Vectra brake light mystery!

Hi,

This concerns the usual 1998 (early) 2.0L DTH Vectra Estate I married in haste two and a half years ago. Why did I ever walk out on my eighteen year old bought-from-new 1.3 Astra? (Well mainly 'cause it was dissolving but it had been a great, easily maintained vehicle.)

Well, every now and again recently, say at monthly intervals, the rear brake light 10A fuse blows. I just measured the current today and it reads 3.5A which is just about fine for a pair of 25 Watt bulbs (engine off). the correctly listed fuse is 10A and I have fitted 3 recently.

I thought the add-on wiring to the tow bar hitch might be damaged so I disconnected that a month or so ago and presumed I had cured it. No such thing!

Is there anything else on the brake light circuit? I don't think so, and there's no apparent harness damage I can see (not that that says much as it is mostly hidden). Nothing else seems to be affected.

Any bright ideas or (particularly welcome) similar experiences?

Tony.

Reply to
Tony
Loading thread data ...

The message from Tony contains these words:

Does the bulb go at the same time - or do they survive?

Reply to
Guy King

Hi Tony,

If you have a high level brake light at the rear (can't remember if they were standard on that year of Vectra), check the wiring running up the N/S C pillar and through the rubber grommets between the body and tailgate. If nothing found there, check the wiring in the tailgate and the brake lamp itself.

There are probably several other items on the same fuse (is it marked KL.15 on the fuse box lid?), such as the cigarette lighter and reverse lights. Can't remember for sure, the Haynes manual may point you in the right direction. Intermittent short circuits are probably the most awkward fault to find. You have to work out what consumers are connected to the fuse and check ALL of the wiring for chafing between the fuse and the consumer. I have spent many hours on jobs like this. If a visual check reveals nothing, the next step is to install smaller value fuses in the supply line to each consumer and see which one blows to narrow the search down.

HTH

Anthony Remove eight from email to reply.

Reply to
Anthony Britt

The bulbs survive every time.

Tony.

Reply to
Tony

cut here

cut here

Yes, it does have a high level light and I had not thought about that. I use the tailgate every day and that could be a source of extra wear on the harness. I might disconnect the high light to see if that's the culprit but it is so inconsistently bad. I.e. it takes weeks and then suddenly blows again. But that is a good area for investigation.

Yes, it is KL15 but the reversing lights work even when the fuse is blown. I will try and fathom the Haynes diagram on this point. They used to be as easy as anything to follow at one time but now seem totally confusing. I am a technician by trade but never relish their recent wiring diagram layouts.

Thanks as always. I will investigate further in the next week.

Tony.

Reply to
Tony

Quick tip for tracing short circuits.......

Take a 21w bulb, solder wires to it. Attach 2 Male spade connectors to the wires, then remove the fuse from the circuit, and insert the spades where the fuse was. In this way, the current must flow through the bulb, instead of the fuse. Switch everything on on the circuit, and the bulb will glow dimly, as the current is flowing thought both the bulb, and the brake lights (or whatever is on that fuse).

Then go and wiggle the harness about, or open and shut the tailgate, whatever to try and make the short appear. As soon as the short occurs, the bulb will get brighter. You should be able to work your way round the circuit, and when you get the bulb to stay bright, you have found your short.

Reply to
SimonJ

That's a nice idea and it'll save me using a stack of fuses.

Thanks for that one.

Tony.

Reply to
Tony

cut here

cut here

Since my first reply to your posting I have now had some time to look at the vehicle. Yes, the N/S tailgate pillar wiring loom has got 2 wires with exposed copper conductors where the insulation has cracked at the rubber sleeving nearest the grommet area as it enters the tailgate.

Now there is no sign of arcing having taken place but I have repaired the cracked insulation and recovered them. They certainly needed doing. I will just try that for now.

Yes, there are things like the radiator cooling fan circuit and the heating circuit which come off the same fuse (although the internal heating fan and hot air system seemed to be still working fine at times when the fuse had actually blown). I don't have Air Conditioning as this vehicle has a sun roof and they don't seem to supply these two items together - so that's another thing it won't be.

Anyway, I think I will let that do for the time being and see what develops.

So that's another good diagnosis, Anthony! Perhaps if I took a Polaroid photo of my vehicle and sent it to you, you could use a paper clip and a bit of cotton thread held over the picture and tell me what else ails my car?

My sincere appreciation for your pointers as always. I can't be sure that this problem is yet cured but it certainly is a good place to start.

Tony.

cut here

Reply to
Tony

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.