zanes said:

As per JR's photo, it appears there are many wires- I can see at least 8 so it appears to be a mix of CAN bus (presumably, as already speculated, for the boot lock mechanism) and "traditional" switched feeds for the high level brake and number plate lights (and presumably wiper motor and heating element too- hence the very thick wire).

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That's my take on it also. I'll know better once I've taken off the internal hatch trim. The fine wires can't be intended to carry any significant current.

I'll try to work out what each wire does & document this properly to help future sufferers.

jrkitching said:

That's my take on it also. I'll know better once I've taken off the internal hatch trim.

I'll try to work out what each wire does & document this properly to help future sufferers.

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The diagram is probably in the Haynes manual. I'll check mine this weekend.

It's not the most logical design but I'd put strong money on it that this arrangement was mostly carried over from the Panda- which may even have used a simple switched wire to drive the boot lock.

zanes said:

The diagram is probably in the Haynes manual. I'll check mine this weekend.

It's not the most logical design but I'd put strong money on it that this arrangement was mostly carried over from the Panda- which may even have used a simple switched wire to drive the boot lock.

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Logical? This is not a German car to be logical! haha

zanes said:

If that was the case, would it not be wired as per:

As per JR's photo, it appears there are many wires- I can see at least 8 so it appears to be a mix of CAN bus (presumably, as already speculated, for the boot lock mechanism) and "traditional" switched feeds for the high level brake and number plate lights (and presumably wiper motor and heating element too- hence the very thick wire).

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Nope, as that (CAN+/CAN-) is the CANbus level that speaks to other ECUs etc, the canbus / body computer monitors number plate bulbs through the existing bulb wiring, so still feeds info into the canbus network (via the body computer I believe), which could be damaged if it receives an incorrect back feed. Certain features will be relayed, and certain are not and fed directly by the body computer.

TBH I'm not sure if the above makes sense, but I know what I mean

ahmett said:

Logical? This is not a German car to be logical! haha

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It's a fairly classic case of standardisation I think- why spend money on a fairly large redesign for the sake of eliminating a few pence worth of wiring?

I'd also presume that the boot lock has only gone to CAN bus because other FIATs use CAN based remote locking systems. I can't particularly see a reason the 500 would need CAN bus based locks otherwise.

Most Easterly Pandas said:

Nope, as that (CAN+/CAN-) is the CANbus level that speaks to other ECUs etc, the canbus / body computer monitors number plate bulbs through the existing bulb wiring, so still feeds info into the canbus network (via the body computer I believe), which could be damaged if it receives an incorrect back feed. Certain features will be relayed, and certain are not and fed directly by the body computer.

TBH I'm not sure if the above makes sense, but I know what I mean

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What you're saying makes sense- but if you were doing controlling the lights etc. that way (ie. with a local CAN node) why not use the CAN node you've now got in the boot lid to monitor those bulb currents locally (presumably only via a single SMD sense resistor) and rely that info over the CAN bus back to the body computer?

The method you suggest seems to be the "worst of both worlds"- you end up with a CAN node in the boot (not just a "dumb" one integrated into the lock mechanism) controlling the lights AND a load of wiring running the length of the car current sensed by the body computer. Why not roll switching and monitoring into the boot node or the body computer?

I am, of course, presuming that FIAT will have approached things logically.....

TL;DR: Still not convinced there's a CAN node in the boot, aside from maybe the boot lock- which could be driven by a single wire.

zanes said:

It's a fairly classic case of standardisation I think- why spend money on a fairly large redesign for the sake of eliminating a few pence worth of wiring?

I'd also presume that the boot lock has only gone to CAN bus because other FIATs use CAN based remote locking systems. I can't particularly see a reason the 500 would need CAN bus based locks otherwise.

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I think fiats cheap approach doesn't work so well in the long run.

I wanted the fiat 500 so I bought it despite the warnings of rubbish fiat help and reliability.

I learnt the hard way and simply won't buy a fiat again. The money I spent on repairs (over 2000 euros) could have been used for a better car

zanes said:

but if you were doing controlling the lights etc. that way (ie. with a local CAN node) why not use the CAN node you've now got in the boot lid to monitor those bulb currents locally (presumably only via a single SMD sense resistor) and rely that info over the CAN bus back to the body computer?

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Good question, I don't think there is a CAN node in the boot (there isn't on the mk3 Panda or Stilo), so assume the 500 would be similar.

ahmett said:

I think fiats cheap approach doesn't work so well in the long run.

I wanted the fiat 500 so I bought it despite the warnings of rubbish fiat help and reliability.

I learnt the hard way and simply won't buy a fiat again. The money I spent on repairs (over 2000 euros) could have been used for a better car

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F-ix
I-t
A-again
T-omorrow

We all learn the hard way. I have vowed not to buy another Fiat!

ahmett said:

I think fiats cheap approach doesn't work so well in the long run.

I wanted the fiat 500 so I bought it despite the warnings of rubbish fiat help and reliability.

I learnt the hard way and simply won't buy a fiat again. The money I spent on repairs (over 2000 euros) could have been used for a better car

Click to expand...

This is what always gets me about FIAT though- the majority of the common issues on the 500 wouldn't be particularly expensive or difficult to put right- a few extra pence of wiring (I think it's a length issue rather than a flexibility issue but obviously I'm not sure) for this- a slight redesign and a service note to lubricate door handles, etc. etc.

It's not like we hear many horror stories of total engine failures so the basic design is sound- it's just little niggles that really would be peanuts to sort once and for all.

Unfortunately, and I don't mean this in a derogatory manner, these little niggles often turn into bills for hundreds of pounds to the average 500 owner.

zanes said:

This is what always gets me about FIAT though- the majority of the common issues on the 500 wouldn't be particularly expensive or difficult to put right- a few extra pence of wiring (I think it's a length issue rather than a flexibility issue but obviously I'm not sure) for this- a slight redesign and a service note to lubricate door handles, etc. etc.

It's not like we hear many horror stories of total engine failures so the basic design is sound- it's just little niggles that really would be peanuts to sort once and for all.

Unfortunately, and I don't mean this in a derogatory manner, these little niggles often turn into bills for hundreds of pounds to the average 500 owner.

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That's what I mean most owners don't know enough about cars to effectively deal with fiats common problems.

And fiat main dealers are only too happy to charge you a lot for basic services. For ppl who rely on cars a lot, they do not have much of a choice and in many cases do not have enough time to go from dealer to dealer asking for the best solution.

I just want a car that doesn't let me down, and if it does, for the manufacturer to actually help not rip me off or wait a month for the spare part !

ahmett said:

That's what I mean most owners don't know enough about cars to effectively deal with fiats common problems.

And fiat main dealers are only too happy to charge you a lot for basic services. For ppl who rely on cars a lot, they do not have much of a choice and in many cases do not have enough time to go from dealer to dealer asking for the best solution.

I just want a car that doesn't let me down, and if it does, for the manufacturer to actually help not rip me off or wait a month for the spare part !

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And for the sake of a few extra pounds to use stronger or longer wires. It baffles me how they can use parts that fail at doing the most basic jobs. If these wires failed in the engine compartment they could be quite dangerous. Another argument as to weather fiats cars are actually that safe.

And yes thats what gets me Fiat dealers don't seem to stock any pars outside of the most basic service parts. Ie Top Mounts took me 3 to 4 days on back order whilst my car was in the garage, (normally replaced in pairs). I ended up replacing one which had failed. And ordered an aftermarket on for the other side which was failing, with a company I knew well in Cornwall with next day delivery.

To fix this issue do you think the re-soldering the wires and re-insulating them better, then resetting the warning lights on the diagnostics will fix it ?. I will be checking my wiring when it gets back from the garage.

aarontennant said:

To fix this issue do you think the re-soldering the wires and re-insulating them better, then resetting the warning lights on the diagnostics will fix it ?. I will be checking my wiring when it gets back from the garage.

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In a word, no.

That section of the loom is damaged beyond repair; I'll need to cut back both ends of all the wires to sound material that's not been previously flexed repeatedly and patch in new material. The new wire I patch in will need to both have more flexible insulation and have a higher number of strands per cable (much like the kind of wire that's used for test leads), so that it can cope with the bad design of the cable routing (that can't easily be fixed; new holes in the hatch + a custom grommet would be the minimum that was needed). It'll likely be a pain to source the right cabling, since several different gauges have been used and only a small length of each will be needed. I'll also need to regularly monitor the repaired section until I'm sure the new cable I've chosen is up to the job.

Just soldering up what's broken and adding a bit of extra insulation may give a temporary fix, but it won't last five minutes. Both the sheath and the cores of the existing cables near to the point of failure will already be much more brittle than the rest, due to work hardening from the repeated flexing. Folks who take their car to an auto electrician need to make sure they cut back to sound cable, or they'll soon be repairing it again for a second time. All the wires will need a new section splicing in; thre isn't enough slack in the cable to do otherwise.

Also replacing what's there with 'like-for-like' wire (which is what I suspect a Fiat dealer would do) won't be durable in the long term; such a repair isn't likely to last any longer than the original.

Fiat need to either change the basic design or use a different type of cable for this section of the loom.

As to whether a simple reset using diagnostics will restore full functionality once the wiring has been fixed, only time will tell. Aircraft systems are designed as far as possible to be resistant to stray electrical feeds and spurious grounding (this tragic accident is one of the reasons why), but somehow I doubt Fiat will have built the necessary electrical protections into the various electronic modules.

Hifi enthusiasts might remember how you could ruin a cheap amplifier by shorting out the speaker connections; better quality amps had sufficient extra protection circuitry to cope with such things.

I've taken lots of pictures of the damaged wiring before cutting or moving anything. If a simple reset isn't sufficient, I'll use these pictures to establish which electrical circuits on the car could have either shorted to ground, or received an undemanded live feed, which could help me work out how other modules on the car might have been affected.

I've said it before, but a close examination of this wiring should be an essential part of any pre-purchase inspection on a used 500.

JRK, a good source of flexible wire is the R/C model trade. Most model aircraft and cars are now electrically powered, and use silicone wire with lots of strands for carrying the high currents. Google Hobbyking and look on their UK warehouse for quick delivery.
Ahmett, you keep quoting Fiat's poor reliability compared with BMW's. The only objective source of info I can find in the UK is the Warranty Direct index. The 500 is rated as 66 (100 is average, anything less is better), the 1 series is 123. Time off road and average repair cost for the 500 is 1.36hrs and £272, for the 1 series it's 2.71hrs and £482. I'm sure BMW are more helpful than Fiat, though!

TrevC said:

JRK, a good source of flexible wire is the R/C model trade. Most model aircraft and cars are now electrically powered, and use silicone wire with lots of strands for carrying the high currents. Google Hobbyking and look on their UK warehouse for quick delivery.
Ahmett, you keep quoting Fiat's poor reliability compared with BMW's. The only objective source of info I can find in the UK is the Warranty Direct index. The 500 is rated as 66 (100 is average, anything less is better), the 1 series is 123. Time off road and average repair cost for the 500 is 1.36hrs and £272, for the 1 series it's 2.71hrs and £482. I'm sure BMW are more helpful than Fiat, though!

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yeah its not so much if something that breaks that is the issue here, its the fact that Fiat don't help you much when it breaks = )

and ive driven both BMW's and Fiat's and everyone will agree with me that the BMW feels MUCH more solid and less likely to break, and of course, higher quality parts.

With due regard to JRs excellent photographs, I took a sneaky peek at our Rosa (500TA). I peeled off the grommet/hose away from the hatch but couldn't see any wires at all.

She's a September 2011 baby but seems different to JR's Maybelline.
Rosa has a thick padded felt(?) tubing covering over the wires and I would have to cut(!) it off to see any wiring at all. I couldn't slide it or move it.

Is this padding a good thing? Is it a modification to stop this problem occurring in the first place?
What year did this come in?

Regards,
Mick.

Mick F said:

With due regard to JRs excellent photographs, I took a sneaky peek at our Rosa (500TA). I peeled off the grommet/hose away from the hatch but couldn't see any wires at all.

She's a September 2011 baby but seems different to JR's Maybelline.
Rosa has a thick padded felt(?) tubing covering over the wires and I would have to cut(!) it off to see any wiring at all. I couldn't slide it or move it.

Is this padding a good thing? Is it a modification to stop this problem occurring in the first place?
What year did this come in?

Regards,
Mick.

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The wiring on mine was wrapped with plastic insulating tape, with a felt tape outer covering. I removed that, and pushed back the felt outer covering, after pushing back the grommet.

If it's not too much trouble, please can you post a photo of what's beneath the grommet?

I wonder also if it's possible to do some preventative maintenance on the loom early on prior to failure,ie, lubricate cables now and again to keep supple etc? And yes, NOT with WD40 obviously but there must be some rubber or plastic lubes that would do the trick.

There you go!

Mercky said:

I wonder also if it's possible to do some preventative maintenance on the loom early on prior to failure,ie, lubricate cables now and again to keep supple etc?

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Unfortunately that's very unlikely to do anything, and could potentially make things worse if there were to be arcing as the cables strip/fray/snap. And oil could flow down the wires into places you really don't want it to be.

I suspect this isn't a case of "if" it happens to every 500 but a case of "when" it happens to every 500.

Mick F said:

There you go!

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Does that actually go through the grommit or is it just a wrap that holds the bundle together in the boot lid?