i have heard somewhere that you aren't supposed to hear the glow plugs clicking when turning the key on? My girlfriend's parents own a 1999 chevy sub 4x4 6.5td. it starts ok till its gets around 40degrees and below then it is a bare to start. are the glow plugs bad or is there nothing wrong?

 

There is a relay that's suppose to click when it closes. I'd say you got a few dead glow plugs. Fortunately, they are easy to check.

 

When were the last time they were changed?

 

 

i dont know the last time. They recently bought it from a guy in texas and it was owned by the military. well it's in the shop now cause the overdrive went out of it