no reversing lights help please

[alfaman]

Hello all.


After a long search for answers I still cant fix my reversing light problem so thought I'd try one last go here before giving up. I'll explain what gone on so far.


So ive never had working reversing lights since I bought the car (ALfa 156 2.4jtdm SW). The bulbs work and connecting power directly to the units makes them work. If I then go to the gearbox and put a tester across the two poles on the sender switch ( just under the battery tray) I get continuity when I select reverse ( telling me the sender works). So I took out the interior and physically traced the wires from the rear lights back as far as I could until they reach a three pole plug situated just at the base of the gear stick on the side wall of the center tunnel in the passenger foot well. That plug isnt connected to anything and there is no other plug anywhere nearby to plug back in. The three poles consist of one live and two i'm assuming neutrals. If I connect one of the neutrals to the live then my reversing lights come on.


As a temporary fix I am using a rocker switch connected to these two wires to manually switch on my lights whenever I reverse. This has obvious draw backs so I ran two more wires from the sender switch on the gear box all the way up to the plug and connected them together. Now this didnt work. My assumption would be that the sender switch would do exactly the same job as the rocker switch and complete the circuit, switching on the lights. It doesnt and so then causes my confusion.


Is there any auto electric experts out there that might know the answer to why this fix doesnt work? In my experience and basic electrical knowledge then I just cant see why it should. The rocker switch fix works, the sender switch seems to be working, so why doesnt the sender do the same job as the rocker?


Any thoughts or advice would be great. If I fix this then with any luck that s my car sorted until the next issue shows its ugly face.


thanks everyone

 

[Darkwood]

You be better on an automotive forum with such a question,

To tidy your query up cars run DC from the battery thus your terminology is incorrect you need to state Positive and Negative
Car usually have the chasis and bodywork grounded to Negative so often you may see just positive wiring looms but not always. You wont be shorting positive to negative as this would short circuit the battery and hopefully blow a fuse.

If the limit switch (sender as you call it) dosn't work yet paralleling a switch off it does then one of 2 things is happening -

Either the limit switch is faulty or the gear selection is not making contact with it correctly, at the cost of probably a few quid from the scrapyard id firstly replace the limit switch then go from their.... dont get into the mind set that the colour of the cable will identify its function unless you have to hand a schematic for the car and the original wiring is present.

PS im not an auto electrician so others may correct me or further my post but its my take on your issue.


Welcome to the forum.

 

[Richard Burns]

I would agree with Darkwood automotive fora may be better. But please feel welcome here anyway!

OK not my area of expertise but from an electrical point of view:
The switch by the gear box that shows continuity when reverse is selected: with the ignition on, test for voltage from each of the connectors to the car bodywork there should be voltage on one of them (with reverse selected there should be 12V on both).
This confirms that the switch is doing what it is meant to, but does not confirm its operation under load.

The connector plug found by the base of the gear stick sounds like it may be a previous attempt to resolve the problem as, usually, tracing a cable from a light back to a connector plug there would be no connection that would permit the lights to work as the 12V positive would usually be supplied from the other plug and this is not the case here. Therefore someone seems to have arranged a 12 positive and a connection to the lights at this point.

If the gearbox switch has 12V and then is connected to another 12V nothing will happen which maybe what you have done.
If you have removed all connections from the gearbox switch and just run two wires from that switch to this loose plug and connected them across the two connections you have used previously for the rocker switch then based on what you have described this should work.

As far as I can tell the wiring should be in accordance with this diagram (I have added a quick simplified picture as well) that you have no doubt seen before. It may help.
That is as far as I can go.

 

[overskilled]

Missing or a blown fuse somewhere perhaps?

 

[alfaman]

Thanks for the replies. I will go back and try some of the tests suggested. I have been considering changing the sender even though it appears to work. the annoying and typical thing though is that its a bout a 2 hour job having to remove half the engine bay to get to. I'll let you know how I get on.

cheers
Rich

 

[Darkwood]

Missing or a blown fuse somewhere perhaps?

The fuse will serve other lighting so if it was the case of blown or missing then it would be evident with other lights not working also reading through the OP you can see he has got it working on a rocker switch suggestion the problem lies with the micro switch, the contact lever on the gear stick or as Mr Burns suggests it been altered or tampered with adding additional problems if they were originally trying to fix it.

 

[overskilled]

Just a suggestion, my vectra had no speed 2 on the wipers, garage reckoned failed wiper motor, did a bit of digging and found out speeds separately fused.
Ergo train of thought was that by using the rocker switch he might be bypassing a faulty fuse /switch somewhere.

Alfa owners site might be the best bet.

 

[overskilled]

reverse light not working - Alfa Romeo Forum

 

[Darkwood]

Apologies Overskilled im advising of the cuff and it just weird a dedicated fuse for reverse light(s) but as i said before im no auto electrician ....

 

[telectrix]

also worth checking to see if the gearbox switch does actually operate on the +ve. might well supply the -ve. to the lights.

 

[overskilled]

Apologies Overskilled im advising of the cuff and it just weird a dedicated fuse for reverse light(s) but as i said before im no auto electrician ....

Apology accepted, nothing surprises me with cars anymore....especially that vectra.....