I will take a picture tomorrow and post it up. So that red wire is connected to the battery input and the relay signal post which would normally have received voltage from the ignition switch? The writeup I followed just puts a momentary switch on the ground wire but your setup seems to make much more sense as it rules out the ignition switch and turns the WTS light into a sort of tester to show you that it is sending signal to the gps.
Yes there is a red wire (doesn't have to be red
) that is about 3 inches long or so - just a small guy. One big loop crimped on one end and a little loop terminal crimped on the other so that power is provided from relay input (which is always hot) to the relay signal post. Then just run a wire directly from the ground post to the switch, then ground the other switchs' post. This bypasses the ignition switch entirely - I like to glow my plugs without having to have the keys in and in the run position. Yes using the WTS light on the relay output side will tell you if the relay is working. No light means either the light burnt out or your relay is bad or there is a problem with the wiring.
Originally (meaning the automated system) the ignition switch sent a signal to the glow plug controller, which sent a signal for several seconds to the relay signal post. There was another wire that came from the controller to turn on the WTS light. Real fun diagnosing something when every time to switch the key on and off it tries to glow 'em. And if one glowplug was dead the controller freaks out turning the relay on and off repeatedly. Multiple plugs out you'd get stranded. You can tell when they start failing with manual-pushbutton-control as it just takes a little longer to get started, starts rougher depending on how many are out and cleans up as it warms. But you won't get stranded near as easy too. I had an idea to test for glowplug health but that was with a custom harness...
You can also do all of this stuff similarly on the starter relay - same principles. I have two switches for the starter to help with diagnosing and whatnot. I have a switch right on the relay that is a toggle switch - if I ever need to be under the hood and cranking over I can do it alone now. And I have a pushbutton starter next to the glowplugs. The ford ignition system WILL break if you use the keys to crank the engine over. There is a cast piece of junk in the steering column that gives up after years and could leave you stranded if you don't know how to bypass it (and break the steering lock)...
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Here is my switch panel on one side - the black one was a test run to see how I like it. Metal was too thin, I cut up an old computer case panel from a cheap computer... After I liked everything and the function a year or so later I used aluminum. The buttons are called bulgin switches, also known as vandal resistant switches. They are meant to be very reliable and durable. You can get momentary and toggle buttons in this type, although I strongly recommend momentary so someone else doesn't accidentally leave your plugs on.
The only thing I had to move was the tank selector switch. How often do you swap tanks, I bet less often than you start the truck up! I also removed the WTS light and put in another plate in place of it to switch off my stereo and tank selector switch. Some people sacrifice their change cubby but I like that space and the rest of those things were junk on here
I use an LED for my "WTS" light, next to the glowplug button. The toggle switches are for fog light and reverse light, the reverse having a blinking LED to help prevent leaving them on accidentally