failed the MOT if it wasn't for the fact that I had a spare switch.

So it must also be link somehow to the sliding mech as well as the melting of the plastic around the contacts.

Jon.

 

[petel]

Hello Jon.
What you say is fair comment.

I have dismantled several of these switches over time and I would certainly question the quality of their manufacture, so I can fully appreciate your on-off theory.

However, this still does not explain why the switch gets hot enough to melt plastic and to discolour the plug shroud around three of the four connectors?

Further relevent comment invited.
Rgds.

 

[Pandaki]

Hello Jon.
What you say is fair comment.

I have dismantled several of these switches over time and I would certainly question the quality of their manufacture, so I can fully appreciate your on-off theory.

However, this still does not explain why the switch gets hot enough to melt plastic and to discolour the plug shroud around three of the four connectors?

Further relevent comment invited.
Rgds.

Hi,
Considering the bad quality of the contact and long time of no use might have as a result the increasing of the contacts internal resistance which will cause a rise of the temperature after some hours of driving with lights on. Some contact cleaner with no oil might help preventing dust to build up since nothing is mooving inside the switch housing.
If there is dust on the contact the possibilities to create an arc while switching off are bigger. And this arc will burn the dust and create carbon particles which will reduce the conductivity or even make contact imposible. Also this carbon is a resistor which rises the temperature which now is dificult to escape because of the dust. If you use the heating a lot, it's all happening a bit quicker due to the possition of the switch on the dash.

These conditions are more effective as the current (Amp) that flows through the contact pins is higher, so it will happen later in a car with a relay.

Possible cause of icreased current is a low relay coil resistance or a leackage.
You can change the relay with a bigger resistance coil one (I don't know if this exists) or you can put a high power ressistor inline before the switch to decrease the current in the loop, but be carefull because the resistor can became extremely hot. And ofcourse you should check for leakage if it's happenig often!

In my motorbike ther's no relay so I have to clean the contcats from time to time to keep the switch running

Hope this is of help and not too long!
regards

 

[petel]

Hello Pandaki and thank you for your reply.

Your comments are all valid and any or all of the things you mention could well be contributary factors. As you say, dirt inside the switch could be a factor ( given that I know the internal workings of the unit ) but I would have to say that in all the switches I have dismantled over the years, I have never found dirt to be a problem.

Thanks again.

I would like to clarify one point, with which forum members might be able to assist.

I am aware of many switch failures on cars prior to 1992 but not on vehicles after 1992?

1992 in UK was noted for two main reasons :-

1. The change from Carb to SPI ( Officially August 1992 )

2. With the introduction of the SPI fuel system, Fiat changed the vehicles earthing from the use of " hedgehogs " to ring terminals onto a single bolt.

Can anyone please advise if they have had, or know of, a switch failure on a post 1992 Panda with either type of SPI system?

Many thanks.

 

[Most Easterly Pandas]

Hello Pandaki and thank you for your reply.

Your comments are all valid and any or all of the things you mention could well be contributary factors. As you say, dirt inside the switch could be a factor ( given that I know the internal workings of the unit ) but I would have to say that in all the switches I have dismantled over the years, I have never found dirt to be a problem.

Thanks again.

I would like to clarify one point, with which forum members might be able to assist.

I am aware of many switch failures on cars prior to 1992 but not on vehicles after 1992?

1992 in UK was noted for two main reasons :-

1. The change from Carb to SPI ( Officially August 1992 )

2. With the introduction of the SPI fuel system, Fiat changed the vehicles earthing from the use of " hedgehogs " to ring terminals onto a single bolt.

Can anyone please advise if they have had, or know of, a switch failure on a post 1992 Panda with either type of SPI system?

Many thanks.

No not on the July 1993 Selecta, but has at times felt like its not far off of going. I have a 6th sence about it saying it will probably go within the next 6-12 months. Having had so many go in the 750L it could be me being paraniod though.

 

[nitro_warrior]

It's been a while since I looked at switch but from memory its not a very good design. Any connector or switch's contacts should be self cleaning by sliding metal on metal a bit to wear off corrosion. I don't recall the Panda light switch being very good on that front, so corrosion will build up, the electrical resitance increases, and the switch gets hot.

 

[petel]

Thanks for the reply Nitro.

I fully agree with you that internally, the switch is not a good design.

However, I would argue that although not of the best quality or design, the switch is only supposed to be a very low voltage unit, design to send trigger impulses to the relay, which then handles the high voltage/amperage side. The switch itself, should not be receiving any voltage/amperage high enough to create heat.

As to corrosion, I have never found any in the switches I have dismantled. It seems more the case, that overheating has melted the plastic around the contact rails, the resulting deformation of the plastic preventing the ball making proper contact with the rail and thus, " switch failure ".

Further relevent input would be welcomed.
Rgds.

 

[Most Easterly Pandas]

Petel, you mention that the switch is designed to cope with only small amounts of power to trigger the relay. I would agree with you on this, and there is no was a relay can become fault in such a way that is chucks to much power through that switch.

The only other thing that I can see it being it the car heater. That would explain the melting around the prongs, and the effect of this happeing again and again would dis-colour the plug at the back of the switch?

The 750L we have, which always suffered from the problem, has an extreamly effective heater, the 1000CL which has never suffered has a rubbish heater, luke warm (keep meaning to sort it out) and my Selecta has only been used for one winter by me, and with the low mileage it has done before my ownership I exect the heater was never on long enough to heat up and melt the switch.

Jon.

 

[petel]

Morning Jon and thanks for the reply.

Note your comments but would ask this:-

If the cars heater was getting hot enough to melt the plastic of the body of the headlight switch, would we not also see plastic melting in the area between heater and switch and would we also not see this on the other switches which are grouped with the headlight switch?

Rgds.

 

[Most Easterly Pandas]

Morning Jon and thanks for the reply.

Note your comments but would ask this:-

If the cars heater was getting hot enough to melt the plastic of the body of the headlight switch, would we not also see plastic melting in the area between heater and switch and would we also not see this on the other switches which are grouped with the headlight switch?

Rgds.

Yes, And I've just remembered its not all of the pins in the switch which melt :doh:, But it might also be to do with the type of plastic its made out of? Is the headlight switch different?

I know the screws in the dash have go hot enough before to mark my hand. There is one placed just about the CD Player.

 

[petel]

Hello Jon.
Quite so, it is terminals A,B & C that show signs of overheat, terminal D ( in my experience ) does not.

A check with my " Fluke " indicates as follows:-

OFF = No contact between any of the four terminals.

1st pos (sidelights) = Contact between C & D.

2nd pos (mainlights) = Contact between all terminals (A,B,C & D)

It should be remembered that 1st pos (sidelights) will also include the dim/dip function with its electrical components. This function is present on pre and post 92 vehicles.

Further comment/thoughts invited.
Rgds.

 

[oldernowiser]

IMHO the switch is _just_ up to the job as designed, but only for the specified low wattage headlamp bulbs.

Put 55 watt bulbs in, and it's only a matter of time before the switch fries.

It's a bit like 13 amp mains sockets - overload one of those and they char around the rivets for the fuse.

The business of adding a relay and heavy gauge wiring has been mentioned many times in the past, but the advice is generally buried by all the "I haven't bothered and it's still fine" replies..

 

[Most Easterly Pandas]

IMHO the switch is _just_ up to the job as designed, but only for the specified low wattage headlamp bulbs.

Put 55 watt bulbs in, and it's only a matter of time before the switch fries.

Sorry, but no.

A) because the switches fried on our 750L many times before the brighter bulbs were fitted (just over 18 months ago, and B) because the brighter bulbs will be in turn putting a bigger load through the relay, NOT the switch!

 

[Alan.D]

Hi Pete, trying not to go off topic and sticking with the purpose of your thread. As already stated The bulb wattage should not be a factor and as i have had 55/60 bulbs in both Sisley's for over 4 years without trouble can pretty much say that should not and confidently say does not affect the switch.

The only problems I have ever had electrically have been due to the poor earth connections on the hedgehogs. However fluctuating electrical current due to poor earthing points can cause all sorts of problems one of which would be a fluctuating current. During this period the low voltage circuit could and may contain a higher voltage and current than normal and I think this may point to the melting switch problem. It is near impossible to forsee this and therefore as near as impossible to try to predict and capture any voltage change by way of multi-meter. It may be worth someone who has that problem to drive round with a mate who continually assesses the multi-meter for fluctuations whilst the other is driving. Not ideal but may help towards the question to which you seek the answer.

 

[Most Easterly Pandas]

The only problems I have ever had electrically have been due to the poor earth connections on the hedgehogs. However fluctuating electrical current due to poor earthing points can cause all sorts of problems one of which would be a fluctuating current. During this period the low voltage circuit could and may contain a higher voltage and current than normal and I think this may point to the melting switch problem. It is near impossible to forsee this and therefore as near as impossible to try to predict and capture any voltage change by way of multi-meter. It may be worth someone who has that problem to drive round with a mate who continually assesses the multi-meter for fluctuations whilst the other is driving. Not ideal but may help towards the question to which you seek the answer.

You could be onto something here Alan, The 750L which uses the headlight switchs has had several earth and hedgehog problems!