1992 BMW 325i Instrument Cluster 1.0

Picked up a spare BMW 325i Instrument Cluster including the three attached male plugs and 4 inch wire leads from a local salvage yard to learn more about how it can be interfaced to the EV.  The donor was from vin # BABF4319PEK09282 which according to Mitsuhiko’s BMW VIN Decoder (http://www.bmw-z1.com/VIN/VINdecode-e.cgi ) was a 1993/06 BMW 325is E36 M50 Coupe with automatic transmission.  To facilitate the testing, each of the cable wires were terminated into plastic terminal blocks (McMaster Carr part #  7618K618) that were bolted to acrylic and labeled with both wire color and function.

 

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Showing the fully wired instrument cluster attached to terminal strips.
 

 

 

                                                                 
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Showing the labelled terminals and the individual wires that originated from the three sockets on the back of the instrument cluster.  Wire color description on the top, and function on the bottom.

Study of the backside of the cluster and comparison with the wiring diagram printed in the Bentley BMW 3 Series Service Manual determined the following:

(1)  There are three plugs that connect the cluster to the wiring harness.  A white Siemens 26 pin part # B0126-S501 (described as CONN A in Bentley), a blue Siemens part # B1026-S502 26 pin plug (described as CONN B in Bentley), and a black AMP 12 pin part # 1-963003-2 BMW1383712 PBTP plug (described as CONN C in Bentley).

(2) Pin 3 of CONN B is the chassis ground
(3) Pin 2 of CONN A is wired to three 3 watt illumination bulbs that provide back lighting of the instrument cluster.

One of the bulbs was burned out and it was sourced at Patrick BMW dealership and replaced.  Note that the 3 watt glass bulbs used for back lighting (second from left in picture) actually plug into a green socket (far left).  The green plug assembly could be removed from the back of the instrument cluster after rotating a quarter turn.

 

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Showing the two types of bulbs that can be replaced from behind the instrument cluster.  The larger 3 watt back lighting bulbs (left side) are two pieces, while the smaller bulbs on the right appear to be a single unit.

After connecting the negative terminal (ground) of the 12 volt battery to CONN B pin 3 and then a jumper from CONN A pin 2 to the positive of the 12 Volt battery, the back lighting of the instrument cluster was illuminated !!  Each of the indicator and warning bulbs will be tested later.

 

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Showing the back lighted instrument cluster after connecting 12 volts to CONN A pin 2 and ground to CONN B pin 3.

 

The coding plug was not included with the instrument cluster as obtained from the salvage yard and consequently the original mileage and service status lines at the bottom of the cluster can not be illuminated.  

It is intended that the 1992 BMW 325i’s EV build will retain the original ECU and the CAN bus.  The speedometer appears to be actuated from a signal produced by the vehicle speed sensor located on the differential.  The ICE gas gauge signal was produced by a pair of variable resistors wired in series as an integral part of the floats in the original ICE gas tank.  Replacement of these variable resistors with a new circuit might simulate a measurement of residual battery pack capacity.  It may be possible to replace the engine/radiator temperature gauge sensor with a thermocouple or equivalent device whose temperature range and performance corresponds to the approved temperature range of the Warp 11.

The original ICE RPM gauge obtained its signal from the crank position sensor (CPS), also referred to in Bentley as the Front Harmonic Balancer, or the Vibration Damper.  (A good drawing can be downloaded from the following link from realoem.com  

(http://realoem.com/bmw/showparts.do?model=CB33&mospid=47498&btnr=11_0335&hg=11&fg=18 )

Builder’s Note:  The web page located at realoem.com is a tremendous resource of both BMW exploded view diagrams and BMW part numbers. 

If the vibration sensor, its mounting hub, and the crankshaft position sensor are removed from the original M50 engine and the parts mounted at the commutator end of the Warp 11, it should be possible to directly activate the tachometer when the Warp 11 is rotating. 

It may not be possible to incorporate the MPG gauge at the bottom of the RPM readout, but it would be a great if it could provide a measurement of watts per mile or equivalent measurement of energy efficiency.

 

From study of the wiring diagrams in Bentley it was possible to print an excel file that was then cut out and attached to the underside of the acrylic mounting plastic.  The descriptions listed below will be edited and updated as more is learned about the wiring of the circuits.  Readers are very welcome to contribute any information that they are willing to share about different ways that the BMW instrument cluster can be rewired for EV application. 

Wire Color		Conn	Description
Brn/Org		A24
Grn/Vio		A23
Red/Yel		A22
Wht/Blk		A21	Eng Control Sys
Blk		A20	Eng Control Sys
Yel		A19
Brn/Vio		A18	Brake Fluid Ind
Brn/Grn		A17	Park Brake Ind
Gry		A16	Check Eng Light
Vio		A15
Blu/Blk		A14	Supp Restraint Sys
Wht/Vio		A12	Data Link Conn
Wht/Yel		A11	Data Link Conn
Gry/Brn		A5	Transmission
Blu/Grn		A4	Left Turn Ind
Blu/Brn		A3	Right Turn Ind
Gry/Red		A2	Interior Lights (3)
White		A1	High Beam Ind
Brn/Gry/Yel		B23
Blu/Blk		B22
Brn/Grn		B19	Oil Ind
Brn/Vio		B18
Brn/Yel		B17
Vio/Yel		B16
Wht/Grn		B15
Blu/Vio/Yel		B14
Gry/Blk/Yel		B11	ABS Ind
Wht/Gry		B10
Blk/Red		B9
Yel/Brn		B8	Front Fog Lt Ind
Blu		B6	Start/Charging
Grn		B5	Charge Ind
Grn/Blu		B4
Brn		B3	Ground
Blk/Wht		B2
Wht/Red		B1	Exterior Lights Sys
Blu/Vio/Wht		B24
Blu/Brn/Yel		B26
Brn/Yel		C1
Brn/Blk		C3	Vehicle Ground
Brn/Red		C4	Hazard Ind