Interior Light Keeps Blowing

[stree]

04 1.3VVTi T- Spirit

Just got the car. Noticed the interior light , which is a centre fitting because there is a sunroof so no room for the usual one above the rear view mirror, was not coming on.

Got a new 31mm festoon bulb, 10Watt, put it in and still not working, so checked and replaced blown 15 amp fuse in the under bonnet fuse box.

48 hours later and bulb not lighting again. Fuse us fine this time. No othere electrics affected at all..I suspect if I replace the bulb again it will blow quite soon.

Symptoms indicate either an intermittent dead short or a surge in the circuit.

So I was wondering if this fault is common in this model, or just one of those things.

The radio/CD is all factory standard and no additional third party electrical items fitted to the car.

[FROSTYBALLS]

Are the door switches working OK?

[Raistlin]

Sounds like a bad earth, especially if it has been jerry rigged in the past...

[orangezorki]

I'm sure you did, but did you handle the bulb with a clean cloth instead of your hands?

I don't know if 10W is enough to cause the bulb to blow from the oils on your hands, but a few quid is definitely a better cost than trying to chase an elusive electrical gremlin...

David

[stree]

Well certainly no oil on hands, but that would make absolutely no difference to this type of filament/bulb............The heat is not as nearly instantaneous as a halogen, where any substance on the glass wall will cause uneven heating to it when the current is switched on, creating stresses which cause the glass to shatter or the seal to fail allowing the gas to escape..

A straightforward 10w heated filament festoon merits no such precautions really just good practice to keep a job clean.

The door switches all operate as they should, so any problem they might have is not apparent.

There is no "jerry rigging" in this car, it is a genuine car with no additional electrical items or features, as I tried to point out in my first post. However, there may be some mileage in the poor earthing suggestion, so the next step is to trace where this circuit earths points are...Although I think it more likely that it will end up being a live circuit issue rather than a poor earth, which would make a poor connection with a dimmed bulb output or stop the current, but not blow the bulb or cause a fuse to fail.

[MikeSh]

I'm a bit concerned about the blown fuse. Now the lamp isn't working again I'd be suspecting a connection that's come adrift and is sometimes making the circuit to the lamp ("It's working!"), sometimes waving in the breeze ("No it's not!") and sometimes touching 'ground' ("The fuse has popped").

The door switches usually ground the lamp connection to light it (they are on the negative side), so a faulty switch will either not light it or light it all the time - it won't blow the fuse.

Oily fingers on halogen bulbs is because the oil affects the quartz capsule (remember when they were called 'quartz halogen'). Doesn't apply to ordinary glass bulbs, though as you say keeping them reasonably clean is sensible anyway.

[Konrad C]

I had the same problem a while back.

You need to get a replacement interior lamp unit. I sourced mine through eBay. Paid about £10.

I checked the part numbers on ToyoDIY, and the Yaris and Avensis are the same.

My replacement second hand unit is better built than my faulty one, that kept blowing the dome fuse, when I tried to put a new bulb in.

The metal parts may be shorting, and the replacement unit had good metal parts that were more sturdy, and different design internally.

If I am correct, a lot of Toyota models use the same design interior light unit with various internal modifications. They all fit and connect the same.

Konrad

[stree]

In order:

Thanks Mike for the useful comments,

Konrad, that may well be a solution worth trying! thanks for that, appreciated.

[Phil01]

So one blown fuse and one dodgy festoon?

Just try another festoon and then if that blows then that's the time you start to become concerned with electrical gremlins

[stree]

Well Phil, I cannot argue with the logical sequence you suggest, in fact that is exactly what I have done, hence my first step in asking for advice here, where I am more likely to get specific rather than general advice.

Mike and Konrad have given excellent advice each, which I will be acting upon.

[Raistlin]

Kudos, That was nice....

[stree]

It did rather have a certain "essence" to it..............Thank you,

[Phil01]

I can be more specific than most, but why try and complicate things before it has happened.

I have learnt during the last 38 years working as a Toyota Master tech not to always worry about what if, and it was not general advise, you asked for help and I gave you a logical answer

I bought some LED strips from eBay, they stopped working after a week, asked for a replacement and they again broke,,, changed the supplier and all is well

Sometimes the simplest things are the easiest. I could have started to worry about earths, 12v+ etc, I just chose the easy option and not worried as it was crap quality rather than electric gremlins

[Phil01]

oh and try a 30mm festoon bulb as a 31mm is too tight for the metal retaining clips and that puts strain on the securing rivetts and become loose and can in time cause the contacts to have a high resistance in either the minus side or the positive side spring connector

Check for zero resistance on the earth side contact to a good earth point further down the body, a good point to use as an earth reference is the door looking hoop that is bolted to the "B" post, if that reading is near on zero ohms all is good.

Then do a volt drop check from the 12v side, please report back on your findings.

Also check from the fuse box, follow wire down to pin21 on JB (junction block) B2 making sure there is Battery voltage there, if all ok check the mechanical (crimped) connection, at the white 12 pin multi connector in drivers footwell, if this is still ok then do a volt drop test from that connector up to the live feed wire in the actual lamp unit itself.

Generally my experience has shown it to be poor/loose securing rivetts caused by trying to fit a slightly longer festoon.

If the rivetts are loose, simply take the lamp unit out and re-secure with a punch and a tap with a hammer.

A volt drop test is not checking for voltage, it is used for checking continuity when Battery voltage is present, it will hiight and lead you to where the actual fault is. If you "Youtube" volt drop test, it will explain what I am talking about because it is a hard subject to digest and understand. It is not checking for 12v feed. if you need anymore info then ask.

A good vid to watch

[Phil01]

Kudos, That was nice.... youareapurejoy.gif

Do I get Kudos point as well or was there a hint of, better not say as you are a "Moderator" super poster

[Raistlin]

Kudos, That was nice.... youareapurejoy.gif

Do I get Kudos point as well or was there a hint of, better not say as you are a "Moderator" super poster

I was complementing him for thanking other members of the forum that had helped him, it's nice to see a positive attitude.

You have to spread the lurve...

[Phil01]

Be careful what I wish for?

Now what is meant by that? as I do not wish for anything

[Raistlin]

Be careful what I wish for?

Now what is meant by that? as I do not wish for anything

You wished for Kudos points and your write up and video are worth so much more...

[Phil01]

To the OP, if you need any more info just ask or shoot me a PM, but I really do think it is just a simple matter of coincidence or bad luck as the boot light runs off the same power source as the interior circuit, but wired slight different as only using one pin switch

[markiev]

Hi, do you have the part number for the replacement lamp unit? I have a potentially similar problem: interior light won't come on with ON/OFF/DOOR switch in any position. Fuse OK, lamp appears to be fine by visual inspection (no obvious break in filament in bulb, although I'll by a new one just to check).

Thanks

Mark/.

[Konrad C]

The part number for the interior lamp is 81240 - xxxxx. The xxxxx are the various trim, colour or internal wiring. They are fully compatible and interchangeable.

My interior lamps look the same but the electrical tracks are different. My older fitting had spring type contact/bulb holder at each ending. One of the contacts was loose and shorted against another part of the car and/or fitting. The replacement has one fixed end and the other spring contact. I believe this is a more durable.

The following picture shows the replacement fitting with the bulb, and the older faulty fitting.

Konrad

[markiev]

Thanks for the response. I've since discovered that the bulb is faulty although I couldn't see a break in he filament. I've ordered some replacement LED bulbs as filament ones seem difficult (and expensive) to source.

[Konrad C]

Sounds like you were sold faulty bulbs.

Can I add that when handing any car bulb, halogen or tungsten, I always try to wear gloves. I had side bulbs blow quickly until I started to avoid touch the bulb directly. Same for instrument bulbs.

Another issue is if you get bulbs from a local motor factor not packaged (they have bought a job lot), I tend to clean the bulb with isopropyl alcohol to remove any contamination.

Hopefully you will get good quality LEDs.

Good luck.