Help identifying a part please. (1 Viewer)

[Semiazai]

While the Wilson switch sounds intriguing I have to ask if the potentially offending timer also controls the dash glow light, because if it does then it appears to be working. I know this thread started about identifying parts, but at this point I'm curious if anyone watching it can help me with a related question. In the picture I'm attaching I hold the plug that connects to the glow system and if it is not plugged it the multimeter reads 6.5v in the powered end, but if I plug it in I get 0v out the other side. I've taken the ends apart and cleaned them, but to no avail. Any thoughts?

Drive train and wiring: Canadian 1984 BJ60
Body and frame: US 1987 FJ60

 

[Fey1]

The connector you are holding is part of the a current measurement shunt. Not sure what the voltage issue is that you are having. What end do you consider the 'power end'? I suspect that what you are seeing is normal. The part that is important here is the shunt itself.

If you consider the end of the wires that lead to the timer control relay, the 'power end' I believe that is the incorrect assessment. It is not providing any power. This is an input from the shunt. When the glowplugs are active, a voltage is developed across the shunt. This voltage is then measured by the timer control. At the current provided by the timer control, the 6.5V is basically shorted out by the nearly zero ohm shunt.

This of course leads me to my question: Just why is Toyota interested in the glow plug current anyway? This aspect of the glow system is poorly explained (as in, not at all) in the engine manual. It goes into great detail about the water temperature sensor and everything else, but not a dicky bird about the current measurement. Does anyone out there have an answer?

 

[bj40green]

While the Wilson switch sounds intriguing I have to ask if the potentially offending timer also controls the dash glow light, because if it does then it appears to be working. I know this thread started about identifying parts, but at this point I'm curious if anyone watching it can help me with a related question. In the picture I'm attaching I hold the plug that connects to the glow system and if it is not plugged it the multimeter reads 6.5v in the powered end, but if I plug it in I get 0v out the other side. I've taken the ends apart and cleaned them, but to no avail. Any thoughts?View attachment 912118


Drive train and wiring: Canadian 1984 BJ60
Body and frame: US 1987 FJ60

Yes, the glow indicator light on the dash is part of the glow system. However, the way it indicates is still a puzzle.

The connector you are holding is part of the a current measurement shunt. Not sure what the voltage issue is that you are having. What end do you consider the 'power end'? I suspect that what you are seeing is normal. The part that is important here is the shunt itself.

If you consider the end of the wires that lead to the timer control relay, the 'power end' I believe that is the incorrect assessment. It is not providing any power. This is an input from the shunt. When the glowplugs are active, a voltage is developed across the shunt. This voltage is then measured by the timer control. At the current provided by the timer control, the 6.5V is basically shorted out by the nearly zero ohm shunt.

This of course leads me to my question: Just why is Toyota interested in the glow plug current anyway? This aspect of the glow system is poorly explained (as in, not at all) in the engine manual. It goes into great detail about the water temperature sensor and everything else, but not a dicky bird about the current measurement. Does anyone out there have an answer?

This a basic diagram of a super glow system. Not specifically yours but for explanation purposes it will do.
Things to understand: The glow plugs are 6V.
The Glow Plug Current Sensor is a heat dependent resistor. In other words; the ohm value goes up when it gets hot due to the current flow.

We have to start somewhere so we start in a "cold" situation. At this point the water thermo sensor plays no role.
- Turn the key to the "on" (IGN) position.
No.1 Glow Plug Relay (Pre Heat) will be activated and sends 12V via the Glow Plug Current Sensor to the 6V Glow Plugs.
The Glow Plug Current Sensor will heat up and increase resistance. This creates a voltage (drop) over the sensor which will be noticed by the Pre-heating Timer. When this voltage is .....? Volts the Glow Plug Indicator light goes "off" which indicates that you can start the engine.
- Turn the key to the "start" position and crank the engine.
The voltage on pin #9 (Lamp terminal on the Voltage Regulator) is 0Volts at this point and is 12V when the engine runs. So this tells the Pre-heating timer that the engine is running.
Ahaaaa thinks the timer..... engine is running but the water temperature is cold so I have to activate the No.2 (After Glow) Glow Plug Relay.
This relay sends 12V via the Glow Plug Resistor (to lower the voltage) to the Glow Plug Current Sensor and from there to the 6V glow plugs.
Because of the lowered voltage by the Glow Plug Resistor, the Glow Plug Current Sensor plays no longer a role.
This After Glow process is active until the Water Temperature Sensor tells the Pre-heating timer to stop the After Glow (which can be as long as 180 seconds).

Clear as MUD??????

Rudi

 

[Dieseler]

Nice play by play Rudi I will have to file this for those days I have a brain fart on why my system is not responding.

 

[Fey1]

Thanks Rudi!

So it sounds to me like the current sense resistor is a rudimentary indication that the glow plugs should be 'at temperature' once the voltage across the shunt reaches a specific voltage. (any idea what this voltage should be?). I see from the manual charts that the light goes out long before the preheat relay drops out (typically about 1/10 the time of the relay itself). These same charts indicate that the water temperature does have an effect on the preheat time.

Any idea why the afterglow relay is still energized basically permanently, regardless of the water temperature. (I have check the temperature sender all the way back to the timer relay).

Cheers!

 

[bj40green]

Here is a BIG picture with some more explanation from a FSM manual for L engines.

Hope this helps in understanding the super glow system.

Rudi

Note: This picture is actually over 600KB. This forum reduces it to "fit screen".
If you want the original, send me your email address.

 

[bj40green]

.....any idea what this voltage should be?

Any idea why the afterglow relay is still energized basically permanently, regardless of the water temperature.

I assume that the voltage ACROSS the GPCS is 6Volts. So 12V on top from the relay and 6V on the other side to the glow plugs.

The after glow cycle should stop after 180 seconds. If not..... the Water Temperature Sensor is not OEM or out of spec, The Pre-heat Timer is defective or the after glow relay is defective (stuck contacts).

Rudi