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Name the part!

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earthing
7K views 33 replies 5 participants last post by  Spanner_Brain 
#1 ·
I can't figure out what this part is, can anyone name it?

Next to the main body earth behind the battery on my 2001 espace is a thin white wire (also going to earth) with a black plastic covered component of some kind attached to it.

It can be seperated from the wire so it's a replaceable part.

Can anyone tell me what it's called; or exactly what it does? :confused:

I have a basic understanding of electrics but i'm not up on my components and a white wire to earth seems odd. I also want to know what the difference is between a normal earth and an "electronic earth".

It's been doing my head in trying to figure out what that part is and the differences between earth types.

Consider this a challenge!!! :d

Winners get......erm.....kudos.

And my gratitude - for what it's worth.

pics of said part to follow.
 
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#4 ·
Nah, sorry, no idea what it is, I guess nobody else knows either.

Bigger picture:

My dash display is wonky, if it is cold it can take up to 15mins to come on, if it is warm and sunny out it will take a few minutes the first time you run the car but will come on instantly the rest of the day.:confused:

After much messing about, research and discussions with folk who know a bit about electrics I figure it's a resistance issue as resistance is affected by temperature.

It may be a circuit component within the display that needs replaced but I am trying to check the rest of the system before I go forking out, this particular earth has me interested because the display pin outs have both an earth and an electronic earth listed.

In my belief, if it isn't a board component in the display unit, it is most likely to be an earth. There seems to be a gradual fading of the permanent positive feed after the car has been parked.
Since temperature affects it I am hunting the engine bay and this one sticks out as being pretty individual.

Most likely a circuit component but I just want to draw a line under this bit of investigation before I go for a new/repaired display.

Agreed it may be a radio suppressor but these days I wouldn't have thought it necessary given the use of resistor type spark plugs.
 
#6 ·
Sorry Lag, I didn't - will do it when I get out my scratcher in the morning LOL

Been slightly distracted, selling the wifes old car, a reliable one no less.....:rolleyes: hello madness...

Seems stupid to trade up a known reliable car for a car that doesn't want to play ball.

Ho hum, needs must. Thank heavens I enjoy a challenge in the true spirit of automotive DIY. hahaha

Pics tomorrow, see if we can clear up at least one of my mysteries.

Got the display out again tonight, checking another possibility I read about. :crazy: determined to sort it out myself or break it trying. :rofl:
 
#8 ·
So here we are.

Ok, here's the part.

No, I haven't checked out the numbers on the part on the internet yet, going to have a look after I've posted this.

It lives behind the battery, below the expansion tank - I had to remove the battery to get decent pics.

As you can see in the 3rd and 4th pictures it has a simple male/female connector so it is a replaceable part.

Vehicle Car Auto part Engine Family car


Font Metal


Metalworking hand tool Rotary tool Wire Cable


Auto part Wire Cable


It seems to disappear into the ECU area, I couldn't track it after it went under the ECU so it may be connected directly to the ECU. Didn't feel like taking the whole metal surround gubbins out again to check, was a PITA the first time. :mad: more stupid engineering.
 
#9 ·
OK, here's what I can find - not much really.

It appears to be a capacitor of some kind, possibly to do with starting the car as something of that nature came up in my search.

I have emailed Facon themselves to ask, doubt they will get back to me but worth a shot I say.

That reminds me, need to phone RCS and get some clarification on this RF-less keyfob debacle.

I'll check what a capacitor normally does if I get more time to sit this afternoon, I was doing something similair last night and found a neat little site for electronics dummies. :d
 
#10 ·
It is a capacitor, rated at 220 microfarads.

You'd use this kind of component to act as a "slow" suppressor, as it stores a voltage for a short while when not in a charged circuit. Kind of like a miniature battery.

I can only guess it's in a circuit that would be harmed by voltage spikes
 
#11 ·
You'd use this kind of component to act as a "slow" suppressor, as it stores a voltage for a short while when not in a charged circuit. Kind of like a miniature battery.
Cheers, Shambles, is it the sort of thing that could then supply some functions with accessories feed/permanent live when the ignition is off?
(ie; for the trip computer memory or other data that requires a small voltage to keep it's memory?)

Seems weird as it only has one wire and is connected like a body earth.
:think:

Does it have something to do with alternating current?
(ie; stores energy when engine is running, releases energy when ignition is off)

Could it be referred to as an "electronic earth"?

:idunno:

Not very up on my electronics at all, not bad with general basic electrics but this stuff is beyond me for the most part, once I see how it works then it won't be but for the moment I'm still stumped.
 
#13 ·
... is it the sort of thing that could then supply some functions with accessories feed/permanent live when the ignition is off?...
No. That capacitance would yield a potential of 12v for around a couple of seconds, no more, depending on the circuit in which it is fitted. In an open circuit, following a charge, it would keep its yield for weeks if not months. In a closed circuit, it would expire its charge quite quickly, as I mentioned.

It might look like it would need more than one connection, and capacitors always do, but as fitted in the picture the body of the vehicle is providing the -ve while the single white lead is taking the +ve potential, thereby creating a suppressor effect.

As martin inferred, it will be there to protect against spikes when whatever circuit it is part of is turned on, or off. If in fact it turns out to be part of an operational circuit (ie, always on during engine running) then it could well be protecting against unsolicited peaks and troughs.

Don't hold your breath awaiting a reply from Facon who will simply be suppliers or rebranders of the component, and yes I agree - it would appear to be easily replaceable as it probably blows (goes to open circuit contingency) after a prolonged period of use.
 
#12 ·
Most likely the other side is connected to the feed to the ECU or multiplex module. If it is, then it will be there to protect against spikes when the power is applied. (the reason that some people advise to have your sidelights on when you change the battery as the bulbs will have a similar effect). Unusual to have it located away from whatever it is protecting though, as the suppression would normally be designed in to whatever it is protecting.
 
#14 ·
Thanks again, I looked into it and it is definitely some sort of "motor start" capacitor, so I'd imagine it works in the way you describe. Worth replacing anyway one would think. Where to get one the same as it though?

OK, new questions then, could a dodgy capacitor on the display units' circuit board cause memory loss, (ie; loss of data)???

Still interested if anyone can shed light on that big capacitors ACTUAL useage or what it is protecting?
(if not the entire electronic system)

Always happy to learn, I should actually know this stuff but my technological studies class way back at school consisted more of flying E&L boards than completed circuits. Not me though, I like learning stuff like this.:d
 
#16 ·
I think we'll call it that then :d

I understand what shambles has been saying but can't quite get my head around WTF it's actually doing on there even though I'm sure it's obvious to him and he's probably explained it a couple of times but it isn't quite registering.
I need an overall blanket answer here and radio suppressor seems to be the top answer so far LOL I can get my head round that one.

I haven't looked yet but do these 2.0 16v engines use resistor plugs? Like I said, seems pointless to suppress something twice over....better still, I fitted dvd screens and they are getting a small amount of interference....if that's what it is, does the capacitor/suppresor? in question do all things electrical or just the radio signal?

More questions than answers here, got my brain in knots.

Anyway....it's late and I'm tired.
 
G
#18 ·
Its an interferance capacitor
CAPACITORS FACO FACO Film Capacitors MKT and MKP Radial and Axial Film Capacitors MKT and MKP radial and axial film capacitors Precision Precision Capacitors Film Capacitors Start Start and filtering capacitors and filtering Film Polyethylene and polypropylene polyethylene and polypropylene film
 
#21 ·
Hi Spanner, sorry for the delay responding, I do Hyundai car stuff and get a bit busy moderating those forums. :eek:

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 :crazy:
 
#22 ·
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.
 
#23 ·
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!
 
#24 ·
Cheers Martin, interesting stuff (read it all LOL - that's me for you - dedicated to learning new things :d)

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 cold....wtf?

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.
 
#27 ·
Thanks Chaps!

It is not unheard of, but unusual to switch the earth. I have never heard the terminology 'electronic earth' but if this is the case, I would hazard a guess that it would be a 'clean' earth used for all the delicate electronics. It's a good idea of yours though, to run an earth from the battery as it should point you in the right direction if the fault is earth related.

I take it that the 'display' we are referring to is the complete dashboard display (assuming the Espace has a completely electronic dash), or is it just one part of it?

BTW, Good luck job hunting!
 
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