2012 Jeep Grand Cherokee intermittent no start - brake switch?

Factual Questions
1

Since I WFH I don’t drive nearly as much as I used to. My Jeep will often site for several days before I drive it again. The last two times I tried starting it after sitting for 2-3 days, it did not start at all for 4 or 5 tries-- no crank attempt, nothing, before suddenly starting up normally on try 5 or 6. After that it seems to start up normally if I turn if off and start up again.

To start my Jeep, I push down on the brake and push a start button. I understand there’s one brake switch that not only turns the brake lights on, but allows the Jeep to be started. When the Jeep does not start, all the dashboard lights go on just as if I had pushed the start button without engaging the brake. And when the Jeep finally does start, the starter seems to engage at full power, so I don’t think it’s a battery issue. Also, I have a remote start, and I don’t seem to have a problem with starting the Jeep remotely… but since this is a newish issue, I haven’t thought to try the remote start until after the button / brake method started working again.

So, I’m thinking it may be a failing brake switch…? A few questions:

  • Am I right to think it’s likely the brake switch, or could it still be anything?
  • Can a brake switch fail intermittently like that, or would it be a ‘once it fails, it’s done’ situation?
  • If it is the brake switch, it’s a $20 part, and looking at where it is, as well as doing a bit of googling, it seems to be pretty easy to swap one out. But is it as easy as it seems, or are there any complications I should be aware of? I’m pretty mechanically handy, but I’m also kinda lazy, so if the job is going to be any kind of hassle or take me more than an hour (or if it could be something else), I think I’d rather just pay to have a mechanic do it :blush:
2

Quite possibly, although there are typically other interlocks too, like transmission position (transmission must be in Neutral or Park).

But you can test the brake switch theory: put the back of the car against a wall and see if the brake lights illuminate every time you press the brake pedal. (Although the brake switch could also be a multi-pole switch in theory, and the lights could be a separate circuit from the starter.)

3

I think gnoitall got it in one. I would just add that the brake switch may fail intermittently. Depending on its mode of failure (corrosion in the contacts, partially broken wire breaking continuity, broken insulation causing a short), there is a good chance that the failure coud happen with increasing frequency until the switch doesn’t work at all anymore. Good luck.

4

Thanks @gnoitall and @Tired_and_Cranky .

I tried starting up while checking the brake lights yesterday to see if the brake lights also don’t work when the Jeep won’t start. But of course it fired right up when I wanted to reproduce the problem :roll_eyes: