Hi All,

 

First post here, trying to get some help with my problem. Grateful for all input!

 

I have a Octavia mk 2, 1.9 TDI (1Z5). The problem started with power steering and ESP lights turning on randomly after my car had stayed unused for a month. Also the gauges on the dash did not zero once the car was turned off. I checked fuses and relays but did not find anything. The problem seemed to get better for a while, but as summer game it suddenly went worse. At the moment there is nothing happening on the dashboard, no clock, no lights, nothing. Radio is not working either. If I try to start the car nothing happens, nothing on dashboard, no sound of relays pumps or anything. The central locking is working and interior lights.

 

What I have checked so far:

- Changed the battery

- Checked the fuses several times, no issues there. Both cabin box and engine bay box.

- Replaced some relays and switched places on rest (between similar relays) to check if there would be any problems.

- Been going through the grounding points, but they look fine.

 

Any ideas how to proceed are appreaciated!

 

Thanks,

T

Any communication with ECUs etc?

I am not sure about that. What is the best way to test it?

 

And to clarify: even when there is no key in the ignition switch there seems to be no power in the dashboard / radio. So the digital clock that is usually shown in the dashboard is not there, or any door lights. Same with radio, it does not work. And same thing with the key in at any position. Could the issue also be with some wire or relay? Is there an electric diagram available anywhere?

7 hours ago, Tipi said:

The problem started with power steering and ESP lights turning on randomly after my car had stayed unused for a month

 

These symptoms are typical of low volts from the battery. I know you said you had tried another battery without success but was that a known good battery and fully charged?

Low voltage is also caused by poor supply or earth wiring. For example corroded cables, corrosion of the connection at the main fuse box (the one in the engine bay) or earthing points.

7 hours ago, Tipi said:

At the moment there is nothing happening on the dashboard, no clock, no lights, nothing. Radio is not working either. If I try to start the car nothing happens, nothing on dashboard, no sound of relays pumps or anything

 

That says to me that you have a loss of power at the fuse/connections soon after the battery.

 

So the first thing to do is use a voltmeter to measure the volts at the battery initially, at the battery while cranking (if it will) and then at various points around the car such as at each fuse box.  If ok then follow through to the other side of the fuses to find dead fuses. In particular look at the vertical fuses in the engine bay.

 

It needs a logical systematic approach so that we can conjecture on the cause of the problem based on further evidence.

My guess so far is that it a failing battery or corrosion on the main fuse box printed circuit board or connections.

 

One final point on safety. A battery contains a lot of energy. If you are not happy about using a voltmeter etc on something that can cause a fire, then ask a competent electrician. 

Hi pikpilot,

 

Thank you for your suggestions! I will look for those issues. There is a new and recharged battery in the car so that should be OK, but will double check with a voltmeter (I am fine using the voltmeter but I am not well aware on car electronics).

Just an update. I measured the battery and fuses. The battery was about 12.5-12.6V and all the fuses seem to be OK, 12.5 on both sides of the fuses. Not all the fuses were powered. The ones that were not powered are marked here with red. Does this this seem normal to you? The situation was same if ignition switch was turned on.

 

https://i.imgur.com/nl4Eps9.jpg

 

https://i.imgur.com/11f7mRg.jpg

 

The vertical fuses also gave 12.5 volts on both sides. Any suggestion on what to look next?

The function of each fuse location varies between models and years. However your handbook will tell you what each fuse is protecting. If you don't have a handbook then you can download it from the sticky thread above the current threads.

 

The fact that you have no power in a cluster of fuses at the top suggests that all of these are supplied through a larger fuse or relay elsewhere. Please post here the functions assigned to the circled fuses as a guide to find the source.

 

 

[If you want to try my guess first after looking at a generic wiring diagram, it is that relay 1 has failed on the fuse panel under the bonnet.  It supplies power to what is called Terminal 15 (a supply point for many of the fuses in the cabin fusebox).]

 

I checked my manual and did some translations (sorry if the terms are not exact). But here are the fuses:

 

Under bonnet: https://i.imgur.com/PpgCHTs.png

Cabin: https://i.imgur.com/gC6j78x.png

 

So it looks to me as well that missing power at the top cluster could be indicating the issue. At least there is the instrument panel fuse and ESP and power steering control units. But I am not sure whether the problem is with the relay 1 under bonnet. I have already changed it to a new one. Could it still be a corrosion problem with the under bonnet fuse box?

I opened up the bonnet fuse box. It looked fine, some discoloration with some connectors but you could wipe that of: https://i.imgur.com/2dBewPF.jpg

 

So I think my problem must be with some wire or grounding point. Though I need to find the wiring diagram to figure out where the wire is going.

Start simple, check your battery leads and all the heavy leads to the ground, starter and alternator for damage and corrosion.

 

There's a little fuse box on top of the battery with your maxi fuses in, I'm pretty much expecting one of these to be damaged, probably just a hairline crack. Inspect these carefully and give them a prod with a little screwdriver to see if the crack shows. 

Have you tried putting a jump lead from the body to engine/gearbox? This could help tell you if you have a bad earth/ground issue somewhere.

Hello guys, thanks for the tips. I continued measuring the electronic connections of the system and found one possible culprit. I understood that there should be live feed from the battery to the steering wheel control unit. Measured the voltages from the connector and there was one pin that gave 11.6V. Considering this is around 1 volt lower than the battery voltage could in mean that there is some high resistance point in between (bad connector or broken wire). Does anyone know where is the other endpoint of this wire?

 

Are there any usual locations that I should check. Or should I try with a jumper wire if it changes the situation?

 

Quote

There's a little fuse box on top of the battery with your maxi fuses in, I'm pretty much expecting one of these to be damaged, probably just a hairline crack. Inspect these carefully and give them a prod with a little screwdriver to see if the crack shows. 

If you mean the engine bay fuse box with the main fuses, those are all OK.

 

Quote

Have you tried putting a jump lead from the body to engine/gearbox? This could help tell you if you have a bad earth/ground issue somewhere.

Those body ground points I have looked at are OK. I can measure same voltage from both of the fuse boxes. Or did I understand this correctly?

Have you checked the fuses on battery? Like metal strips. They sometimes blow and have a hairline crack commonly missed.

Hey, I have checked the big main fuses next to the battery. All of them provides 12.x volts to the other side of the battery. So I think they are fine.

 

So at the moment I have a feeling that the issue is with cable feeding the power to the steering wheel control unit. Measured from the connector there was one cable that gave 11.6 volts. That seems a bit low, maybe due to corroded wire or connector. Would just need to track down where it goes.

I was a bit wrong . I bought access to erWin to see the wiring diagrams. The cable I had measured was CAN cable. But in the steering wheel control unit connector H, pins 19 and 20 are connected to the terminal 30 and 31. Those refer to direct connection to battery (via fuse box I assume) positive and negative respectively. I measured those both wires to be ground. So wire going to pin 19 must be broken or somehow short circuited to ground. It won't be easy to trace the wire as it is inside the harnesses, considering just putting a jumper.

 

Here is a post from another current thread. This is exactly the type of fault I was referring to in my posts above. 

 

Update: Issue was investigated by Medlicott Motors (CW12 1NJ, Congleton) and eventually found some evidence of copper oxidisation on contacts inside the engine compartment fuse box. Cleaned up and put back together. So far the error has not repeated so this may be the root cause. 👏😃

 

 

Hey fellows, good news (well, at least for me). I found the broken wire. It was the one I discussed above (terminal 30 wire to the steering wheel control unit). It had went broken just below the engine bay fuse box, inside the wrapping. I went to check the wires extra carefully and found a small hole in the wrapping with something blue inside. That blue was an end of a copper wire with some corrosion on it. It was pure luck that I found it, there were no any kind of a wear on the harness just a tiny hole. The wire ends were quite far from each other so I think there has been some tension with the wire and maybe the time has taken its toll and broke the wire.

 

Here are some pictures: https://i.imgur.com/dqkrTxC.jpg https://i.imgur.com/lVqdBQN.jpg

 

I soldered an extension to the wire, shrink wrapped it and added new insulation tape around the harness. Car works now! No warning lights or anything.

 

Thank you all for your contribution!

Glad you found it. It is the wire that supplies power to the top group of fuses as we suspected.

 

Nice, I've had the same problem with A3 in same area

On 25/07/2024 at 16:55, pikpilot said:

Glad you found it. It is the wire that supplies power to the top group of fuses as we suspected.

 

 

Hey pikpilot, actually those top row fuses are connected to terminal 15 (I suppose), so it was a different wire. Those are powered only when the car is running.

 

The terminal 30 wire is going directly from the engine bay fuse box to devices that need constant power. But anyway, it was a good tip to start measuring the electric system of the car to figure out which cable is broken.

Edited 28 July, 20241 yr by Tipi