Rule of thumb is that a good non-open glow plug will have a resistance value of 0.8-1.0 ohhms of resistance.
65
The controller, glow plugs and batteries have been replaced and the 7.3 diesel is still hard to start in temperatures below 65 degrees. Can the heating duration of the glow plugs be lengthed or bi-passed to manually time their heating? If this is an indirect injected diesel I would not recommend bypassing the controller as it will more than likely burn out the glow plugs, swell the tips of them and make removing them to replace them impossible without head removal. The plugs can stay on no longer than 12 seconds max in the absolute coldest weather. If you are having starting problems maybe you have a fuel leak on the low pressure side that is introducing air to the system, or maybe the pump is sticky. For this try a lubricity additive with cetane booster like PowerService. Power Strokes have a different type of glow plug that can handle more time. They stay on a max of 180 sec. even though the wait to start light goes out the glow plugs do in fact stay on. They also benefit from the above additive. Also the glow plug system on a power stroke has a lot of variables like under valve cover harnesses and valve cover gaskets that can create resistance and cause the glow plugs not to work properly.
.035
NGK BR8ECM
65 degrees
65
6.5 is one-tenth as much as 65.
65% of 980 = 637
65 Miles = 104.6km
No, the voltage difference is too high.
NGK - BPR4EY AUTOLITE - 65
65*1.6=104 kph