Avensis 98 Alarm

[Penfold]

Helpppppppp.

I have a bog standard '98 2.0GLS 4dr saloon. In Nov04 someone parked a van in the n/s/r wing resulting in a panel change (window out job). During the summer of 05 whenever it got hot the alarm decided to go off and would not reset cleanly. I can no longer leave the car in direct sunlight between march and september unless it is only locked by the key. The vehicle was fine through the summer of 04 after I bought it.

Thanks to various forum searches I have;

replaced the batteries in the key fobs

disconnected the vehicle Battery for 24hrs and drained the residual current before reconnecting

cleaned all the multiconnectors (except the siren unit)

wound down the sensitivity of the little black box to the bottom left of the steering column behind the dash

vacuumed all the airvents and speaker grilles for spiders etc

Seems to come on once the external temp in sunlight hits 21degrees.

It is still driving me potty - any clues please?

[purvesh81]

It sounds to me that you've actively tried to remedy the fault but to no avail. I don't have anything technical to add over and above what you have already tried.

As your in North Kent, it may well be worth giving Tech-One a try.

Good luck, let us know how you get on. :)

[rf76]

Its prob a short circuit inside the siren thats triggering off the alarm. Its located underneath the osf headlight and is notorious for water ingress due to its location. Once removed, open it up n you'll probably find the terminals are corroded causing the problem. If its ok, it might be something to do with the radar sensor but not sure on the location of it.

[ae111sr]

I had a similar problem with my Corolla a year or two back. It turned out to be switch that turns the light on when the boot is opened - near the catch. Just needed cleaning - it has to be worth a try.

[Penfold]

Thanks for the feedback everyone. I'll go for the bootlid switch option first as it stands to reason that this might not have been put back properly after the repair (or even the 2nd repair after being rammed by a fiesta and needing a new rear valance and bumper)

I thought it might be a heat expansion of the n/s/r door seals so have packed out the door switch to allow for this as this door was removed to fit the new wing but the bootlid switch never even crossed my mind (and it's not a very big journey either.....)

If that doesn't work then its on to the siren unit - could be corrosion on the circuits shorting out when heated up.

Out of interest - does anyone know where the radar sensors are hidden?

[Iain l]

If something is so on the edge that 21' causes the fault to occur then you will probably be able to trigger it by thumping parts of the car. You may be able to loaclise the fault that way. Another thing to try is a hair dryier, instead of opening stuff up and cleaning contacts which can cause other problems heat it up and see what happens.

Random fixing of parts is never a good idea as it disturbs other previously OK parts.

[Penfold]

OK, so I dropped the rear seat and laid in the boot pushing upwards on the inside of the lid until I could see daylight through the seals around the edge - couldn't get the courtesy light to come on. This is heading the wrong way...

I noticed however that the cabin interior light had blown again. This is approx the 4th time in as many years and at £2 a pop is not particularly funny for such a small bulb. I decided to put an AVO on the unit, set it to 20volts DC to see what the Battery was giving it, blue flash & crackle and no volts. I open the door to get out of car and the o/s/f wing starts beeping at me. No interior light or alarm or central locking. I refer to owners book for which fuse box to attack. Anyway, turns out that the 'dome' fuse had blown, which isn't too much of a problem but the interesting thing is that the owners manual says that this is one of the fuses you can rob to get you home in an emergency. You just need to remember that you can't lock the car or alarm it when you get there unless you change it back.

Time for a trip to the auto electrician I think.