Project EXI

The building of a Marlin 5EXi kit car, using a Seat Leon 1.8T 20v Donor
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Mar 06 2010

Making the first wiring loom


Over the last 2 nights I made my wiring loom.
I removed the rope mock-up and used this as a template to route the cables.
Where I had a jucntion in the wiring loom, I fixed cable ties to the rope, then routed each cable around the rope and added heat shrink cable ID markers as each cable went into the loom.
I didnt label any black cables as it was obvious these are intended to be ground, and these route to one of three places.
Once in place I taped the cables together, every 6cm or so, until I had bundle of cables, this is the loom!!
After 2 nights work, about 7 hours in total, sore knees and a bad back, the first marlin VAG loom was made. Ive taken some pictures of the completed loom, laid out my driveway,the same way it would end up the chassis.
The loom then went into the chassis and cable tied, just to hold it place. I was quite pleased as it fitted easily enough, and I might not have to move any junctions. I will use the rope to create a wiring board, to develop future looms from.
Now the loom was in place, it was time take another look at the donor wiring and drive down another level of iidentifying what cable was what.
I found out some more about the relay box that was attached, to the exisiting donor. One is for the secondary air pump, and the other is for a voltage supply relay. I looked on my engine and the secondary air pump isnt there, it is supposed be under the alternator? I guess Mark at Marlin has removed it. Will have to have a chat to see if the idea was to remove it, or its just been forgotten about. From what I can tell the APP engine is the only one to have this fitted. So hopefully its not needed. I labelled the cable for this on the ECU (single purple wire), just in case it is fitted later, and cut the remainding cables and relay out.
The marlin loom wont have the voltage supply relay, so again labelled before cutting and removed from the cirucit. That makes the donor wiring a little simpler to look at, although there is a huge mass of unknown wires at the moment.
Once these two relays were out of the way, the rest of the ECU wiring loom is pretty striaght forward. It all ends up being mostly single wires, that need to be connected. This section is all the ECU input side. There is a connector for the lambda sensor, knock sensors etc.
The lambda sensor is a brown 4 way connector.
The rest is mainly for throttle fly-by-wire inputs and such like
There is a 14 way connector on the donor wiring ECU putput side, which when idenitfying wires, has things like oil level / oil temp senders, Speed signal, so these are needed.
Almost all of the ECU wires are now identified and label with masking tape. Its a matter of finding the corresponding input/output wire and joining them up.
You'll be pleased to know that the donor alternator cable will reach the battery fuse plate. This cable has a 2 way connector on it at the end which connects to the alternator. At the other end this connects to a 4 way connector. The other 2 way connector connects to the now, hopefully, defunct 2nd air pump, so this can be removed/or ignored.
The 4 way connector on this alternator loom, connects with the 4 way connector that goes off to the fan control resistor, we dont need this, so I cut the out, my 4 way connector now has only 2 wires on it, that complete the alternator circuit. I think this end up going to pin 30 on the ECU.
There are alot more cables to identify. I think i may end up making a new page, to document the above notes, and include the ECU pinout page I have at the moment. This may make integrating the Marlin loom and VAG donor loom a little simpler.

Posted by Steve | Permanent link | File under: electrical