*pioneer YELLOW: connects to UB +12V power supply
*pioneer RED: also connects to UB; no IGN/ACC wire in the alfa plug
the results will mean:
*the RED ACC wire usually makes the headunit turn on/off when you turn the key to ACC, but alfa's do not have an ACC key position; if you wire it as above, it will always be on, regardless of key position (incl key not inserted), which means you must manually turn the headunit off, or use the detachable face feature and actually take the face off, which will automatically turn the headunit off; you will become used to this soon enough; if you DO want the headunit to turn on/off with the key (at ON), then you must connect the RED wire to a suitable 'switched +12V' wire behind the dash, so it's up to you to use a multimeter to find such a wire
*no dimming/illumination feature: the purpose of the orange/white ILL wire on the pioneer is to dim the backlighting/buttons when you turn the sidelights/headlights on, because at night, overly bright buttons can be distracting; because there is no suitable wire in the alfa plug to connect to, you won't have this feature; IF you want it, then you must use a multimeter to find a suitable wire behind the dash to connect to; one that is 0V when the sidelights/headlights are OFF, and switches to +12V when you turn them ON
Sorry for 'raising from the dead' with this 2008 thread, but I have been surfing these and other forums for a while trying to understand the complexities of wiring up an after market head unit to an Alfa 156...
I have an Alfa 156 SW '04 (facelift) with the factory fit CD head unit (Blaupunkt 7 643 311 316 [wiring diagram # 8 631 122 619]).
I've just fitted a Blaupunkt Seattle CD72 head unit (has pre-outs & more toys) and noticed a few threads describing the problems with pin 4 & pin 7 for live wires for the HU power feeds.
I then also noticed this thread & the quoted description - what's confusing me further is that my cars original ISO wiring doesn't match these statements.
- My car does
have a switched +12V ignition feed (in pin A.4[red], which matches the factory HU wiring diagram, but doesn't match the after market HU diagram which uses pin A.7[red]).
- My car does
have an illumination feed which goes to 12V when the lights are on (pin A.6[yellow]).
The perm 12V feed is on pin A.7[red] on the car & original HU, but it is supposed to be on pin A.4[red] for the aftermarket HU.
So (for my example), I can switch the pin 4 & pin 7 wires round (using an extension harness to avoid altering the standard wiring) to get perm 12V & ignition switched 12V in the correct places for my new HU.
I understand from another thread that the problem that often arises is that a drain on the battery can be caused by having a perm 12V feed on the HU's ignition/switched input while there is no power connected to the HU's perm 12V input (as the after market HU's were never designed to be used/connected this way).
Can anyone shed any light on why my cars wiring appears to be different?
Or, have I just misunderstood and the statements are not relevant to all Alfa's of this age but only to the op's 147 (not 156's)?
P.S. Just to add further information that doesn't tie up - the ISO wiring diagram in my Alfa owners manuals shows perm 12V as pin A.4 & switched ignition 12V as pin A.7, which is different to the factory fit HU and my DVM measurements from the connector itself lol. Good old Alfa...