Dear fellow alfisti,
I discovered this forum after a couple of weeks spent bashing my head – sometimes literally – on my 1977 Alfa Spider’s electrical system. My ambitious goal was to get all the electrics working on my Alfa over the winter. Yeah right, I hear you say. How long are winters in Britain? But, I have made a good start, thus far fixing:
1. Boot/trunk light
2. The bonnet/hood light
3. The reversing lights (weird that they are only powered when the lights are on … may have to change that later!)
4. The handbrake warning light
5. The windscreen wiper switch
Of these by far the most challenging has been the wipers. That was where the forum came largely to my rescue, with wiring diagrams that confirmed what I suspected … namely that either I have the wrong handbook/wiring diagram or else there is simply a mistake in the diagram! To spare anybody else the two days of head scratching and electrical probing that it took for me to get the result, and as a thank you for the helpful posts I found on the forum please find attached some supplementary information. Apologies if this is already there and I just couldn’t find it.
Switch Wiring Diagrams
Assuming that your Alfa has a two-speed wiper motor then the switch located on the console will have three states: off, slow and fast. These are shown in the three pictures attached. In each the switch position is shown and the cable to which the power is directed shown highlighted. The switch connectors are numbered on the back of the switch. My first (broken) switch had internal connection between connectors 2,4 and 6 with no external connectors, although on my replacement switch this was not the case and I had to fabricate and install an external jump lead to do this. This is shown in red. The internal connectivity in each switch state is also shown in red between the numbers, e.g. between 3,4 and 7,8 in the OFF state.
In crude terms the two motor speeds are achieved by feeding power to two separate circuits within the motor. Note that the motor itself is earthed locally (in the event of complete failure then this earth should be suspected!) so none of the wires leading from the motor/switch should be earthed. Consider each of the three diagrams in turn:
The ‘hot’ black/blue cable on pin 5 is isolated. No direct power then to either pin 1 (fast) or pin 3,7 (slow). However, all is not as it seems! The blue/white cable on pin 8 is connected to pin 7 in this state, and this is how the ‘park’ feature of the wiper motor works, i.e. how the wipers, no matter where they were, return to the bottom of the windscreen when OFF is selected. The secret is that the blue/white cable comes from
the motor to the switch and also provides +12V, BUT ONLY IF THE WIPER BLADES ARE NOT
ALREADY IN THE PARK POSITION. Outside the park position an internal ‘switch’ in the motor is closed, and therefore supplies power via the blue/white cable to the SLOW circuit via the 7,8 connection. Incidentally, that is why a constant power supply is connected to the motor itself via a blue/black cable. So even though the switch is OFF, if the wipers are outside the park position, power is supplied to the SLOW circuit, keeping the wiper blades moving until they reach the PARK position. At that point the internal switch opens, power is removed and the wiper … stops! Very clever indeed. Obvious, no.
The ‘park’ blue/white cable on pin 8 is isolated. The constant ‘hot’ power supply is directed to the SLOW circuit via 5,6,4,3. Simple.
The ‘park’ blue/white cable on pin 8 remains isolated. The constant ‘hot’ power supply is directed to the FAST circuit via 5,6,2,1. Simple.
Some Testing Tips
This can be tested at the switch by direcly injecting 12V into individual cables at the switch and observing the results. The GREY wire should give FAST operation, and the BLUE wire should give SLOW operation. If either fails then the fault will lie elsewhere than the switch. Using a multimeter check for connection between the switch end and motor end of the grey and blue cables. If OK then suspect the motor itself.
If SLOW and FAST both work and the only problem is the failure of the wipers to ‘park’ when switched off then the problem is at the other
switch involved in the wiper circuit. Conveniently (not) located beyond the clutch pedal is a foot-operated plunger switch that is both a manual
washer pump and override for the FAST wiper mode. If this is disconnected or otherwise broken then not only is it useless it also breaks the PARK circuit. If connected then in its OFF mode, i.e. not pressed, there should be a connection between the two blue/white cables. When pressed, apart from water appearing on your windscreen, that connection is broken and you should get a connection between the other two cables, i.e. +12V to FAST … wash and
fast wipe! In extremis
, if the footpump is completely buggered (technical term) or missing then just jump the two blue/white connectors 1,2.
Given that only an orangutan (
) could reach that foot pump I now harbour vague plans to install a powered pump (you can get a replacement bag with integral pump) and a separate push switch on the console.
But first I’m off to the pub to celebrate. Fortunately it’s walking distance.