Caddy 2k 1.8t conversion

Discussion in 'General Vehicle Chat' started by Ashleymark, Oct 5, 2020.

  1. Ashleymark New Member

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    Hi was hoping for a bit of help with a caddy 1.8t build I am doing with my son. We are both reasonably clued up when it comes to the mechanical side of thing, but we are both incredibly stumped when it comes to the wiring side. I know I can purchase a "plug and play" loom, but wheres the fun in that? Also not really a great example for the boy. I have lots of wiring diagrams etc to work with. I was just hoping someone could push me in the right direction as to where I should be splicing wires to. Ie caddy body loom or fuse box etc.

    Many thanks
     
  2. rubjonny

    rubjonny Administrator Staff Member Admin

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    you might struggle to find a plug and play loom for a caddy 2k, not many loom builders would take it on I dont think. most are just doing mk1/2/3 kits

    what I would do is split all the covering off the caddy loom and de-pin the ecu, strip out all the wires which go to the engine. if its got the same ECU plug as the 20v engine you want to fit you can then re-pin the old caddy interior side wiring to the correct positions for the 20v big plug half and make any adjustments needed bay side such as swap the MAF wiring over, add the ECU relay if needed etc. This stage comes down to what age/engine is in the caddy now. if its a diesel you'll have to change the throttle pedal for mk4 making sure to re-pin the plugs either end so the ecu is happy

    then assuming its a mk4 20v add the t10/14a plug to suit to the caddy bay side and the small ecu loom will plug right in, may need to mod it slightly for the dash temp and oil switch but I think the mk4 oil switch plug will fit the caddy oil switch, and the mk4 coolant temp sensor will also suit the caddy

    I've a fair wedge of diagrams in my signature, if you dont see omne for your caddy let me know I'll print one off. this thread will help you work out the MK4 side assuming its one o them engines:
    https://clubgti.com/forums/index.ph...install-faq-now-with-added-dieselness.267196/
     
  3. Ashleymark New Member

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    Thanks for reply @rubjonny. Unfortunately caddy big plug is very different to 20v 1.8t plug. The caddy one has twice the wires that the 1.8t has so dont think I can repin it into the 1.8t plug. I must be wrong but I was hoping I could splice 1.8t loom into the caddy side of wiring and then use the original plugs from 1.8t, but I imagine I would have trouble with the fusing/power of sensors etc. I'm guessing getting the engine to run will be the easier part. But having it work is the hard bit
     
  4. rubjonny

    rubjonny Administrator Staff Member Admin

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    ok so strip all the engine side out, snip off plug this will leave you with just the car side wires at your ecu plug. using the wiring diagram ID whats left, then compare to your 20v wiring using my guide plus the wiring diagrams in my signature matching up as you go. can then splice up whats needed and tape off whats not.

    the caddy should have plenty of power feeds you can use, for the coilpack/ecu perm live on the T6 plug you could run a fused power straight off the battery to save any load on that, re use any old power feeds form caddy for your 20v such as maf to maf, lambda to lambda etc. theres probsably some kind of plug joining main loom to sensor side similar to the mk4 'T14a' which you can splice together

    dash side the mk4 sensor will probably work just fine, if not you can use the tip in the oem guide with the a/c sensor flange, sweap caddy sensor to that. assuming it has a sensor at all, sometimes the later cars dont have a dash sensor at all instead its fed off the ecu via can-bus. what age and engien code is the caddy?
     
  5. Ashleymark New Member

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    Thank you again for replys. I probably should of provided more info on the build. 2008 Caddy had a 1.9 tdi 105 bls engine which has been replaced with a 1.8t auq 20v engine from a skoda Octavia. I have Octavia here still as donor for any other bits needed. I have both halfs of 1.8t loom removed, with ignition side all plumbed in. I have also identified some of wires needed on big caddy plug. Just dont know how to go about joining them up. Do I just use wires from individual coloured plugs to splice into caddy big plug? Caddy side of loom has a t10/14a plug but pins are in different locations.

    Thanks again. Sorry if I'm failing to understand the obvious. I'm struggling a bit with wiring. If it was software or mechanical based I would be ok and could potentially offer advice. But I still have a very old school way of thinking when it comes to wires. Lol
     
  6. rubjonny

    rubjonny Administrator Staff Member Admin

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    ok printed off a diagram for you, 2kblsecu.pdf.

    main issue from what I can see is as I suspected theres no coolant temp sensor for the cluster, it pulls the data out of the CAN-BUS. It also reads rev counter and outputs speed signal over the can-bus as well, its possible the MK4 ECU might be able to talk to the caddy cluster if you hook up the wiring for it worth a try anyway.

    theres only a single oil switch same as mk4,. not sure on the pressure rating caddy cluster expects worst case just swap that over if need be.
     
  7. Ashleymark New Member

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    Cheers mate. Any ideas how I can view that pdf? I know of a couple of builds that had everything working. Coolant oil pressure revs etc. So it can be done. My main goal atm is to get engine turn and rev etc. I can resolve dash issues once I know I have it running. I will spend some time trying to put ur advice into practice and post again if and when I'm stuck again. All of ur advice is greatly appreciated. I just wish i understood it better.

    Thanks again. If i can do anything to help the cause i would love to do so. Donate etc
     
  8. rubjonny

    rubjonny Administrator Staff Member Admin

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    sorry forgot to say, its in my google documents link which is in my signature. signatures are hidden on mobile devices, direct link here
     
  9. Kevcaddy New Member

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    Hi there do you have a wiring diagram for what needs to be used on t14a plug on caddy mk3 for 1.8t conversion thanyou
     
  10. rubjonny

    rubjonny Administrator Staff Member Admin

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    use my mk4 wiring guide for the pinout, then its a case of use the caddy diagrams in my signature to work out all your main feeds for the caddy ecu
     

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