Here is some advice from Alfaowner.com, where more tips and fixes are available.
Electric windows opening
If you hold the unlock button on the fob for a few seconds then the windows will move down. Holding the lock button will cause the windows to close. As well as moving the windows down it will obviously unlock the car. Once the door is unlocked the car waits about 2 minutes and if no door has been opened then it relocks the doors as a security measure. It will not wind up the windows.
Parking sensors error
Getting a error indication on the rear parking sensors, steady beep for 3-4 seconds and then the error on the dash. Switching on the ignition, putting the car in reverse and its throwing up the fault straight away. The parking system throws up the ‘parking unavailable’ error with only a single faulty sensor. I’d check the parking system fuse first. I cant remember which one it is but it is detailed in the owners manual.
Removed the bumper last night only to find nothing out of place. The sensors themselves are pretty well made and were showing no signs of water ingress or signs of corrosion on the pins or plugs. Even the connector block which connects the 4 sensors to the module in the boot was free from any signs of corrosion even though its position leaves it open to the elements.
Before you start anything the first thing’s to check will be the fuses. The passenger and driver seat each have their own fuse which in my sports wagon is located in the boot fuse box to the right inside the storage compartment.
If both seats are not working it could also be worth checking the relay which is also located in the boot fuse box in location ‘t21’ – you will need a multimeter and 12 volt power supply.
First of all it’s worth understanding it a bit better so you can determine what fault you have.
Your car has a heated seat element in both the lower cushion and the back rest. The element is basically a thin wire sandwiched between fabric which gets warm when a current is passed through it. As well as the elements the lower cushion also has a thermo cut out switch which cuts the circuit when the seat is hot enough to protect the elements from burning out.
Assuming the fuses and relay are fine you can determine potential problems:
Q1. Bottom cushion doesn’t heat up but the back rest does.
A1. This would indicate the bottom element has an open circuit (burnt out) but the thermo cut out is still working
Q2. Neither bottom or back rest heat up.
A2. We need to gain access to the various plugs located at the back of the seat to understand what needs to repaired / replaced.
To start move the seat as far forward and as high up as you can to gain access.
1. Floor plug ( D070B ). This is located in front of the Air Bag plug so be gentle when you unplug it as disturbing the air bag plug will cause a warning light on the dash board (this can be turned off by disconnecting the battery for 10 minutes it will remain stored in the ECU until reset )
The car needs to be running to test you’re getting power into the seats via the floor plug. The floor plug in a black oblong plug with four pins, two either end. Using your multimeter you can test the two pins nearest the dashboard should have a 12-volt circuit whilst touching either of the two ground pins at the back of the plug. If you have power at the floor plug move on.
2. You now need to unclip some of the backing upholstery of the seat to gain access to plugs etc. Under the seat you’ll find four clips which can easily be unclipped from the underside and pulled apart down the sides to reveal a black fabric parts of the seat which cover’s the plugs we need to check. Now you need to pull the lower cushion leather towards you to gain enough slack to pull the black fabric over the four white nylon / plastic prongs which hold it into place under the seat.
Heated Seat Module is a black box. If only one of your seats do not work you can always swap the modules to check if it’s faulty or not but as I’ve traced power further up the wiring loom I’ve assumed mine is working.
3. Using your multimeter you can now test the element and thermo switch for continuity, checking both circuits are intact.
I’ve guessed the two blue wires are the thermo switch. Using your multimeter test the circuit between the two wires. If your multimeter beeps the thermo switch is still functional.
4. Back rest element (O040B). This is a two-pin connector which is fed from the bottom cushion thermo switch power. You test this for continuity in the same way as you tested the bottom cushion. If you find you have continuity like I did you can test it by running a 12-volt power supply through it. Please note the wiring loom from O040B continues onto the side air bag so be careful.
5. Hopefully by now you’ve worked out what your problem is. My seat wasn’t working because both the thermo switch and bottom cushion element had blown however, I found if I complete the circuit on the plug which is fed by the thermo switch I can at least get the back rest to heat up as normal however, please remember you have no cut out switch protecting it so do not leave it on too long or it may burn out.
There is no need to take the seat out or unplug airbags etc.
Heater blower failure
The connection to the blower resister was a bit dodgy. The connector was loose and the high current going through it had cooked the circuit board and plastics (smells like burning and TCP).
The resister is hidden beside the blower at the passengers footwell. According to the Alfa dealer the part number is 7736-3393 and costs around £80 to replace.
Not a big job to change, just remove a tray of carpet above the passenger footwell, remove two connectors and then it’s just two nuts to replace the part.
Water in the foot well
A recently acquired 56 plate 159 JTDM SW which seems to have a problem with very wet carpets front and rear offside.
I’ve checked all the ‘wet carpet’ posts on this fine forum and they mostly point to water ingress through the door membranes. My wet carpets appear to be directly related to the air con (it dries out if the air con is off despite the Manchester rain, and I and the rear offside passenger float when the air con is on).
So my questions are: where does the air con drain exit the car? And has there been a problem with the air con drain pipe as is indicated in some posts?
When our 159 was new, we had the same problem. It went back and forth to the dealer until eventually the problem was found and solved. It was indeed the condensate pipe from the air con had not been inserted through the floor pan of the car and was being released into the cabin. Now after nearly 4 years, the problem has come back, so I am assuming that the pipe has slipped backup into the cabin again.
I recently had the same problem, it turned out to be the water wells in the engine bay. Just under the wiper arms. the drainage pipe had clogged with debris. hope this helps. Exactly this problem on mine. In very heavy rain the water would wet the carpet. As soon as I cleaned out the drains in the bulkhead by the wipers the problem went away.
I did a full strip on our 159 to find the answer to the water ingress faults. The first is in the drain under the offside wipers scuttle which was blocked with debris. By design, it does not take much to block it.
The second is the air con drain which inside the car is the black plastic elbow fitting located behind the footrest (peel back carpet and unscrew plastic footrest plate cover) which is held in place by 3 nuts.
Inside the engine bay; the air con drain is seen behind the engine as a short bent pipe over the offside bulkhead over the front axle.