On board computer hack - how long is the wiring harness?
 

I have all the parts pulled together to complete the addition of the onboard computer to my 2001 Boxster S, but rather than spending $80 on the special unobtainium plated Volkswagen wires specified in most builds, my plan is to solder up my own wiring harness.

I have plenty of wire and the appropriate molex connectors laying around, and my soldering iron is plugged in and warmed up, but I'm not exactly sure how long to make the harness, and I prefer to make the harness up before I take the instrument cluster off. From pictures of the hack it looks like it could be somewhere between 12 and 24-inches long, but it's a bit hard to tell. I searched Google and I searched the forums and I couldn't find anything on the length to make this harness.

Do any of you remember roughly how long this wiring harness should be? To be clear we are talking about the five wires that go from the back of the instrument cluster to the plug on the new computer control stalk I'm adding to the steering wheel controls...

Many thanks in advance for your wisdom

I have an unused pigtail in the garage that I bought off a member who used to make them up.
It's 21 inches from the far end of the plug to the end of the terminals on the 4 wires. The 5th, ground wire, is a couple inches longer with a ring connector on the end

You need to place 4 wires into the connector on the back of the cluster. At the moment the 4 spots will be empty. Will you please share how with solder and wire you are going to do what you say?

Yosiefs original instructions say two feet, so that's how long mine is. You could go a littler longer having some extra length won't hurt anything. :cheers:

Thanks all, that's perfect. Obthomas, I already have the correct molex pins that fit inside the existing cluster connector on hand, plus I have the new connector for the steering wheel stalk and more pins that fit in there - so i'm soldering the wires to to the molex pins... If you are not familiar, molex is the biggest company that makes electronic connectors, And they've standardized lots of the sizes and layouts of connectors and the shapes and widths and lengths the pins inside that make the actual electrical connections...

ddrucker

I am familiar with molex. That is why I asked the question. As best I can tell Molex does not make a pin as small as the VW pin needed for this connector. I just finished this project and can say that the wires from the stalk need only be about a foot long. Also the stalk can be installed without removing the steering wheel. Turn the steering and remove 2 screws that hold the cap. Turn the steering the other way and remove 2 more screws. Then the side screws each side. Remove the bottom steering cover. Install the 4th stalk and run the wires into and up to the cluster, put the lower steering cover back the same as it came out. Good Luck.

Once you figure out what the correct part numbers are, you and order "samples" from them for free. They send you a bunch. Also, by ordering both solder and crimp pins, you get even more for free

Thanks again all. The official Molex description and part number for the very tiny pins needed to connect the wiring harness to the steering wheel stalk for this project is "Molex 16-02-0096 Series 70058 Female 24-30AWG Crimp Terminal." You can get them from Digikey or eBay, for a few cents apiece. From your help above, I now know I need Five 24-inch strands of 24 gauge hookup wire - I like to use silicone jacketed wire for this kind of application. One you crimp and solder the molex pins onto to these wires, you insert the stalk end of the pins into Porsche connector 999-650-513-40 (which costs about $5.00) which then plugs its counterpart on the new steering wheel stalk. I've been assuming the same pins are needed on the other end of the wires that connect to the existing cluster connector, I now realize I should probably confirm that the cluster connector requires the same size of molex pins before I start soldering the harness up. I'll be taking the cluster off tomorrow...

I finished this project up today and everything worked fine on the first try.

18 inches is plenty of length if you are making your own wiring harness rather than buying the premade Volkswagen wires specified in many of the guides.

I can confirm that the molex pins I listed above do work for both ends of your cable. They are a little bit wiggly when you place them inside the gray connector that connects to the cluster, but they do fit correctly with the male pins built into the cluster from an electrical perspective.

Now that I'm done I would say I am very modestly impressed with this hack. I guess it's state of the art for 2001. I suppose it's kind of nice to know the outside temperature and how many miles the box thinks it can go before empty, but overall it's a bit underwhelming now that I actually see it in action...

I am curious... I have a 2001 and understand that a stalk or rocker switch is required to be installed in order to even get the temperature reading.

These are essentially momentary switches though... once I attach a switch (and have the computer activated for OBC) and advance until the temp shows, can I then remove the switch? Will the car show temp then by default next time I start or do I have to use the switch to select it with each restart?
Dave

The OBC is turned on by the dealer with a PIWIS, PST2, or you can do it yourself with a durametric. The switch does not activate the OBC features, and if the OBC is activated without a switch or stalk it will always default to the first "page" which is the exterior temp (EDIT - This is only for earlier cars, see JFP's response below). If you cycled to a different "page" the next time the battery was disconnected it would default back to the first page which is the temp display. A switch is only required if you want to cycle through the other "pages" including avg. MPG, miles to empty, avg. MPH. With 2 switches or the stalk you can also set the speed gong feature.

You are correct, on the 2001 just activation of the OBC system will not result in any display; there must be either a momentary switch attached or the fourth stalk, which is nothing more than a fancy momentary switch. If you remove the switch, the display will go dark. Once the switch is installed and system activated, the display will retain the last setting on restart of the vehicle.