79 cad deville no turnover

[rodldean]

Got in and turned key and turned over but no start. Turned key again and hot no sounds. All lights come on but nothing happens.

[TJ Hopland]

Giving the battery cable connections a very close inspection would be top on my list.   If you have an assistant have someone wiggle the cables at the battery while the key is being turned.    If there are any signs of corrosion best bet other than replacement would be to get a knife and cut away the rubber from around the terminal so you can properly clean and inspect it.  With the rubber gone that makes it easy to use a standard 9/16-18 bolt with a nut too.   You thread the bolt in till it fully seats in the battery then snug up the nut to hold the terminal in place. 

Also don't overlook the possibility that your battery suffered an internal failure and just can't put out enough power to run anything other than lights.  This is especially the case if the dash lights go out when you turn the key.  You could also try the headlights.  If the battery was that dead the headlights won't stay on very long.

When you turn the key do some of the dash lights change their states?   IF so that is an indicator that the switch is actually moving and probably working so next most likely place for an issue would be the park/neutral switch.   IF the lights don't change state you could have a mechanical issue in the column.  Try turning backwards to accessory and see if things like the radio works.   

If the accessory works and the lights change state then I would be back to the park neutral switch.  With your foot firmly on the brake and with the expectation of the car starting and trying to move try starting it with the shifter in various positions to see if there is a position where it will start.    You could also have a helper observe the reverse lights to see if they come on only when in R.  IF they are always on or never come on your switch could have completely fell apart.

The switch is on the steering column between the firewall and dash.   Its got quite a few wires and a couple vacuum hoses on it and there are a million other wires down there so its not a fun job.   Not sure if 79 is a year that is easy to find or not.  Some years for Cadillac are darn near impossible to find.    What fails on them is they are made up of a cast metal section that clamps to the steering column then a plastic section that contains the switches and valves.  There are little tabs that hold the plastic to the metal and they fail so the sections separate.