CE2 into an A1 Wiring Conversion Walkthru Overview

As you can imagine a good majority of the wiring from the A3 car is unnecessary. I wanted to eliminate as much of the excess as I could, and the CE2 harness made this very easy.

My first step was to label every connector so I knew what each one did. I then unwrapped the harness and was able to pull out the connectors and the associated wiring for the accessories I would not longer need. In most cases things like AC and cruise control could just be pulled out without cutting a single wire other than maybe a ground or two.

Here's a link to the complete connector by connector and pin by pin layout of the CE2 wiring system.

Splicing

Due to the number of splices this conversion requires I highly recommend the investment in a good quality soldering iron. Below is my procedure for splicing wires, it may be overkill but I hate electrical problems, and with this many splices that last thing you want to do is have bad splice somewhere.

1. Crimp wires together with a non-insulated butt splice leave a little copper exposed on both ends
2. Solder the wires and butt splice together
3. Coat the entire connection in liquid electrical tape (Available at Home Depot or Radio Shack)
4. While the liquid tape is still setting up slide over the heat shrink tubing and heat it up.
5. There you have it, a perfect wire splice; impervious to water, a great conductor, and structurally robust.

Mounting the CE2 Fuse Block

Mounting the fuse block is surprisingly easy, the two slotted hooks for the A1 fuse panel are the exact width for the A3 panel. I only had to cut out the bottom bar where the A1 panel screws in and the A3 fuse panel hook right into the two slots of the A1 hanger.

A little messy in this pic but this how the fuse panel hangs

The Steering Column

I’m not going to lie, this is probably the most tedious part of the whole wiring job. You will more than once go why am I doing this, but trust me it’s worth it. The A1 and A3 Steering columns are just different enough to be confusing. I would give a specific wiring diagram of the procedure but there are significant variances to wire colors depending on the car. So instead I’ll give an overview and some tips of how to go about sorting it out for yourself.

• Almost all the wire colors from the A1 harness match up to colors in the A3 harness.
• The A1 ignition switch matches up exactly wire for wire with the A3 ignition switch, though the wires are different gauges.
• Something to look out for; the Warning Light Switch is part of the A3 steering column and a separate switch on the A1. You will have to run wires from A1 Warning Light switch back to the A3 Harness.
• The pins of each connector and switch are identified by code on the back of each item with small black lettering in the plastic (It’s very hard to find on some connectors). These pin codes match up exactly with the labels in the Bentley and are the same for the A1 and the A3. Match the pins with the wires and you’re golden.
• Just to give you a sanity, check in a couple of cases 3 or more of the same color wire will be spliced together. There are also 2 white wires on the A3 harness which are spliced together with one white wire on the A1 steering column.
• Finally, the easiest way to do this is to test your connections one by one. I hooked up one thing at a time, ie a turn signal bulb, and worked out the wiring till I got it to work.

Interior Wiring

Well I spent a good deal of time looking at this but was able to make it extremely simple. I essentially cut out anything I didn’t need and it boiled down to 4 main wires that come straight from a connector on the A3 fuse block that can power the interior.

1. Constant Power (+) Red
2. Switched Power (+) Blk/Red
3. Interior Lights (+) Gray/Blue
4. Ground (-) Brown

On my car I used a terminal strip with spade connectors and made a power distribution block for each of these items. You could also simply splice all of the same color together. I did this to mine as I plan a dash swap in the future and wanted a simple way to wire up the new dash.

Interior Lighting

I’m still working on this, but the door switches essentially provide ground (-) to the interior light when the doors open. So if you find the positive (+) wire running to the dome light and you hook it into a constant power in the interior they will work since ground is used to do all the switching. If you want the cool delayed dimming feature of the A3 like me, you’ll have to find the appropriate power lead from the fuse block.

Front Lighting

This part is extremely easy, I recommend using the A3 connectors and bulb holders where possible but all the wire colors match up by connector. Simply cut off the A3 connector and splice the wires with matching colors to the A1 connectors.

Rear Wiring

The rear wiring is very similar to the front, but in my car a couple of the wire colors didn’t quite line up and I had to go to the Bentley. I have the pin outs here on my website for the connectors for the rear wire harness which makes it very easy to line things up. Another thing I did was run my own ground wire in the harness. The Jetta’s ground wires for the rear of the car seemed to spider web out into a huge and un-needed mess.

The rear harness also has the wiring for the fuel pump and the fuel tank sender, and the A1 wires match up directly with the same color wires from the A3 harness.

As a side note since I used a Jetta, I was lacking the wiring for the rear window wiper which I am removing anyways. To use this option you will need the rear wiring harness from a Golf.

Headlight Switch Wiring

I have to admit I was getting lazy and I just used the A3 headlight switch and harness. You can sort it out fairly easily and hook it all back up to the A1 switch.

Rear Defroster

Still working on that, the wiring and colors all match just need to hook it up.

Radiator Fan

The A3 2.0 uses a more complex fan setup than the A1. The A3 has two speed fans while the A1 has a single speed fan. Because the A3 has a 2 speed fan it has multiple fan temperature sensors and a fan control box just behind the battery. To make things simple I cut the fan control box off the harness at the main power wiring going in from the fuse block. I then ran this power wire to the A1 fan switch on the radiator and used the rest of the A1 fan wiring which consists of a positive (+) from the other side of the fan switch and a ground running to the fan motor.

Brake Light Switch

Depending on your year of rabbit you may or may not have a brake light switch on your pedal cluster. I was lucky and was able to just splice the two wires into the switch on my pedal cluster. Other A1 cars have their brake light switches on the master cylinder in the engine bay and will need these wires extended into the engine bay or to have a pedal switch somehow retrofitted.

Horns

I used the A3 horns as they plug into the harness and bolt in place of the A1 horn.

Windshield Wipers

A3 wires match up by color and wire by wire with the A1 connector.