In this guide I am going to cover the area regarding the Heated front window.
This was an optional extra on higher spec Fiestas such as the Ghia, XR2I, RS Turbo and RS1800.
In this guide I will show you how to wire up one of these little gems using a loom from a mk4 fiesta.
Why a mk4? Its because you have more chance of coming across a mk4 Ghia with a heated screen than a mk3 Ghia.
Believe me I have been looking for 3 years, so I decided to take a look at the mk4 loom and to my surprise
it is the same as the mk3 but the wiring colour is different and it does not any fuse holders and uses a different
plug on the switch.
So in this guide I will show you what to do at each stage to make it work correctly,
from changing the wiring at the switch to extending vital connections. .
Tools Needed:
Socket Set
Torx bit set
Screw Drivers
Knife
Wire cutters/strippers
Soldering Equipment
Drill and bits
Insulation Tape
|
Push the button
|
Electric...
Heat me!
|
|
First off you need the heated window-wiring loom, you can either buy it new
from ford or get it from Ebay or scrap yard.
Below is the price of the items new.
Switch 6200512 £14.61
Relay 6143397 £8.87
Loom 6929967 £34.77
Glass 7108842 £189.57
Total cost £247.82
As you can see it's very expensive! But the bulk of that is the screen.
I managed to get the mk4 version if this loom including relay from my local scrap yard
for £3 and that included a mk3 switch multiplug from a Granada or Escort.
Then a mk3 switch was bought from Ebay for £5 including postage.
So the total spent so far for the loom is £8.
Right you need to remove the loom from a mk4, this is harder than it looks as the
loom on a mk4 goes up the back of the dash, instead of under the front of the dash in a mk3.
This means that to get to the loom you will need to remove the dash completely, or near enough as you can.
To do this firstly you need to remove the steering wheel and surrounding plastic,
and unless the airbag has gone off you should exercise caution as an airbag contains explosive.
Unscrew the air bag from behind, pull it away and disconnect the wiring, place well out of the way.
Remove the rest of the wheel using a using a 15mm socket undo the fixing bolt.
When loose but not all the way out, gently tap wheel upwards with the palm of your hands.
DO NOT rock it as it will damage the steering column.
The reason why I advise leaving the bolt in, is so the wheel doesn't fly off and hit you in the head!
Remove the surround from around the dash clocks and unscrew the fixings from
around the clocks and with draw while unclipping the Speedo cable and multiplugs.
Make sure you unclip all the switches.
Under the steering column there are 2 10mm bolts holding the impact bar in the dash to the car body.
This impact bar is also joined to the two A pillars together.
Remove the side air vents by prising them out, and then prise out the side covers of the
dash to reveal the fixing screws on the A pillars. Use a Torx bit to remove these screws on both sides of the dash.
Remove the centre console and radio surround to reveal yet more Torx headed screws,
remove these and move to the area above the glove box, hopefully the airbag will be gone,
if not it will need to be prised out.
If it's an airbag less model then prise out the plastic cover and undo a number of Torx screws again.
Before you go any further, prise off the A pillar trims and disconnect the wires from the
lower half of the screen and also the tabs at the top, please remove these tabs and keep them safe with the screws.
Unscrew the fuse box and drop it from the dash and cut the cable ties holding the loom to the body.
Notice that the grey relay with the big F on the top is for the front screen and is clipped
to the side of the fuse box, unclip this and move to the next bit.
Now pull the dash forward and it should come away from the car and follow the relay
wiring from the fuse box up the back of the dash, unclipping as you go until you get to the passenger
side where it is connected to the main loom via a multiplug. Disconnect this and remove the loom.
Then go back to the multiplug and trace all the wires from it as far back as you can and but them
all and take the multiplug with you.
That's all the mk4 mutilation over with, now lets look at the loom and compare it with a mk3 loom and adapt
it to fit the mk3.
Here is the mk4 loom
|
|
Here is the diagram for the mk4 wiring with the mk4 colours
|
|
| Mk4 wiring |
| Switch (Green Plug) |
| Pin no. |
Mk4 Wire Colour |
Purpose |
| 1 |
Black/White |
To Relay |
| 2 |
Black |
Earth |
| 3 |
N/A |
N/A |
| 4 |
Black |
Dash Illumination Earth |
| 5 |
N/A |
N/A |
| 6 |
White |
To Relay white/red and Screen |
| 7 |
N/A |
N/A |
| 8 |
Orange |
Dash Illumination |
| Mk4 wiring |
| Relay (Black Plug) |
| Pin no. |
Mk4 Wire Colour |
Purpose |
| 1 |
Black |
Earth |
| 2 |
Black/White |
To Switch |
| 3 |
White/Red |
To Switch white and screen |
| 4 |
Red |
12v + Supply |
| 5 |
Black/Blue |
Alternator charge light |
| Mk4 wiring |
| Loom Plug (Black Plug) |
| Pin no. |
Mk4 Wire Colour |
Purpose |
| 1 |
Red |
12v + Supply |
| 2 |
Orange |
Dash Illumination |
| 3 |
N/A |
N/A |
| 4 |
Blue/Black |
Alternator charge light |
| 5 |
Black |
Eartht |
| 6 |
Red |
12v + Supply |
Now here is the diagram and wiring colour table for the mk3 loom.
|
|
| Mk3 wiring |
| Switch (Grey Plug) |
| Pin no. |
Mk3 Wire Colour |
Purpose |
| 1 |
Brown |
Earth |
| 2 |
Brown/Yellow |
To Relay |
| 3 |
Black/Violet |
To Relay, fuses and Screen black/violet |
| 4 |
Grey/Yellow |
Dash Illumination |
| Mk3 wiring |
| Relay (Black Plug) |
| Pin no. |
Mk3 Wire Colour |
Purpose |
| 1 |
Brown |
Earth |
| 2 |
Brown/Yellow |
To Switch |
| 3 |
Black/Violet |
To Switch black/violet and screen |
| 4 |
Red |
12v + Supply |
| 5 |
Blue |
Alternator charge light |
| Mk3 wiring |
| Loom (Black Plug Behind Radio) |
| Pin no. |
Mk3 Wire Colour |
Purpose |
| 1 |
Red |
12v + Supply |
| 2 |
Red |
12v + Supply |
| Mk3 wiring |
| Central Locking Plug (Black Plug) |
| Pin no. |
Mk3 Wire Colour |
Purpose |
| 1 |
Red/White |
Boot Release |
| 2 |
Black/Yellow |
12v + Switched Supply |
| 3 |
Red/Yellow |
12v + Switched Supply |
| 4 |
Blue |
Alternator charge light |
| 5 |
Grey/Yellow |
Dash Illumination |
| 6 |
Brown |
Earth |
As you can see there are some slight differences between the two,
the most noticeable is that the mk4 wiring does not use any fuses.
I am unsure why ford removed these and whether or not they had any affect on the system,
all I can see is that it must have been cheaper to do it that way.
Right the part you have been waiting for, fitting it into an mk3.
Not so fast! You need to swap the multiplugs over first so you can use the mk3 switches and loom.
Lets start with the switch wiring,
If you want you could leave the original plug on the mk4 loom and splice the mk3 one to it,
just in case you want to do a mk4/5 dash conversion at a later date, entirely up to you.
Here is a picture of the mk4 plug
|
|
Below is a table that shows which wire from each plugs need to be connected to what
| Mk3 to 4 wiring |
| Switch Plug |
| Mk4 Pin No. |
Mk4 Colour |
Mk3 pin No. |
Mk3 Colour |
Description |
| 1 |
Black/White |
2 |
Brown/Yellow |
To relay |
| 2 |
Black |
1 |
Brown |
Earth |
| 3 |
N/A |
| 4 |
Black |
1 |
Brown |
Earth |
| 5 |
N/A |
| 6 |
White |
3 |
Black/Violet |
To Relay and Screen |
| 7 |
N/A |
| 8 |
Orange |
4 |
Grey/Yellow |
Illumination |
|
|
|
I decided to splice them on as I may do a dash conversion at a later date and I don't fancy soldering the plug back on.
Identify the correct wire on the mk4 loom and use a knife to strip the insulation away.
Strip the insulation away on the end of the mk3 wiring and twist round the exposed section on the mk4 wiring.
Use your soldering iron and apply heat to this connection and add solder to make the perfect join.
Repeat for all the wires, leave to cool then insulate the join with insulation tape.
Wrap all the wires together to make them loom neat and make sure you tape up the
end on the mk4 plug to reduce the risk of short circuit.
|
|
Now move onto the loom multiplug,
| Mk3 to 4 wiring |
| Loom Plug |
| Mk4 Pin No. |
Mk4 Colour |
Mk3 pin No. |
Mk3 Colour |
Description |
| 1 |
Red |
1** |
Red |
12v + Supply |
| 2 |
Orange |
5* |
Grey/Yellow |
Illumintion |
| 3 |
N/A |
| 4 |
Blue/Black |
4* |
Blue |
Alternator charge light |
| 5 |
Black |
6* |
Brown |
Earth |
| 6 |
Red |
2** |
Red |
12v + Supply |
*Central locking multiplug on main car loom located under the dash drivers side
**Power loom if fitted, located behind radio
Behind the radio there will be a large multiplug on the fiesta mk3.5 that looks very similar
to the mk4 one but the wires are different
|
|
Alter the positive red wires from the multiplug to fit a plug that will be there
inside the car behind the radio. These connectors and pins should be available from ford,
if not, get one from a donor car with the same thickness of wires.
Solder or professionally crimp the connector onto the red wires.
On base spec fiestas the power connector behind the radio will not be there,
this means that you either have to fit it or directly wire the positive from
the multiplug direct to the battery via a 30 amp fusible link or fuse, DO NOT connect it to the fuse box.
The rest of the wires connect to the multiplug under the drivers'
side of the dash that is for the central locking loom.
Start with the illumination wire , this needs to be connected to the central locking loom,
simply take off the insulation tape and strip a small section of the
grey/yellow wire in the loom and solder the wire to it.(on the picture it looks red but I had to extend the wire)
|
|
Now move onto the earth wire, again this needs splicing onto the loom.
When this is done, insulate the joins.
|
|
Alternatively you could wire up the complete mk4 multiplug directly to the main
loom somewhere near to the fuse box, where all the wires are accessible. Then simply plug in.
|
|
Below are the wiring colours from the mk4 loom and where they should be on a mk3
| Mk3 to 4 wiring |
| Loom Plug |
| Mk4 Pin No. |
Mk4 Colour |
Mk3 Colour |
Description |
| 1 |
Red |
Red |
12v + Supply connect direct to battery terminal via a 30amp fuse |
| 2 |
Orange |
Grey/Yellow |
Dash Illumination in main loom under dash |
| 3 |
N/A |
| 4 |
Blue/Black |
Blue |
Alternator charge light from pin 7 on the back of the Speedo, find in loom under dash. |
| 5 |
Black |
Brown |
Earth connect to a good clean earth point |
| 6 |
Red |
Red |
12v + Supply connect direct to battery terminal via a 30amp fuse |
Solder and insulate all exposed wires and secure the multiplug to the loom.
The final option is that if you have the mk3.5 connector behind the radio like so:
|
|
|
You could take the plug apart and using the pin outs given above alter the mk4 loom
so that the wires match up with the mk3.5 plug.
The picture below left is of the mk4 loom and the picture below right
is of the mk3.5 plug(Removed from the car for clarity), notice the wiring differences.
That way you wont have to alter the mk3.5 wiring.
|
|
Plug the multiplug into the loom, attach the relay socket to the side of the fuse box and plug the relay in.
|
|
Remove the A pillar trims, on a mk3 these are held on with screws.
Route the red/white wires under the dash up the corners to the bottom of the A pillars,
these wires may need lengthening to reach their destination. Press these into the clips provided.
|
|
You will need to get the screen professionally installed as it provides most of
the strength of the car should it roll, and a badly fitted windscreen can result in catastrophe.
Connect up the wires then screw the earth point tabs to the metal of the A pillar using
the holes provided and refit the trims.
|
|
Now install the switch, this is done by removing the ashtray, the heater slider
controls and the heater control knob, simply pull all these out.
Remove the radio if its there, although sometimes it can be left in and pulled out with the panel.
Then remove the panel that surrounds all the above, done by removing two screws at the bottom
and one in the middle inside the ashtray aperture, using a small flat bladed screw driver,
prise out the top of the panel.
The heated window switch will live in the far left hole in the panel.
Push the wiring multiplug through the hole and click it to the switch.
Push the switch back into the hole and you will hear it click and latch in place,
remove the blanking cover from the panel.
Refit all the trims and facia, same as above but reversed.
Making sure all wires are secure.
|
|
That's it, not really a big job, just time consuming,
Start the car and make the window steamy, I'm sure you will think of a way!
Press the button and it should start to clear the mist, you will also notice
that the revs will drop quite a lot as it draws a huge amount of power,
but it wont need to be on long, but remember to turn it off!
One final note, with the mk4 not having any fuses, you need to check the condition of the relay,
I found 2 that were melted,
Spot the melted one!
|
|
Well that's it,
Hope you enjoyed it and stay tuned for the guide on fitting the mk3 loom.
Enjoy
Guide Written and © On 1 Nov 2005 by Andrew Whiteman (AW3K)
|
