Sounds like at the time you experienced this failure that it's a failed glow plug controller
relay = when the battery was quickly drained the secondary contacts (the high amperage part that connects the two large terminals) were stuck together inside the relay drawing full current from the batteries and being stuck it would not disconnect, very quickly draining the batteries, probably burning out at least 2-3 glow plugs, probably ALL of them if they are not Motorcraft/Beru ZD9 glow plugs.
That is what causes the clicking noises you hear = some burnt out glow plugs. The sizzling noise sounds like pitted out secondary contacts (the high current contacts) inside of the GP controller RELAY. Motorcraft/Beru ZD9s which are the
only glow plugs you should be using can actually accommodate a GP controller
relay failure like this and still be good but it sounds like whatever glow plugs you have in there didn't survive.
If the GP controller relay did stick you should be able to see the evidence of substantial overheating of the metal ribbon resister connected to the negative OUTPUT side of the GP controller
relay. The current goes through that resister to the glow plugs. Rather than being a bright steel color it's going
to be discolored, brown or even look like it's been in a fire. If the original plastic cover was over the controller it will be burnt through/melted near the resistor.
There is a fair chance that the GP Controller itself is still good, but your electrical system related to it
is messed up - it was messed up before this happened so I guess you'll eventually find out if the controller is still good if you try to fix it
right.
From my truck in July 2017:
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To answer one of your questions, the correct GP controller relay is the brown one on the left in the photo you posted.
One of the probable causes for the GP Controller Relay failure in my truck was a bad Hood to Cowl Seal which allowed rainwater to fall into the vicinity of and on top of the controller cover and eventually the moisture got into the relay, probably from around the posts. This photo shows quite a lot of rust on the bottom side of the relay which tends to support the leaking cowl seal explanation. I'll cut that relay open today and post a photo of the inside.
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Will replacing the relay and glow plugs fix your main problem? MAYBE but only partly or MAYBE NOT.
1) Apparently there was a problem with the GP controller
or more likely it's wiring or glow plugs and a bypass of that problem was attempted by installing a push button. There is only one right way to
fix a solid state GP controller issue and that is to
fix it the right way which is actually very simple so then you will have all of the advantages and benefits that the controller provides including reduced smoke and emissions during start and warm up. You can't duplicate what the controller does with a push button.
2) Apparently there was a new
or continuing electrical problem AFTER the push button was installed so you installed a 300 Amp Relay to disconnect and isolate the electrical system
and the electrical problem(s) from the batteries when you are finished driving the truck each time. That didn't fix the problems, it only shuts them off when you turn the key off and shut the truck down and it turns the problems back on again when you energize that relay and start the truck again.
Usually a problem that isn't fixed will lead to another problem, then another and so on... sometimes very expensive problems result because a simple problem was neglected. Apparently there was/is a short somewhere drawing down the batteries? So what does that lead to next? Burnt wires or components?
You can handle this however you want but I think the
BEST solution is to install and wire the solid state gp controller as it was from the factory. I think that most people would be happiest with that set up.