Posted this to Luke's wiring thread, but think it warrants it's own post. Should probably sticky this too.
Radios like the CM5908 (Alpine) and KE83ZBM (Pioneer) have 4 amp channels (and a CD changer connector). The earlier radios like the CM5905, CM5907 and KE81ZBM only have 2 amp channels. You have probably seen pics with early model E30s showing an external fader knob below the center AC vents. That fader was how a 2 channel radio drove 4 sets of speakers in the early model cars.
All cars with the BMW Sound System came with a 4 channel Blaupunkt car amp in the trunk, tweeters in the doors and for coupes and sedans tweeters on the package tray shelf as well. Regardless of whether your radio was 2 channel or 4 channel, if it came with the Blaupunkt amp the output wires from the radio / head unit share a common “signal ground”. This means there is a single shared ground connection for all audio channels out of the radio, not separate ground wires for each channel. This common speaker ground is 1 or 2 brown wires that get screwed on to the back of the radio heatsink
AUDIO WIRING ON COUPE/SEDAN VS CONVERTIBLE VS TOURING..
If you really go nuts on realoem, or even better are fortunate enough to study the actual audio wiring on the various E30 body types, you will note that the audio wiring on a coupe or M3 is different from a convertible - or a touring. This is mostly due to speaker placement, but also wiring changes were introduced in Europe during E30 production that were not present elsewhere.
Coupes/Sedans with the BMW SOUND SYSTEM (premium sound)
A: 2 Channel Radio with BMW SOUND SYSTEM (with the fader knob, up to early 88)
B: 4 Channel Radio with BMW SOUND SYSTEM (starting late 88)
Coupes/Sedans with Radio Only (standard setup)
C: 2 Channel Radio Only installation (with the fader knob, up to early 88)
D: 4 Channel Radio Only (starting late 88, very similar to the 2 channel radio only wiring, but there is no fader)
E: Convertibles with BMW SOUND SYSTEM (premium sound)
F: Tourings (not available in USDM) equipped with a new 17 pin radio connector that was later included with E36 vehicles, radio only or with BMW SOUND SYSTEM. Electrically this wiring setup was identical to the equivalent E30 sedan radio only or BMW SOUND SYSTEM install. The difference is primarily as follows:
- there's no separate fader connector
- except for the antenna cable itself, all the audio wiring routed to the dash radio area terminate at the 17 pin connector.
HARNESS ADAPTERS IN 4 CHANNEL CARS (EXCEPT TOURING)
In common speaker ground, 4 channel premium sound cars, the headunit wiring included a 2 to 4 channel adapter harness that replaced the fader, plugged in to the same connector the fader used. One end of this adapter plugs into the fader socket in the wiring harness. The other end is a rectangular connector with 4 blades labeled LH (links hinten = left rear) and RH (rechts hinten = right rear). Those are the rear head unit output connections that get sent to the amp in the trunk.
Here is a standalone picture of the 2 to 4 channel adapter for BMW SOUND SYSTEM / premium cars, part number 61-10-1-388-934
Note that there are no ground wires in that harness.
There is also a separate 2-to-4 channel E30 adapter harness for radio only installs, 65-12-1-379-329. This harness includes individual speaker grounds for each channel.
RADIO / HEAD UNIT AUDIO OUT WIRING (ACCESS FROM THE RADIO OPENING OF COURSE)
You can tell what the head unit output wires do from the color coding:
blue head unit wires are for the right channels
yellow head unit wires are for the left channels
if they have no stripes they are for the front channels
wires with red stripes are also for the front channels
if they have black stripes then they are for the rear channels
TRUNK AMP WIRING FOR BMW SOUND SYSTEM
Now regarding the BMW SOUND SYSTEM wiring, those head unit outputs get routed to your blaupunkt trunk amp harness - NOT TO THE SPEAKERS. Unfortunately, due to age it's about 90% certain that a 30 year old unserviced power amp is fried, even if the system was lightly used. If your OEM radio hasn't been serviced either, it's also likely that the amp inside the radio needs service as well - both need to be functioning properly to get good amplified sound. If your trunk amp is indeed damaged, you will either not hear sound from some or all of the speakers, or it will be severely distorted. Right now there are three options available to resolve this situation (I hope to have some others for the community soon):
(Case 1) replace or rebuild the blaupunkt trunk amp. if you're a collector this may be your preference, but honestly it's pretty old tech.
(Case 2) run headunit only, and bypass the trunk amp by modifying the harness at the amp connector in the trunk or under the rear seat. how you do that depends on whether you have a 2 channel radio+amp harness or a 4 channel radio+amp harness. Once you do this the headunit is now directly connected to your car speakers.
(Case 3) cut the trunk amp connector or splice in to the trunk wires, then replace the trunk amp with an aftermarket 4 or 5 channel amp. This gives you the most flexibility to do things like add a trunk sub, and also preserves the option to keep the factory radio.
HOW TO DO A TRUNK AMP BYPASS PROPERLY - DIFFERENT FOR 2 AND 4 CHANNEL
SPEAKER GROUNDS, OUTPUT GROUNDS AND CHASSIS GROUNDS - THEY ARE NOT THE SAME!!
The speaker ground connections on the actual speakers vs the radio and amp grounds. with a no-amp system the speaker grounds are the same as the output ground connections on the radio. that's not the case on a BMW SOUND SYSTEM setup with trunk amp. you can see all of this in the schematics:
1) in a no amp system, the speaker grounds are connected to the radio outputs, not to the radio chassis. the radio chassis itself is grounded separately.
2) if you have the trunk amp, the speaker grounds are connected to the amp outputs, not the amp chassis. the amp chassis is grounded separately. the radio chassis is also grounded separately, and only the positive radio outputs are used.
If you read the above carefully, you'll notice the speaker grounds are never grounded to the chassis directly in either setup.
4 CHANNEL TRUNK AMP BYPASS
@Rontgen's post on Luke's amp bypass thread beautifully captures the 4 channel radio harness wiring changes you need for case 2,
2 CHANNEL TRUNK AMP BYPASS
UPDATED DESCRIPTION OF 2 CHANNEL GROUNDS Mar 10 2023
CORRECTED Sep 4 2022: with the older 2 channel amp bypass is similar, except that there is a single brown/black ground wire between the radio and amp that MUST STAY SEPARATE from the amplifier output ground wires going to the speakers.
See this post further down for additional clarification https://www.r3vlimited.com/board/for...9#post10067179
BMW SOUND SYSTEM AFTERMARKET AMP HARNESS MODIFICATIONS
For case 3 you route the yellow and blue wire pairs to the aftermarket amp's speaker level inputs, and the aftermarket amp's outputs get wired to the black and grey striped wires that go to the four speaker sets.
Here are the power amp output wiring colors (probably posted for the 135th time lol).
for both the 2 channel and 4 channel radio harnesses:
grey amp wires are for the front speakers
black amp wires are for the rear speakers
grey or black wires with red stripes are left channel
grey or black wires with violet / purple stripes are left channel ground
grey or black wires with white stripes are right channel
grey or black wires with brown stripes are right channel ground
and for 2 channel radio harnesses only:
brown wire with black stripes are chassis grounds between the amp and the radio. They are connected to a brown chassis ground wire, separate from speaker grounds
the three remaining power amp wires are self explanatory, red for battery, white for amp on/off and brown for ground.
FYI I'm working on a couple of plug and play adapter harnesses for all this so no wire cutting is needed, but will be a while. First install will be Cosmo, my 86 Cosmoblau 325. It will be running an Infinity REF 4555A 5 channel amp and a JBL 1224SS trunk sub.
ADVICE ON READING BMW ELECTRICAL DIAGRAMS (SCHEMATICS)
Don't be afraid of them. Some rules of thumb:
- diagrams are usually drawn with the positive polarity at the top, ground at the bottom
- every wire has two letter color codes (e.g. BK/BR means Black wire, Brown stripe) and a wire size in mm (usually 1.5, 1, .75. .5). This is super handy to identify specific wires in the car by both how big they are and their color scheme
- the diagrams just show connections between things, not where they are in the car, or how long the wire really is. this is usually what confuses people.
A. TWO CHANNEL BMW SOUND SYSTEM (COUPE / SEDAN)
for completeness, here's a 1986 BMW Sound System schematic for TWO CHANNEL RADIOS showing the wiring for the radio, amp, speakers and power antenna. Note the radio output wiring is common ground. NOTE AS WELL - 1986 and earlier cars used a FLAT BLADE FADER rather than the ROUND PIN FADER used 1987-1989.
B. FOUR CHANNEL BMW SOUND SYSTEM (COUPE/SEDAN)
Here's the same set of schematics for a 1989 late production BMW sound system car with FOUR CHANNEL RADIO wiring. Again the radio output wiring to the power amp is a common ground setup.
C. TWO CHANNEL RADIO ONLY (COUPE/SEDAN)
This is how the 2 channel radio was wired up to early 88, which uses a fader switch with widely spaced ridges on it and round pins. There's actually an older setup that is missing a ground wire from the fader switch too. The older fader adjuster has a much smoother finish to it.
D. FOUR CHANNEL RADIO ONLY (COUPE/SEDAN)
Finally, here's an 1989 4 CHANNEL RADIO ONLY late production schematic. Note each speaker has its own ground wire. Early production is electrically the same with some harness connector differences
NOTE The 1989 325i / 325is electrical troubleshooting manual has 4 different radio + amp schematics based on early vs late production, radio only vs BMW Sound system. Make sure you're looking at the right version for your car!
-- 2 channel (up to early 88 or so) or 4 channel radio
-- radio only, or BMW Sound System with amp
-- coupe/sedan or convertible. Convertibles with BMW Sound System do not have rear tweeters, or crossovers on the rear speakers.
E. FOUR CHANNEL BMW SOUND SYSTEM (CONVERTIBLE)
This configuration is electrically identical to a four channel BMW SOUND SYSTEM install in a coupe or sedan, with exceptions due primarily to the rear speakers being in a different location:
Radios like the CM5908 (Alpine) and KE83ZBM (Pioneer) have 4 amp channels (and a CD changer connector). The earlier radios like the CM5905, CM5907 and KE81ZBM only have 2 amp channels. You have probably seen pics with early model E30s showing an external fader knob below the center AC vents. That fader was how a 2 channel radio drove 4 sets of speakers in the early model cars.
All cars with the BMW Sound System came with a 4 channel Blaupunkt car amp in the trunk, tweeters in the doors and for coupes and sedans tweeters on the package tray shelf as well. Regardless of whether your radio was 2 channel or 4 channel, if it came with the Blaupunkt amp the output wires from the radio / head unit share a common “signal ground”. This means there is a single shared ground connection for all audio channels out of the radio, not separate ground wires for each channel. This common speaker ground is 1 or 2 brown wires that get screwed on to the back of the radio heatsink
AUDIO WIRING ON COUPE/SEDAN VS CONVERTIBLE VS TOURING..
If you really go nuts on realoem, or even better are fortunate enough to study the actual audio wiring on the various E30 body types, you will note that the audio wiring on a coupe or M3 is different from a convertible - or a touring. This is mostly due to speaker placement, but also wiring changes were introduced in Europe during E30 production that were not present elsewhere.
- There's a 61-12-1-381-719 harness part number used sound system on coupe, sedan or M3.
- There's a different 61-12-1-381-718 harness part number used for sound system on convertible
- Convertibles add a *really* bizarre speaker harness that routes from the driver side kick panel to the other 3 corners of the car. Also weird is that this harness uses the "radio only" wiring color scheme (more detail follows) that connects to a 6 pin connector near the driver front kick panel speaker with the rear amp out speaker wires. It seems that BMW intended to connect to all four speakers with this added harness at one point, but decided to use only the rear speakers for production. The most likely explanation was the need for individual speaker grounds (i.e., there can only be 2 grounds available for 4 speakers on a 6 pin connector)
- The late model E30 tourings used the 17 pin connector found in early E36 cars that basically combines all the wiring for the fader connector with the other power and ground wiring that went to the radio. Part numbers 61-12-1-394-213 (sound system) and 61-12-1-394-212 (radio only).
- The wiring in both the 718 and 719 sound system harnesses changed to a twisted pair setup at some point, but the part number was not changed. BMW Classic could not confirm the exact date of the production design change, but it most likely was most likely near the time 4 channel radios were being introduced.
Coupes/Sedans with the BMW SOUND SYSTEM (premium sound)
A: 2 Channel Radio with BMW SOUND SYSTEM (with the fader knob, up to early 88)
B: 4 Channel Radio with BMW SOUND SYSTEM (starting late 88)
Coupes/Sedans with Radio Only (standard setup)
C: 2 Channel Radio Only installation (with the fader knob, up to early 88)
D: 4 Channel Radio Only (starting late 88, very similar to the 2 channel radio only wiring, but there is no fader)
E: Convertibles with BMW SOUND SYSTEM (premium sound)
F: Tourings (not available in USDM) equipped with a new 17 pin radio connector that was later included with E36 vehicles, radio only or with BMW SOUND SYSTEM. Electrically this wiring setup was identical to the equivalent E30 sedan radio only or BMW SOUND SYSTEM install. The difference is primarily as follows:
- there's no separate fader connector
- except for the antenna cable itself, all the audio wiring routed to the dash radio area terminate at the 17 pin connector.
HARNESS ADAPTERS IN 4 CHANNEL CARS (EXCEPT TOURING)
In common speaker ground, 4 channel premium sound cars, the headunit wiring included a 2 to 4 channel adapter harness that replaced the fader, plugged in to the same connector the fader used. One end of this adapter plugs into the fader socket in the wiring harness. The other end is a rectangular connector with 4 blades labeled LH (links hinten = left rear) and RH (rechts hinten = right rear). Those are the rear head unit output connections that get sent to the amp in the trunk.
Here is a standalone picture of the 2 to 4 channel adapter for BMW SOUND SYSTEM / premium cars, part number 61-10-1-388-934
Note that there are no ground wires in that harness.
There is also a separate 2-to-4 channel E30 adapter harness for radio only installs, 65-12-1-379-329. This harness includes individual speaker grounds for each channel.
RADIO / HEAD UNIT AUDIO OUT WIRING (ACCESS FROM THE RADIO OPENING OF COURSE)
You can tell what the head unit output wires do from the color coding:
blue head unit wires are for the right channels
yellow head unit wires are for the left channels
if they have no stripes they are for the front channels
wires with red stripes are also for the front channels
if they have black stripes then they are for the rear channels
TRUNK AMP WIRING FOR BMW SOUND SYSTEM
Now regarding the BMW SOUND SYSTEM wiring, those head unit outputs get routed to your blaupunkt trunk amp harness - NOT TO THE SPEAKERS. Unfortunately, due to age it's about 90% certain that a 30 year old unserviced power amp is fried, even if the system was lightly used. If your OEM radio hasn't been serviced either, it's also likely that the amp inside the radio needs service as well - both need to be functioning properly to get good amplified sound. If your trunk amp is indeed damaged, you will either not hear sound from some or all of the speakers, or it will be severely distorted. Right now there are three options available to resolve this situation (I hope to have some others for the community soon):
(Case 1) replace or rebuild the blaupunkt trunk amp. if you're a collector this may be your preference, but honestly it's pretty old tech.
(Case 2) run headunit only, and bypass the trunk amp by modifying the harness at the amp connector in the trunk or under the rear seat. how you do that depends on whether you have a 2 channel radio+amp harness or a 4 channel radio+amp harness. Once you do this the headunit is now directly connected to your car speakers.
(Case 3) cut the trunk amp connector or splice in to the trunk wires, then replace the trunk amp with an aftermarket 4 or 5 channel amp. This gives you the most flexibility to do things like add a trunk sub, and also preserves the option to keep the factory radio.
HOW TO DO A TRUNK AMP BYPASS PROPERLY - DIFFERENT FOR 2 AND 4 CHANNEL
SPEAKER GROUNDS, OUTPUT GROUNDS AND CHASSIS GROUNDS - THEY ARE NOT THE SAME!!
The speaker ground connections on the actual speakers vs the radio and amp grounds. with a no-amp system the speaker grounds are the same as the output ground connections on the radio. that's not the case on a BMW SOUND SYSTEM setup with trunk amp. you can see all of this in the schematics:
1) in a no amp system, the speaker grounds are connected to the radio outputs, not to the radio chassis. the radio chassis itself is grounded separately.
2) if you have the trunk amp, the speaker grounds are connected to the amp outputs, not the amp chassis. the amp chassis is grounded separately. the radio chassis is also grounded separately, and only the positive radio outputs are used.
If you read the above carefully, you'll notice the speaker grounds are never grounded to the chassis directly in either setup.
4 CHANNEL TRUNK AMP BYPASS
@Rontgen's post on Luke's amp bypass thread beautifully captures the 4 channel radio harness wiring changes you need for case 2,
2 CHANNEL TRUNK AMP BYPASS
UPDATED DESCRIPTION OF 2 CHANNEL GROUNDS Mar 10 2023
CORRECTED Sep 4 2022: with the older 2 channel amp bypass is similar, except that there is a single brown/black ground wire between the radio and amp that MUST STAY SEPARATE from the amplifier output ground wires going to the speakers.
See this post further down for additional clarification https://www.r3vlimited.com/board/for...9#post10067179
BMW SOUND SYSTEM AFTERMARKET AMP HARNESS MODIFICATIONS
For case 3 you route the yellow and blue wire pairs to the aftermarket amp's speaker level inputs, and the aftermarket amp's outputs get wired to the black and grey striped wires that go to the four speaker sets.
Here are the power amp output wiring colors (probably posted for the 135th time lol).
for both the 2 channel and 4 channel radio harnesses:
grey amp wires are for the front speakers
black amp wires are for the rear speakers
grey or black wires with red stripes are left channel
grey or black wires with violet / purple stripes are left channel ground
grey or black wires with white stripes are right channel
grey or black wires with brown stripes are right channel ground
and for 2 channel radio harnesses only:
brown wire with black stripes are chassis grounds between the amp and the radio. They are connected to a brown chassis ground wire, separate from speaker grounds
the three remaining power amp wires are self explanatory, red for battery, white for amp on/off and brown for ground.
FYI I'm working on a couple of plug and play adapter harnesses for all this so no wire cutting is needed, but will be a while. First install will be Cosmo, my 86 Cosmoblau 325. It will be running an Infinity REF 4555A 5 channel amp and a JBL 1224SS trunk sub.
ADVICE ON READING BMW ELECTRICAL DIAGRAMS (SCHEMATICS)
Don't be afraid of them. Some rules of thumb:
- diagrams are usually drawn with the positive polarity at the top, ground at the bottom
- every wire has two letter color codes (e.g. BK/BR means Black wire, Brown stripe) and a wire size in mm (usually 1.5, 1, .75. .5). This is super handy to identify specific wires in the car by both how big they are and their color scheme
- the diagrams just show connections between things, not where they are in the car, or how long the wire really is. this is usually what confuses people.
A. TWO CHANNEL BMW SOUND SYSTEM (COUPE / SEDAN)
for completeness, here's a 1986 BMW Sound System schematic for TWO CHANNEL RADIOS showing the wiring for the radio, amp, speakers and power antenna. Note the radio output wiring is common ground. NOTE AS WELL - 1986 and earlier cars used a FLAT BLADE FADER rather than the ROUND PIN FADER used 1987-1989.
B. FOUR CHANNEL BMW SOUND SYSTEM (COUPE/SEDAN)
Here's the same set of schematics for a 1989 late production BMW sound system car with FOUR CHANNEL RADIO wiring. Again the radio output wiring to the power amp is a common ground setup.
C. TWO CHANNEL RADIO ONLY (COUPE/SEDAN)
This is how the 2 channel radio was wired up to early 88, which uses a fader switch with widely spaced ridges on it and round pins. There's actually an older setup that is missing a ground wire from the fader switch too. The older fader adjuster has a much smoother finish to it.
D. FOUR CHANNEL RADIO ONLY (COUPE/SEDAN)
Finally, here's an 1989 4 CHANNEL RADIO ONLY late production schematic. Note each speaker has its own ground wire. Early production is electrically the same with some harness connector differences
NOTE The 1989 325i / 325is electrical troubleshooting manual has 4 different radio + amp schematics based on early vs late production, radio only vs BMW Sound system. Make sure you're looking at the right version for your car!
-- 2 channel (up to early 88 or so) or 4 channel radio
-- radio only, or BMW Sound System with amp
-- coupe/sedan or convertible. Convertibles with BMW Sound System do not have rear tweeters, or crossovers on the rear speakers.
E. FOUR CHANNEL BMW SOUND SYSTEM (CONVERTIBLE)
This configuration is electrically identical to a four channel BMW SOUND SYSTEM install in a coupe or sedan, with exceptions due primarily to the rear speakers being in a different location:
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