How to Install a Boost Gauge and Wires in an MKIV VW or Audi
Installing a Boost Gauge
This is a great mod for any turbo car. It's cheap, easy, it looks good, and, most important, it helps you monitor your boost. For a nice stock look I would recommend Autometer Cobalt boost gauges, I personally think that they look the best, but they can be expensive. For a cheap but still quality gauge I would recommend VDO. In between the cost of those two gauges, there are numerous brands to choose from. Just make sure the gauge you choose allows you to change the light so you're not stuck with a lime-green light that doesn't match anything in your car. As long as you can change the bulb, you can use any color LED size 194 light you would like.
You will also want a gauge pod for your gauge to sit in. Whether you want the gauge attached to the pillar (next to the window) or the steering column (more of a stock look), I would recommend the company NewSouth for your pod. The nicer full-column pod costs around $40, and once it's installed it looks like it is part of the car. In this DIY, I'm using the half-steering-column pod, which in my opinion is a little ugly. The pods are made for 2 1/16th inch boost gauge, so when buying your gauge keep the size in mind.
In this DIY I will be primarily focusing on installing the wires correctly. I will also cover the boost hose installation briefly, but that information can be widely found on the wonderful world wide web! Also, a boost hose was already installed on this car by the previous owner, but I will show what vacuum tube to tap into for your gauge; it is a simple part of the installation.
Tools and Parts for Installing Wires
Only standard tools are needed. The only tool I'd recommend buying if you don't have it is a wire stripper which is completely optional.
- Tape: Teflon plumbing tape, electrical tape, double-sided tape
- Needle-nose pliers
- Vise grips
- Various wrenches (at least a 10 mm)
- Flathead screwdrivers
- Torx screwdriver or bit
- 14-16 gauge wire (around two feet)
- Butt connectors
- Boost gauge tubing kit and pod
Install Time and Tips
This instillation should take about 30 minutes to 2 hours depending on how fast you work and any complications you might come across. The biggest time killer for me was screwing the clip into the back of the boost gauge to secure it to the housing. Depending on the brand of the boost gauge you may or may not have to use the supplied clip; some boost gauges are a little fatter and secure themselves tightly in the pod. Also, before you get it all hooked up in the pod, check the light to make sure it illuminates. I forgot to do that and had to take it all back apart to reverse the LED. I might also recommend you remove the negative battery cable from the battery, so you do not blow out any fuses or shock yourself while cutting wires, but I'm not your mother, so make that decision on your own.
Installing the Boost Gauge Wiring
- At the bottom of your knee panels beneath the steering wheel there will be 3 Torx screws, I believe size 20 or 25. Remove those three screws, and the plastic panel above the pedals can now be removed. (No picture here, as mine was missing).
- Take a flathead screwdriver—with some electrical tape folded over the blade so you will not scratch the button or vent—and lightly pry at the sides of the dimmer switch. With very little pressure you should be able to release it. Once it is released, wiggle it out as much as you can. The switch is being held on by two metal tabs on the sides. If one should fall off, don't worry, they can be slid back onto the switch during re-installation.
- You should be able to work the switch out enough to reach the wire harness clipped into the back. Squeezing the sides of the harness will release it from the dimmer switch.
- Pull open the fuse panel door, use a screwdriver in the little notch if needed and place it to the side. Now pull directly out on the panel surrounding the fuses. (It is placed in there the same as the fuse door, clips around the front and sides and slides out in the back). Pull it like in the picture and once it starts to pop out wedge your fingers in the crack and gently pry it off.
- The piece of trim directly above the steering column will also need to come out, but does not need to be completely removed (it is connected in the middle by a piece of leather). Just grab it on both sides of the steering column and pull forward; it should slide out pretty easily.
- Reaching into the side panel that you removed, you can pull out the harness that you disconnected from the dimmer switch. The harness will have three wires attached to it: a grey one, a grey one with a blue stripe, and a brown one. Cut the grey wire with the blue stripe about two inches down from the harness, and strip the ends of both sides.
- Take whatever wire you will be using as your positive connection and feed it through the trim you removed on the steering column. Looking through the side panel you will be able to see it flapping around in there, grab it and pull it to the dimmer wire harness.
- Twist it together with one side of the grey/blue wire and crimp your butt connector hard—yeah crimp it hard, real hard, make it call you daddy—so the connection will not come loose. Before you crimp the other side on, it helps to fold over the wire to make it a little thicker. Once both sides are crimped you should have a connection like in the picture below.
- Optional. For the negative wire, you can go through the same process to attach it to the brown wire on the harness. But if you would like to avoid cutting more stock wires, then follow the directions below.
- If you look above the pedals under the dash, you will see a relay panel with four different bolt posts (pictured). To the left side of the bolt post labeled "75x" (circled in green), there is another 10mm bolt (circled in red) that holds the panel to the car. This bolt is a great place for the negative wire.
- Feed the wire through the steering column, like you did with the positive wire, and pull it through near the pedals. After you loosen the 10 mm bolt you can wrap the wire around it and retighten it, but I would recommend instead using a small terminal ring crimped to the end of the wire then screwed back on around the bolt. Keep it clean and stock looking.
- Your wiring is done! The gauge light will turn on and off with you dash lights and brighten or darken with the dimmer switch. Before you screw your gauge into the pod, remember to check and make sure the bulb lights up, if you are using an LED light. If it doesn't light up, flip the bulb around and try it again.
Boost Gauge Tubing Install
Like I said I'm not going to cover this topic extensively as it is pretty simple and there are hundreds of DIY's out there covering this part. This is the most common way that people route in the boost gauge hose. Once I get my DIY article on N249 delete written up, I will show you a cleaner method using the extra hard vac line. Also, I know the vac lines look like a sloppy mess ... I just had to get everything hooked up and attached to pass emissions. Also if the hose for your boost gauge is hard plastic, I've found ¼ inch silicone hose from the hardware store for about 50 cents a foot is a nice replacement.
- In the picture above, the item circled in red is your FPR (fuel pressure regulator). This is the easiest and most common vacuum line to tap into that shows both vacuum and boost coming from the intake manifold. It is located on the right side of the fuel rail (towards the windshield if you have an Audi), and unlike in the picture, the hose will be black braided fabric. It will look somewhat like bicycle-pump hosing.
- Cut that hose in half a few inches or so from the FPR and insert your "t" coupler for your boost hose. You can use tiny hose clamps to tighten it on, but I suggest using zip ties instead. It may sound trashy, but if you use black you can't see them, and they seal a lot better than small hose clamps.
- Now on the firewall (under your windshield in the engine bay), you will see a black disc about a foot across stuck to it (your brake booster). Just to the top of the disc and to the left, there is a little rubber round grommet about a centimeter in size. That is where you will be running your boost hose into the car; it is also where you would run an amplifier cable for sub woofers. I like the cars, the cars that go boom! My name is....
- With some needle-nose pliers, pull that grommet out, or push it through to the other side and you should be able to find it somewhere by your pedals. With a razor blade, cut an X in the middle so you can run your boost hose through it and re-insert it into its hole.
- Push your boost hose through until you can reach it under your pedals; once you can, grab it, route it up through the steering column trim, and attach it to your boost gauge.
- Back on the engine side, cut off the extra hose, leaving a little slack, and connect it to the "T" coupler you inserted into your FPR hose. Done.
The 75x 12-Volt Switched-Power Bolt
I figure it can't hurt to go over this bolt post circled in green in the picture. This post supplies 12 volts of power whenever the car is turned on. So if you don't mind having your boost gauge light constantly on when the car is running, you can attach it to this bolt post.
This post is useful if you have a Mark IV Jetta, GTI Golf, etc., with a double-DIN stereo and you would like to run an aftermarket stereo. Trying to connect the aftermarket stereo ignition wire, which is usually yellow with a red stripe, to the Volkswagen radio harness will not work. Connecting the ignition wire to another wire and running it to the 75x post will allow the stereo to work properly when the car is turned on and off.
You can also use this post if you want to run floorboard LEDs (loser) or anything else that runs off of 12-volt power that you want to turn on once your car is switched on.
The two posts next to the 75x, which I believe are labeled 30x. are constant 12v power supplies. I can't think of any logical use for them besides blinking alarm lights, unless maybe you want to set up surveillance equipment in your car.