stick_witch
Full Access Member
So, I did a manual bypass of the glow plug controller with a switch in the cab actuating the solenoid rather than the controller. But, I like and still want the functionality of the controller’s ability to detect the temp of the gp’s, when to turn them on and off, and the “wait to start” light telling me when the gp’s are warm enough to start the engine, so I wanted to find an alternate way to incorporate the controller without it actually “controlling” the gp’s and the solenoid. Here’s what I came up with.
First things first though, for those who don’t know already, you need to know a little bit about how the glow plug controller on these trucks work so here is a brief description and diagram.
The controller essentially uses the resistance of the glow plugs and gp harness to determine their temperature. Heat = more resistance, so as the resistance increases the controller assumes their temperature and cycles the wts light and gp’s on or off accordingly. First, the controller turns on the wts light and actuates the gp solenoid and gp’s as soon as it gets power from the ignition being turned to the “run” position. This initiates the pre-glow cycle, which warms the glow plugs up to starting temp. Once the glow plugs reach starting temp, which usually takes anywhere from 3-15 seconds, the controller turns off the wts light, but THE GLOW PLUGS STAY ON. This is now the after-glow cycle. Best way to see this is with a voltmeter to plug into your 12v socket in a truck with a stock gp system. Voltage drops to ~11.2v when you turn the key, indicating the gp’s are drawing power, and then it stays there even after the wts light goes out. It may creep up slowly to maybe ~11.4v because the gp’s draw less as they get warmer, but thats about it. The controller does not cycle the gp’s on and off during this time, which is what some will say, but is just not correct. If this were the case the voltage would vary and the solenoid would click on and off after the wts turns off and they just don’t on these trucks when functioning properly. This cycle lasts really anywhere under a minute, totally dependent on glow plug temperature. Then, the controller toggles the solenoid back off to keep them from burning out.
This is why people have a hard time starting their idi’s, because they try to crank it over right after the wts light goes out when the gp’s are due to run for a lot longer. Its also why many guys use their manual gp systems completely wrong. They will only run their glow plugs in cycles of no more than 15 seconds when they can run, and are supposed to run them longer and should be able to start their rig in one full cycle, rather than many small cycles. But, it’s impossible to determine how long you should cycle them after the pre-glow cycle because first the controller is bypassed so you have no way of knowing when the pre-glow cycle ends, or when the after-glow cycle ends, and second because it varies so greatly depending on temperature and how heat soaked the plugs are already, and if you can’t determine the temperature of the plugs, you can’t determine the duration. So, without some sure way of knowing, 15-20sec cycles are really the only safe answer, which is why that is what people do and say to do. Unless, of coarse, you use the controller to your advantage, which is what I intend to do.
So, what I ended up doing was this. If you refer to the diagram, the white wire from the controller is what toggles the solenoid via a gate inside the controller which is on the ground side of the gp circuit. So first I took this wire off its post on the solenoid (don’t cut it!), disconnecting the controller from the solenoid. Now the controller no longer controls the gp’s and solenoid actuation.
All that must be done now is to run a wire from the cab to the small ground post on the gp solenoid, plug it into a momentary switch in the dash, and run a ground wire from the switch to some place on the frame, to complete the low amp circuit of the gp solenoid, and then bam! You have a successful gp bypass.
Now to complete the “partial” bypass aspect of this I went this route. I installed 2 small indicator lights above the wts light in the cab.
The one on the left will be my “gp on” indicator, which will be hooked up to the gp harness post on the controller after the bus bar, and grounded in the cab to the frame to indicate that there is power coming from the gp solenoid to the gp harness. This is a great indicator if you’re solenoid goes out in the future since your solenoid will no longer do the infamous clicky clicky.
The light on the right will indicate the end of the after-glow cycle and that the controller is communicating to turn the gp’s off.
To do this you must first run a hot wire to the light in the cab. I chose to get this from the positive low amp post (small post) on the gp solenoid which gets its power from the ignition solenoid when the key is turned. Then you must run a wire from the light back to the controller via a separate wire to be mated with the white wire from the controller I was talking about earlier. This must be done because the white wire doesn’t emit power when the controller gate is closed, its merely a ground side gate that is grounded via the controller’s own ground wire. So you must first take power from someplace else, to create a functioning circuit to take advantage of the controller’s internal gate.
The wts light will keep its normal function, indicating the start and end of the pre-glow cycle. This light gets it’s info from the dark blue wire running from the controller to a black and green sealed plug and then to the cab. Do not cut this wire or unplug it if you want this function.
That’s essentially it, now you have a partial bypass in that you physically control the glow plugs, but you are also putting your controller to work for you. No more guessing and counting seconds in your head.
***IMPORTANT!
For this to work properly, you need to have your glow plug switch/button held on before you turn the ignition key and keep it held on for the remainder of the gp cycle. This tricks the controller that it is functioning normally (don’t worry, the gp’s won’t turn on unless the key is in the “run” position). If you don’t the wts in particular won’t function right. It will come on very briefly and then turn off and won’t come back on until you cycle the ignition again. The after-glow cycle light on the other hand should and seems to function regardless, but it’ll just blink on and off if you aren’t running glow plugs until it times out.
For this reason I use a switch that has an upward momentary latch and a downward locking latch. For morning cold starts I just flip the switch to the locking position before i turn the key, and then when my after-glow cycle light goes out I promptly flip it off. And then when I just need a little bit of glow for any reason I hold the momentary switch on till the wts light goes out and then I turn the key.
If you do use a normal switch, make sure you monitor the “gp on” light so you don’t accidentally leave the gp’s on. Also its good to monitor to make sure your solenoid isn’t sticking for some reason and burning up your gp’s.
First things first though, for those who don’t know already, you need to know a little bit about how the glow plug controller on these trucks work so here is a brief description and diagram.
You must be registered for see images attach
The controller essentially uses the resistance of the glow plugs and gp harness to determine their temperature. Heat = more resistance, so as the resistance increases the controller assumes their temperature and cycles the wts light and gp’s on or off accordingly. First, the controller turns on the wts light and actuates the gp solenoid and gp’s as soon as it gets power from the ignition being turned to the “run” position. This initiates the pre-glow cycle, which warms the glow plugs up to starting temp. Once the glow plugs reach starting temp, which usually takes anywhere from 3-15 seconds, the controller turns off the wts light, but THE GLOW PLUGS STAY ON. This is now the after-glow cycle. Best way to see this is with a voltmeter to plug into your 12v socket in a truck with a stock gp system. Voltage drops to ~11.2v when you turn the key, indicating the gp’s are drawing power, and then it stays there even after the wts light goes out. It may creep up slowly to maybe ~11.4v because the gp’s draw less as they get warmer, but thats about it. The controller does not cycle the gp’s on and off during this time, which is what some will say, but is just not correct. If this were the case the voltage would vary and the solenoid would click on and off after the wts turns off and they just don’t on these trucks when functioning properly. This cycle lasts really anywhere under a minute, totally dependent on glow plug temperature. Then, the controller toggles the solenoid back off to keep them from burning out.
This is why people have a hard time starting their idi’s, because they try to crank it over right after the wts light goes out when the gp’s are due to run for a lot longer. Its also why many guys use their manual gp systems completely wrong. They will only run their glow plugs in cycles of no more than 15 seconds when they can run, and are supposed to run them longer and should be able to start their rig in one full cycle, rather than many small cycles. But, it’s impossible to determine how long you should cycle them after the pre-glow cycle because first the controller is bypassed so you have no way of knowing when the pre-glow cycle ends, or when the after-glow cycle ends, and second because it varies so greatly depending on temperature and how heat soaked the plugs are already, and if you can’t determine the temperature of the plugs, you can’t determine the duration. So, without some sure way of knowing, 15-20sec cycles are really the only safe answer, which is why that is what people do and say to do. Unless, of coarse, you use the controller to your advantage, which is what I intend to do.
So, what I ended up doing was this. If you refer to the diagram, the white wire from the controller is what toggles the solenoid via a gate inside the controller which is on the ground side of the gp circuit. So first I took this wire off its post on the solenoid (don’t cut it!), disconnecting the controller from the solenoid. Now the controller no longer controls the gp’s and solenoid actuation.
All that must be done now is to run a wire from the cab to the small ground post on the gp solenoid, plug it into a momentary switch in the dash, and run a ground wire from the switch to some place on the frame, to complete the low amp circuit of the gp solenoid, and then bam! You have a successful gp bypass.
Now to complete the “partial” bypass aspect of this I went this route. I installed 2 small indicator lights above the wts light in the cab.
You must be registered for see images attach
The one on the left will be my “gp on” indicator, which will be hooked up to the gp harness post on the controller after the bus bar, and grounded in the cab to the frame to indicate that there is power coming from the gp solenoid to the gp harness. This is a great indicator if you’re solenoid goes out in the future since your solenoid will no longer do the infamous clicky clicky.
The light on the right will indicate the end of the after-glow cycle and that the controller is communicating to turn the gp’s off.
To do this you must first run a hot wire to the light in the cab. I chose to get this from the positive low amp post (small post) on the gp solenoid which gets its power from the ignition solenoid when the key is turned. Then you must run a wire from the light back to the controller via a separate wire to be mated with the white wire from the controller I was talking about earlier. This must be done because the white wire doesn’t emit power when the controller gate is closed, its merely a ground side gate that is grounded via the controller’s own ground wire. So you must first take power from someplace else, to create a functioning circuit to take advantage of the controller’s internal gate.
The wts light will keep its normal function, indicating the start and end of the pre-glow cycle. This light gets it’s info from the dark blue wire running from the controller to a black and green sealed plug and then to the cab. Do not cut this wire or unplug it if you want this function.
That’s essentially it, now you have a partial bypass in that you physically control the glow plugs, but you are also putting your controller to work for you. No more guessing and counting seconds in your head.
You must be registered for see images attach
***IMPORTANT!
For this to work properly, you need to have your glow plug switch/button held on before you turn the ignition key and keep it held on for the remainder of the gp cycle. This tricks the controller that it is functioning normally (don’t worry, the gp’s won’t turn on unless the key is in the “run” position). If you don’t the wts in particular won’t function right. It will come on very briefly and then turn off and won’t come back on until you cycle the ignition again. The after-glow cycle light on the other hand should and seems to function regardless, but it’ll just blink on and off if you aren’t running glow plugs until it times out.
For this reason I use a switch that has an upward momentary latch and a downward locking latch. For morning cold starts I just flip the switch to the locking position before i turn the key, and then when my after-glow cycle light goes out I promptly flip it off. And then when I just need a little bit of glow for any reason I hold the momentary switch on till the wts light goes out and then I turn the key.
If you do use a normal switch, make sure you monitor the “gp on” light so you don’t accidentally leave the gp’s on. Also its good to monitor to make sure your solenoid isn’t sticking for some reason and burning up your gp’s.
You must be registered for see images attach
You must be registered for see images attach
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