Super Glow - explained (1 Viewer)

[LevinBR]

That is how the sysytem is supposed to work. If you leave the key on and wait you will here two clicks of relays. The first is the 24 volts kicking off and the seconde when the whole system shuts off. If you start right away after the seconde click you timer will "re-glow"at low voltage for a while before turning off again. Hypothetically if you were to leave the key on for a really long time and the system clicked off, but had a warm enough engine to start without glow, you will see that the system would give you the after glow again for a bit, after the engine starts. After about 20 to 30 seconds (ish gussing here never really looked it up or timed it) the after glow will stop. If you real curious you can connect a multi meter to the glow plug bar and watch the voltages change during the start and you'll see when and where everything happens.


Looking back on previous post, I was having some trouble a few years ago, if you don't use Toyota or NGK glow plugs the timer doesn't seem to work right. Or let me rephrase, if you use VSP 14 volt plugs the timer doesn't work right and stays on all the time and you cook the plugs.

@Bandit_guy thanks so much for the reply. That makes sense, I was hoping it was the case that it's normal.

When I first got the truck last summer, a previous owner had put 23V plugs in. I eventually learned about the Superglow system and swapped them for some 14V Bosch plugs (part# 0250202076, equivalent to Toyota 19850-68060). They work well, seemingly as designed, and haven't burned up yet! Every part lookup site I've used has steered me wrong, so this thread and the one by lostmarbles have been my best resources.

 

[Bas Zuidberg]

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!

View attachment 639687

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.
View attachment 639687

Hi there. Great write up. I hope you are able to help me. My joining plate is broken and I can’t find this part anywhere on the interweb. Do you know if this is ‘just’ a piece of metal connecting the tips of the 2 resistors, or if it has another function as well. In other words, can I make a new connection piece myself? Been having issues with starting (need to glow twice or three times) and it might be due to bad connection due to joining plate being broken. Thanks!

 

[Bandit_guy]

Yes you can make it yourself with steel plate, or large wire. It's high current so you need a something that will be able to handle it. When you take it apart you will see it's nothing too special.

 

[Bas Zuidberg]

Yes you can make it yourself with steel plate, or large wire. It's high current so you need a something that will be able to handle it. When you take it apart you will see it's nothing too special.

Thanks. I have a related question that I haven't been able to find an answer for. What do the 2 resistors do that are mounted on the intake
manifold? it would appear that they heat up something inside the manifold? or do they just provide the resistance needed to reduce the amps going to the glow plugs for the afterglow? hope you can enlighten me! Cheers

 

[Bandit_guy]

They warm up the air in you manifold, just some more glow plugs. I'm not a 2H engine guy so I don't know if they are used in the whole cycle, or just during after glow, (I would assume the whole time). It's because the manifold is so big that cold air would hinder the job of the plugs in the cylinder on a cold start up. You can check with a multi meter to see if there is a voltage drop and when they turn off completely.

 

[tlaporte]

I ran into the same problem with this part on my HJ47. I had a friend who is handy with CAD, etc., to make a quick model and we had OSHcut.com make a bunch of copies (minus the screw).

I’d be happy to send you one for the cost of shipping, @Bas Zuidberg.

 

[Bas Zuidberg]

I ran into the same problem with this part on my HJ47. I had a friend who is handy with CAD, etc., to make a quick model and we had OSHcut.com make a bunch of copies (minus the screw).

View attachment 3636594

I’d be happy to send you one for the cost of shipping, @Bas Zuidberg.

That is very kind of you @tlaporte ! Have sent PM