Super Glow - explained

Joined
Apr 27, 2009
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Newcastle, Australia
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 :eek: #1 has since been replaced with the correct plug. Diagram updated too! ;)

super glow parts.jpg

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.
super glow parts.jpg
 
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Joined
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Sorry. I only got as far as reading "8.5V plugs".

Superglow should be running 6V plugs as far as I'm aware.

:beer:

1988 12 volt HJ6# with superglow = Toyota Plug Part Number 19850-68051 (6volt)

(VSP PT146, Bosch GPT214, Denso DG220 etc)
 
Joined
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I just checked toyodiy, and also based on roodogs online shop, there are at least 3 types of glow plugs on the HJ60:

Early, non-super glow:
19850 PLUG ASSY, GLOW
19850-68010 BOOST VENTILATOR-GV=12V-10.5V, *12V-10.5V

Late, super glow:
19850 PLUG ASSY, GLOW
19850-68050 BOOST VENTILATOR-GV=12V-6V, *12V-6V

1988 on:
19850 PLUG ASSY, GLOW
19850-64031 BOOST VENTILATOR-GV=12V-11V
19850-68051 BOOST VENTILATOR-GV=12V-6V

And none of them 8.5, indeed, it seems.

But very interesting description and calculations.
 
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Slightly off topic but the 8.5 v plugs appear on the 2H in HJ47 configuration, pre-October 1982, pre-Superglow. The difference in voltage in the early HJ60 trucks is that the HJ60 uses a glow timer while the HJ47 uses a glow controller coil on the dash, which provides greater resistance in the circuit.
 
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Hi Bgennette

I want to say right now that it is people such as yourself (who like to delve into the intricate workings of their cruisers) that carry us all forward in our collective knowledge.

And I want to say also that I'm really interested in your cruiser too!

Your signature line says it is an HJ62? Well there is so little info here on MUD about those that many of us (well certainly "meezies" anyway) are really confused about what engine it is supposed to have.

Ooooops. I should make it clear that I don't visit the 60-series forum here on ih8mud .... No doubt everyone there knows all about HJ61 and HJ62 models...:eek:

But even those brilliant people in the UK seem to be confused (and that's saying something eh?):
60 Series - HELLO FROM GEORGIA! hj62 • Land Cruiser Club and Forum

My searches just now show people claiming they have an HJ62 fitted with a 12HT engine and some even saying they have F-series petrol engines in theirs!!!!:eek: .... and all factory-fitted too.

(Incidentally right now I refuse to accept that an F-series petrol engine was ever factory-fitted to an H-series wagon ... but I know I can eventually be swayed to relinguish many of my longheld beliefs.)

Anyway .....The main thing that strikes me in your first post now is the low-ness of your current values in your calculations.

You say your glow plugs have an initial surge (cold start) of only around 15A total yet my engine .... that has 2 less cylinders/plugs and takes far longer to preheat ..... draws about 100 amperes (dropping to between 30 and 40 amperes once the plugs are glowing at full tit).

Have you seen this thread in your searching:
https://forum.ih8mud.com/diesel-tec...gs-should-i-running-b-2b-3b-h-2h-diesels.html

From it, you can see that I like getting deep into these things too. (But in my old age it can take me a while to get back up-to-speed on a topic that I've left for a while so you may need to be patient.)

With your permission I'd like to drop your first post into that thread with a link to this thread. Would that be OK? (I think your studies and findings would add significantly to our bank of knowledge on Superglow and it's nice to have a lot of it in one place.)

And by the way ...

I think it is wise to always replace glowplugs as a matched set (and never replace just one by itself). That's because I think they must have identical resistance-characteristics in order to glow uniformly. And failure to glow uniformly will tend to promote smokey/lumpy firing on start-up.

Mismatched plugs can also promote plug failure.

:beer:

Edit..... Just found out that the "which plugs thread" (linked above) is CLOSED and I can't add to it anyway. That's odd. I've haven't struck a closed thread before. Maybe a new thing? :meh:
 
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Joined
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I don't think there is such a thing as an HJ62. That's just what some people call an HJ60 with square headlights.
They only change the number for a different engine. HJ60 = 2H, HJ61 = 12HT.
FJ60 = 2F, FJ62 = 3F.
If a square headlight HJ60 is an HJ62, what on earth is a square headlight HJ61? An HJ63?

And I'm fairly certain an 'HJ62' VIN number starts with HJ60.
And also in official publications, such as the FSM, there is no HJ62.
 
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What is a xJ62 ?

Darthvincor is pretty right, the 62 is a tweaked 60 introduced in may 1988.
The differences include the curved dashtop, the more integrated grab bar over the glovebox, the 4 rectangular headlights and a heap of small 'improvements' that nobody notices. It appears to be mostly marketing hype to revive sales for a nearly 10 year old design.
The 61 got the changes too, but kept its name. ???

Lostmarbles - the closed thread is why I needed a new place for the description.

bye.
 
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BreckenridgeCruiser

I break things.
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I always thought it was as follows:

US:
FJ60: Manual, Carbed 2f, Round, manual everything
Fj62: Auto, 3fe, Square, lots of electronics

NonUSA:
HJ60: Manual, 2H, Round, Manual
Late HJ60: Auto, 2H, Round, Electronics
Late Late HJ60: Auto, 2H, Square, Electronics
Early HJ61: Japan only. Auto, 12HT, Round, High Roof, Electronics
Late HJ61: Japan only. *Auto, 12HT, Square, High Roof, Electronics

my .02 cents

K
 
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Joined
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Darthvincor is pretty right, the 62 is a tweaked 60 introduced in may 1988.
The differences include the curved dashtop, the more integrated grab bar over the glovebox, the 4 rectangular headlights and a heap of small 'improvements' that nobody notices. It appears to be mostly marketing hype to revive sales for a nearly 10 year old design.
The 61 got the changes too, but kept its name. ???

Lostmarbles - the closed thread is why I needed a new place for the description.

bye.

Yeah, it's strange.

I wonder why the thread is closed.

I think it would also be useful to have a thread about different brands of glow plugs, and people's experiences with them.
 
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I've read this thread at least ten times now and I'm trying to figure out if I have a problem with my rig. How long should the after start glow last ? What tells the timer to shut off, the internal circuitry (max time) or input from the water temp sensor ? It's around around -10C right now and after it's started for at least 5 minutes I still see 10 volts on the plugs. My rig is canadian spec BJ42 so it has 24 volt super glow.
 
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After some more research, Thanks Rudi for the Diagram, I see that my controller may be back up and running fine. I had a blown capacitor which I replaced and then the normal operation scared me.

On my 24 volt rig aside from the voltage numbers for the plugs the system seems to run identical to the 12 volt.

On initial start cold plugs, the combined plugs at 0.9 ohms.

Turn the key to IG and the bus bar receives 24 volts for a time determined by the water temp sensor. Same as the chart posted above warm no time at all cold up to 20 seconds.

The indicator light will click off at 3 or 4 seconds, (6 to 10 or the colder days -15C ) but 24 volts gets fed to the bus bar until the current sensor sees that there is less more current flowing. Then it clicks off the No. 1 relay and max power to the bus bar is half the total system voltage available. Just as previously explained power minus what's not drawn from the battery accessoires ect. after a start I see 10 volts for at least 10 minutes then it will climb to 11.5 volts slower if I have all accessories running.

Here's where I'm a bit shaky please correct me if I'm wrong. As the glow plugs get hot they will increase the resistance and the current will be minimal on the buss bar but there will always be voltage (Half of the system) This increase of resistance is what controls the afterglow process and having only the low voltage you can't burn out the plugs.
 
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Looks like I found out the expensive way, the bus bar must indicate zero or you burn out four new plugs. I found where the power is coming from. The glow plug timer. I have to figure out how to fix this. Why doesn't the timer shut off ?
 
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....Here's where I'm a bit shaky please correct me if I'm wrong. As the glow plugs get hot they will increase the resistance and the current will be minimal on the buss bar but there will always be voltage (Half of the system) This increase of resistance is what controls the afterglow process and having only the low voltage you can't burn out the plugs.

Yes. The resistance of a glowplug does increase significantly as it gets hot and this lowers the preheat current flow accordingly.

And if the voltage spec of a glowplug is never exceeded (for example if 14V is not exceeded for a 14V plug) then it should be able to glow a very long time without burning out.


Looks like I found out the expensive way, the bus bar must indicate zero or you burn out four new plugs. I found where the power is coming from. The glow plug timer. I have to figure out how to fix this. Why doesn't the timer shut off ?

Yes I'm pretty sure you're right in that afterglow should be limited in duration and should never remain on permanently while an engine is running.

Since I don't have superglow on my BJ40 however, I don't know (or can't remember ... which is the same thing) offhand what terminates the after glow (ie. which sensor .. if any) or what afterglow duration you should expect.

Of course once the engine is started, your system voltage increases roughly from around 12V to as much as 14.7V for a 12V system or from say 24 to 29V for a 24V system and I'm picking that perhaps, if afterglow is stuck on, once the battery/batteries have recovered their charge (that's been expended somewhat during cranking etc) the busbar voltage could rise slightly beyond your plug spec (promoting plug failure).

Regardless of the effect of your alternator though, running around with plugs that are permanently glowing is bound to shorten their lifespan.

:beer:

(Very likely this is simply a timer fault though ... as you are concluding.)
 
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i had a problem with my glow system in my nz spec bj74 eating the batterys down to about 8v from 24v within about 30 seconds of starting the vehicle, finaly found the problem today :)
it turned out to be the glow water temp sensor was broken in half, fixed it buy joining the to terminals with some solder... problem solved
 
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My super glow 24V system seems to stop heating the cylinders after about 30 seconds if I do not start to crank the engine. Is that normal? Or should it "glow" for as long as I have the key in the preheat position? I'll leave the ignition in the pre-heat position as I scrape ice / snow off the car, then when I get in and crank, the engine struggles to start.
 
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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.
 

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