My Z3 has an aftermarket JVC radio/CD player, but when bought, the front footwell speakers and the door tweeters didn't work and the rear speakers were wired left to right, right to left.
Initially, I thought the problem with the front speakers was the amplifier relay, which many online posts seem to indicate fails. I decided to take the left front speaker and integrated amplifier out and test them.
All the following relate to my UK spec, 1999 1.9 Roadster. Disclaimer - this is what I deduced from looking at the circuit, plus internet socket pin-outs and might not be accurate for all models!
The amplifier is mounted on the passenger side on a board with the speaker integral to the unit. The amplifier drives only the front left and front right speakers.
Removal:
Remove speaker cover trim, which is held on by one plastic screw.
Remove the 4 speaker screws and remove the speaker/amplifier unit (still connected via the wiring).
Disconnect the cable by pushing the locking hoop forwards and pulling the cable connector off.
Remove the two spade connectors from the speaker terminals (note which connector goes where) and the single screw from the back of the speaker magnet and prise the speaker off (it's held in place by a double sided adhesive circular pad). You don't need to remove the speaker unless you want to remove the circuit board from the unit.
Note: if you do the next step, you'll need heatsink thermal paste to reassemble again.
Remove the two amplifier integrated circuit heatsink screws and the metal plate (torq T10).
Remove the two screws (torq T10) holding the circuit board to the chassis and cut the glue from the front corners holding the circuit board in place to the metal chassis. Pull the circuit board out.
The amplifier circuit works as follow:
A 12v power switching signal from the radio (sometimes labelled 'power aerial' or 'remote equipment') is used to switch a relay in the amplifier when the radio is switched on. This relay connects the 12v from the car's power supply to the amplifier power circuit. This avoids the car battery draining when not in use and allows you to use the radio with the ignition off (assuming your radio is powered directly from the battery circuit and not the ignition circuit). On my car, this signal had not been connected when the aftermarket radio was fitted and therefore no power was supplied to the amplifier (and neither door tweeters had been reconnected when the door cards were refitted!).
The left and right channels from the radio are amplified through 2 sets of amplifier integrated circuits:
TDA8563 is a 2 channel 40W amplifier mounted on the heatsink. ('Power Amp Chip'). This directly drives both the left and right speakers.
TL0841 is a 15-pin quad amplifier, of which there are two: one for each channel (L/R). ('Pair Amplifier chips'). These provide gain to the input stage of the power amplifier.
Underside view of circuit board...
With the unit removed but still connected, you might be able to hear or feel the relay switching on when the radio is switched on (with volume set to zero). This could be a way to test that the relay circuit is working.
The power-on relay switching circuit comprises three switching transistors, with the large one (a BCP54) in the final stage used to drive the relay coil.
On the picture below, the relay switching signal passes through three stages:
Power switching signal from connector cable (1)
Stage 1 switching (2)
Stage 2 switching (3)
Stage 3 relay coil switching (4).
The following is a pin-out of the amplifier connector (source internet).
Note that the front left speaker connections are on the circuit board itself. I believe that the two front door tweeters are connected directly to the radio output/input of the amplifier (there are no connections from the amplifier circuit board to them). My car also had door connectors for midrange speakers, but these speakers were not fitted.
When replacing the circuit board, apply some heatsink thermal paste to the power amplifier chip when mounting it to the heatsink.
My car's aftermarket JVC radio had been fitted by somebody (prior to the previous owner), by cutting the wires from the BMW 17-pin connector (which also has a CD changer connector) and joining the radio's ISO plugs to the cut wiring harness.
socket side...
Small white 10-pin socket is for a CD autochanger.
Rear showing original cut wires and 'twisted pair' speaker wires in the background (more about this later).
I disconnected the ISO plugs and reinstated the cut wires back to the 17-pin connector (by soldering and covering the solder joints with shrink sleeving) and bought a generic 17pin BMW to ISO radio adaptor cable. There seem to be lots of these available for many different types of BMW.
This needed a modification to connect the 17-pin permanent +12v supply (pin 9) to the ISO +12v (pin12), to supply constant power to the radio (apparently Japanese radios don't always follow a standard to these connections).
The +12v to the radio can be wired to the ignition circuit connector if you want to avoid a small amount of current drain by the radio when not in use (e.g. my radio has a permanently illuminated power-on button). The radio won't work unless the ignition is on in that configuration.
On my 17pin adapter plug, I had to cut off the 4 plastic locking tabs on each corner (see above), that are supposed to lock the adapter to the BMW 17 pin socket. Without removing them, the adapter plug and 17 pin socket couldn't be pushed together at all to make electrical contact. Once the tabs were removed, the adapter is a firm fit in the socket and won't come apart easily.
Wiring diagrams are below: (note the pin numbering on these two diagrams are different. The adapter diagram shows the ISO pin number connections to the BMW 17-pin socket).
BMW 17-pin socket (viewed from the socket side NOT the wire side) - source internet.
Wire colours (main wire colour/stripe):
1. yellow/red**
2. blue/black***
3. yellow*
4. white/brown
5. purple/white (thick wire)
6. blue****
7. not connected
8. yellow/brown**
9. red/white (thick wire)
10. black/white
11. blue/brown***
12. brown*
13. white/red
14. brown****
15. brown (thick wire)
16. white
17. not connected
In the BMW wiring loom connections to the 17-pin socket, four sets of wires are twisted together as pairs as indicated above by *, **, ***, **** e.g. the blue and brown wires marked **** are twisted together. This is how the two thin brown wires (pins 12 and 14) are differentiated.
Pin 16 white is the+12v power amplifier relay control signal from the radio, which was originally not connected on my car (blue wire pin 10 on the ISO connector).
Adapter cable:
I hope this is useful information to anybody fault-finding on their stereo system. Any errors omissions, please let me know or post in the comments.
Initially, I thought the problem with the front speakers was the amplifier relay, which many online posts seem to indicate fails. I decided to take the left front speaker and integrated amplifier out and test them.
All the following relate to my UK spec, 1999 1.9 Roadster. Disclaimer - this is what I deduced from looking at the circuit, plus internet socket pin-outs and might not be accurate for all models!
The amplifier is mounted on the passenger side on a board with the speaker integral to the unit. The amplifier drives only the front left and front right speakers.
Removal:
Remove speaker cover trim, which is held on by one plastic screw.
Remove the 4 speaker screws and remove the speaker/amplifier unit (still connected via the wiring).
Disconnect the cable by pushing the locking hoop forwards and pulling the cable connector off.
Remove the two spade connectors from the speaker terminals (note which connector goes where) and the single screw from the back of the speaker magnet and prise the speaker off (it's held in place by a double sided adhesive circular pad). You don't need to remove the speaker unless you want to remove the circuit board from the unit.
Note: if you do the next step, you'll need heatsink thermal paste to reassemble again.
Remove the two amplifier integrated circuit heatsink screws and the metal plate (torq T10).
Remove the two screws (torq T10) holding the circuit board to the chassis and cut the glue from the front corners holding the circuit board in place to the metal chassis. Pull the circuit board out.
The amplifier circuit works as follow:
A 12v power switching signal from the radio (sometimes labelled 'power aerial' or 'remote equipment') is used to switch a relay in the amplifier when the radio is switched on. This relay connects the 12v from the car's power supply to the amplifier power circuit. This avoids the car battery draining when not in use and allows you to use the radio with the ignition off (assuming your radio is powered directly from the battery circuit and not the ignition circuit). On my car, this signal had not been connected when the aftermarket radio was fitted and therefore no power was supplied to the amplifier (and neither door tweeters had been reconnected when the door cards were refitted!).
The left and right channels from the radio are amplified through 2 sets of amplifier integrated circuits:
TDA8563 is a 2 channel 40W amplifier mounted on the heatsink. ('Power Amp Chip'). This directly drives both the left and right speakers.
TL0841 is a 15-pin quad amplifier, of which there are two: one for each channel (L/R). ('Pair Amplifier chips'). These provide gain to the input stage of the power amplifier.
Underside view of circuit board...
With the unit removed but still connected, you might be able to hear or feel the relay switching on when the radio is switched on (with volume set to zero). This could be a way to test that the relay circuit is working.
The power-on relay switching circuit comprises three switching transistors, with the large one (a BCP54) in the final stage used to drive the relay coil.
On the picture below, the relay switching signal passes through three stages:
Power switching signal from connector cable (1)
Stage 1 switching (2)
Stage 2 switching (3)
Stage 3 relay coil switching (4).
The following is a pin-out of the amplifier connector (source internet).
Note that the front left speaker connections are on the circuit board itself. I believe that the two front door tweeters are connected directly to the radio output/input of the amplifier (there are no connections from the amplifier circuit board to them). My car also had door connectors for midrange speakers, but these speakers were not fitted.
When replacing the circuit board, apply some heatsink thermal paste to the power amplifier chip when mounting it to the heatsink.
My car's aftermarket JVC radio had been fitted by somebody (prior to the previous owner), by cutting the wires from the BMW 17-pin connector (which also has a CD changer connector) and joining the radio's ISO plugs to the cut wiring harness.
socket side...
Small white 10-pin socket is for a CD autochanger.
Rear showing original cut wires and 'twisted pair' speaker wires in the background (more about this later).
I disconnected the ISO plugs and reinstated the cut wires back to the 17-pin connector (by soldering and covering the solder joints with shrink sleeving) and bought a generic 17pin BMW to ISO radio adaptor cable. There seem to be lots of these available for many different types of BMW.
This needed a modification to connect the 17-pin permanent +12v supply (pin 9) to the ISO +12v (pin12), to supply constant power to the radio (apparently Japanese radios don't always follow a standard to these connections).
The +12v to the radio can be wired to the ignition circuit connector if you want to avoid a small amount of current drain by the radio when not in use (e.g. my radio has a permanently illuminated power-on button). The radio won't work unless the ignition is on in that configuration.
On my 17pin adapter plug, I had to cut off the 4 plastic locking tabs on each corner (see above), that are supposed to lock the adapter to the BMW 17 pin socket. Without removing them, the adapter plug and 17 pin socket couldn't be pushed together at all to make electrical contact. Once the tabs were removed, the adapter is a firm fit in the socket and won't come apart easily.
Wiring diagrams are below: (note the pin numbering on these two diagrams are different. The adapter diagram shows the ISO pin number connections to the BMW 17-pin socket).
BMW 17-pin socket (viewed from the socket side NOT the wire side) - source internet.
Wire colours (main wire colour/stripe):
1. yellow/red**
2. blue/black***
3. yellow*
4. white/brown
5. purple/white (thick wire)
6. blue****
7. not connected
8. yellow/brown**
9. red/white (thick wire)
10. black/white
11. blue/brown***
12. brown*
13. white/red
14. brown****
15. brown (thick wire)
16. white
17. not connected
In the BMW wiring loom connections to the 17-pin socket, four sets of wires are twisted together as pairs as indicated above by *, **, ***, **** e.g. the blue and brown wires marked **** are twisted together. This is how the two thin brown wires (pins 12 and 14) are differentiated.
Pin 16 white is the+12v power amplifier relay control signal from the radio, which was originally not connected on my car (blue wire pin 10 on the ISO connector).
Adapter cable:
I hope this is useful information to anybody fault-finding on their stereo system. Any errors omissions, please let me know or post in the comments.
