Electrical Problem - Need Some Help.

[ferrariboyuk]

Hey,

The previa has developed a potenially lethal fault with its electrics. Randomly these happen:

1. I brake and the side lights come on.

2. I put the lights on, either side or dipped, and the centre brake light is also on. When i brake the brightness is increased.

The second is particularly worrying for obvious reasons.

Is there an obvious thing i can do like disconnect the Battery in the hope it resets some how. Any ideas what the problem might be?

Any advice would be great.

DOM

[T600]

It's almost certainly due to a poor earth. The lights are all linked together on the earth side, and if that connection is earthed properly then the electricity just returns directly to earth. But if the earth isn't present then the electricity finds a route to earth through the other bulbs.

Test by wiring the light unit's earth to a known good earth - should solve the problem. Then permanently repair or recreate a good earth for each light unit.

HTH.

[Boro Sera]

definitely a bad earth.

Check all the electrical connections to and around the lights for contamination/corrosion. That's a common cause.

[ferrariboyuk]

Yes, thats great. :) Sounds a bit beyond me lol. I;ve replace the bulbs behind the speedo before so i've seen some of the wiring looms. Looks very confusing and much of it is covered by black tape. I wouldn;t know where to start. Unless i get my hands on a haynes manual again. :hokus-pokus:

The cost of toyota looking into this could spiral out of control i guess?

[T600]

It's probably one of those jobs that Toyota won't be able to give you a definite time for, so yes, hard to price.

You might have more luck with an auto electrician if you need input.

But it really shouldn't be as complicated as the dash bulbs.

The problem's very likely at the rear lights themselves. Quite often the earth connections on these are shoddy.

Assuming you can access the back of the light cluster easily then it really shouldn't be too difficult. And if you can get your hands on a Previa wiring diagram that would help a lot.

First step, as Boro Sera says is to check the earth connection there. It's possible that the earth is supposed to be achieved through the bolt that attaches the cluster to the bodywork and if that has rusted at all, then that's your problem.

The confusing thing is that a faulty earth on just one side can lead to problems all around the car - because the electrickery from the brake light on that side may be able to route through the tail light on that side, through the tail light circuit, and then back to earth through the tail light on the other side, so both will light up a bit, and so might the front side lights too. To figure out whether this is the case, you could try removing the brake lights one by one and see whether that solves the problem; if it does you've probably found the location of the problem. That said, if the earth on one side is rusted, it's likely that the earth on the other side is also on its way, so clean that one up too.

It's less likely to be the centre brake light as that unit has no other bulbs in it.

Good luck.

[propnut]

Checking of the earthing is not that big a job and if you want to save yourself some money one that you should bite the bullet and try. I am assuming you have a MK1 Previa. If so

1. Take off the Battery leads and clean them. Mix a few teaspoons of Bicarbonate of Soda with hot water and pour this mix over the terminal. This will remove any traces of batt acid. Then clean both the terminals on the Battery and the connectors, apply some vaseline to both and reconnect securely.

2. Then follow the negative cable to its anchor point. Unbolt it and with a wire brush or sand paper clean both the terminal and the anchor point.

The Previa has a number of these. One goes from the batt to the starter motor and there is one underneath the car that goes from the chassis to the engine mount (left hand bottom). There is one at the top and one on the right that earths the ignition coil but if you concentrate on the Battery and the main one from chassis to engine you should be ok. If not then just keeping going to the next one until the problem goes away.

Garages are nothing more than a rip off. The more self sufficient you become the sooner you will start saving money. I appreciate that everyone needs to earn a living but what garages (Toyota especially charge) is just criminal. I did the CV joints on a friends new shape Previa a short while ago. Each joint cost £77 and took me about 20mins a side. Toyota quoted her £970 to do the job !!!!!!!!!!!!!!!!!!!!!!!!!!

THEN same car the MIL light kept coming on. She took it to Toyota numerous times, they reset the lights ummed and ahhed and eventually told her it needed a new Cat, yes another £1000. I took a look traced the problem to a frayed connector on the Lamda sensor.

DUDE DO THE ****ing job YOURSELF

[Boro Sera]

The more self sufficient you become the sooner you will start saving money.

DUDE DO THE ****ing job YOURSELF

All very true !

It's a straight forward enough fault to tackle yourself successfully. IF you decide to get a pro on the job then use a private auto electrician, not a dealer !

[ferrariboyuk]

Ok, I'll have a look into midweek.

Thanks for all ya help.

I know what you mean about garage prices. I changed the water pump and drive belt on my old yaris, now driven by my dad. Was satisfying.

I'll let you know how i get on. :D

DOM

[ferrariboyuk]

Good news.....

I have managed to fix the problem :D I tracked it down to be as simple as a rear light bulb. Was testing each of the rear bulbs as recommended (well done T600 B) ), out comes the second bulb and problem found. It was black as if it had blown but was still working. Luckily we had a spare so its all as good as new.

Great news.

Thanks for all ya advice

DOM

[T600]

Result, glad you got it sorted.

Never heard of a blown bulb causing that problem before; it must have blown in such a way that it was bridging the two circuits together or something.

Worth checking for anyone else who gets a similar problem.