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A bit ago, I went out to my van (1998 Toyota Sienna), unlocked, and got in with nothing unusual. When I put the key in the ignition and turned it to the on position, all the appropriate lights came on and the accessories started up just fine. When I turned it to start the car, everything went dead except the alarm system which decided to start sounding off (would like to kill the alarm too, but that's another problem). After I got the alarm shut off, I noticed the headlights were dim (set to turn on and off automatically with the ignition/door), but everything else came back. Shut everything down, turned on and off the alarm to make sure, and then tried again with the same results. Since the lights were dim, and the alarm started sounding, I'm wondering if this is a dying battery problem (and resetting the alarm to keep going off), or if my alarm is dying and trying to take the rest of the van with it. Any ideas? Thanks

Update: Got the car to Les Schwab last night. The battery tested good. We noticed two things that seem to point to a possible partial solution, either individually or together. 1. My fob's battery had died, and replacing the battery let it work again. 2. There is a lot of corrosion and gunk on the negative battery cable head. I'm thinking that replacing that head should help, but not sure yet. We also did find out that the alarm system is factory instlled, and the battery appears to be about 3 years old to my eye.

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Aftermarket alarm? –  Tim Jun 7 '12 at 20:53
    
I have no idea. The fob I have appears to be a third party fob (no Toyota logo, labelled Python on the front, and looks different than manual), but I don't know if the alarm came with the car or not, nor do I know how to check it. –  Tom Jun 7 '12 at 21:00
    
How old is the vehicle main battery? –  Brian Knoblauch Jun 8 '12 at 12:33
    
So did the new fob battery sort this out? –  Tim Jun 14 '12 at 13:17
    
new fob battery let me reset the alarm, so no more screaming in my ear. –  Tom Jun 15 '12 at 16:18
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1 Answer

up vote 1 down vote accepted

We seem to have found the issue. I found I was able to just pick up the negative cable off of the battery, and noticed there's a bit of a gap, so it looks like the problem was enough expansion to make contact intermittent, hence the alarm resetting every time it lost contact and sounding off all the time (also, part of the alarm's functions is to kill everything if it is active).

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