Troubleshooting help: Ignition locked out?

[scottcot]

I've had this on-again off-again problem for a little while, haven't gotten to the bottom of it yet, but I may have some new info so trying again...

2004 SRT - very rarely when I try to start the car, upon pressing Start the ignition system will make a rapid loud clicking sound and the car will lose all power. What happened this last time is I sat in the car stewing for a moment or two, tried the ignition again a few times (all I got was a brief lighting of the Passenger Airbag is Off lamp) but no luck. Then got out, manually unlocked and opened the trunk to grab my stuff, closed the trunk and then reached in and locked the door manually and closed the driver door. Then I thought to myself, it shouldn't lock without power - better check. It was locked. Then I tried the key fob and unlocked the car and got the blinker response. Then I hopped back in and started the car up successfully.

No codes off the OBD2 reader this last time or any time.

So I'm wondering if this sounds like a short in the alarm system and whether this sounds like an anti-theft circuit going off when it shouldn't, cutting fuel? If it were, would manually keying open the trunk have anything to do with the anti-theft system? I've got to troubleshoot the electrical system clearly but it helps to have some place to start and I wonder if I've homed in on something.

-scott

 

[Steve-Indy]

How old is your battery? What does it read for voltage at its terminals? Condition of battery cable connectors?

 

[scottcot]

The battery is a year old, two tops, and I had just disconnected it from a trickle charger that day. I think the connectors are in good shape, just the usual light powdery build up. Though if I've got a short perhaps maybe I'm draining faster than I should be also. Car started fine after whatever transient problem I had cleared up.

 

[Steve-Indy]

Re-reading your posts makes me wonder about condition of cable-connections within the connectors to the battery since wires can "dissolve" from acidic gases in a car that is 8-9 years old. Would also measure battery voltage, check for loose wires to starter, and possibly consider ignition off draw test if you think you have an abnormal drain on battery. Hopefully, others will make more helpful guesses!!

 

[ViperGeorge]

Same thing happened to one of our locals. Bought a new battery, same problem. Turned out to be a loose cable (not on the battery but somewhere slightly away from it - ground maybe?).

 

[Cobraken]

Battery and/or the connections.

 

[scottcot]

Ok thanks, I'll check out my cables and take a look at the battery voltage. For the ignition off draw test what kind of current should I expect? And I think the way you test that is with a milliamp meter between the disconnected negative cable and the negative battery terminal?

 

[Dan Cragin]

This sounds like a ground or battery issue. Even if a battery is two years old it could be bad. There are two grounds that are very important. Battery to frame and frame to engine. If either of these are loose or have a bad connection the problem you describe could happen. First you need to do a open resistance and load test on the battery, then a voltage drop test on the ground. Both of these can be done by any competent auto shop.

If the battery checks bad, replace it, if its good then you either have a bad ground or a starter issue. If you have excessive voltage drop the ground is suspect. The two ground straps to check are the one from the battery to the left rear frame rail and the right motor mount to the frame.

The reason you are having alarm problems is because the voltage to the alarm/body module is dropping below 9 volts and making it freak out.

My 2 cents.

 

[scottcot]

I never looped back here to close this but it turned out it was a ground problem, but with a twist.

I said the car failed to start and after I opened & closed the trunk it started successfully. Puzzling, and I was ready to start tracing the electrical system. It turns out the negative cable wasn't making a good, reliable connection. The negative terminal clamp, which is bolted to the grounding cable, was very loose where it attaches to the cable. So loose that sometimes the terminal clamp was just barely making contact with the cable and I'm sure driving the car simply broke the connection. So when I opened & closed the trunk, shutting the trunk jostled the clamp and cable enough to make contact! I took all the cables off, wire-brushed all surfaces to remove corrosion, tightened the negative clamp down to the cable, and it appears to be fine.