Car wouldn't start after sitting in sun

Took my 03 envoy that is having some voltage/electrical issues to get tested! Everything checked out fine! But then in the afternoon after sitting in the sun I went to start it an when I turned the key all that happened was the check engine light came on and nothing else. Would not turn over nothing, not a sound! That was about 4pm… Now I got home and at 10pm went out to check it and it started right up! I’m scratching my head here! Any ideas? :crazy:

When was the battery replaced last? The heat may have expanded the battery breaking an internal connection. Testing at normal temps won’t reveal the problem. What are these other voltage problems? If the battery is still the OEM one from '03 I’d definitely replace it. If it is a newer battery, I still suspect it is bad and could be the source of your problems.

Uncleturbo, when driving it and it gets warm outside to voltage gage fluctuates and headlights flash, the door locks unlock and lock… Repeatedly. And the car loses power! Can a bad battery still cause this?
Any help is much appreciated.


@Brandoaj It sounds like it’s more than your battery, although I would replace it as well since it is 10 years old. You need the electrical system checked out thoroughly by a competent teach. Usually these shops call themselves “auto electric” specialists. A dealer can do the same but they charge a lot more.

I’d check the battery terminals.

Next time it does not start, take a booster cable but use just the negative side. Leave the positive (red) side alone. Just let it dangle. Clamp one end (BLACK) on the NEGATIVE battery terminal and the other side (also BLACK) on a large bare metal piece of your engine. DO NOT FOOL WITH THE POSITIVE TERMINAL!
See it it wants to start.
If so, your negative battery terminal, the way the black wire is seated into it or a connection to ground is bad somewhere.

Of course, the same could happen to your positive terminal but you wouldn’t want to diagnose that with a booster cable on account of it being dangerous.

So the battery and alternator are fine, but all of a sudden the security warning light comes on and the radio locks, door locks won’t work with remote, and windows won’t roll up or down! The headlights flicker when on, along with the dash lights, and there is a buzzing noise coming from the rear doors! I am at a loss and feel like in in for an money pit of a time! Any ideas?

Yes. Bad ground.

The problem might be with the positive battery cable assembly.

Your vehicle has the side mount battery terminals. And corrosion can form under the red cover for the positive cable terminals causing a voltage drop to the vehicle.

Ever since GM came out with this brilliant type of battery connection, and someone complains about electrical problems with their GM vehicles, the positive cable assembly is the first thing I check.