Leaking rear washer pipe might have caused electrical damage

[andyseatrout]

My bug bear is that my boot courtesy lights have stopped working. On further investigation, it seems that the leaking washer pipe might have caused the problem, but I still do not seem to have rectified it.

I have had a towbar installed, so many of the wires have been cut and rejoined to allow for this, so I already have a bit of a jumbled mess around the cd multichanger . Someone had cut and reconnected a small blue and white wire and another that both used to be joined by multi lead plugs and they had used household connectors to do so. These had become corroded due to the leaking washer fluid. They had also rejoined a brown and black wire in the same way. I have since replaced these with better quality connectors, but this does not seem to have helped. I also noticed four brown and black wires were connected together inside a long clear rubber sleeve and these were also very corroded, so I have reattached these together.

I don't have a multimeter, so I asked the mechanic where I get my car serviced to test the continuity of the switch in the boot and he confirmed that was OK. He also said that he was able to detect a live feed to each of the lights, but I have not been able to get the bulb to light by holding a piece of wire from the other end of the bulb and grounding it, so I am still not convinced by this.

My only other thought is that there are some much larger diameter brown wires earthed at the back of the car and their connectors also seem to be fairly corroded, so I might have a go at removing those and cleaning them up, but as everything else works I am reluctant to do so as I don't want to cause any damage.

There are other multi lead plugs that have become wet and I am considering cutting the wires from either side of these and reconnecting them using male and female connectors, but I am nervous of doing so as I don't want to damage anything else.

Please could someone point me in the right direction here, as I really would like to fix this myself? Ideally I would like to know what I should be fiddling with and what I shouldn't!

Thanks.

[mbames]

I also noticed four brown and black wires were connected together inside a long clear rubber sleeve and these were also very corroded, so I have reattached these together.

iirc that is standard factory fit.

Edited 17 October, 2010 by mbames

[mbames]

Multimeters can be picked up for a few quid and would certainly aid the continued diagnostics with this.....

[andyseatrout]

I will pick up a multimeter this morning and feed back my findings.

Am I likely to do any damage if I don't disconnect the battery when disconnecting and cleaning up the earth terminals?

[mountie66]

I will pick up a multimeter this morning and feed back my findings.

Am I likely to do any damage if I don't disconnect the battery when disconnecting and cleaning up the earth terminals?

No as long as you don't touch wires togather you will only blow a fuse....

[rwbaldwin]

Just a thought...

Are these the the domed lens courtesy lights. If so, you can turn them on and off by pressing on the lens. I don't think this type was fitted as standard.

[mbames]

I don't have a multimeter, so I asked the mechanic where I get my car serviced to test the continuity of the switch in the boot and he confirmed that was OK. He also said that he was able to detect a live feed to each of the lights, but I have not been able to get the bulb to light by holding a piece of wire from the other end of the bulb and grounding it, so I am still not convinced by this.

I am sure that in a reason discussion someone said these bulbs have a +12v supply, and a switched earth from the boot lock. Thus if your mechanic is detecting the +12v at the light, and then light does not come on when you earth the otherside, then maybe just the bulb is faulty?

[rwbaldwin]

I am sure that in a reason discussion someone said these bulbs have a +12v supply, and a switched earth from the boot lock. Thus if your mechanic is detecting the +12v at the light, and then light does not come on when you earth the otherside, then maybe just the bulb is faulty?

It is the earth that is switched

[mbames]

It is the earth that is switched

Excellent - as I thought I don't like to post things which are wrong

Right, I should stop playing on my computer and go and fit some insulation.

[andyseatrout]

Thanks so far for all your thoughts.

I now have a multimeter and can confirm that I can only detect a 2V feed on each light which would explain why the lights are not lighting (these atre the standard fit lights and not the domed ones). I have checked the continuity of the bulbs and fittings and these are both fine. The switch (on the earth side!) is working correctly on the boot.

So I now assume that I have an issue with the live feed, so I also assume that I can leave the earthing terminals alone?

Please can someone tell me how to proceed now, as I don't want to go chopping wires for the sake of it? Is it possible that another component is deliberately keeping the voltage low for some reason?

Thanks

[pikpilot]

Thanks so far for all your thoughts.

I now have a multimeter and can confirm that I can only detect a 2V feed on each light which would explain why the lights are not lighting (these atre the standard fit lights and not the domed ones). I have checked the continuity of the bulbs and fittings and these are both fine. The switch (on the earth side!) is working correctly on the boot.

So I now assume that I have an issue with the live feed, so I also assume that I can leave the earthing terminals alone?

Please can someone tell me how to proceed now, as I don't want to go chopping wires for the sake of it? Is it possible that another component is deliberately keeping the voltage low for some reason?

Thanks

I recommend the use of a good multimeter normally but sometimes the high input impedance can allow wrong conclusions when the problem is a high resistance in the supply or ground (such as a high resistance switch contact or connector).

I would do the following:

1) take a known good bulb (such as the good part of a blown twin filament bulb) and solder to it two wires - one about the length of the car and the other about three feet long. Wrap insulating tape or similar over the connections. Check the bulb lights on a known good supply.

2) Connect the long wire to the battery -ve terminal

3) touch the other wire to the light feed on the courtesy light in the boot (red and blue wire). Do this with the courtesy light bulbs in and out. If any difference then there is a short in a holder - see also 5)

If it lights with and without the bulbs then go the 4) as the problem is the switch or its earth connection

If it doesn't light then the problem is in the supply. Follow the wire back as far as you can, touching your short wire on the cable at each connector you find until your test bulb lights. See also 5)

4) Connect the long wire to a known good supply point (or via a fuse to the battery +ve) Connect the short wire to a known good earth point and check it will light (as a test) then connect it to the brown and black wire on the light fitting. It should light. If it doesn't, then the fault is in the switch or its earth connection (brown wire). Repeat the test at the two connections on the switch. If still no light from your test bulb, clean up the earth connection point for the brown wire and any connectors along its route.

5) the supply comes from the convenience system and is switched electronically. As such, you may see 2V on your meter due to one of the following. Firstly, using a high impedance multimeter you are seeing the leakage current of the switching device times the input impedance of your meter (one of the gotchas of good multimeters). Secondly, 2V is about the voltage you see when the switching device is on but protected by a current limiting feature and is feeding a short. To check, disconnect the red/blue wire as far back in the harness as you can and connect your test bulb between the wire at this point and a known good earth or battery -ve. If your test bulb lights then there is short to ground somewhere between that point and the lights - sharp edges on holes the wire passes through are one cause.

My best guess is that the light switch has gone high resistance, the earth connection is poor or that the supply wire is shorted or has a high resistance connector.

I hope that by following this logical sequence you will find the cause. If not, just post the results and the world of Briskoda should help you further.

Mike

[andyseatrout]

Thanks very much Mike for a very comprehensive reply.

I will feed back when I have had a go at all of the above.

Andy

[rwbaldwin]

IIRC, the circuit is fed from a module on the relay panel. It's the relay in position 3 and if it has a number printed on it, then it will be 456. The 2V you see may indicate this module is faulty. What voltage do you see when the relay is removed?

[andyseatrout]

IIRC, the circuit is fed from a module on the relay panel. It's the relay in position 3 and if it has a number printed on it, then it will be 456. The 2V you see may indicate this module is faulty. What voltage do you see when the relay is removed?

Please could you direct me to a picture or diagram so that I can be clearer about what I am going to look for?

Also, to get to the relay panel, what do I have to remove?

Thanks

[rwbaldwin]

Remove the horizontal panel immediately above the pedals. Remove the screws marked A, squeeze the clips B and then pull forward so the slides C come out of the white clips.

When you look up, you will see the relay plate.

There are three rows of plug-in relays most of which are about 30mm square and many have numbers printed on them. We tend to call them all relays, but many are electronic modules.

The one you are looking for is in position 3. That is bottom row, 3rd from the left. There is an arrow on the pic.

It is known as J166, the Instrument Lighting Amplifier (don't be put off by the name) or Relay 456 (may be printed on the end of the relay). Go by position, as some of the relays are interchangeable and some may have been superceded.

HTH

[andyseatrout]

Remove the horizontal panel immediately above the pedals. Remove the screws marked A, squeeze the clips B and then pull forward so the slides C come out of the white clips.

When you look up, you will see the relay plate.

There are three rows of plug-in relays most of which are about 30mm square and many have numbers printed on them. We tend to call them all relays, but many are electronic modules.

The one you are looking for is in position 3. That is bottom row, 3rd from the left. There is an arrow on the pic.

It is known as J166, the Instrument Lighting Amplifier (don't be put off by the name) or Relay 456 (may be printed on the end of the relay). Go by position, as some of the relays are interchangeable and some may have been superceded.

HTH

Thanks very much for the pictures and instructions.

I have just removed the relay and now have no voltage reading from the live feed to the interior light and now no other interior lights work (as expected). Does this suggest that the relay is working as it should, or are there any other tests that I can perform on it to check that it is working?

Incidentally, the voltage from the live feed (to the light) was only 1.2V before I removed the relay, whereas it was 2V yesterday. Is this significant?

[rwbaldwin]

Thanks very much for the pictures and instructions.

I have just removed the relay and now have no voltage reading from the live feed to the interior light and now no other interior lights work (as expected). Does this suggest that the relay is working as it should, or are there any other tests that I can perform on it to check that it is working?

Incidentally, the voltage from the live feed (to the light) was only 1.2V before I removed the relay, whereas it was 2V yesterday. Is this significant?

Pulling the relay confirms that it is controlling the rear courtesy lights. The feed for the courtesy lights are red/blue wires and connect to pin 2 of the relay.

Do you see 12V (ish) at this point? If not the relay is faulty.

When taking measurements, you need to take into account that this relay may kill the feed after a period of time. Leave the keys in the ignition after turning it off and open the tailgate.

[andyseatrout]

Pulling the relay confirms that it is controlling the rear courtesy lights. The feed for the courtesy lights are red/blue wires and connect to pin 2 of the relay.

Do you see 12V (ish) at this point? If not the relay is faulty.

When taking measurements, you need to take into account that this relay may kill the feed after a period of time. Leave the keys in the ignition after turning it off and open the tailgate.

Thanks for staying with me on this, I'm afraid I'm feeling a bit "special" at the moment, so please bear with me a little further!

How do I go about testing the voltage on pin 2 of the relay and how do I identify pin 2? I cannot see behind the relay, so I assume that I will have to push the relay most of the way home and then hold the positive probe of the multimeter onto pin 2 and the negative probe of the multimeter onto an earth?

Am I on the right track?

If you could send me a picture, diagram or description to identify the slot or pin that I am looking for that would help greatly!

Thanks,

Andy

[rwbaldwin]

You should find the pin numbers on the relay or socket. If not - post again.

At this point I would just use breakout connectors or undo the panel mounts to get to the back, but I suggest you do the following.

Take a length of the finest insulated wire you have and strip 10mm at one end. Insert the bare wire half way through the hole in the pin and bend both sides flat to the pin towards the relay body.

Make sure the meter is measuring volts. Strip a couple of cm from the other end, wrap it around the +ve probe, connect the -ve probe to earth and carefully plug in the relay so you don't dislodge the wire.

[andyseatrout]

You should find the pin numbers on the relay or socket. If not - post again.

At this point I would just use breakout connectors or undo the panel mounts to get to the back, but I suggest you do the following.

Take a length of the finest insulated wire you have and strip 10mm at one end. Insert the bare wire half way through the hole in the pin and bend both sides flat to the pin towards the relay body.

Make sure the meter is measuring volts. Strip a couple of cm from the other end, wrap it around the +ve probe, connect the -ve probe to earth and carefully plug in the relay so you don't dislodge the wire.

Hi,

I have removed the relay and there are no pin numbers on it, but there are some on the socket. I have taken a picture, but can't see how to upload it onto the forum, so I will describe the numbers and locations.

Top left: 10; top middle: 13; top right 15

middle left: can't see; middle: 12; middle right 14

bottom middle: 11

The code numbers on the relay are: 1UO 941 243 C

AEV 0306

VK7

MADE IN CZECH REPUBLIC

>ABS<

I have phoned around for quotes for the part and have found a Skoda Dealer that will do it for £13 + VAT and another independent has offered it for £19 inc. VAT. A VW/Audi dealership wanted £85.91 for it!

If this is a faulty part, could this also be responsible for the intermittent fault I have with my headlamps turning off for a few seconds as I switch to full beam?

Thanks,

Andy

[rwbaldwin]

I will post the pin info you need tomorrow.

Unfortunately, the problem with your headlights is almost certainly a problem with the stalk.

[andyseatrout]

I will post the pin info you need tomorrow.

Unfortunately, the problem with your headlights is almost certainly a problem with the stalk.

Thanks very much.

I will have a go at cleaning the switch in the stalk when I am feeling brave!

In the meantime, is it worth me trying to get inside the relay to see if I can see if there is a problem with it, or am I likely to do more harm than good?

[rwbaldwin]

...is it worth me trying to get inside the relay to see if I can see if there is a problem with it, or am I likely to do more harm than good?

It's not a relay - it's a electronic module so you won't be able to do anything and as it does about four different jobs, I would not mess with it.

[rwbaldwin]

Hi Andy,

Pin 2 on the connector maps to pin 15 of the relay in position 3. It's the one I've marked on the pic below.

What I suggest you do is get a piece of wire long enough to reach one of the courtesy lights from the driver's footwell.

Unplug BOTH light fittings, and push a piece of wire into the socket for the Red/Blue wire on one of the plugs. Attach the other end of the wire to the negative probe of the meter.

With the meter on resistance, connect the positive lead to pin 15. You should get almost zero ohms. If you do then replace the relay.

Edited 22 October, 2010 by rwbaldwin

[andyseatrout]

Hi Andy,

Pin 2 on the connector maps to pin 15 of the relay in position 2. It's the one I've marked on the pic below.

What I suggest you do is get a piece of wire long enough to reach one of the courtesy lights from the driver's footwell.

Unplug BOTH light fittings, and push a piece of wire into the socket for the Red/Blue wire on one of the plugs. Attach the other end of the wire to the negative probe of the meter.

With the meter on resistance, connect the positive lead to pin 15. You should get almost zero ohms. If you do then replace the relay.

Brilliant, thanks for that.

I will have a go tomorrow and feed back,

Andy