Technical Tailgate Latch Won't Open even after replacing wiring

[FrostyForrester]

Hi All,

I have just replaced the tailgate wiring harness on my 2017 Fiat 500 after the number plate lights stopped working! On diagnosing that issue by freeing up the wiring loom, the tailgate stopped releasing. After a lot of swearing, I got it done, with the hope of never needing to look at it again.... However, after replacing the wiring, one issue remains. The tailgate still won't open! I know the emergency release, so we're all good for the minute, however I am trying to diagnose the root cause. The replacement wiring has continuity to both the switch and the latch, so it's not that something is broken. I was wondering if someone had some idea as to how to diagnose if there is actually an issue with the latch or the switch, or something else!

The wiring diagrams I have found seem to show that the latch has three wires: ground, open signal, and release. Mine has four, so I am a little perplexed. I have tried applying 12v to the latch from the battery (off the car, obviously), and I get nothing, hence why I think it is the actual latch failing. I stuck a meter on the switch, and I believe the change in voltage would be enough to trigger it.

The only sense that it is something else is that the Release Wire (Purple, I believe appears too short to ground. Now, I don't know if that is the expected behaviour if it's not being activated; I mean, I can't see why not, as if it's not doing anything, it may as well be?! But I could do with someone who has actually toned it out or knows the expected voltages to these circuits before I go mad and get an auto-electrician involved.

Also, to top my day off, I was trying to disconnect the wiring for the rear window demister to free it up a bit, and well, the one connector helpfully detached from the window rather than the connector releasing. Has anyone got a good suggestion as to how to get it reattached?

Any help would be greatly appreciated!

 

[portland_bill]

Two immediate possibilities spring to mind.
1. Switch not working.
2. Release motor not working.

My Panda switch stopped working a long time ago. The switch is sealed into the plastic, and is part of the complete handle assembly. So I fitted a separate switch, and extended the wires to it. Very subtle, works a treat.

The switch receives a voltage through the White/orange wire, and earths it to tell the body computer you wish to open the boot. A multimeter should show if that voltage is present. Could be battery voltage, or maybe only 5v. You could earth that feed, and the latch should release. Check the switch operates by earthing the feed.

The latch motor is fed through the Purple wire, and earths through the black wire. Again, not sure what voltage it uses, but a voltmeter on that should show the feed when the switch is pressed. Momentarily feeding it with 12v should operate the latch.

Ensure the tailgate earth is secure, including through your repaired wires.

Does the latch operate when the remote is operated? Again, operate that and check for a feed on the purple wire.

 

[FrostyForrester]

Hey,

So weirdly, I’d not tried the remote release - honestly forgot it even had one! Anyway, giving it a bash seems to have woken everything else up. The tailgate released, and the handle/button works as expected now too… strange, maybe it got in an odd state and that’s all it needed to sort it out! Will keep an eye on things.

Just need to find something to glue the demister contact back on and we’re set!

Many thanks!

 

[John202020]

Did you lock the car, then go back and all good? Not sure but think it needs this to fully re set things?

This may work but could turn out to be a real issue

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[FrostyForrester]

Hey, so as an update to the above - I have now attempted and failed to repair the heated window terminal, and frankly as a warning to anyone else, it was quite catastrophic.

Basically, I tried a Permatex 21351 - A conductive adhesive product, that reads like it is meant for the job. It glued like no-ones business and I was impressed, until there was no detectible continuity between the terminal and the contact point on the window so it didn't work. I was a little concerned as to what the next steps could be so did some more research, soldering it wouldn't work as gravity exists and it didn't want to play ball. Again, back to the drawing board. I then found some examples where people use conductive paint - put it on thick between the terminal and the contact patch, it initially seemed promising after hitting it with some heat - it was conductive and returned similar values on a multimeter to the good side, so hoped that'd be it!! Connected the terminal back up, great, hit the button on the dash and it lit, brilliant..... Then a smell and a hint of smoke. S**T! Turned it off and took a look. It appears that the heat had caused the bond of the epoxy to fail, no harm no foul I thought, back to square one. However, a day later, just taken a call from the wife..... Window has cracked.

It was fine first thing, was fine on her journey to work, but now, not so much! So having to replace the window. Not a great day, we're lucky that we can work around having one car for a week, but it's not ideal.

So yeah, thought an update may be in order, I guess as more of a note of caution to anyone else looking to attempt this than anything.

 

[portland_bill]

..... Window has cracked.

A sad outcome. I'm surprised it has cracked, as I'd have expected it to be toughened glass, so would shatter into lots of tiny pieces. It may still do, so if not under cover, may need covering with a plastic sheet until replacement.
Have a look at your incurance policy. Glass cover usually includes all glass. Tell them it is broken, not why. Then it just costs the excess.

 

[John202020]

That's exactly what "glass/windscreen "cover is for? And shouldn't cause no claims issues
Once had the rear window on our Micra shatter, was parked up against a wall so nothing to hit it

 

[Benscott]

Hi All,

I have just replaced the tailgate wiring harness on my 2017 Fiat 500 after the number plate lights stopped working! On diagnosing that issue by freeing up the wiring loom, the tailgate stopped releasing. After a lot of swearing, I got it done, with the hope of never needing to look at it again.... However, after replacing the wiring, one issue remains. The tailgate still won't open! I know the emergency release, so we're all good for the minute, however I am trying to diagnose the root cause. The replacement wiring has continuity to both the switch and the latch, so it's not that something is broken. I was wondering if someone had some idea as to how to diagnose if there is actually an issue with the latch or the switch, or something else!

The wiring diagrams I have found seem to show that the latch has three wires: ground, open signal, and release. Mine has four, so I am a little perplexed. I have tried applying 12v to the latch from the battery (off the car, obviously), and I get nothing, hence why I think it is the actual latch failing. I stuck a meter on the switch, and I believe the change in voltage would be enough to trigger it.

The only sense that it is something else is that the Release Wire (Purple, I believe appears too short to ground. Now, I don't know if that is the expected behaviour if it's not being activated; I mean, I can't see why not, as if it's not doing anything, it may as well be?! But I could do with someone who has actually toned it out or knows the expected voltages to these circuits before I go mad and get an auto-electrician involved.

Also, to top my day off, I was trying to disconnect the wiring for the rear window demister to free it up a bit, and well, the one connector helpfully detached from the window rather than the connector releasing. Has anyone got a good suggestion as to how to get it reattached?

Any help would be greatly appreciated!

Hi did you get to the bottom of this as I have just changed my rear loom and not my boot handle dosnt work and no lights on number plate
I didn’t remove battery strap when checking this so not sure if I have blown something,,,

 

[John202020]

Does the boot release with the key fob? Note lock and unlock car first, do the other rear lights work?
Did you have the battery disconnected when fixing it?

 

[Benscott]

Does the boot release with the key fob? Note lock and unlock car first, do the other rear lights work?
Did you have the battery disconnected when fixing it?

All rear lights work
It works with key fob

Just number plate lights and boot handle don’t work

I didn’t disconect battery when I was checking for broken wires
Only after I found them

 

[John202020]

Some more investigation required there's a wiring fault/break somewhere if the handle previously worked, same with number plate lights, check the supply and earth with a meter?
The earth is common to both lights and boot release

 

[Benscott]

Some more investigation required there's a wiring fault/break somewhere if the handle previously worked, same with number plate lights, check the supply and earth with a meter?
The earth is common to both lights and boot release

Thank you
I think it’s over to the auto electrician from here

 

[The Panda Nut]

Hey, so as an update to the above - I have now attempted and failed to repair the heated window terminal, and frankly as a warning to anyone else, it was quite catastrophic.

Basically, I tried a Permatex 21351 - A conductive adhesive product, that reads like it is meant for the job. It glued like no-ones business and I was impressed, until there was no detectible continuity between the terminal and the contact point on the window so it didn't work. I was a little concerned as to what the next steps could be so did some more research, soldering it wouldn't work as gravity exists and it didn't want to play ball. Again, back to the drawing board. I then found some examples where people use conductive paint - put it on thick between the terminal and the contact patch, it initially seemed promising after hitting it with some heat - it was conductive and returned similar values on a multimeter to the good side, so hoped that'd be it!! Connected the terminal back up, great, hit the button on the dash and it lit, brilliant..... Then a smell and a hint of smoke. S**T! Turned it off and took a look. It appears that the heat had caused the bond of the epoxy to fail, no harm no foul I thought, back to square one. However, a day later, just taken a call from the wife..... Window has cracked.

It was fine first thing, was fine on her journey to work, but now, not so much! So having to replace the window. Not a great day, we're lucky that we can work around having one car for a week, but it's not ideal.

So yeah, thought an update may be in order, I guess as more of a note of caution to anyone else looking to attempt this than anything.

The crack maybe is unrelated and if so insurance will cover it. I have unfortunately had two broken screens in the Panda the screens are thin glass.

 

[The Panda Nut]

That's exactly what "glass/windscreen "cover is for? And shouldn't cause no claims issues
Once had the rear window on our Micra shatter, was parked up against a wall so nothing to hit it

Mine were mower incidents. Thankfully paid no problem.