I have recently had a problem with my Super Glow system. During my initial diagnosis of the problem I read a great deal about Super Glow - much of it wrong, so I have drawn up a diagram of the workings of the system and done calculations to understand exactly how it works (well as close as I can get).
The following information is for an Australian 1988 12V Super Glow Timer for a 2H engine using 6V glow plugs that have a resistance (cold) of about 2.5 ohms each (0.4 ohms when 6 are wired in parallel). The quick heat type plugs resistance increases to more than double (~5 ohms) at their operating temperature (~1000°C). This is what's on the engine and working, I don't know if its the correct pieces, but it works !
Note - Lostmarbles pointed out that I originally had the wrong plug ID and voltage. So I looked at the (harder to reach) other plugs and found that all except the (easy to get to #1) plug were Repco 110-006420 6V #1 has since been replaced with the correct plug. Diagram updated too!
Here's how (I think) it works -
1 When powered up the Timer checks for voltage at the Charge Lamp - if the alternator is running the Timer does nothing.
2 If allowed to run, the Timer starts a timing process that is controlled by the resistor in the Temperature Sensor on the engine.
3 The Glow Indicator light is turned on for the duration of the first stage of timing.
4 Then it turns on both relays. The output from Relay #2 does nothing at this time, but Relay #1 supplies Battery Voltage (13.8V) to the connector plate.
5 The resistance in the Sensor Strap (0.5R) and the paralleled resistance in the Glow Plugs (0.4R) divides this voltage up so that 13.8V x (0.4R / (0.5R + 0.4R)) = 6.27V is delivered to the Glow Plugs. 6.27V / 13.8V = 50%
5 Current flows from the battery at 13.8V / 0.9R = 15A. The 15A draw quickly drops the voltage (that the chemical reaction in the battery can deliver) down to ~10V. The voltage division drops to 10V x (0.4R / (0.5R + 0.4R)) = 4.5V. 4.5V / 10V = 45%
7 As the Glow Plugs heat up their resistance increases (to around double) and this also decreases the current to 10V / 1.3R = 7.5A.
8 The increased resistance also changes the voltage at the Sense Point towards 10V x (0.8R / (0.8R + 0.5R)) = 6.25V. 6.25V / 10V = 62%. The Glow Plug tips will reach ~900°C at this time.
9 The first stage of the timing ends and the Glow Indicator light is turned off. Relay #1 remains on.
10 When the Sensed Voltage reaches 60% of the (instantaneous) Battery Voltage Relay #1 is turned off. This usually takes only a few seconds.
11 Relay #2 now supplies Battery Voltage through an extra 0.4R resistance. The voltage in the Buss Bar is 10V x (0.8R / (0.8R + 0.5R + 0.4R)) = 4.8V and the current is 10V / 1.7R = 5.8A.
12 The engine will be easy to start now. Once started the alternator will lift the system voltage up to around 12V while the battery is sucking up almost all of the alternators output. Voltage on the Charge Lamp will not turn off this second stage.
13 Relay #2 now supplies Alternator Voltage. The voltage in the Buss Bar is 12V x (0.8R / (0.8R + 0.5R + 0.4R)) = 5.75V and the current is 12V / 1.7R = 7A.
14 6V @ 7A maintains the 1000°C Glow Plug temperature during engine warm up. This 'After Glow' reduces pollution and engine shaking.
15 At the end of the second stage of the timing Relay #2 is released. The voltage may have risen to a maximum of 6.25V with the current dropping towards 6.3A before the shut off time.
16 After running for ~5 minutes the battery will be back to ~fully charged and the system voltage will rise to the voltage regulator's set point ~13.8V.
At no time does the Toyota Super Glow system supply more than 6.25V to the 6V plugs thanks to a 0.5 ohm 'Sensing Resistor' fitted between the relays and the Buss Bar delivering the power to the plugs. Actually it will be even lower due to the fact that a discharging chemical battery will output lower and lower voltage as the stored charge is used up.
The system is VERY sensitive to the resistance of the Glow Plugs and ABSOLUTELY reliant on the change of resistance in them as they heat up.
I don't have access to a 24V system, so no data is given (can anyone help ?) And please let me know the missing part numbers (or give a link where I can find them).
Now about my problem -
My Australian 12V Super Glow system has been working fine, but last month the Pre Heating Timer got wet.
After scrubbing the corroded components on the circuit board with an old toothbrush soaked with metholated spirits and drying it, it still works, but the times are much too short (some resistors must have permanently changed their values).
Solution - add a resistor in series with the temperature sensing resistor to fool the computer into thinking it is colder.
4,700 ohms for ~ -5°C, 10,000 ohms for ~-10°C. You can switch it out for hot starts if you want, but the extra time it adds when hot is not so very much.
bye.
The following information is for an Australian 1988 12V Super Glow Timer for a 2H engine using 6V glow plugs that have a resistance (cold) of about 2.5 ohms each (0.4 ohms when 6 are wired in parallel). The quick heat type plugs resistance increases to more than double (~5 ohms) at their operating temperature (~1000°C). This is what's on the engine and working, I don't know if its the correct pieces, but it works !
Note - Lostmarbles pointed out that I originally had the wrong plug ID and voltage. So I looked at the (harder to reach) other plugs and found that all except the (easy to get to #1) plug were Repco 110-006420 6V #1 has since been replaced with the correct plug. Diagram updated too!
Here's how (I think) it works -
1 When powered up the Timer checks for voltage at the Charge Lamp - if the alternator is running the Timer does nothing.
2 If allowed to run, the Timer starts a timing process that is controlled by the resistor in the Temperature Sensor on the engine.
3 The Glow Indicator light is turned on for the duration of the first stage of timing.
4 Then it turns on both relays. The output from Relay #2 does nothing at this time, but Relay #1 supplies Battery Voltage (13.8V) to the connector plate.
5 The resistance in the Sensor Strap (0.5R) and the paralleled resistance in the Glow Plugs (0.4R) divides this voltage up so that 13.8V x (0.4R / (0.5R + 0.4R)) = 6.27V is delivered to the Glow Plugs. 6.27V / 13.8V = 50%
5 Current flows from the battery at 13.8V / 0.9R = 15A. The 15A draw quickly drops the voltage (that the chemical reaction in the battery can deliver) down to ~10V. The voltage division drops to 10V x (0.4R / (0.5R + 0.4R)) = 4.5V. 4.5V / 10V = 45%
7 As the Glow Plugs heat up their resistance increases (to around double) and this also decreases the current to 10V / 1.3R = 7.5A.
8 The increased resistance also changes the voltage at the Sense Point towards 10V x (0.8R / (0.8R + 0.5R)) = 6.25V. 6.25V / 10V = 62%. The Glow Plug tips will reach ~900°C at this time.
9 The first stage of the timing ends and the Glow Indicator light is turned off. Relay #1 remains on.
10 When the Sensed Voltage reaches 60% of the (instantaneous) Battery Voltage Relay #1 is turned off. This usually takes only a few seconds.
11 Relay #2 now supplies Battery Voltage through an extra 0.4R resistance. The voltage in the Buss Bar is 10V x (0.8R / (0.8R + 0.5R + 0.4R)) = 4.8V and the current is 10V / 1.7R = 5.8A.
12 The engine will be easy to start now. Once started the alternator will lift the system voltage up to around 12V while the battery is sucking up almost all of the alternators output. Voltage on the Charge Lamp will not turn off this second stage.
13 Relay #2 now supplies Alternator Voltage. The voltage in the Buss Bar is 12V x (0.8R / (0.8R + 0.5R + 0.4R)) = 5.75V and the current is 12V / 1.7R = 7A.
14 6V @ 7A maintains the 1000°C Glow Plug temperature during engine warm up. This 'After Glow' reduces pollution and engine shaking.
15 At the end of the second stage of the timing Relay #2 is released. The voltage may have risen to a maximum of 6.25V with the current dropping towards 6.3A before the shut off time.
16 After running for ~5 minutes the battery will be back to ~fully charged and the system voltage will rise to the voltage regulator's set point ~13.8V.
At no time does the Toyota Super Glow system supply more than 6.25V to the 6V plugs thanks to a 0.5 ohm 'Sensing Resistor' fitted between the relays and the Buss Bar delivering the power to the plugs. Actually it will be even lower due to the fact that a discharging chemical battery will output lower and lower voltage as the stored charge is used up.
The system is VERY sensitive to the resistance of the Glow Plugs and ABSOLUTELY reliant on the change of resistance in them as they heat up.
I don't have access to a 24V system, so no data is given (can anyone help ?) And please let me know the missing part numbers (or give a link where I can find them).
Now about my problem -
My Australian 12V Super Glow system has been working fine, but last month the Pre Heating Timer got wet.
After scrubbing the corroded components on the circuit board with an old toothbrush soaked with metholated spirits and drying it, it still works, but the times are much too short (some resistors must have permanently changed their values).
Solution - add a resistor in series with the temperature sensing resistor to fool the computer into thinking it is colder.
4,700 ohms for ~ -5°C, 10,000 ohms for ~-10°C. You can switch it out for hot starts if you want, but the extra time it adds when hot is not so very much.
bye.
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