Problems with fuse 49

[Jackieeeeeee]

Hello everyone,

 

im having problems with my Skoda fabia from 2014 (model 2007-2014).

Fuse 49 (blinkers and brake lights) is constantly blowing.

I checked various places, unplugged a lot of connectors, but can’t find the problem. I think it’s a damaged wire that touches the ground somewhere. 
Does anyone have a wiring diagram?

or does anyone know where the red wire with two white stripes go to?

 

thanks in advance!!!
 

Breezy_Pete already told me where it goes in the white connector.

 

if I unplug this connector the fuse doesn’t blow.

so the piece of cable between fuse and connectoe should be good.

 

But does anyone know where the cable goes after the white connector?

 

thanks!!!

[Breezy_Pete]

Hi again Jackieeeeeee, according to fuse descriptions, fuse 49 is just for the indicators, and the output wires to left and right indicator bulb trios are on pins 14 and 15 of the same connector, black/white wire for left, black/green for right.

I don't know what happens inside the BCM, but on mk1 Fabia there is a single integrated circuit (chip) that deals with the indicator outputs. I suspect the problem is external but it might not be.

What I would recommend is doing a pair of resistance measurements with a multimeter. With the white connector unplugged from the BCM mark the positions of pins 14, 15 and 38, then set meter to measure Ohms, on the lowest range it has. Measure between pin 14 and 38 (an earth connection), record reading. Measure between 15 and 38, record reading.

If one reading is significantly lower than the other it suggests a short-circuit to earth on that side's wiring to the bulbs. If they are identical and non-zero, the problem may be inside the BCM.

This image shows the pin numbering on the BCM connectors, pin 17 of the white connector is red-ringed due to using the same picture for some other purpose. 

 

[Breezy_Pete]

I haven't tried these measurements myself by the way, but since each side's three bulbs are all in parallel, and cold incandescent bulb filaments have quite low resistances, the Ohm numbers are likely to be quite small. They should be noticeably higher than when the meter probes are shorted together, to each other though.

Let us know what numbers you get, please. 🙂

[Jackieeeeeee]

I measured the pins you said.

On both mesurements I have 0 ohm and my meter beeps. So then the problem should be between the white connector and the fuse connecting? 
Does it go straight from the connector to the fuse connection?

 

Thanks in advance for your help!

[Jackieeeeeee]

Another question, goes the red white white wire go directly to the connector?

If it does, could the problem be just that piece of cable? Or are there connections made in the connector to different pins?

Because my fuse doesn’t blow when I unplug the connector, just because no current can pass anymore.

[Jackieeeeeee]

Just measured between pin 13 and 38 and strangely enough there is unlimited resistance.

getting confused now!

[Jackieeeeeee]

The problem even occurs by the way when the key isn’t in the ignition.

So does the BCM send out current with just the doors open?

[Jackieeeeeee]

This was without the fuse in it.
 

As soon as I plug in the connector the fuse blows. With the connector pulled out, there is no connection to the ground on both sides of the fuse. 
So if the wire from the fuse goes directly to the connector, then I think the problem is in the BCM that puts current on pin 13 which makes the fuse blow.

or am I missing something?

[Breezy_Pete]

Just eating but yes, you are missing lots.

I'll sketch you a little diagram soon.

 

[Jackieeeeeee]

I measured some more.

between pin 14 and 15 I measure 1 ohm. So if I’m understanding it now, both blinkercircuits are connected to the ground when they shouldn’t?

[Breezy_Pete]

This is the circuit as far as I can see.

[Breezy_Pete]

Did you measure from 14 to 38, and 15 to 38 on the contacts of the loom connector, not the BCM itself, with white connector not connected to BCM?

A low reading is to be expected in both cases.

 

 

[Jackieeeeeee]

I measured on the connector side. 
previously I cut the black/white on the driver side (steering wheel on left side).

same problem. So could not be the wiring to the back blinker driver side. Will do the same on the other side. 
but it’s strange that I have a shortcircuit on both sides, as both sides are fed separately…

[Breezy_Pete]

Just to talk you through the diagram. A permanent 12V supply is connected to one side of Fuse 49, the other side goes to the power input for the indicators on the BCM. With white connector unplugged this power no longer goes to the BCM. You say the fuse doesn't blow in this case, which means that red/white wire is probably not short circuited between fuse and BCM.

 

The round things with crosses in are the individual indicator bulbs, Front, Side, Rear on each side of car.

 

 

Just now, Jackieeeeeee said:

I have a shortcircuit on both sides, as both sides are fed separately…

You probably don't, as I said, the Ohms number should be low (but not zero) from either pin 14 to 38, or pin 15 to 38, what are those two numbers please?

 

[Jackieeeeeee]

Between 38 and 14. -1.2 ohm

between 38 and 15.  0.3 ohm

[Breezy_Pete]

OK, that suggests there is a short circuit somewhere on the right side wiring, I'm assuming that the negative sign in front of the 1.2 Ohm is accidental?

Most likely would be water ingress into one of the connectors that go onto the bulb holders, but obviously other possibilities exist.

 

[Jackieeeeeee]

Measured again

14-38    2.9 ohm

15-38.   1.8 ohm

 

measured it several times. 

[Breezy_Pete]

OK, see if the readings become the same as each other if you disconnect both rear light clusters (if that is easy to do)?

If they now read the same, the problem is at the rear right.

 

If the readings are still different, reconnect the rear clusters and try with both fronts disconnected. 

 

[Jackieeeeeee]

I tried something drastic. Just cut the black white and green black wire right after the connector. Can solder it again after.

but fuse still blows! 
so can’t be in the blinkercircuits anymore right?

do you know the wire for the brake lights?

in my manual in the description it says that that fuse is also for the brake lights…

[Breezy_Pete]

Does it look like the BCM can be removed from the car and inspected internally quite easily?

 

[Jackieeeeeee]

Or it is the wire of the brake lights that is shortciruiting or it’s the big that is broken

[Jackieeeeeee]

I can remove it in 10 seconds. Will try to open it

[Breezy_Pete]

Brake lights are fed from pin 16, try measuring 16 to 38.

[Jackieeeeeee]

Can’t open it. Also cut cable 16. Same result.

BCM smells burned also. Quite sure we found the problem. Will try to get another one as soon as possible.

 

Already one hell of a thank you man!!!

[nige8021]

Looking at the wiring diagrams the brake lights are fed from fuse #8 and fuse # 49 is only for the turn signals