Hello

 

I recently bought a 2002 Fabia which I really enjoy. Although it is a great car, it has accumulated some minute flaws which previous owners have not repaired. I am in the process of fixing them all and in this topic I'll share the process of repairing a cracked solder joint that caused the backlight LEDs in the headlights switch to flicker.

 

1. First you have to remove the switch unit from the car.

 

To do this, you will have to turn the switch to the "0" position, push it in, turn it to the sidelights position (vertical) and pull. You will probably also have to use some kind of a trim removal aid (such as the dull kitchen knife that can't be used for anything but you haven't thrown it out because you do not throw away these things).

 

The switch unit in place:

 

 

The switch unit pulled out:

 

 

A bonus picture of the system that keeps the unit in place and lets you remove it. With some imagination you can figure out the mechanics: first you'll have to turn the shaft clockwise (from this point of view), then push the knob in to bring it into alignment with the two trapezoid-shaped pieces and finally turn it back in order to move the two claws inward:

 

 

The connecting wires are held in place by clips. Push the clips in and jiggle the connectors to remove them. Since I did it in the wintertime with -15 degrees centigrade, I managed to break a noncritical plastic part off the smaller connector. In warmer weather the plastic would be more flexible:

 

 

2. Now dismantle the switch unit itself. Gently ease your dull kitchen knife in between parts and bring them apart. There are four claws holding the switch unit to the faceplate and a few holding the knob assembly to the switch itself. Standard methods of plastic component disassembly apply:

 

 

 

The PCB with the LEDs is held in place by the electrical connectors that power it. Gently ease it off:

 

 

3. Now for the main event. Locate cracked solder joints and repair them:

 

 

If you do not have a soldering iron, you can construct something like this: a thick copper wire heated up by a gas lighter. This is also faster and safer than a soldering iron, if you use it correctly. Don't heat the tip directly, rather a portion of wire above it:

 

 

That's pretty much it. Reassembly is the reverse of dissassembly.

 

Thanks for reading.

 

Raul

Nice work and welcome to the site

 Words of warning from an experienced electronics /associated fields engineer.

1- use an earth strap on wrist, or discharge any static on the body by touching something earthed

2-Use a soldering iron which has a low/nil leakage current. Better still use a gas soldering iron, and apply flux to the joint to help get rid of muck in the soldered joint. Any excess flux can be removed by a suitable solvent.

3 - check board for solder splashes.

Nice report, BTW.

22 hours ago, VWD said:

 Words of warning from an experienced electronics /associated fields engineer.

1- use an earth strap on wrist, or discharge any static on the body by touching something earthed

2-Use a soldering iron which has a low/nil leakage current. Better still use a gas soldering iron, and apply flux to the joint to help get rid of muck in the soldered joint. Any excess flux can be removed by a suitable solvent.

3 - check board for solder splashes.

Nice report, BTW.

 

Thanks. 

 

The electronics here are to our luck very simple, just some LEDs, resistors and diodes, nothing too sensitive. But of course caution is advised.

 

Right now I'm wondering how many  of these cracked joints may be present elsewhere in my car's electrical system.

Happens a lot to the driver's door lock unit.

 

 

Solder can in extremes of temperature crack and become crystalline, making the joint dry.  Two extreme examples of this are in high power coil connections in a radio transmitter. One old military version specified plumbing ratio solder for all soldered connections in the output stage. I've also seen this on components on the tube of a CRT monitor.

Another example is on track circuit connections on rail signaling systems where the solder crystalises at low temperatures and crimp connectors are now the preferred option. 

TMB- shows the value of temperature testing pre production. 

I think the main cause of the solder failing on the driver's door lock is the constant shocks from the door being slammed over the years.

8 hours ago, TMB said:

I think the main cause of the solder failing on the driver's door lock is the constant shocks from the door being slammed over the years.

 

Actually, the first Fabia I checked out  when I started looking for a car had a driver's side central locking issue. The car could only be locked from the passenger side. Quite possibly the problem was exactly the one you mentioned.

 

Sadly this would not be a 15 minute fix. And definitely not something that I would check prophylactically for fun, what with all the rivets holding the panel in the door. 

5 hours ago, RaKa said:

 

Actually, the first Fabia I checked out  when I started looking for a car had a driver's side central locking issue. The car could only be locked from the passenger side. Quite possibly the problem was exactly the one you mentioned.

 

Sadly this would not be a 15 minute fix. And definitely not something that I would check prophylactically for fun, what with all the rivets holding the panel in the door. 

 

Yes it's not an easy one. I'm lucky in that my car has bolted door panels which makes things a bit easier.

56 minutes ago, TMB said:

I'm lucky in that my car has bolted door panels which makes things a bit easier.

 

I think RaKa's car will have too? Being a 2002 model.

1 hour ago, Wino said:

 

I think RaKa's car will have too? Being a 2002 model.

 

Oh yes

Great! I'll check it out then.