Glow plugs are gone at 540 hours

[2515R Dude]

Ok, checked the Chinese plugs i borrowed from my neighbor, Exactly like the ones which are sold on Amazon for Cummins A2300.
Connected directly to the tractor battery, they are getting hot BUT!!! they NEVER glow! Was holding them connecter for over 10 seconds. The wires already became hot.
Checked the original one which was still good. It starts glowing after approximately 3 seconds.

Now the question, should they glow or very hot is good enough?

 

[oldnslo]

All the glow plugs that I have checked glow cherry red within a few seconds. The purpose of glow plug is to ignite the fuel spray as it enters the combustion chamber. Getting hot will help heat the mix but not certain if would ignite it.

 

[2515R Dude]

All the glow plugs that I have checked glow cherry red within a few seconds. The purpose of glow plug is to ignite the fuel spray as it enters the combustion chamber. Getting hot will help heat the mix but not certain if would ignite it.

My thought also