[johncc]

I've had this ever since I had the car. At least 3 places have said they've fixed it, but it soon returns!

The OS brake light stops working.

On inspection, everything looks fine. All crimps seem tight, the connector is snug, no corrosion anywhere, the bulb connection is tight.

It failed the MOT on it this time, so I'd love to sort it out! Any suggestions what to try?

Waggling the wire/connector doesn't seem to affect it.. tapping the bulb holder assembly usually does. Once it comes back on, I've never managed to make it go off again. But as soon as you drive it, it'll stop working.

Help!

P.S. I actually have an AS level in electronics - sad, isn't it?

 

[Pete A]

Electrical problems like this are a pain in the butt.
I think the next step is to give the earths on all rear lights a good clean (sometimes a bad earth causes problems elsewhere in the system).
Then replace the bulbs AND the bulb holder.

HTH
Pete

 

[bstan]

Have you ever replaced a bulb?

If you replace one bulb, you should probably replace all bulbs or the corresponding bulb in the opposite assembly.

It seems the assembly uses a detection circuit that compares one circuit against the other.

Bulbs that don't behave identically on both sides cause problems.

 

[mark e]

bstan, this is a problem with the lamp not illuminating, not the pictogram

It's obviously a bad contact somewhere, the problem is where...

It could be that the spring of the contact to the lamp is tired, and has been bent back in to plae, and then slowly loses pressure.

Another possibility is the IDC terminal on the bulb socket. IDC is nasty in an automotive environment; it allows possible moisture and thus unseen corrosion in to the joint.

 

[johncc]

I managed to get a meter on it while it was not working, and I got 12V all the way to the bulb holder.

Although lots of parts are plastic riveted in, the bulb holder can be dismantled. So, I took it apart, cleaned the contact points, bent the springs tighter and soldered all the IDC's (the +VE one for the stop light did seem quite loose when I got it out).

If that doesn't fix it, I'll eat my space saving spare wheel

 

[johncc]

So, what's the recommended way to prepare and serve a Saab spare wheel?

 

[xassh]

you mention getting 12 volts at the holder, but were you testing against the ground plug on the holder, or against the frame of the car?

you also mention that the positive feed was loose, but have you inspected the ground? Pete A brought up the grounds, but i do not see you mention that these were checked, JohnCC.

check continuity along the ground wire, check continuity fromt he ground spot in the bulb holder, try using a spare piece of wire, touch it to the ground terminal at the holder with the bulb in the socket and see if it works. be careful not to ground the positive feed!

(as of this post, i can be considered a genuine Saab Nut

)

 

[hugh3lf]

I had similar problem and it turned out to be a faulty bulb - have you tried transfering the "dodgy" bulb from one side of the car to the other and seeing if the fault moves with it?

Regards