Cleaning a F125 switch

[skyegtb]

Has anyone ever refurbished a F125 switch? I have just has the fun of replacing the F125 for the 2nd time in my RS ownership. First time was 2012 and done it again today. First time was due to gearbox limp mode, all of the gear lights on the dash being illuminated and the following fault codes.

Address 02: Auto Trans Labels: 01L-927-156.lbl
Part No: 4B0 927 156 FB
Component: AG5 01L 4.2l5VT RdW 1214
Coding: 00001
Shop #: WSC 00000
VCID: 6CDC191B1C90D69

1 Fault Found:
17090 - Transmission Range Sensor (F125)
P0706 - 35-10 - Implausible Signal - Intermittent

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 4B0-614-517.lbl
Part No: 4B0 614 517 AD
Component: ESP 5.7 RS 6 2310
Coding: 06697
Shop #: WSC 00000
VCID: 63CE7227F14E991

1 Fault Found:
01119 - Gear Recognition Signal
35-00 - -

The change today was not due to limp mode (it never actually put the car in to limp mode), but was due to a constant un-clearable code in the ABS module which prevented the car being started with the key. Strangely the fault was registered as 'intermittent' even though it would return immediately after every scan I made with the Vagcom.

Address 03: ABS Brakes Labels: 4B0-614-517.lbl
Part No: 4B0 614 517 AD
Component: ESP 5.7 RS 6 2310
Coding: 06697
Shop #: WSC 00000
VCID: 63CE7227F155BF913C-5120

1 Fault Found:
01119 - Gear Recognition Signal
35-10 - - - Intermittent

Anyway, I swapped in a spare 2nd hand F125 I had and all is now good again, car starts on the key and fault code gone, but ideally I will get a brand new replacement or clean and re-furbish one of my old ones and fit it. Due to the pretty simplistic nature of these switches I think that a fully cleaned and re-greased used one would probably be as good as a new one, so I am looking for your suggestions as to how best to go about cleaning the internal contacts and what grease I should use to re-grease the rails.

Below is a picture of the F125 I opened this afternoon. As can be seen some of the electrical contacts are quite dark looking, but I don't know what might have caused this. I already buzzed all cables through with the multimeter and all tested fine for continuity, the same for the rails - everything appears to be OK, but I would not re-fit this without a full clean etc.

So, if you did this, what did you use? A chemical, a light acid solution, fine sandpaper? What grease did you use?

Looking forward to suggestions. Here are the pictures:

[Shoppinit]

You sure it's the tracks and not the connector?

[HPsauce]

I think it's been done more than once by people on the A8 Parts forum, including replacing damaged contacts.
I kept my replaced one and cleaned out obvious debris from the inside before bolting it back together but it's not been refitted - that a bit of a mare of a job on a D2 S8.

[skyegtb]

You sure it's the tracks and not the connector?

The connector looked perfect, but I will give it a thorough check when back in the shed. My continuity tests showed nothing unusual.

[skyegtb]

I think it's been done more than once by people on the A8 Parts forum, including replacing damaged contacts.
I kept my replaced one and cleaned out obvious debris from the inside before bolting it back together but it's not been refitted - that a bit of a mare of a job on a D2 S8.

Yep, well while the car is still apart I have a chance to do some swapping or various bits in and out, so I reckon I will try something with both of the units I have and test them out.
I will report back

[Shoppinit]

Someone was talking about getting a cheap Chinese knockoff recently. Might be worth getting one just to see how it looks inside.

[Shoppinit]

I wonder what the tracks are made of. I think if I was going to have a go I’d use some Autosol on the tracks and contacts. Then wash in lots of isopropanol. Not sure I’d put any lube on. Was there any on the one you took apart? I suppose this stuff might work:

https://www.amazon.co.uk/MG-Chemicals-C ... B005T8ROWA

[HPsauce]

I'm not sure you'd want conductive grease, you might risk shorting between tracks?

[bilko1]

I've repaired a few switches before using Brasso and Duraglit that I've had for about 25 years, works a treat as long as theres no pitting.

[skyegtb]

I wonder what the tracks are made of. I think if I was going to have a go I’d use some Autosol on the tracks and contacts. Then wash in lots of isopropanol. Not sure I’d put any lube on. Was there any on the one you took apart? I suppose this stuff might work:

https://www.amazon.co.uk/MG-Chemicals-C ... B005T8ROWA

Yep, definitely grease, you can see the residual white grease blobs in the pictures.

[skyegtb]

Someone was talking about getting a cheap Chinese knockoff recently. Might be worth getting one just to see how it looks inside.

Yeah, seen a few with the correct part number on eBay for about £40. Might give one a punt to see how it looks.

[skyegtb]

I wonder what the tracks are made of. I think if I was going to have a go I’d use some Autosol on the tracks and contacts. Then wash in lots of isopropanol. Not sure I’d put any lube on. Was there any on the one you took apart? I suppose this stuff might work:

https://www.amazon.co.uk/MG-Chemicals-C ... B005T8ROWA

Yep, definitely grease, you can see the residual white grease blobs in the pictures.

You can see the grease here:

[skyegtb]

I've repaired a few switches before using Brasso and Duraglit that I've had for about 25 years, works a treat as long as theres no pitting.

Sounds pretty good to me, might work using cotton buds etc, so will probably give this a go.

[airtite]

when I last had an issue, i had disconnected the plug and had sprayed some contact cleaner into both sides of the plug when I reconnected the plug I obviously didnt push it together properly and after a few drives the plug came loose enough that the car wouldnt start BUT heres the weird part after plugging it in properly again the car has been fine no more f125 switch issues (apart from the reverse lights not coming on) its almost as if with the plug slightly loose the contacts in the plug ends jiggled around and cleaned themselves.

The cheap f125 switch from amazon has arrived but I will see if its worth fitting when I pull the motor again sometime at the end of the month.

[Nobby]

Could the grease be silicon grease?

I’d also look at whether there is any play in the shaft of the selector. It looks like it been or touches the back of the casing (from the grease stain). If it twists and there could be a wider gap between the contacts.

I’ve repaired a few wiper motors which have similar problems - the contact wears out and you can solder a new one in. Last time I just fashioned one out of some copper washers.