Okay this is not for my truck but y'all have always been so helpful and knowledgeable. My co-worker's car won't start but all the lights will work like the battery isn't dead. Is it probably the alt. or starter? Thanks for any help.

 

Check the Battery connection, need to be clean and tight. Starter takes a whole lot more power then lights...
Will it start with a jump?
Pull the Battery and have it tested...

 

Auto or Manual?

What year is the truck?