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      11-10-2017, 03:52 PM   #45
jamesfawcett
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Sorry to post again whilst your question above was unanswered, there's something interesting above on that link about that extra wire that goes to the tail light, apparently its just a failsafe so that if things stop working, the brake lights still work. That could explain why you couldn't find it on your loom.
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      11-10-2017, 07:44 PM   #46
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Yes true, although I think that applies to the brake light? If you have the AHM3+ OR AHM4 this module uses 2 12v feeds, one from fuse 31 and one from fuse 32, as bmw increased this to two power feeds Ito these modules compared with the original 1 power feed in the AHM3. This was to cater for trailers that had extended lighting and drew extra power.

IF YOU HAVE THE AHM3+ OR AHM4 it could be erroring as it is expecting 2 12v feeds to the module?
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      11-10-2017, 07:49 PM   #47
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Actually looking at your INPA screenshot, it looks like you have the AHM4R which means you should have 2 12v feeds to the module, and your connector to the AHM4R should be the newer type which has the fold down lock mechanism rather than the older style plug that just pushes on?
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      11-10-2017, 07:54 PM   #48
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Also my ISTA confirmed I have the AHM_E65 which would be correct as my modules are both dated 2005. Yours should've the AHM_70 if you bought it new in the kit from bmw
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      11-11-2017, 04:49 AM   #49
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I haven't tried INPA yet to look at the AHM but that certainly looks useful!
I can connect to my AHM fine with ISTA so that module appears to be ok, although i cant plug my bike rack into the socket to test all the light outputs until i can get the hitch to release which is annoying!



Here's my 16 pin black AHM3 connector



Your AHM4 connector should look like this



and your pinouts are:



So you should be able to check you are getting 12v from Fuses 31 and 32 to pins 13 and 20 with your ignition on?
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      11-11-2017, 06:01 AM   #50
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Thank you for that, those pin outs are very helpful! I traced back....

I don't want to admit where I went wrong

I missed out this step:
Only vehicles produced after 09/07
Connect branch A18, RT/GE wire, at BO-VI 6-pin
connector X11004, Pin 3.

I didn't realise there were two wires to add into that connector - oops! I only added the one. I noticed when I pulled the fuses and one of them had no metal pin inside. Rookie mistake!

Yes you are correct my module has a different connector to that but also so does the one I removed from the scrap car:


how to upload a photo on fb
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      11-11-2017, 08:11 AM   #51
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Oops glad it was just a schoolboy error and nice and easy to fix!! I definitely win for having the worst error now

I actually ordered the retrofit cable required for the 2nd power supply to the AHM3+ AND AHM4 part no 61129130258 which has the correct connector on each end so im gonna run this along the existing loom in case I change to the newer module or if my one dies etc. Don't want to have to rip the car apart again at a later date! It can just sit there disconnected for now.
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      11-11-2017, 02:05 PM   #52
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I do wish I had done it the same way as you with more research and using the loom from the scrap car, I would have saved a fair bit of money! I thought it would make it easier but it's still quite a task

I'm trying to book a few hours into the family schedule to take my fusebox out again tomorrow, i'm getting quite good at 'that' 4th screw
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      11-11-2017, 02:42 PM   #53
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Yeah it's a fair old job especially with unexpected problems! I'm not shy when it comes to retrofits as I done an analogue clock to full 18 button OBC conversion in my old E36 which was a 'challenge', but this towbar job is much more complex than I thought it would be!
Don't get me started on that 4th fuse box screw - i was on the verge of giving up after discovering that little award winning design
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      11-13-2017, 05:45 AM   #54
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Sounds like a nightmare! I once considered it on my E28 but it even needed extra sensors adding for external temps behind the bumper. Although thinking back it would have been much simpler than this

I added the extra power feed and it's cleared all faults, however it's not good news yet! No error codes, but my AHK module is not communicating with the AVB. I am wondering if it's the two different generations of modules. I am going to email BMW Cotswold where I ordered the trailer kit from to let them know about the missing secondary module and the other little parts, I was hoping to be able to use use the scrap car parts but I've a feeling they might not be compatible.

Here's some progress photos it feels good to have the trim back in!



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      11-13-2017, 05:50 AM   #55
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Yep, I think I am going to go with the removable one... LOL I have the same removeable one on my e87.

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      11-13-2017, 05:57 AM   #56
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UPDATE - I now have a working towbar

I swapped out my hitch release module with a known working module form my mates E91 that has the tow opiton from factory (2010 model) and although initially we had a green light on the hitch release button, it done exactly the same - my motor tried to activate but nothing happened and ended up with a flashing red light. We then tried my module in his car, and it worked perfectly and released his hitch first time, so good to confirm my module is fully functioning at least.

So it had to be my electric motor or the hitch mechanism itself. So off came the bumper





I found the following on TIS which showed that you can remove the plastic cap on the back of the hitch swing arm, so wanted to check from this side before having to remove the entire crash bar to get to the motor and pin on the other side



Removing that revealed a large O ring, a threaded metal section and a plastic cap of some sorts





It looks like something is supposed to be clipped in to the plastic cap - a bit like the fuse remover tool holder on the fuse board maybe, but there was nothing in the cap i removed so no idea If anyone feels like taking their cap off i'd be interested if there is supposed to be something in there!



Anyway the cap would not budge, so i carefully wrapped some parrot jaw pliers around it with a towel to protect it and just tried to ease it back and forth. Eventually it started to move although very stiff. Used some oil in through the centre hole and around the outside and eventually got it off



The threads were perfectly clean with zero rust, but there was a clear hard brittle substance falling out of the threads, so I can only assume it was some sort of clear loctite or even clear superglue holding the threads in place.



This revealed the centre pin which must be the back of the long pin running through the hitch and into the motor with the T piece near the end.
I found the following on TIS which finally explained how the motor works and pulls the T bar piece on the end of the centre shaft down into the motor - against spring tension in the hitch piece, which must realease the outer arm of the hitch and let gravity swing it down into the intermediate position







As the cam inside the motor rotates it moves a horizontal slide piece under spring tension which indiates to the hitch release module the position of the motor via the microswitch. As the hitch arm is pulled into the locked position either out or back in under, the spring tension pulls the centre shaft back up and locks the outer swing arm back into place.

My centre shaft wasn't moving at all, so i figured it must be either seized or somehow stuck out of position so the motor was unable to pull on it to release the swing arm. I gently tapped the end of the centre pin/shaft with a hammer and socket extension just to see if i could get it to move after squirting some oil in around it. It moved in around 15mm or so and then stopped. I tried activating the motor via the boot button and the motor started going and then a clunk and the swing arm moved down a quarter of a turn or so and stopped. Progress! I then pushed the centre pin/shaft all the way in very easily and off popped the entire swing arm!



I figured in for a penny and all that, no going back now so continued to dismantle it



There are 2 sets of 3 ball bearings offset against each other on the inner shaft that the swing arm fits over, and pushing against the spring loaded centre pin moves allows the ball bearings to sink into their recesses and out of their races so you can put the swing arm on or take it off the shaft



I started giving it a good clean up and getting the old dirty grease out - thankfully to my surprise (massive relief) there was zero rust anywhere on the shaft or ball bearings or races, they all cleaned up lovely





The two routed out sections you can see here are for the the locked-in and locked-out positions of the swing arm. In the middle between them is a section rasied up around 10mm which you cant make out in the picture, but this must be to keep the arm and fixed metal balls out of the dimples on the crash bar plate while the arms swings from one position to the other



You can see the cap head bolt in the bottom thread here which moves between these limits



So, after all that, cleaned everything up and applied fresh grease and carefully reassembled, pusing the centre pin in to allow the swing arm to fit back over. Had the activate the motor so i could push it on the last part of the way so the cam inside the motor was out of the way, then it locked into place.

Green light on the button, press = unlocks and swings down. Pull up into locked position = green light again. I now have a fully working hitch!!!
Such a relief I'm not sure why it had seized considering there was no rust, perhaps one of the ball bearings has somehow got stuck slightly out of its holder, or maybe it just hadn't been activated in a very long time.

The centre pin was sitting further in now than when i first investigated so originally it was stuck just too far out and the other end wasnt down inside the motor far enough for the cam to pull on the t bar end of it to move it. All moving free and nice and smooth now.
I had to work out how far the plastic end cap needed threaded on again as this sets the limit of how far out the swing arm moves when activated. You want it so the arm can just move freely enough against the O-ring when the hitch releases. I applied some Loctite superglue to the last couple of threads and wound the cap into position and left for a few minutes. Then double checked everything and put the car back together.

Now I can actually access the 13 pin trailer lighting socket and the next test will be to see if that's all working properly - fingers crossed!!

Hopefully this will help anyone that goes through the same retrofit, or even you guys if you ever have a problem and need to service the mechanism.
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      11-13-2017, 06:12 AM   #57
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Fantastic tear down documentation there! I feel much more confident about having an electric towbar now knowing how it works, thank you for doing that!!!

Sounds like we are both at the same stage now, please keep me updated on how your testing goes! I have emailed Cotswold BMW to let them know about the missing parts, they are always really good to sort things out so fingers crossed
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      11-13-2017, 06:31 AM   #58
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No problem James, hope it helps others and glad you feel more confident about yours now

Will definitely report back after the lighting tests adn let you know how that goes! Good shout about contacting Cotswold BMW, those modules are quote expensive so it's a bit part of the kit to have missing if it should have been in there! Looking up pictures of the retrofit kit online, it does seem to only have the one module for our cars - although i'm sure i found a picture of the kit on schmiedmann a while back where it showed both modules - perhaps it's a different retrofit kit part number?

As i understand it, the pinouts are the same on the older hitch release module as they are on the newer one - however the newer ones send an 'Alive' signal to the AHM on pin 13 of the AHV module to let it know it's there and also it can make the AHM produce a useful idrive check control message if it has a problem.

So yeah it sounds like your AHV module is the older type, probably the same as my one - the newer version should have part number 71606857227

I bet it feels like the car is getting back to normal now the trim is going back in - can't wait to be able to do that as it's driving me mad!

David in Germany - totally understand the choice to go the for removeable option!!! However this thread has probably made the electric OEM choice out to sound harder than it is - just hitting unexpected snags along the way really. If you do decide to go for it you will have us here for tech support as we know the system inside out
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      11-13-2017, 08:28 AM   #59
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I fully agree - David it is worth it in the end!

On my lunchbreak I swapped out the newer module that I did get with the kit with the other older one so I now have both old modules in my car and the iDrive began showing me messages about missing bulbs....

So....

I checked the lights I was testing with.... no bulbs

Fitted some bulbs, hurray all up and running!

David don't let these problems put you off - my problems are down to having missing / incompatible modules and missing one of the power feeds in the instructions, and then not putting bulbs in... It's very worthwhile in the end!
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      11-13-2017, 08:55 AM   #60
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Great news James, well done! Hopefully give my lighting module a test this evening with my bike rack and will report back to hoepfully confirm success all round!
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      11-13-2017, 11:48 AM   #61
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Quote:
Originally Posted by Scoff123 View Post
Great news James, well done! Hopefully give my lighting module a test this evening with my bike rack and will report back to hoepfully confirm success all round!
I am in suspense here, please let me know!
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      11-13-2017, 02:59 PM   #62
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I hate you both for pushing me back towards the swing hitch...

Meant in a nice way.. Lol

Although I can get the complete set with detachable neck, cables and exhaust hangers for right at 500€
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Last edited by david in germany; 11-13-2017 at 03:19 PM..
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      11-14-2017, 05:18 AM   #63
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Quote:
Originally Posted by david in germany View Post
I hate you both for pushing me back towards the swing hitch...

Meant in a nice way.. Lol

Although I can get the complete set with detachable neck, cables and exhaust hangers for right at 500€
My total spend is £460 including buying the full loom and kit from BMW, I can sell the bits i don't need on eBay.
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      11-14-2017, 01:40 PM   #64
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Quote:
Originally Posted by jamesfawcett View Post
My total spend is £460 including buying the full loom and kit from BMW, I can sell the bits i don't need on eBay.
I may be spending a bit more than that in the next days to replace my failed water pump....
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      11-18-2017, 02:49 PM   #65
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Quote:
Originally Posted by david in germany View Post
I may be spending a bit more than that in the next days to replace my failed water pump....
Oh no! Hope it hasn't done too much damage - is it just a leaky pump or has it caused the engine to overheat?

Finally found time to check my trailer lighting module out by fitting my bike rack and can confirm everything works as expected, Indictators, hazards, running lights and brake lights all work correctly, and pdc is disabled when it is plugged in
My reverse camera still works correctly too, and I've now replaced my custom coding after default coding my modules following the retrofit.

Good team effort!
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      11-18-2017, 05:08 PM   #66
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Quote:
Originally Posted by Scoff123 View Post
Oh no! Hope it hasn't done too much damage - is it just a leaky pump or has it caused the engine to overheat?

Finally found time to check my trailer lighting module out by fitting my bike rack and can confirm everything works as expected, Indictators, hazards, running lights and brake lights all work correctly, and pdc is disabled when it is plugged in
My reverse camera still works correctly too, and I've now replaced my custom coding after default coding my modules following the retrofit.

Good team effort!
Thank goodness the car goes into limp mode and protects its self. The pump died, no hiccups just dead. Did the install today, but battery now charging because the failed pump caused the fan to go into overdrive and ate all the power.
In the am I will test drive and recheck for leaks but I think all is good.
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