Part of the ether starting system on these trucks is a thermostatic switch that is located on the passenger side of the engine at the rear. To the way I understand it, the switch is closed below 50°F to allow the ether system a path to ground through the threads of the switch into the engine block. Whether it is a normally open or normally closed switch, I'm not sure.
The TM says to remove this component when draining the coolant from the truck. Recently, when I was servicing my truck, I did not drain the coolant from that location and then later thought better of it and went ahead and removed the switch like it says. I was able to get at least another gallon of coolant out, so I figure it was worthwhile.
The switch on my truck did not leak, but was fairly bad looking. I don't use the ether system here in Arizona - My truck did not come with an ether bottle and I have not replaced it, but since I was servicing the cooling system, I figured I would replace the switch if it wasn't too expensive. There are no part numbers or stampings of any kind on the switch I removed, and the TM says that it is a Phillips & Temro P/N 321028-01. (NSN 5930-01-127-2113) When you look up 5930-01-127-2113, it says "Cancelled without replacement." Oh well. I suspect it is probably nearly the same as any other truck ether start thermostat switch, so a replacement is likely easily found at a truck parts supply house.
A while back, M920 (Soni) told me to remove the fender to work on the alternator rather than to try and squeeze between the air intake tube and the fender. It is simple to remove - one Amphenol connector and 8 bolts to take out. It is a bit heavy for one person to move by themselves.
So three lessons for me, here -
1. Remove the ether thermostat switch to completely drain the truck.
2. The ether start system will not function above 50°F.
3. The lower sides of the engine are a lot easier to access if you remove the fenders.
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