v 20050313 1
C 0 100 1 0 0 ophw-title-A3.sym
{
T 14602 1010 5 10 1 1 0 0 1
date=2005-10-30
T 13420 1305 5 10 1 1 0 0 1
rev=1.0
T 12275 405 5 10 1 1 0 0 1
auth=Ludwig Jaffe
T 9455 700 5 10 1 1 0 0 1
fname=filter_heater.sch
T 9630 1030 5 12 1 1 0 0 1
title=Filter Heater ECU
T 14602 460 5 10 1 1 0 0 1
docid=OHCD00001AA
T 9680 1380 5 12 1 1 0 0 1
project=BMW-M51-Vegoil
T 13420 955 5 10 1 1 0 0 1
license=PD
}
T 400 250 9 10 1 0 0 0 8
This is the reverse-engineered schematic of the fuel filter heater unit found in 
BMW-525TDS, Model E-34, Engine M51 (Diesel)
The aim is to understand the circuit and to modify the switch-off temperature
of the heater for use with vegetable oil. (We need 50-60C then)
The modifications are indicated in boxes denoting external components.
Beeing an external component the PTC-Heater is drawn inside a box,
but it is left in its original state.

C 800 10700 1 0 0 12V-plus-1.sym
C 3300 10400 1 0 0 resistor-2.sym
{
T 3500 10700 5 10 1 1 0 0 1
refdes=R1
T 3200 10200 5 10 1 1 0 0 1
value=100R / 0.25W
}
C 12000 2900 1 0 0 mosfet-with-diode-1.sym
{
T 12900 3400 5 10 1 1 0 0 1
refdes=Q1
T 12900 3200 5 10 1 1 0 0 1
value=BUZ11A
}
C 1200 10300 1 0 0 diode-1.sym
{
T 800 10250 5 10 1 1 0 0 1
refdes=D1
T 800 10000 5 10 1 1 0 0 1
value=1N4004 (?)
}
N 1000 10700 1000 10500 4
N 1000 10500 1200 10500 4
N 2100 10500 3300 10500 4
C 4600 9300 1 270 0 capacitor-4.sym
{
T 3700 9400 5 10 1 1 0 0 1
refdes=C1
T 3700 9200 5 10 1 1 0 0 1
value=10uF / 63V
}
N 4800 10500 4800 9300 4
C 4600 6500 1 0 0 gnd-0.sym
N 4800 6800 4800 8400 4
C 7600 10400 1 0 0 resistor-2.sym
{
T 7800 10200 5 10 1 1 0 0 1
refdes=R4
T 7800 10000 5 10 1 1 0 0 1
value=510R
}
C 6900 10300 1 270 0 resistor-2.sym
{
T 6600 10000 5 10 1 1 0 0 1
refdes=R3
T 6600 9800 5 10 1 1 0 0 1
value=1K1
}
C 6500 9400 1 90 0 resistor-2.sym
{
T 6200 10100 5 10 1 1 180 0 1
refdes=R2
T 5800 9800 5 10 1 1 0 0 1
value=30K
}
C 6500 7600 1 90 0 resistor-2.sym
{
T 6200 8300 5 10 1 1 180 0 1
refdes=R5
T 6300 8100 5 10 1 1 180 0 1
value=33K
}
N 4200 10500 7600 10500 4
N 7000 10500 7000 10300 4
N 6400 10500 6400 10300 4
N 6400 9400 6400 8500 4
C 7400 8200 1 0 0 lm2903-1.sym
{
T 7700 9100 5 10 1 1 0 0 1
refdes=U?
T 7600 10100 5 10 0 0 0 0 1
symversion=0.1
T 7400 8200 5 10 0 0 0 0 1
slot=2
}
C 11000 8200 1 0 1 lm2903-1.sym
{
T 10700 9100 5 10 1 1 0 6 1
refdes=U?
T 10800 10100 5 10 0 0 0 6 1
symversion=0.1
}
N 7000 8400 7400 8400 4
T 6100 6100 9 10 1 0 0 0 1
Disable Heater when Battery is low
C 7200 7200 1 90 0 zener-4.sym
{
T 6700 7500 5 10 1 1 90 0 1
refdes=D3
}
C 13400 8800 1 90 0 zener-4.sym
{
T 12900 9100 5 10 1 1 90 0 1
refdes=D2
}
N 7000 8100 7000 9400 4
N 13200 9700 13200 10500 4
N 13200 10500 8500 10500 4
N 6400 7000 6400 7600 4
N 7400 8800 6400 8800 4
N 13200 7000 13200 8800 4
N 7000 7200 7000 7000 4
N 8000 8200 8000 7000 4
N 8000 9000 8000 9900 4
N 8000 9900 9000 9900 4
C 9100 8800 1 90 0 resistor-2.sym
{
T 8700 9500 5 10 1 1 180 0 1
refdes=R7
T 8450 9200 5 10 1 1 0 0 1
value=33K
}
N 9000 9700 9000 10500 4
N 9000 8600 9000 8800 4
N 8600 8600 9800 8600 4
C 12700 8800 1 90 0 ntc-resistor-0.sym
{
T 11750 9900 5 10 1 1 180 0 1
refdes=R10
T 12300 9700 5 10 1 1 180 0 1
value=10K@20C
}
N 12400 9700 12400 10500 4
N 12400 8400 11000 8400 4
C 9900 9500 1 0 0 resistor-2.sym
{
T 10100 10000 5 10 1 1 0 0 1
refdes=R8
T 10100 9800 5 10 1 1 0 0 1
value=1M5
}
N 10800 9600 11200 9600 4
N 11200 8800 11000 8800 4
N 9900 9600 9600 9600 4
C 11900 3500 1 180 0 resistor-2.sym
{
T 11150 3800 5 10 1 1 0 0 1
refdes=R9
T 11500 3750 5 10 1 1 180 0 1
value=5K6
}
C 12500 7300 1 90 0 resistor-2.sym
{
T 12200 8000 5 10 1 1 180 0 1
refdes=R6
T 11900 7700 5 10 1 1 0 0 1
value=24K
}
N 12400 8200 12400 8800 4
N 12400 7300 12400 7000 4
C 9200 7300 1 90 0 capacitor-1.sym
{
T 8550 7800 5 10 1 1 180 0 1
refdes=C2
T 8300 7450 5 10 1 1 0 0 1
value=100n ?
}
N 9000 8200 9000 8600 4
N 9000 7000 9000 7300 4
C 12400 2300 1 0 0 gnd-0.sym
N 12600 2600 12600 2900 4
N 12600 3900 12600 5200 4
N 12600 4400 13900 4400 4
N 6400 8800 5600 8800 4
N 5600 8800 5600 10700 4
N 5600 10700 11200 10700 4
T 5800 8900 9 10 1 0 0 0 1
~7V
N 12000 3400 11900 3400 4
N 9600 3400 11000 3400 4
N 9600 9600 9600 8600 4
N 9600 8600 9600 3400 4
C 14800 4600 1 0 0 12V-plus-1.sym
N 15000 4600 15000 4400 4
C 13900 4300 1 0 0 resistor-1.sym
{
T 14100 4600 5 10 1 1 0 0 1
refdes=R11
T 13950 4100 5 10 1 1 0 0 1
value=PTC-Heater
}
N 14800 4400 15000 4400 4
B 13600 3600 1800 1800 3 0 0 0 -1 -1 0 -1 -1 -1 -1 -1
T 13700 3400 9 10 1 0 0 0 1
Build into Filter-Unit
T 9800 5500 9 10 1 0 0 0 5
Substitute R6 with C101 (reduce noise from vibrating R102)
R101 and R102 are connected in parallel to evaluate a new value for R6. 
Lower Resistance provides a higher switch-off temperature.


C 15300 8550 1 90 0 resistor-2.sym
{
T 15850 9500 5 10 1 1 180 0 1
refdes=R101
T 15450 9150 5 10 1 1 0 0 1
value=2K2
}
C 15100 8100 1 270 0 resistor-variable-2.sym
{
T 15500 7950 5 10 1 1 0 0 1
refdes=R102
T 15500 7750 5 10 1 1 0 0 1
value=22K
}
N 15700 7600 15800 7600 4
N 15800 7600 15800 7000 4
N 4800 7000 15800 7000 4
N 15200 7000 15200 7200 4
N 15200 8550 15200 8100 4
N 12400 8400 14800 8400 4
N 14800 9600 15200 9600 4
N 15200 9600 15200 9450 4
B 14000 6800 2100 3200 3 0 0 0 -1 -1 0 -1 -1 -1 -1 -1
N 2600 10500 2600 5200 4
N 2600 5200 4900 5200 4
C 4900 5100 1 0 0 resistor-2.sym
{
T 5050 4850 5 10 1 1 0 0 1
refdes=R201
T 5100 4650 5 10 1 1 0 0 1
value=470R
}
C 7000 5400 1 180 0 led-3.sym
{
T 6550 4850 5 10 1 1 180 0 1
refdes=D201
}
N 5800 5200 6100 5200 4
B 4500 4500 4000 1100 3 0 0 0 -1 -1 0 -1 -1 -1 -1 -1
T 4500 4250 9 10 1 0 0 0 1
Add this as heater-on indicator when tuning R102
L 7600 8000 7400 6250 3 0 0 0 -1 -1
L 7500 7900 7600 8000 3 0 0 0 -1 -1
L 7600 8000 7650 7900 3 0 0 0 -1 -1
T 8925 10775 9 10 1 0 0 0 2
Compare Fuel-Temperature  against "reference", switch-on heater if too cold.
Have Hysteresis which also   modifies trip-point for battery-monitor!
L 11300 11025 11400 10200 3 0 0 0 -1 -1
L 11400 10200 12050 9850 3 0 0 0 -1 -1
L 11975 9925 12050 9850 3 0 0 0 -1 -1
L 12050 9850 11950 9850 3 0 0 0 -1 -1
C 15000 7200 1 90 0 capacitor-1.sym
{
T 14600 8000 5 10 1 1 180 0 1
refdes=C101
T 14100 7700 5 10 1 1 0 0 1
value=100n
}
N 14800 8100 14800 9600 4
N 14800 7200 14800 7000 4
N 11200 8800 11200 10700 4
C 7300 5100 1 0 0 resistor-2.sym
{
T 7450 4850 5 10 1 1 0 0 1
refdes=R202
T 7500 4650 5 10 1 1 0 0 1
value=470R
}
N 7000 5200 7300 5200 4
N 8200 5200 12600 5200 4
T 4500 3200 9 10 1 0 0 0 4
The two resistors are protection against short-circuit
if the LED is to be taped on the dashboard.
Place the resistors on the pcb and connect
the LED with wires.
L 11400 10200 10800 9200 3 0 0 0 -1 -1
L 10800 9300 10800 9200 3 0 0 0 -1 -1
L 10800 9200 10900 9200 3 0 0 0 -1 -1
L 10800 6700 12000 7500 3 0 0 0 -1 -1
L 11900 7500 12000 7500 3 0 0 0 -1 -1
L 12000 7500 12000 7400 3 0 0 0 -1 -1