@dome@ Circuit Fault Help!

[Previa Barry]

Our 1992 Previa GL has had a fault for some time whereby most of the standard fit Speakers weren't working and only ever crackled occasionally. We put up with this for some months but now have a greater problem.

The other day the Speakers starting making really loud noises whether the engine was running or not. The only way to get it to stop was to disconnect the Battery. At the same time the inside of the car smelt strongly of TCP or disinfectant.

Today I re-connected the Battery and the noise started immediately, at first it sounded a bit like an electric fuel pump. I started pulling individual fuses until the noise stopped. It stopped when #14 was removed. My handbook identifies this as 'dome' rated at 15amps.

Apparently this protects the following circuits: interior lights, luggage compartment light, clock, open door warning light, radio cassette player and theft deterrent system.

None of these systems are now working due to the lack of a fuse, however, they all work when the fuse is re-connected, although I have been unable to test the theft deterrent system as I don't know how. In addition this fuse also seems to cover the central locking (perhaps linked to switching on the anti-theft thingy?).

Can anyone offer any ideas as to where the problem may be and how I can fix it?

Also, how can I check the anti-theft system without damaging the car?

Replies here or via email at barryblackmore@ntlworld.com

Cheers

[miti-babe]

Barry...

It's difficult to provide specific hgelp for your problem without more detail on your Previa, but here are some general suggestions that may be of use...

The sort or problem you're describing is typical of a bodged stereo replacedment.

If your Previa has had the original Toyota radio/casette and CD (If fitted) replaced with an aftermarket system, then check out the following (listed in order of ease of checking...)

Check that the Audio amplifier is still fitted in the passenger footwell (rectangular box about 4" x 8" covered by a metal "bash-plate"

If the amp is missing, then you'll need to read on about removing the stereo...

If the amp is still fitted, remove it's mounting bolts and check that the amp wiring is still connected to the amp (either 2 or three multi-way connectors, depending on model/part number)... Some "installers" have a nasty habit of butchering this wiring to get to the speaker wiring, which runs under the footwell carpet and (eventually) to the Speakers... If any of this wiring is in poor condition, tidy it up and make certain that you don't have any short-circuits before you continue...

Additionally, the OEM stero takes it's power from a feed from this amp... so this is another prime candidate for "innovative" modifications...

If your amp is still connected and/or the amp wiring is in good nick, then you'll need to remove the stereo to check out what has happened behind it...

try http://www.carstereoremoval.com for details (including pictures) of this process...

In short...

Take the dome cover off (your alarm indicator light is connected via a small plug underneath, if you pop this off, the cover comes away completely)

Remove the two screws that are now exposed, either side of the stero mount at the top and front of the assembly...

slide out the ash-tray...

Slide out the drinks holder...

open the lower storage compartment and working from below, remove the screws retaining the ash-tray bracket in place... (carefully disconnect the cigar lighter and ash-tray lamp before ripping the wiring out of the car...)

Lower the storage flap completely down by pusing in the sides and sliding it past it's normal stops...

Again from below, remove the two screws that secure the stereo assy to the metal plate that is exposed when you remove the ash tray bracket...

(it's much better with pictures....)

The stero comes out complete with the air vents and the plastic trim panel...

Once you've got the who thing slid forward, you'll be able to see if the wiring is anything like it should be (neat Toyota stuff) or if the "Wiring Nutter" has beaten you to it...

If it's the latter... same again... tidy up everything, making absolutely certain that there are no bare wires and short circuits...

If there is an adaptor assembly between your stero unit and the Toyota wiring harness... double check this as the extra cabling can cause chafing simply because it's too long and difficult to squeeze in place (although the Previa has tons of room behing the radio...)

Tip... once you're certain that your wiring is tidied up... try reconnecting the fuse before you refit the stereo... if everything is OK then and turns to rats after the stero is back in, then the fault is probably the stereo... (Geddit?)...

Lastly...

The alarm is really only a "someone has broken into your car" device... If it's the same as my '91 model, you'll have two ultra sonic sensors mounted at the top of the A pillars and a red light that flashes on top of the fuse box dome...

The system works with the central locking and is activated as the locking is switched on by the key (in any of the doors)... there is about a 30 second delay before the system is "active"... Once active, if any of the doors are opened without using the key, the system sounds the car horns (it senses movement in the car at the same time as the doors are still "locked" so it's just a simple logic circuit)...

To test if it's working...

Lower your door window (either side will do)...

close the door and use the key to lock the car...

Wait for the red light to start flashing...

Reach into the car through the window and use the interior handlr to open the car...

"Beep, beep, beep!" means that the system is working... you can turn it off by unlocking the door with the key from outside...

If it's not working, don't go to the expense of getting it fixed... the cost would be frightening and there are far better systems available these days for far less cash...

I hope all this helps...

That's the problem with big cars... there's so much more to go wrong...!

Never ever will I own anything smaller again though!

Good luck

Jeff