VW wiring problems

[steve_k]

Afternoon folks looking for a bit of advice.

Car in question is a mk3 jetta (mk5 golf with a boot) but the questions are more universal.

When I bought the car on November last year it didnt come with any front fog lights.

So I got hold of the lights & a universal wiring harness with a seperate on/off switch.

I (finally) fitted the lights & the harness yesterday, went to try the lights only to find they didnt switch on,

First thought was it the bulbs? Changed them for a spare pair, still nothing.

So today I've been going through the wiring & hit what I assume to be the problem.

The harness has it's own relay to control the lights.

I tried a different relay o had & still nothing.
So I bridged the sockets on the harness with two short lengths of wire.

And guess what? The lights came on, now this happened with both the ignition switched on & the ignition off & the key in my pocket.

This leads me to think that both the relays are duff/dead.

Would I be right in thinking this? I cant get a new relay till Monday so cant check again till then.

Anyone have any ideas?

[steve_k]

Forgot to add.

The power is taken from the fuse box while ground is to the chassis.

I know these are good because if they weren't then they lights wouldn't work when I bridged the sockets on the harness.

I'm completely stumped by this.

[chatstar123]

If I've read correctly you know the lighting circuit is good so for some reason the relays aren't being energised. This could be a problem with the switch, the relay or the wiring in between.

[steve_k]

If I've read correctly you know the lighting circuit is good so for some reason the relays aren't being energised. This could be a problem with the switch, the relay or the wiring in between.

That's true, when I bridge the sockets for the relay on the harness the lights come on whether the ignition is on or not. But wont work on the switch.

So I'm leaning towards either the relay or the switch.
But I'll check the connection for the switch as well to see if theres any power getting to it.

Will be getting another relay on Monday but I've got to 6fpr a new switch to arrive.

[chatstar123]

Do you have a multimeter? If so you can check the switch and wiring by measuring for a voltage at the relay connector whilst turning on the switch. If the switch is providing voltage then the relay is bad. If the switch isn't providing voltage to the relay then you can check for continuity from the relay connector back to the to the switch connector (youd need to know which pin/socket in each connector that the wire should go to) or remove the switch and check it for continuity when on (closed) ruling out one or the other.

Hope this makes sense. As i don't know the specific set up im assuming this is a basic circuit with no control units or anything. Also unlike the voltage for the lights themselves which appear to be independent of ignition positon i guess the ignition and possibly headlights may need to be on when checking for voltage? It could just be that the harness is wired up wrong.

[steve_k]

Do you have a multimeter? If so you can check the switch and wiring by measuring for a voltage at the relay connector whilst turning on the switch. If the switch is providing voltage then the relay is bad. If the switch isn't providing voltage to the relay then you can check for continuity from the relay connector back to the to the switch connector (youd need to know which pin/socket in each connector that the wire should go to) or remove the switch and check it for continuity when on (closed) ruling out one or the other.

Hope this makes sense. As i don't know the specific set up im assuming this is a basic circuit with no control units or anything. Also unlike the voltage for the lights themselves which appear to be independent of ignition positon i guess the ignition and possibly headlights may need to be on when checking for voltage? It could just be that the harness is wired up wrong.

thanks for that,

yeah that makes sense, will dig out the multi meter tomorrow & have a look, fingers crossed its something simple.

[steve_k]

for got to add.

this is the type of harness that came in the kit.

https://www.ebay.co.uk/itm/FRONT-FOG-LI ... SwBm9eMkWo

[chatstar123]

That's good as its just a basic circuit.

One thing i forgot to write was that these checks are assuming that you have voltage to the switch as you said you would check that.

Hopefully something simple as you say.

[steve_k]

That's good as its just a basic circuit.

One thing i forgot to write was that these checks are assuming that you have voltage to the switch as you said you would check that.

Hopefully something simple as you say.

i'll be checking for voltage at the switch & it's connector to the main loom,
as you say hopefully something simple,

if not i'll fit some lower power (35w) bulbs & wire them into a switched live so they come on with the ignition & use them as DRL's (daylight running lights) instead.

[steve_k]

Well I found out the the problem was the pins in the connector for the switch were bent & not making contact in the plug.

Managed to get them straight & lo & behold they now work.

Bit its presented me with another problem.
The switch is on all the time.
Where the instructions say to take power from looks to be a permanent live.

So now I've got to try & find a switched live somewhere in the engine bay.

[steve_k]

well i thought i'd better update this.

after a lot of head scratching & digging around i found the problems.

turned out the the plug for the on/off switch was the main problem, the 3 pins nside had become bent & were't making contact in the other side of the plug, managed to straighten them out & lo & behold the fog lights worked.

then came the 2nd problem.

i followed the instructions to the letter but where it said to take power from was a permanent live, so, after going through more wiring diagrams than i care to thing about i was able to find a switched live to power them, mainly thanks to the use of a fuse tap.

[chatstar123]

Glad you sorted it. Its normally something simple but always a ball ache trying to find that simple thing.