Electrical: Difference between revisions
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== Electrical FAQs == | == Electrical FAQs == | ||
{| class="wikitable" | |||
|- | |||
! FAQ | |||
! Covers | |||
|- | |||
| [[Service Indicator Reset]] | |||
| Reset the Oil Service and Inspection lights | |||
|- | |||
| [[SI Board Replacement]] | |||
| Replace a failed service-interval board | |||
|- | |||
| [[E28 Charging System]] | |||
| Alternator, regulator, battery light, voltage drop | |||
|- | |||
| [[On-Board Computer (OBC II)]] | |||
| Time, units, CODE, range calibration, PPPP | |||
|- | |||
| [[OBC I Went Dead]] | |||
| Inline fuse inside the early OBC | |||
|- | |||
| [[Radio Wiring]] | |||
| Aftermarket radio on the factory harness | |||
|- | |||
| [[Cruise Control Doesn't Work]] | |||
| Brake-light ground, pedal switches, brain, servo | |||
|- | |||
| [[Euro Headlight Wash/Wipe Troubleshooting]] | |||
| Euro headlight washers and wipers | |||
|- | |||
| [[Turn Signals Don't Work But Hazards Do]] | |||
| Fuse 11 or turn-signal stalk | |||
|- | |||
| [[Check Brake Lights Come On at Every Start]] | |||
| Normal E28 startup lamp check | |||
|- | |||
| [[Oil Pressure Light Flickers]] | |||
| Sender, wiring, or real low pressure | |||
|- | |||
| [[Temperature Gauge Troubleshooting]] | |||
| How to read it, sender test, SI board, grounds | |||
|- | |||
| [[Power Window Issues]] | |||
| Motors, regulators, switches | |||
|- | |||
| [[Auto Won't Shift After Cluster Swap]] | |||
| Auto stuck in 1st after a cluster swap | |||
|- | |||
| [[Car Won't Start]] | |||
| Where to start when it will not crank/start | |||
|- | |||
| [[Cold Weather Chime]] | |||
| Ice-warning gong below 37 °F | |||
|- | |||
| [[Spark Plug FAQ]] | |||
| Which spark plugs to use | |||
|- | |||
| [[M20 - e2i Conversion]] | |||
| M20B27 eta-to-i conversion | |||
|} | |||
== E28 Electrical Troubleshooting Manuals (ETM) == | == E28 Electrical Troubleshooting Manuals (ETM) == | ||
Latest revision as of 22:29, 13 August 2026
Electrical FAQs
| FAQ | Covers |
|---|---|
| Service Indicator Reset | Reset the Oil Service and Inspection lights |
| SI Board Replacement | Replace a failed service-interval board |
| E28 Charging System | Alternator, regulator, battery light, voltage drop |
| On-Board Computer (OBC II) | Time, units, CODE, range calibration, PPPP |
| OBC I Went Dead | Inline fuse inside the early OBC |
| Radio Wiring | Aftermarket radio on the factory harness |
| Cruise Control Doesn't Work | Brake-light ground, pedal switches, brain, servo |
| Euro Headlight Wash/Wipe Troubleshooting | Euro headlight washers and wipers |
| Turn Signals Don't Work But Hazards Do | Fuse 11 or turn-signal stalk |
| Check Brake Lights Come On at Every Start | Normal E28 startup lamp check |
| Oil Pressure Light Flickers | Sender, wiring, or real low pressure |
| Temperature Gauge Troubleshooting | How to read it, sender test, SI board, grounds |
| Power Window Issues | Motors, regulators, switches |
| Auto Won't Shift After Cluster Swap | Auto stuck in 1st after a cluster swap |
| Car Won't Start | Where to start when it will not crank/start |
| Cold Weather Chime | Ice-warning gong below 37 °F |
| Spark Plug FAQ | Which spark plugs to use |
| M20 - e2i Conversion | M20B27 eta-to-i conversion |
E28 Electrical Troubleshooting Manuals (ETM)
ETMs are the go-to resource for tracking down electrical issues in E28s. They appear to only have been printed for US market vehicles, so euro cars may have some minor differences.
- 1982 E28 - Electrical Troubleshooting Manual.pdf
- 1983 E28 - Electrical Troubleshooting Manual.pdf
- 1984 E28 - Electrical Troubleshooting Manual.pdf
- 1985 E28 - Electrical Troubleshooting Manual.pdf
- 1986 BMW 528e - 535i Electrical Troubleshooting Manual.pdf
- 1987-1988 BMW 528e - Electrical Troubleshooting Manual.pdf
- 1988 E28 - Electrical Troubleshooting Manual.pdf
E28 Schaltplänes
The Schaltplänes, German for "circuit diagrams", are the BMW factory wiring diagrams. These can be very useful, however they are drawn for a technical audience and not for the faint of heart. We recommend using the ETM unless that doesn't solve your problem.
Scanned copies, originally from the BMW Group Archive, are available in German below. German print copies can occasionally be found on German eBay. English print copies are rare, if you have any please send a PM to Galahad on the forums or reach out to the Holy Grail Labs support email.
- E28 Schaltplane Volume 1
- E28 Schaltplane Volume 2
- E28 Schaltplane Volume 3
- E28 A/C Wiring, up to 1986, excerpt from Schaltpläne
E28 Related Electrical Info and Diagrams
- BMW ECU Wiring diagrams Menu.pdf
- Euro E28 electrical diagrams
- bmw-cruise-control-actuator-technical-data.pdf
- bmw-cruise-control-e23-e28.pdf
- Bosch M-Motronic Technical Instruction.pdf
Other Model ETMs
- E30 ETM
- BMW 635csi - M6 Electrical Troubleshooting Manual.pdf
- BMW 525i - 525it - 530i - 530it - 540i Electrical Troubleshooting Manual.pdf
- e34_90_etm.pdf
E21 Wiring Diagrams
The wiring diagrams are between the more traditional ETM layout and the Schaltplänes.
- 1981 E21 320i ETM Introduction.pdf
- 1979 E21 320i Wiring Diagram.pdf
- 1980 E21 320i Wiring Diagram.pdf
- 1981-1983 E21 320i Wiring Diagram.pdf
The E21 Schaltplänes have drawing errors in the fog light wiring in the fuse box, current best info is the wiring diagrams are correct to the cars.
