Mk3 Cavalier Owners Club | Vauxhall Cavalier Dot Com

Hi. As the title says wiring problem and having not a clue about wiring i could do with a bit of help.

Problem is,
When the key is in the ignition and turned on the lights in the instrument panel are on but the car won't start and nothing else seems to be working inside the car. If I pull the keys out of the ignition and turn the headlight switch on it brings the instrument lights on.

The car got a dash change I think. I prob will need a auto electrician.

If the warning lights are on with the key out, then there is definitely a wiring fault.

If it is just the battery light, then this indicates a faulty alternator.

It is hard to be 100% certain without knowing exactly what was messed with.

Could even be something as daft as a disconnected earth wire causing leakage through other circuits.

In your situation, I would definitely speak to an auto electrician.

Yes trying too get a electrician sorted to come out and have a look.
It done on a few days back wen i hit a small bump coming outa the garage but then was ok after a bit of rattling around.

Hope fully it is something simple. When the hazzard light switch is on the relay makes a buzzing sound and flickers the warning lights on the dash as do when i touch the brake pedal or switch anything electrical on and off.

Definitely sounds like an earth fault.

There are several brown earth wires behind the instrument cluster that should be bolted to a steel bracket under the dash close to left side of the instruments.

I will check that and see how it goes. Thers wires jointed everywhere and some are bare in places.

That doesn't sound good! Sounds like the dashboard needs a complete rewire. No telling what damage has been done or where the wiring issue lies.

Was thinking that as well of a full rewire. I really do hope not. Taking out the dash doesn't seem to be a pretty job. Might need a wire harness if i was going to do that.

How would i know if my cooling fan is a single speed or two speed.

There is a connector low down on the back of the radiator on the UK driver's side.

If it has two wires on it, then it is a single speed fan.

If it has three wires, then it is a 2 speed fan.

2 speed fans tend to be fitted to cars with V6 engines, air conditioning or factory / dealer fit towing wiring.

I presume most will have an extra fuse / relay box on the engine bay bulk head near the UK passenger side suspension turret.

I cant see any fuses or relays any were in the engine bay. Is ther definitely a relay for the fan in the engine bay.

It has three wires but doesn't have air con. I see in places that the thermostat can cause the fan not to come on.

Judging by your last few posts, this sounds like someone has gone to town butchering the electrics.

There is a point where repairs cease to be worthwhile.

The only safe way forward is to get the dash and engine bay wiring looms replaced.

It has taken me 20 years of ownership to learn my way around the Cavalier wiring.
It is not complex by modern standards, but you have an awful lot of work ahead of you that requires a patient, experienced and professionally minded person to get it right to a good reliable and safe standard.

Any one can bodge it together, but I am sure you want it sorted once and for all.

The supplementary fuse / relay box is shown in this image.
Between the scuttle panel and the suspension turret.

Yes really want it sorted so that everything is working perfect. And for peace of mind.

Then again it could be something simple as a faulty earth.

Thanks for the photo. Naw don't have that box at all. Although there are wires around that area. Thought some was for the 4x4 system.

If you have bodge connections and bare wire, I can definitely say it is more than just an earth.

If you do decide to attempt it yourself, the simple rule is.
Red is permanent live.
Black is ignition live.
Brown is earth.
Grey with green stripe is illumination.
Grey with black stripe is illumination with dimming.

Most other wires are of a set scheme,
So a lot of work may be joining wires of the same colour to each other.

Best method of joining is soldering and covering in heat shrink tubing.

At a minimum use crimp on spade connectors with the rubberised clear boots.
I get mine from places like maplins.

I don't like the crimps with hard plastic covers.

Robsey wrote: If it has two wires on it, then it is a single speed fan.

If it has three wires, then it is a 2 speed fan.

If you mean the connector of temp sensor in radiator then this is not the full truth.
If you have a facelifted C20NE without air condition you got three wires but the fan is single speed. The third wire (brown-yellow 4 mm²) is always prewired but unused.

vaux16v wrote:Problem is,
When the keg is in the ignition and turned on the lights in the instrument panel are on but the car wont start and nothing else seems to be working inside the car. If i pull the keys out of the ignition and turn the headlight switch on it brings the instrument lights on.

I would check the ignition switch first. Maybe the switch is defective or the connection between switch and lock cylinder is broken which would explain the non-start-problem.

Thanks all for you help. This is what the projects are all about.

I will try the simple tings first and if they dont work well then im goin to have to rewire. Its just getting started then all wil fall into place. HOPEFULLY.

I have c20ne as well and it has no air conditioning and has the three wires.
The turbo cav has no air-conditioning and has three wires

Tobias has been able to teach me a lot since joining the forum, so I am sure he is 100% correct regarding the 3 wire connection.

I only have 2 wires on mine, because my original engine was only a C18NZ.
It is now a C20NE and the radiator and fan still control the temperatures well.
It is good to know that I didn't need the 3rd wire too.

I would have agreed with the ignition switch, if you had not already mentioned joined up and bare wires.

I haven't heard of this much damage since the early days when police cars used to get their wiring butchered during decomissioning ready for auction.

Im goin to try ignition switch and try to find were all the earths are at before i do start ripping the dash out. I do really tink that its someting loose or some wire is touching something it shouldn't. Fingers crossed.

vaux16v wrote: Theres wires jointed everywhere and some are bare in places.

Surely this MUST be the issue.

Ill let you know how it goes by the end of the week thats if i havnt pulled the hair out by then.

By the looks off things the dash is going to have to come out. Probably be better because it seems there a few things missing.

Its ther any thing i should be doing or checking when the dash is out so dont have to be removing it in a few years time.

If the dash is coming out, then have a good look at everything.

It is hard to gauge what needs fixing such as bulbs etc, if the electrics do not work.

One thing that is always faulty is the heater panel bulb.
I would change it anyway because it is probably the most awkward thing to get at when the dash is assembled.

Beyond that it depends if you have any upgrades planned.
Fuel computer retro fit, heated seats, volt and oil pressure gauges.... and so on.

Well i took the dash out yesterday. I thot it was goin to be worse.
As soon as i took the dash out i plugged a few things in and everything seems to be working again. The hunt is on for the loose wire.
Goin to go through all the wires and reconnect all the bad connections

Were would i buy these bulbs at. I need the electric window switches and see a few on ebay. Does anyone know if they are any good. Thier seems to be a less connects in the black plugs.