Member Since: 04 Sep 2019
Location: Cape Town
Posts: 4
Transfer Case Module TCM relocation options
Hi everyone.
I have recently had to solve HDC fault on my Disco 3 2.7TDV6. Based on the fault finding and solutions on this forum i found the usuall water logged TCM connection points and consequential corrosion of the terminal points.
A thorough dryng, electrical contact cleaning and reinstall the problem was solved.
However, I want to go a step further and possibly eliminate the problem:
1. turn the module upside down, this will possibly reduce water ingress into the connection points
2. relocate the module to a more suitable location either inside the vehicle or engine bay, a drier location.
Both instances will require the wiring harness to be extended.
Are there any plug and play solutions available for wiring harness extension cables? I am hoping there is an after market harness that simply utilises existing plug connections to extend the length of the harness without having to cut existing harness and extending the cable lengths.
Has anyone else done a similar modifcation of the wiring harness?
Thank you for a fantastic forum.
10th May 2022 1:46 pm
Motolab
Member Since: 18 Oct 2019
Location: Sleen
Posts: 1815
Hi,
the water ingres becomes possible because the bonnet sealing rubber, shrinks over time
when is does is goes loose at the corners... and water is comming in.. as you experienced
start with the seal/rubber... make it loose from both sides (front to sides both R & L) until you are at the suspected corner(s) reroute the seal/put it in place again, taking care there is no tension on the corners..
you will end up with a crack in the front, but that crack isn't as dangerous/annoying there as it is on the corner..
second.. there is no reason for the TCM to be NOT water/air tight... so you can easily make it waterproof with a proper kit/sealant
i used Sika 291 (= a not silicon HD kit)
since rerouting... to where? under the bonnet the batterybox is the "most" protected area allready..
and refitting such a multiplug on a such primary unit in the drivetrain electrics, is possibly a challenge by itself..
just my idea..Best regards
Harold
Always looking for Pre '55's & Pre war British Motorcycles! knowing or having one for sale? PM please. I visit the UK 6 times a year
Ps. I edit my texts quite often, english is not my native language, so I will edit My “typo’s” etc.
10th May 2022 3:11 pm
SchyffS
Member Since: 04 Sep 2019
Location: Cape Town
Posts: 4
Hi @Motolab
Thank you for your comments and suggestions.
I agree that the TCM box casing can be sealed, I did not have water ingress into the box itself, and sealing the box with SIKA 291 as suggested is perfectly acceptable. I will seal the box casing as suggested. However, the water seal is required around the plug connectors, this is where water gets into. Also if the module case was installed upside down then water could not run into the plugs, hence my query about installing the module upside down.
There are automotive waterproof plugs, see below, and these would have made better waterproof connections, unfortuantely these were not used:
Compared to the existing current plug connections, these offer zero protection against water ingress:
I found water at the top of the box inside the male plug connection. it was fairly obvious that this was a long term leak and possibly the source of the water came from a defective/worn rubber seal of the engine bay. I will check this as well and refit to make the seal better. I have also read that the battery acid contributes to the acidic environment causing further corrosion of the terminals. So its not the ideal location for this module IMO for two reasons in that it has a bonnet seal that requires occasional maintenance and battery acid leaks from the battery making it not so well protected.
A better location for this module is perhaps in the front part of the battery box away from the seal and battery and most definitely in the passenger foot well space where some other ECU's are located. Its such an important module that it should never have been located where it currently is exposed. As a minimum it should have beeen a sealed unit with waterproof connections, it has been the cause of most of Disco 3 owners HDC fault issues as I have read on this forum.
I do not think that relocating it is problematic, if there is a plug and play harness that can be installed. Three plug extension cable should make easy work of it. Im still hoping that there are aftermarket specialists that have made such an extension to the harness. I would attempt it myself if I knew the name and model number of the plugs to make up an extension harness.
10th May 2022 4:11 pm
SchyffS
Member Since: 04 Sep 2019
Location: Cape Town
Posts: 4
Hi, minor update. I found a post that sums up more or less what I was thinking. On the Disco 4 the TCM has been relocated to the Aux battery box and is mounted upside down with the plugs entering from the bottom. Seems LR has made an improvement there.
https://www.disco3.co.uk/forum/topic177012.html
I ordered plugs that I think match the TCM plugs, will take some time to arrive since Cape Town is far from any suppliers. Hopefully I can find a local harness manufacturer that will take on the small job of making up and extension harness. So many different colour wires, won’t make sense for me to purchase them all.
Stubborn I suppose. But may just work. I do a lot of camping trips and don’t want to have this silly problem come up.
20th May 2022 9:13 am
Motolab
Member Since: 18 Oct 2019
Location: Sleen
Posts: 1815
not a bad idea ...
but TBH i have seen quite a lot of rain het in NL.. my D3 also..
since the bonnet seal , seals the corner again as it is supposed to do, i have seen no water ingress or what so ever again.. Best regards
Harold
Always looking for Pre '55's & Pre war British Motorcycles! knowing or having one for sale? PM please. I visit the UK 6 times a year
Ps. I edit my texts quite often, english is not my native language, so I will edit My “typo’s” etc.
20th May 2022 9:43 am
Trailered Movements
Member Since: 16 Jan 2020
Location: East/West Sussex Coast Borders
Posts: 1198
Many moons ago I had a rally mini that had the floor start button, and basically the first puddle would mean the engine cut out, now being in the mid 70's silicone was not an option.
After a new rubber gaitor was fitted, a tuperware lunchbox was trimmed and screwed over said switch, and hey ho, problem solved.
Not saying this would do, but a fix of sorts would be to have a piece of plastic over the plugs so water ran down it, rather than into the unit, a sort of roof.
Dave2011 Discovery 4 Commercial SDV6 (Gone)
2010 RRS TDV8 (Gone)
1980 OBLIC 4.0ltr Range Rover (went a long time ago)
20th May 2022 9:53 am
SchyffS
Member Since: 04 Sep 2019
Location: Cape Town
Posts: 4
Motolab wrote:
not a bad idea ...
but TBH i have seen quite a lot of rain het in NL.. my D3 also..
since the bonnet seal , seals the corner again as it is supposed to do, i have seen no water ingress or what so ever again..
Yes, on the short term and probably it will solve the issue completely, I will do the refitmet of the bonnet rubber seal as well what else can be done with the plastic box covering the TCM.
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