Wiring Glow plugs on 93 7.3 idi to a momentary switch

Aleverflys

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I'm new here but I've used this site for many my idi problems and you guys always have some great stuff so I have an idea for my glow plus and want to see if anyone thinks it'll work or not. I'm thinking I could just wire a momentary switch to control the glow plugs versus having the timer. Reason being I replaced everything in the glow plug system and it still gives me issues, it will start off right with the wait light but then after about 5 or so second it starts to do the clicking, I'm fed up with it and I'm just seeing if you guys think it would work or if there's something special I would need to do. Has anyone else don't it?
 

ROCK HARVEY

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The switch will definitely work, others have done it and had success. What’s the condition of your glow plug wiring harness? If you’ve replaced the main components and your controller is still turning the plugs off after 5 seconds, the of old wiring might be causing resistance in the system.
 

Aleverflys

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Ok, it's still the factory harness, i had to rebuild the motor last January and it looked in good shape so I think it's fine but i hadnt thought to replace that, maybe I'll try that thanks!
 

franklin2

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Your 93 should have the controller on the back of the engine. Climb up in the engine compartment after you take a few things off to see it, and find the white wire bolted to the controller. Take the white wire off and tape it good so it doesn't short out. Then get a new piece of wire, put a end on it and bolt it were the white wire once lived. Run this new piece of wire through the firewall and to your momentary switch. On the other side of your switch run another wire from there to a good ground under the dash onto a metal bracket or something. That's all you have to do. When you ground that terminal where the white wire was, it activates the glow plug solenoid and glows the plugs as long as you hold the button.
 

Aleverflys

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Thanks guys, yeah I'll do that with the white one, I've had to replace that thing twice now, some how the grounding strap for the hood came off and it landed perfectly on that metal strip and it shorted it out, so I should be able to figure that out, thanks again!!
 

chillman88

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it will start off right with the wait light but then after about 5 or so second it starts to do the clicking

That's completely normal operation. The controller is designed to cycle the plugs a couple times after start to help with emissions.

I'm not going to talk you out of the pushbutton mod, but I wanted you to know it's not malfunctioning, it's operating as designed.
 

Aleverflys

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Well the fact that it is clicking after a few seconds and dimming my everything that's in when it does leads me to believe that it is not functioning correctly lol
 

ISPKI

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The controller and relay tend to either work correctly or not at all and generally speaking the only reason to bypass the controller with a momentary switch is if the controller stops functioning. Its a fairly expensive part for what it is. As others have said, the clicking after the "Wait to start" light shuts off is normal, its the controller keeping the plugs primed while it waits for you to crank the motor.

If the wait to start light is not staying on long enough to reliably start the truck, that usually means there is a resistance somewhere in the harness. The most common cause of this *I Think* is the plugs that connect to the glowplugs. The shielding on those tends to get brittle and crumble over time and that results in them getting dirty and creating higher resistance in the circuit. That resistance confuses the controller, causing it to cycle for less time.

Thing is, if the controller was cycling on for a few seconds and that didnt seem to be enough to start the truck, that usually means something else is wrong with the system. While bypassing with a momentary switch can get around the issues, it will also place more wear and tear on the remaining parts of the system as you cycle the plugs longer to overcome the issues. If you have higher resistance in the circuit, then you manually cycle your plugs longer, thus causing higher heat in the electrical connections and wearing everything out quicker and leading to more issues down the road.
 

franklin2

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The controller and relay tend to either work correctly or not at all and generally speaking the only reason to bypass the controller with a momentary switch is if the controller stops functioning. Its a fairly expensive part for what it is. As others have said, the clicking after the "Wait to start" light shuts off is normal, its the controller keeping the plugs primed while it waits for you to crank the motor.

If the wait to start light is not staying on long enough to reliably start the truck, that usually means there is a resistance somewhere in the harness. The most common cause of this *I Think* is the plugs that connect to the glowplugs. The shielding on those tends to get brittle and crumble over time and that results in them getting dirty and creating higher resistance in the circuit. That resistance confuses the controller, causing it to cycle for less time.

Thing is, if the controller was cycling on for a few seconds and that didnt seem to be enough to start the truck, that usually means something else is wrong with the system. While bypassing with a momentary switch can get around the issues, it will also place more wear and tear on the remaining parts of the system as you cycle the plugs longer to overcome the issues. If you have higher resistance in the circuit, then you manually cycle your plugs longer, thus causing higher heat in the electrical connections and wearing everything out quicker and leading to more issues down the road.
I disagree the manual switch puts more strain on the rest of the system. What it does is get the engine started. Yes the engine will smoke and throw a fit because some of the cylinders are not firing, but at least that can be a project you can work on later when you get time. If you need your truck to run, the factory controller can and will leave you sitting on a cold morning. It's not a matter of if it will leave you sitting, its a matter of when it will happen. Of course if you plug your truck in every night, you don't even need the glowplug system.
 

ISPKI

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I disagree the manual switch puts more strain on the rest of the system. What it does is get the engine started. Yes the engine will smoke and throw a fit because some of the cylinders are not firing, but at least that can be a project you can work on later when you get time. If you need your truck to run, the factory controller can and will leave you sitting on a cold morning. It's not a matter of if it will leave you sitting, its a matter of when it will happen. Of course if you plug your truck in every night, you don't even need the glowplug system.
With all due respect, you can disagree all you want but the fact is, in an electrical system and particularly the electrical system on these trucks, if the controller isnt priming as long as it should, that means there is a resistance buildup somewhere in the circuit that should remedied. Having bad or corroded or dirty connections is very common and installing a manual switch to overcome those bad connections increases the heat generated at those points which is really really bad in an electrical circuit. The extra heat caused by longer priming is going to damage connections eventually.

I didnt say that a manual switch itself will put more stress on the system, I am not implying that, I have rigged them up plenty of times, they work fine, but the rest of the system needs to be maintained as well. Installing a manual switch to overcome a circuit in poor condition is not good, it will lead to more severe failure. Like I said in my post, if the controller just outright fails, then a manual switch is fine, but if the controller is functioning but it just isnt priming as long as is needed, that usually means there are other issues that should be sorted out.

With regards to the controller leaving you stranded...The same can be said about a manual switch, theyre just cheaper and easier to replace. They are cheap devices and can also fail, at least the controller has some quality and consistency in them, whereas anyone can go grab a 5$ manual switch off amazon that could fry itself after a week. People have run the factory controller for decades and hundreds of thousands of miles without issues.
 

NeverHave-I-Ether

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I agree about the resistance in the circuit which isn't getting solved being an issue. That's reasonable. Also, about being stranded if the controller or switch fails. If you have a controller, you can take a jumper cable and bite the solenoid and hold it there for about 10s in a pinch. It'll spark when it's out on and take off, that's normal. If the switch fails, just pull the wire off and ground it for a cpl seconds to the steering column and your good to go. Just make sure to insulate it so it doesn't turn on.
 

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