Ford Focus MK2 (2009) - Electric problems (Fuse 100 fails)

[Redhawk]

Dear all!

I have some problems with my Ford Focus MK2 (2009 / 120.000km/DA3/1,6L). 2 Fuse boxes (1 engine room / 1 front passanger feet).

I have the following non worling electic devices:

- circulation air button dead

- Air climate button dead

- Interieur lights front & back dead

- front & rear window heating dead

 

I have checkt nearly all fuses: Fuse 100 is damaged. If I put a new 10 A fuse, it burns when Ih turn the key on 1st step.

Fuse 100: "Switched power supply for electrical control units"

I have plugged out both cables of the temperatur/interieur fan unit to be sure, that this is not damaged. However, fuse 100 still burns.

Fuse 100 is in the german manual explained as:

 

It would be great if someone could help me. In 2 weeks, my familie (2 kids) are visiting Italy. Couls be very hot without air climate funktion.

[Tdci-Peter]

26 minutes ago, Redhawk said:

I have plugged out both cables of the temperatur/interieur fan unit to be sure, that this is not damaged. However, fuse 100 still burns.

F100 goes to a number of optional modules as well as the heater head:

Rain Sensor, if fitted (auto wipers or autolamps)

DPF additive control module (FACM) if you have the 1.6TDCI.

Auto transmission control if fitted.

Heated Windscreen & Rear Window Indicator lamps (heaters may still work)

Connector C378 on the Heater Control Unit.

PTC heater (electric cabin heater) if fitted.

Sunroof control (if fitted)

Heated Seat control switches (if fitted)

Power Convertor option in High Centre Console (Whatever that is!)

Park Aid (reversing sensor) control module.

So depending on what your car is fitted with, it could be any one of those, or even a short circuit in the wiring Harness.

 

[Redhawk]

Wow, fast support: Can you give me an information how I get off the Cover for the windscreen & Rear heater Buttons? I have already dismantled the big front cover (radio / climate) - but The cover for the heating buttons dont get off?

Rain Sensor, if fitted (auto wipers or autolamps) - YES!

DPF additive control module (FACM) if you have the 1.6TDCI - NO!

Auto transmission control if fitted. - NO!

Heated Windscreen & Rear Window Indicator lamps (heaters may still work) - YES!

Connector C378 on the Heater Control Unit.

PTC heater (electric cabin heater) if fitted. - NO!

Sunroof control (if fitted) - NO!

Heated Seat control switches (if fitted) - NO!

Power Convertor option in High Centre Console (Whatever that is!) ???

Park Aid (reversing sensor) control module. - NO!

[Redhawk]

Does it make sensor to take out the relais?for window heatings an rain sensor? Where are the relais?

[Tdci-Peter]

2 hours ago, Redhawk said:

how I get off the Cover for the windscreen & Rear heater Buttons?

With the audio unit surround trim removed, there should be two bolts just underneath the heater controls, that release the switch panel below.

The rear window heater relay is R17 in the passenger fuse box.

The front windscreen heater relay is R7 in the engine bay fuse box.

The rain sensor is under the rear view mirror, and has a little 3 pin connector, C526.

F100 goes to 3 of the biggish connectors in the passenger fuse box:

C102 to Heater Control panel

C98 to rain sensor

C100 to park aid

These connectors carry a lot of other circuits as well, but unplugging them in turn to see which one causes F100 to blow might narrow it down. I can not track down anything that shows which connector is which, but can extract faceviews (pin layouts) for each connector from the circuit diagram, which can be found here:

https://www.fordownersclub.com/applications/core/interface/file/attachment.php?id=42087

Faceview of C526 below.

 

[Redhawk]

I tried some more stuff and lost the last Fuse 😞

- rear and front window heat siwch disconnectes (in the front console under the climate module)

- disconnected R7 Relay (fromt heating relay)

I have trubbles to disconnect the autom. rain sensor plug - didn't get it off.

 

--> the Fuse F100 stoll fails... What can I do next? Does it make sense to disconnect one of the "big connecters" in the passanger floor fuse box?

 

I have to add one very interesting thing. I put in the last 10A fuse and checked constanly via multimeter for "status" (two metal pins on top of the Fuse). Then I started the engine. The Fuse was running for approx. 10sek - BUT the buttons for air circulation or climate "on" have still no function. --> could it be that an electric  controll unit / smart box "PJB" has an error?

Is it possible simply to exchange the Boxes:

https://www.ebay.de/itm/Ford-Focus-II-DA-1-6-ab-2008-Steuergerat-Sicherungskasten-7M5T-14A073-JE/333146962265?hash=item4d911b3959%3Ag%3ADUMAAOSwX4BcpxIS&fits=Year%3A2004|Model%3AFocus+II|Type%3A1.6|Platform%3ADA_%2C+HCP%2C+DP|Make%3AFord|Engine%3A1596+ccm%2C+74+KW%2C+100+PS

Last info: I also tried the GEM/PJB Box test mode. Press rear window heat button an the turn key on positon II.

Result. No noise for air circulation button, climate button,  rear window heat button.

[Tdci-Peter]

11 hours ago, Redhawk said:

Is it possible simply to exchange the Boxes:

The PJB needs to be from a near identical model, as there will be software differences for all the options. But I do not believe that it is coded to match the other modules in the car, so it can be interchanged. The Cluster (IC) and ECU (PCM) are coded together by the PATS system, but not the PJB.

For the big connectors, it is little use disconnecting C102, as this carries the input power from the ignition switch, so will power down F100 and all F100 circuits. But C98 and C100 look to be worth trying, as these carry output power from F100 to various places.

Using a multimeter on a low voltage (mV) range, you can get an idea of the current passing through F100. If this current was low with the engine off (for quite a long time), then shot up once the engine was running, it might help narrow it down a bit. If that happened, I would then use a charger to raise the battery voltage to the running level (>14v) without starting the engine to see if it was just the effect of the voltage increase, or if it was because the PJB was enabling some circuit when it got the "engine on" signal over the CAN buses.

It seems very odd that the rear window heater button made the PJB enter test mode, yet gave no sound when the button was tested. Was this with F100 intact or blown? It could suggest a PJB internal fault.

 

 

[Redhawk]

Some news:

Interieur light is running again. F104 was blown.

I also checke for a short in Fuse F100. There is a short between the right fuse slot and the battery ground.

Can you give me some Tipps, where I should look for a short or how I can reduce the search are?

Thx a lot!

 

[Redhawk]

-

[Tdci-Peter]

5 hours ago, Redhawk said:

Interieur light is running again. F104 was blown.

That is good news, I was a bit confused about the lights as they had no apparent connection to F100. Nice to rule that out.

5 hours ago, Redhawk said:

where I should look for a short or how I can reduce the search area?

Be a bit careful with low resistance readings on a multimeter. A resistance below about 1.2 ohms is needed to blow a 10A fuse, and multimeters do not give accurate readings at the sort of resistance.

But the starting point is to identify and remove the connectors C98 and C100 pictured above. You can do this with the battery disconnected for safety and simplicity. Then recheck for a short to ground. With any load disconnected, there should be a good high resistance reading between F100 tabs and ground.

C102 can also be disconnected if testing with a multimeter. Unfortunately it looks almost identical to C100, there is a tiny difference near the top, but otherwise I would compare the colour codes of the fat wires.

A short to ground is possible in a lot of places: In the PJB, in the wiring looms, and in the equipment that is being fed by the wiring. Disconnecting connectors is the only simple way to isolate circuits. Even that has pitfalls as some of the connectors also carry ground wires, so could hide the short circuit by disconnecting its route back to the car body. So checking with each one of the three connectors disconnected in turn is needed.

The F100 wires are:

C102 pin 5, Green/Black.

C98 pin 11, Green/Black.

C100 pin 3, Green/Yellow.

I can not see anywhere where the F100 supplied wires go through flexible or hinged joints, eg to doors. This would be a prime suspect area, but none of the F100 supplied kit is in doors or the tailgate.

[Tdci-Peter]

18 hours ago, Redhawk said:

how I can reduce the search are?

Just came across these pics of the PJB with connector locations marked up. Off a Russian site (drive2.ru), but it looks to be sensible.

1st pic is the Mk2a version (post 2008 approx), 2nd is the Mk2 version (2005 to 2008 approx).

[Redhawk]

i found the electrical short!

It's the Rain Sensor. It was screws into the roof of the car. This screw hit the sensor wire...

Thx a lot for the support! Thx

[FatHead1979]

3 hours ago, Redhawk said:

i found the electrical short!

It's the Rain Sensor. It was screws into the roof of the car. This screw hit the sensor wire...

Thx a lot for the support! Thx

Good man, at least it wasn't a massively expensive fix and fair play for posting back with a root cause as it might help someone else out someday.