Name the part! - Page 5 - Renault Forums :: Independent Renault forum

Electronics In Car Entertainment (ICE), Sat-Nav, lighting, wiring etc.

LinkBack Thread Tools Display Modes
post #21 of 34 (permalink) Old 19th May 2009
Join Date: Jun 2008
Posts: 40
Nominated 0 Times in 0 Posts
TOTW/F/M Award(s): 0
Thanks: 0
Thanked 0 Times in 0 Posts
Send a message via Skype™ to Shambles
Hi Spanner, sorry for the delay responding, I do Hyundai car stuff and get a bit busy moderating those forums.

Anyhow, I would discount any audio-related suppression as those circuits involve wire-wound chokes (measured in micro-henrys (yeah, it always raises a smile)) with a capacitor used to smooth any spike raised during a power-on/off event.

To diagnose which circuit this component comprises a part of, would need you to follow the white wire to its delivery module, to see/show what it is connected to.

FWIW: I studied high-energy physics (for BNFL) and microelectronics at what used to be known as Manchester Polytechnic in the 70's. I appreciate the technology has moved forward at an impressive rate but the basics are still there, hopefully
Currently in Shambles's garage:
2008 Hyundai i30 CRDi 1.6L Black; 2003 RAV4 vvti NRG
Shambles is offline  
Sponsored Links
post #22 of 34 (permalink) Old 20th May 2009 Thread Starter
Diamond member
Spanner_Brain's Avatar
Join Date: Apr 2009
Posts: 298
Nominated 0 Times in 1 Post
Nominated TOTW/F/M Award(s): 3
Thanks: 0
Thanked 0 Times in 0 Posts
Shambles - it appears to terminate at the main engine ECU . (in a housing beside the battery)
I can't be 100% on that though as I didn't want to take the whole assembly out again as it was a PITA the first time.

I wonder, does such an individual looking capacitor carry the possibility of draining the memory of the circuits it serves if it's faulty?

Like I said, my understanding of electronics is very limited, though through this thread and some research I am gradually building up a degree of knowledge. I have improved my soldering skills and theory and figured out a few other things that are helpful.

Some things are still a mystery to me inside my display unit but I'm determined I will fix it myself, man made it so I can Ruddy well learn to fix it.

Basically, the display unit works fine, but only once the car has been run for a while, there doesn't appear to be a large enough voltage drop from the battery when the car is started so poor battery output is unlikely to be the cause of my problem.

When the display does come on, the trip computer memory has been zeroed but the display functions fine after that, it works better in warm sunny weather than it does on colder days.

This is the whole reason I'm looking into all these things as I want to fix it and learn a few things along the way.

Another big question that needs answered is this:

Eeproms; I understand they are known as IC's (integrated circuits). I read that if the main number on the chip is the same it will operate the same way, regardless of the other letters (manufacturer reference codes etc)

Does this mean a simple like for like replacement or does it need programming?

I suspect an eeprom on the board may possibly be goosed but I have no idea how to test it or whether it needs programmed for it's particular functions in this setup.

If no programming then I'd maybe try and replace it, any ideas on this one or the bold question above?

I have already replaced 2 capacitors and a power diode on the displays' board and re-soldered some possible disturbed joints to no avail.
Currently in Spanner_Brain's garage:
2001 Grand Espace 2.0 16V privilege, Audi A4 2.8 V6 Quattro
Spanner_Brain is offline  
post #23 of 34 (permalink) Old 21st May 2009
Platinum member
martin999's Avatar
Join Date: Apr 2008
Posts: 2,447
Nominated 0 Times in 0 Posts
Nominated TOTW/F/M Award(s): 2
Thanks: 0
Thanked 14 Times in 9 Posts
First an apology.... this could be a long post!

The mystery part will remain a much of a mystery unless the exact location in the circuit can be identified. That said, an educated guess can be made based on the information so far. It is almost certainly there to protect something from a voltage spike. If it goes to the ECU , my educated guess would be that it was added to the design of the Lag due to problems experienced with a previous design. I have seen threads where the delicate French electronics can be damaged by replacing the battery, so this would make sense. (as previously stated, some like to keep the sidelights on when changing the battery as this helps stop and spike when the battery is reconnected)

Now some other answers...

When capacitors fail, they will normally go 'open circuit' or 'short circuit'. When they go 'open circuit' it has the same effect as removing them from the circuit. When they go 'short circuit' it has the same effect as replacing it with a piece of wire. The effects of either of these failures depends on how they are used in the circuit.

If we assume that the mystery part is spike suppression, going 'open circuit' will simply mean that whatever it is protecting will be vulnerable to spikes, so you probably won't notice any symptoms of failure. Going 'short circuit' will effectively connect whatever it is connected to down to earth. If it is a 12V supply, then it would either blow a fuse, or whatever it is connected to would not work as it would not get 12v where it needs it. In this case you would almost certainly notice failure symptoms.

Now on to 'memory'....

An EPROM is an IC (integrated circuit) or 'chip' which is Erasable Programmable Read-Only Memory. These are used for holding information used that is not changed. There is a window on the top of the IC that is used for erasing. The IC is removed from the PCB (printed circuit board) and put into an EPROM eraser with is a box with a UV light. The UV light will erase the information on the EPROM. EPROMs are programmed by copying the required information from one device (could be another pre-programmed EPROM or a PC) onto the erased EPROM.

A further development from the EPROM is the EEPROM. This is Electronically Erasable Programmable Read-Only Memory. They are identical in use to EPROMS, but can be erased and programmed electronically, so there is no need to expose them to UV light.

I could also start to talk about other programmable devices like PLC (Programmable Logic Controller) but if you have managed to get this far into the post without falling asleep, going further will send you into a coma!

Bottom line - ANY device that is progammable will need programming. If you buy a programmable IC using the type number of the device it will be blank and of no use unless you can program it.

The good news is that it is highly unlikely that a 'goosed EPROM' is causing your fault.

OMG this post is getting epic!!!

Right.... Remember devices like EPROMs, EEPROMs, PLCs, Flash ROM and the like are used for storing information that does not change, like the engine mapping. If you have the ECU re-mapped, then they will change this information to increase performance and the like. If this is held on an EPROM, they must remove the EPROM, erase it and reprogram it with new information. If this information is held in something like a Flash ROM, then re-programming can be performed with the right kit (PC and interface) without removing the ECU from the car.

All of the above are known as 'non volatile'. This means that once programmed they do not need any power to retain their memory.

So far, we have only talked about information that is not changed. If we look at information that is routinely changed (trip computer information, odometer reading etc) then we use a different type of memory called RAM or Random Access Memory. ROM is exactly what is says... Read Only Memory. It can be read from, but not written to. RAM can be read from and written to.

The problem with most RAM is that it is volatile, meaning that when power is removed from the IC, all the information is lost. This means that you need something to keep it alive. This can be achieved in a number of ways:

1) Always keep power applied to the device. Anything on a car that is lost as soon as you remove the battery will use this method.

2) A capacitor (keeps alive for minutes). If you look at the label in the battery compartment of your SKY remote, you will see that it says 'insert new batteries within 10 minutes of removing the old ones' This is because if you programme it to work your TV, this information will be kept alive using a capacitor, and will be lost after a few minutes.

3) Rechargeable battery, or Lithium battery (keeps alive for weeks, months or even years). An example would be the BIOS battery in you PC. You could turn your PC off for a long time and when you boot it back up your changeable BIOS settings (like time and date) are still there. When these batteries eventually fail (as they will) you get a message saying something like 'time and date not set' when you boot your PC because the information was lost.

Also available is Non Volatile RAM or 'NVR' this means that when power is removed, the information is retained, so no stay alive is required.

Surely your not still reading this are you??

The odometer is very important and not worth risking any of the previously mentioned stay alive methods, so I would have thought it would use NVR.

To figure out what is going on with your display, it would be useful to know what the normal behaviour is when you disconnect the battery. The trip computer, clock etc are unimportant and I would be surprised if they have anything to keep the settings when the battery is disconnected. Having said that, if someone can confirm that these settings are retained when the battery is disconnected, then I would be looking for whatever is keeping them alive when the power is disconnected, as I know from experience that failing memory backup batteries can lead to very strange symptoms.

The fact that your display works (eventually) would first point me towards a poor connection. Unfortunately this could be anything from a poor connection in a connector or a poor earth connection right through to a hairline crack in a track on a multi layer printed circuit board that will be impossible to find.

Ideally you would borrow a known working display, try it and at least isolate the fault to the display or the connections to it. Without knowing this I think you could be spending a long time trying to find the fault!

Earth problems are very common. Can you identify an earth connection for the display? If you can, I would make sure that it was a good 'solid' connection.

Final notes..... although I am an electronic engineer by training, I am no expert on automotive electronics, so I apologise if any of the above is not applicable in automotive electronic design. Also, it is getting late and this is an EPIC post, so apologies for any spelling mistakes or general ramblings that are inaccurate or don't make sense!!

If you have read this entire post, my sincere condolences and your medal is in the post!

Why do today what you can put off until tomorrow...

Wanna see what I drive? No pics of the latest Passat, but you can see the Scenic II here and the CB1000R here!

Previous Passat here and Bandit here.
Currently in martin999's garage:
2011 (11) VW Passat 2.0 TDi SE + options in Island Grey, 2011 (11) Honda CB1000R in Pearl Cool White... oh and a 2004 (54) Secnic II 1.5dCi Dynamique in Ottoman Blue !
martin999 is offline  
post #24 of 34 (permalink) Old 22nd May 2009 Thread Starter
Diamond member
Spanner_Brain's Avatar
Join Date: Apr 2009
Posts: 298
Nominated 0 Times in 1 Post
Nominated TOTW/F/M Award(s): 3
Thanks: 0
Thanked 0 Times in 0 Posts
Cheers Martin, interesting stuff (read it all LOL - that's me for you - dedicated to learning new things )

I found when researching that they require programming, will need to check if the ICs in the display are EEPROMS or EPROMS just for confirmation of the type.

I agree it is unlikely that either one is goosed based on what I've been reading and discussions I've had.

I think I can identify the earth wire for the display, there are two though, one is an earth, the other an electronic earth. So far as I can tell an electronic earth is one that only connects to earth when the circuit is active.

I intend on running a pure undisturbed earth to the battery earth and testing it along with the existing display earth to create a closed loop and make sure it is doing its' job.
I am also going to check the live feed to see what it is doing when it's active, I reckon the live feed is fine though as the immobiliser light is active with the ignition switched off and the seatbelt and handbrake warning lights flash rapidly along with the immobiliser light when the ignition is switched on.

If an electronic earth is only active when the circuit is receiving a current, surely it must have a related component/switch to activate it?

I have actually had some developments in the display function, it has started coming on, then going off, coming on, then going off, not sure quite what to make of that.....

It also briefly came up with a red coolant temperature warning at the same time when the engine was as good as

I think I have disturbed something, maybe the very thing that is causing this problem (or made it worse), seeing as I have been Rsing about with a lot of stuff I can't be sure exactly what....starting to think it's stemming from the BII box as I resoldered a couple of disturbed connections on it.

Maybe worth throwing a grenade in the car now as i have probo about killed it anyway. Ho hum.

The answer is here somewhere but I can't put my finger on it, wish I knew how to test the circuits at least.

I know I should probo have left the BII box alone but I feel I may have inadvertantly stumbled across the cause somewhere, I was able to replace the capacitors and the power diode on the display PCB without ill-effect so I may see about replacing the replaceable components on the BII box also, if I kill it then the car will be getting torn apart and sold in bits to help fund a better replacement. It just means the Audi will be getting sold for a grand to help pay for the rest of it.

Not like I'm going to get a job any time soon given that nobody will even interview me, so I'm not going to need the Audi anyway, will sorely miss it though, punchy acceleration and bulletproof reliability.
Local council wouldn't even give me an interview for dogsh*t duty so there's little hope for me employment-wise, funny that, I'm a man of a great many talents too.

I think people call it "Jack of all trades" you know the rest. LOL.

I think I said it before but I'll say it again, I will find the problem or kill the car trying as I have very little respect for it and my financial situation is already up the swanny thanks to the government and blind employers who can't spot an ideal candidate. What's another few hundred quid and the loss of my beloved Audi in the grand scheme of things? Nothing, that's what.

Too tired and annoyed to think anymore, probo just as well as I'm going on a fair bit.
Currently in Spanner_Brain's garage:
2001 Grand Espace 2.0 16V privilege, Audi A4 2.8 V6 Quattro
Spanner_Brain is offline  
post #25 of 34 (permalink) Old 22nd May 2009
Veteran Member
Technical Supremo
Lagdti's Avatar
Join Date: Dec 2005
Posts: 40,429
Nominated 2 Times in 20 Posts
Nominated TOTW/F/M Award(s): 18
Thanks: 149
Thanked 1,103 Times in 942 Posts
Awesome post Martin.I nearly understand some of it too.

Have a TOTW nomination old bean.

I'd rather push my Alfa than drive a BMW....
Currently in Lagdti's garage:
2004 Saab 9-5 HOT Aero and a 2001 Audi A3 1.8 Turbo
Lagdti is offline  


Quick Reply

Register Now

In order to be able to post messages on the Renault Forums :: Independent Renault forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome