325i Auto reverse light switch working backwards? Sorted!

[M3KUK]

Hi posted this before but can't find my original post.
The reversing lights are coming on in Neutral and going
off in reverse any ideas?

[Brianmoooore]

If it happened suddenly, check your engine and gearbox mounts.

[M3KUK]

It was like that when I bought it.

[Brianmoooore]

Does the P, N, R, D by the selector lever correspond exactly to what mode the gearbox is actually in?

[M3KUK]

Yes they do.

[Brianmoooore]

This problem is all tied up with your other thread in which you've hit a wall.
The starter inhibitor and reverse light switches are part of the same assembly which is fixed to the side of the selector lever mount, under the centre console.
The gearbox is connected to the selector lever by an adjustable rod, which is set so that the P, N, R and D indicator lines up properly with the light mounted on the lever. If the gearbox moves over or back, it will move the selector indicators out of line, and the electrical functions of the switch along with them.
If, as you say, the indicators are lined up properly, there is something adrift with the switch assembly. You can get a restricted look into there by pulling off the brush carrier and the plate with the slot for the lever in it, but to get unrestricted access you'll have to remove the rear centre console, followed by the front one.

[M3KUK]

Thanks mate, I've removed the console and tested the switch according to the Bentley manual.
It must be the wrong switch as it's all messed up.
I have sourced another switch off a Zoner, will try that.

[Brianmoooore]

A thought occurred to me that it may be that someone has misadjusted the rod to the gearbox at some time, found that the P, N, R and D didn't line up, and somehow modified the light to correct it, without realising that the switch was still misaligned. I don't even know if this is possible, but it may be worth checking.

[M3KUK]

Got a replacement switch today, tested it as per the Bentley Manual and it's reading wrong, it's exactly like my original switch in the car. So either I've bought another dud or the Manual is wrong!
Help please! This is doing my head in!

[Brianmoooore]

A thought occurred to me that it may be that someone has misadjusted the rod to the gearbox at some time, found that the P, N, R and D didn't line up, and somehow modified the light to correct it, without realising that the switch was still misaligned. I don't even know if this is possible, but it may be worth checking.

[Brianmoooore]

A thought occurred to me that it may be that someone has misadjusted the rod to the gearbox at some time, found that the P, N, R and D didn't line up, and somehow modified the light to correct it, without realising that the switch was still misaligned. I don't even know if this is possible, but it may be worth checking.

[M3KUK]

Just to double check the gear sequence
From the front is P,R,N,D,3,2,1. The gearbox
Is selecting in this order and working
Perfectly. There is not a separate reverse
Switch mounted on gearbox is there?

[Brianmoooore]

Reverse light switch and starter inhibitor switch are both in the part you've just wasted time and money on.
My guess is that it's the indicator that's wrong some how, and that the switch problem is down to incorrect linkage adjustment to the gearbox.
Before anything is adjusted, it's essential to ensure that the engine and 'box are sitting where they should - that the engine and gearbox mounts are not distorted and are intact.

[M3KUK]

Yes I get that mate, but I think the gearbox mounting
Etc is fine. The spare switch I have is free to move
From one top to bottom of the PRND123 scale.
When it is in the reverse position, ie adjacent to Park
It is not making. However move it again to Neutral
Position and it makes the switch, activating the
Reverse lights. This is exactly what my switch on
The car does.

[Brianmoooore]

Can you crank the engine with the lever in '1'? In fact, go through the lot and tell us which positions will allow the engine to crank, and which positions turn the reverse lights on.

[M3KUK]

Hi just tried it and got the following results;

Will start engine in Park and Drive, will not start in Reverse, Neutral and 3,2,1.

Reverse lights come on in Neutral, stay off in all other selections.

Cheers Mike.

[Brianmoooore]

Put the gearbox into reverse, then shorten the linkage to the gearbox until the reverse lights come on, continue shortening it, counting the turns, until they go off again, then lengthen it by half the number of turns you just counted. Check that the engine will then crank with the gearbox in neutral and park. Note that this may no longer be the indicated N and P positions on the scale.

[M3KUK]

Yes that looks like it, everything is one gear out!
Where can you adjust linkage, underneath the car?
Thanks for the help, Mike.

[Brianmoooore]

Definitely underneath the car, and I think, at the bottom end of the gear lever - the front of the linkage.

[M3KUK]

I've sorted it! Thanks Brian! I adjusted the threaded rod and end underneath the car on passenger
side of box.

[Brianmoooore]

How well are the D, N,P, R, etc. beside the selector lining up with the indicator light?

[M3KUK]

They are ok, they were a little bit out but I adjusted the display slightly and it's
bob on now. Cheers!

[Brianmoooore]

They are ok, they were a little bit out but I adjusted the display slightly and it's
bob on now. Cheers!

That's what I thought. Someone has reinstalled the selector rod to the gearbox incorrectly, and then, finding the display didn't line up, someone 'adjusted' that as well, instead of finding the real problem.
In the words of the old saying, "two wrongs don't make a right."

[M3KUK]

Or twenty wrongs in the case of my car's previous owner!

[Mr-Lachs]

Glad you got to the bottom of this