Why won't this car start when the windows are closed on a hot day?

Dear Car Talk

Dear Car Talk | Oct 01, 2001

Dear Tom and Ray,

I need your help in solving a problem that really has me stumped. My 1992 Nissan Sentra has a few strange habits, most of which I can live with -- but not this one: When the car sits in the sun with the windows closed, it just will not start. I turn the key and get absolutely nothing. If I open the window and wait about five minutes, it starts up just fine. I replaced the battery, the starter and the battery cables. Nothing worked. Then I took it to a shop, and the mechanic wanted to replace the battery, the starter and the battery cables. Naturally, I declined. It started fine all winter. But now every time I go to the beach, it won't start. -- Erik

TOM: You gave us two excellent hints, Erik. Now, wouldn't it be impressive if we could actually put them to some intelligent use?

RAY: It would, wouldn't it? Well, one hint is that it's related to high temperatures inside the passenger compartment. So that would limit it to parts located where, Tommy?

TOM: Inside the passenger compartment!

RAY: Very good. And the second hint is that absolutely nothing happens when Erik turns the key. And that means what?

TOM: It means Erik's sleeping on the beach tonight.

RAY: Thank you, Dick Tracy. It means it's got to be a part that can completely interrupt current to the starter, because otherwise you'd get at least some sound or hear some effort by the car to start.

TOM: So my guess is that it's a bad ignition switch.

RAY: Good guess, but probably wrong. My guess is a bad clutch interlock. Assuming this car has a stick shift (you don't say, but many Sentras of this vintage do), there's a switch on the clutch pedal that prevents you from starting the engine unless the pedal is fully depressed. My guess is that the contacts are being affected by the extreme heat.

TOM: It's an easy thing to test, Erik. Have your mechanic remove the clutch interlock and just shunt those two wires together -- taking the interlock completely out of the circuit. If the problem goes away, have him install a new clutch interlock (it's cheap), and you'll be all set.

RAY: Just be careful during the test period, when you're driving around without a clutch interlock. You'll be able to start the car with the transmission in gear. And your delight in having the car actually start might dissipate quickly as you realize you just "started it" into a sand dune.

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