Starter, battery, or something else?

I have a 2003 Nissan a Frontier that won’t start. I go out in the morning, turn the key, and nothing… no clicks, no sound at all. All lights work fine, radio works, all interior lights work and don’t even dim when I turn the key. Searching these forums, I thought it might be the starter so I got a new starter about a month ago. Seemed to work fine until a few days ago when it started doing it again. When I go back out a couple hours later, sometimes it’ll start up perfect, like nothing happened, sometimes it won’t. Somebody suggested I shift it to neutral and try starting it, so that’s what I just did this morning and it worked… Tried starting it for an hour and got nothing, shifted it to neutral and it started right up. Turned it off, shifted it to park and tried starting it again. Started right up! Any ideas? Starter is 1 month old, so it’s hard to believe it would be that. Battery weak or loose terminals? Well if it were that, why would it start right up when shifted to neutral? I don’t know how long the “shifting to neutral” trick will work so I really want to get the problem solved instead of relying on a work-around.

There is a switch in the gear selector that prevents starting unless the selector is in Park or Neutral. It sounds like the contacts in the Park position have become unreliable but the in the Neutral position the switch works fine…The exact location and difficulty in changing these switches varies from car to car and model to model…But they are usually part of the gear-shift selector…

The neutral safety switch will be bolted to the side of the transmission. It will have 2 bolts holding it on. Some cars its a pain to get at but it sounds like the contacts for park are worn out. The switch is adjustable so if you replace it you will have to adjust it so it works in both park and neutral.

Ok, so am I looking at the actual shifter inside the car or am I looking at the transmission under the car?

Battery connections are the first place to begin when you have a “No start” situation. Even
if you have a new battery, if the connections are loose, dirty or corroded, you will not be
allowing the full flow of current to pass thru the connections. The connection may be
enough to turn on the lights, but not enough for the huge flow that is needed to operate the
starter. This is where many people say that they know the battery is good….”because the
lights come on”. This is no more a battery test than licking a 9volt battery. It only tells you that there is electricity…not how many volts or the amperage that flows from the battery.
Jump starting may have wiggled the terminal just enough to allow the current to pass and start the engine, but tomorrow you have the same problem.

First remove the cables from the battery and use a wire brush to remove any corrosion and dirt from the battery posts and the cable terminals. There is a tool with a round wire brush for this purpose, found at any auto parts store for less than $10 http://shop.advanceautoparts.com/p/kd-tools-terminal-battery-brush-kdt201/25980576-P?searchTerm=terminal+brush.
Before connecting the cables, apply a coating of di-electric grease to the battery posts this will keep oxygen away from the connection so that it will not corrode as fast.

It is just as important that the other end of the cables also have a clean connection. Remove the positive cable from the battery again so that you do not short anything out. Follow both cables to their far ends, remove this connection and wire brush the connection and the cable terminal clean and retighten these connections.

If there was work done recently, there may have been an “engine to body” ground that was not installed following the work. These grounds normally run from the rear of the engine to the firewall and are uninsulated and most are a braided wire. If any of these are found unattached…reattach them.
Remember….this is not a “Sherman Tank” don’t over tighten the connections.
Tight…tight………………too tight…broke!!!

Yosemite

The switch SteveC is referring to is attached to the transmission itself…It’s called a “Neutral Safety Switch” Let Google find it for you…