After drilling you can remove any burrs or sharp edges with emery paper or with a larger diameter drill bit on the holes. The inside surfaces of your template must be perfectly smooth to prevent marring the front of your tach dial. You can also soak the paper template off the front of the aluminum template with a bit of water or leave it on (we preferred it off). What we then did was cut another one of the paper drilling templates out and sandwiched it into my aluminum drilling template. Use the socket in the centre hole and the smooth ends of the .25" and 0.067" or #51 drill bits in the other holes to act as guide pins. We drilled this to simulate the drilling of my tach dial. Checking it after, all the holes lined up as they should. If they hadn't we guess we would have to make a new aluminum base and start drilling again. We also took a colour photocopy of my dial when we had it out of the cluster. We trimmed this colour photocopy out, sandwiched it in the aluminum drilling template and drilled it. It also came out the way we wanted it:

Step 4 - Drilling the Tach Dial

Okay, now here is where your palms should be getting sweaty! You have one chance at this because if you screw up you can't go down to your local VW Parts counter and buy a new tach dial face for $10. You either have to buy a whole cluster from them (very expensive) or buy a used cluster from someplace like an auto-wrecker or eBay. This is why we took the extra steps in the previous step to ensure my holes were going to fall in the correct spots and that they were evenly placed. Double check and triple check everything at this stage to ensure accuracy. Insert the socket and drill bits you're using as your guide pins. NOTE: the .25" bit is missing in this picture because it wouldn't stand up on it own properly and we were afraid it would fall over and scratch the face of the dial:

Set the top section of the aluminum template on top of it and carefully thread on the wing-nuts until just firm. Then gradually tighten them firmer in a circular fashion to ensure even pressure on the dial. Remove the guide pins and examine the holes to ensure that nothing has twisted in there.

Now it's time to drill. The Dremel drill press was very handy for this because we could get it up to a high speed and it's light to use. Insert a new fresh built into the chuck and start drilling the holes:

IMPORTANT TIP FROM THE DESIGNER: Drill each hole only once, this is important because entering the hole multiple times can make the hole slightly bigger, causing the LEDs to not fit as tightly and therefore be more difficult to work with and bond to the back of the tach dial in the preceding steps.

Remove the tach dial, breath a sigh of relief that it came out the way you wanted it to and relax now, that was the trickiest part of the procedure:

Step #5 - Applying the White Type to the Dial Face

Being a graphic designer by training we had to have the type on my dial match the existing style exactly. We had done a 400 dpi scan of my dial previously so we imported it into Adobe Illustrator and used it as a template to work from. The VW font used is a variation of the classic Futura font that falls between the font weights of Book and Heavy. We chose to start with the Book weight, set a line of characters that we'd need and then convert to vector outlines for editing. We then dragged my outlines over the template in the Illustrator file and started modifying the characters. Once we had tweaked all the characters to my liking, we arranged them onto an 8" X 10" area duplicating them to fill up the sheet and then we emailed the computer file off to a local firm that converts my file into a dry transfer lettering sheet. You can compare the difference between the standard futura fonts and my font in the following sample and compare that to characters on the actual dial. Sure, many of you can't see much of a difference in the end and think this my be overkill but we had to do it.

And here a computer generated test of the font on the dial:

Of course, if all you can find at your local hobby shop is a sheet of Commercial Script, that could be pretty swanky too:


When applying the type, we would recommend starting at the top and working down. We made a special template on the computer that aligns with the tick marks We added to my type sheet to allow easy positioning. You just need to trim along the guide line and then match up the tick marks. It also has the benefit of protecting the dial as you apply the type:

We don't have a picture of me applying the type with the template in place but we think you get the idea by seeing this shot with the aligning tick marks under the characters. We accidentally ripped my type positioning template prior to applying the "20" so we positioned it manually:

When applying the type firmly hold the carrier sheet in position by pressing down in spots on the sheet where there is no type. Use a smooth tipped tool or a very dull soft pencil. When burnishing the characters down, only rub the actual area of the letter to prevent any residual carrier sheet adhesive from transferring to the dial. After transferring the character, slowly lift one edge of the carrier sheet while continuing to hold down the other spots, to see if the complete character has transferred. If not you can drop that one corner down again in registration and burnish the type further to transfer all parts. After transferring each group of type, take the backing sheet that came with the type and carefully place it shiny side down on the newly transferred type and burnish down again for the best bond; this is a critical step to get long lasting type. The good thing is if you do make a mistake applying the type, you can use a good quality painters masking tape (it's the green stuff you see in some of my pictures) and use the corner of a small piece to pick up the damaged type and then reapply it. After your type is applied you can hold your dial up to a light to ensure you didn't place any type over top of the other gauge warning icons:

What we did at this point was was cut out a piece of paper a bit larger than the dial and with a semi-circular window around the LEDs cut out as well. We taped the dial face down on this to protect it and the newly applied type. We then taped a few of those flat plastic pieces to that paper to use as spacers (not near the LED holes or where the type is) and then taped the whole dial face down to a smooth clean sheet of paper with some of the green masking tape. This will protect the dial face, the type and allow a clearance for the LEDs to be inserted in the next step. In fact we left it taped together like this to protect it until we were ready to install it back into the cluster.

Step 6 - Inserting and Bonding the LED Indicators

You can now insert your LEDs into your drilled holes. Remember that you're now working in reverse and that "0" is on the right and the "20" (or your gauge max) is on the left. We found that the blue LEDs slipped into the holes with very little resistance but the reds required a bit more force though all easily stayed in position when inserted. It's because of this that we only drilled each hole once as per the important note in step 4 above. If the holes were any looser you may have problems keeping the blue LEDs in their holes as you work with them. We positioned my LEDs so the anode lead (the long one) would be on the inside of the circle:

If you notice in this picture with all the LEDs inserted, we had to twist the ones near the "20" and "60" to keep them from obstructing the numeral:

Okay, now it's time to permanently attach the LEDs to the dial face. What you need to do is place a small dab of caulk between each LED. Only touching the facing sides between each LED and the dial face. Not along the inside or outside of the LED circle and not above the level of the plastic LED body. Probably with a small tube of caulking you can poke a small hole in the end of the plastic applicator and apply the amount of caulk you need in this step but we accidentally cut too much off the applicator end without thinking. Therefore we had to use something to apply the caulk to the LEDs. It was suggested to me to use toothpicks but we were out and we ended up using wooden skewers. These actually worked great because we could hold them like a pencil and they were probably much easier to control than a short toothpick:

You can see in these pictures that we also applied strips of masking tape to the dial where the dial numbers come close to the LEDs. This will protect them from getting messed up with the caulking, paint and other stuff. Here's the first step of bonding done:

When this step is dry (4 to 6 hours) you need to add a very very small amount of caulking around the inside of the LED circle and a small amount around the outside edge. Let this now sit for 12 to 24 hours to dry.

Step 7 - Soldering the LED Indicators

Trim all of the anodes to about 0.5" and the cathodes to 0.125". We did these at this step but you can also trim the leads before inserting them into the dial:

Using small needle-nose pliers or tweezers bend all anodes over 90° to touch the neighbouring LEDs anode. You can also hold the LED firmly with the pliers and using a small flat blade screwdriver, push the lead over as required. The wiring will all be running out the left side so we bent all the anodes in a counter-clockwise direction. Solder each anode lead together using a soldering iron with a clean nicely tinned tip. Be quick with the soldering iron and add a bit of solder to the tip before touching the anode leads. If you're not too experienced soldering then we would recommend practicing on about 25 test joints of solid core 24 AWG wire before starting on the LEDs. You can also get an aluminum heat-sink clip to clip on to the leads between the joint to be soldered and the LED. We used it on one or two of the more pesky joints. REMEMBER, too much heat during soldering can kill your LEDs!

It was at this point we first tested our LEDs to ensure we didn't fry any of them with this first wave of soldering. Using your 12V power supply connect the 3.3k Ohm resistor between the positive lead on the power supply and the common connected anodes on the dials and then using the negative wire on the power supply touch each separate cathode lead to ensure each LED lights.

You should now paint the completed LED assembly with the black enamel paint to opaque the LEDs. This is to prevent the stock tach dial LEDs from shining through the boost gauge LEDs when the dash is lit. Paint all sides of the LEDs and even the soldered anodes since it doesn't matter at this point. IMPORTANT: Do not paint the unconnected cathodes or they will be difficult to solder. Hold the whole assembly up to a bright light to see if you can see any light coming through the LEDs from behind. If you see light you need more paint in some spot. Let the paint dry for about 4 hours.

Now it's time to solder the the LED wires to the cathodes and one wire to the common anodes. Do this anode wire first and mark it well with a piece of tape to make things easier for you. We started by cutting 21 (1 anode wire and 20 cathode wires) 18" lengths of 28 AWG wire and removed 0.125" of insulation from one end of each wire. I also bent the cathode leads over about 45° beforehand. Starting with the "20psi" LED we soldered on the cathode wire and continued soldering the wires on clockwise going down numerically. We then tested each LED again with my power supply to ensure we didn't fry any of the LEDs.

Bundle all of the wires up into a neat package and tie down every .5" to .75" with the fishing line. Run the fishing line under the soldered loops of the anodes and over the wire bunch finishing with a surgeons knot (that's a regular knot but crossing over the ends twice instead of once and then finishing with just a single knot crossing once):

You can now go over the whole assembly with the black paint to ensure no light can come through the LEDs at this point. Let the paint dry. We also had to trim back a bit of the caulking we applied since it was interfering with the dial type:

Step 8 - Attaching the LEDs to the Control Unit

NOTE: You may skip this step if your LED wires are already soldered to your control unit.
 

These pictures show a complete Boost Control Board with the "Dimmer" technology and a wiring layout diagram.




We first trimmed about 0.125" of insulation off the "connector" ends of the wires. We then taped a 15" piece of making tape, sticky side up to my work surface and with a felt marker wrote the numbers 1 to 20 about .5" apart along the tape. Then using my power supply we checked each wire to see to which LED it belonged to and then pressed it into the tape over top of the corresponding number. Once we had these all figured out We were able to press the wires into the female connectors in the appropriate spot using a small flat blade screwdriver. Once they were all in position we could close the main clip over all the connections. We double checked my connections in these connectors by hooking up the positive wire of the power supply to the anodes and sticking the negative in each hole on the female connectors:


We hooked up my own power wires and boost signal wire to the control unit but yours will probably come pre-installed so we won't cover that for that reason and/or you can probably figure it out for yourself if you've gotten to this point.

Here are some pics of my completed unit:

Step 9 - Installing the Completed Tach Dial back into the Cluster

Your cluster needs to be out of the car and the front portion of it needs to be removed at this point. If it isn't, do it!

It has been suggested to me to add a piece of reflective foil along the inside of the edge of the white dial support. We don't know if it makes a difference or not but it can't hurt and it takes no more than 2 minutes to do. We added about 4" of double-sided tape along the inside of the white tach housing and applied tin foil (shiny side out) on top of the tape:

It's now time to replace the tach dial assembly. You will not be able to twist it on, reversing the procedure you followed when removing it, because the LEDs and wires are now in the way. Just place the tach dial on top and gently press it onto the white plastic centre post until the dial snaps on over the white tabs. Trust me, they will snap over. The wires are going to need to make a sharp left turn under the LCD display and then make a sharp right turn out of the cluster housing... which you will also need to cut a hole for. We just used the Xacto knife to whittle my way through the plastic and that only took me about 4 minutes so it's up to you how you do it. You could drill it out or file it but the most important thing is try not to get any dust into the front of the housing because it might be difficult to get out of some of the cracks and crevices in there. That's why we chose the whittling method since it keeps the waste bits larger and easier to see and remove:

Step 9a - Testing the Completed Unit

It is best to test the whole setup before you put the cluster back in the car just to make sure you have everything all in order. It is far easier to troubleshoot a problem when the cluster is still on the workbench as opposed to being in the vehicle.

Perform the following:

• Turn the Zero Adjustment Control (P1) fully Clockwise
• Connect  +12v to the RED main unit Power wire (Pin 5 of the I/O array) and Ground or -ve to the Black wire (Pin 1 of the I/O array)
• Take the MAP sensor input wire (Pin 4 of the I/O array) and touch it momentarily to +12v, all the Indicators should come on. They may go out or stay on when you remove the MAP signal wire from +12v.  You should not leave the MAP signal wire connected to +12v for any length of time or you could do damage to the unit. Nut momentarily will not do any harm at all.
• If the lights remain on, you can momentarily touch the MAP sensor signal wire to Ground or the -ve, this will turn all the indicators off.
• If +12v and Ground Power is left to the unit for any length of time, the indicators will eventually all come in starting slowly from 1 - 20. This is normal and cannot damage the unit. However, it is NOT recommended to leave all indicators on for extended periods of time. The Boost control unit will get quite warm to the touch if this occurs.

Step 10 - Installing the Completed Gauge Cluster into the Dash

Okay, time to head back out to the car to install the modified cluster. The first thing to do is splice the +12V power, ground and boost signal wires on to the respective wires on the harness at your ECU. The first thing to do is turn your ignition on the the accessory position and then turn on your windshield wipers. When the drivers side wiper is pointing straight up turn off the car. You want the wiper to stop in this position so you can remove a plug in the black plastic rain gutter to give you access to the back bolt on the ECU box.

IMPORTANT: Please disconnect the positive and ground cable on your battery before proceeding. You may want to make note of any radio pre-set stations since these may be erased when the battery is disconnected.

We were going to do some pics of the ECU access and removal but passaturbonium on ClubB5 has already done a great article on how to get the ECU out. Here's the link: ECU removal info/pics

Remove the 5 - 8mm hex screws from around the edge of the ECU box. Three of them are easy to get at with a socket wrench and the one towards the centre of the car requires either a regular open ended wrench or small adjustable wrench. The one at the back under the black plastic rain gutter requires you to pop out the black plastic plug with your fingers from behind. Using both hands so you don't drop the socket, carefully place just the socket on to the hidden screw in back, then down through the hole in the rain gutter insert a long socket extension or socket driver handle into the socket. With this last screw out you can remove the black plastic cover from the ECU.

With the cover off you will see the ECU which is held down with a spring steel strap. To remove the strap take a large flat blade screwdriver and place it into the lower hook closest to you and lever it towards the centre of the car to disconnect the catch at that end. It will release and can be removed.

The ECU will now be loose but still connected to the two harnesses with a large and small connector. There are handles on the outboard end of each connector. As you pull these handles out the connector will pull away from the ECU. Once disconnected, set the ECU aside.

Starting with the smaller of the two ECU harnesses, start unwrapping the hockey tape from the harness. There was an available end on mine that we could start unwrapping at and take about 6" off. If you can't find an end, just carefully cut the tape with your hobby knife. Don't try to save this tape to reuse it because it's not worth it. Locate the grey/blue wire and splice the boost signal wire from the control unit to this one. If using just a ScotchLok splice you can now wrap the harness with two layers of electrical tape. If you choose to solder this splice as we did, wrap the splice with two layers of electrical tape and then wrap the harness with two layers of tape.

Now do the same on the large harness for the control unit power wire connecting to the black/blue wire, and the control unit ground wire connecting to one of the brown wires. Pass the other end of these wire down into the cabin through the hole in the back of the ECU box. From under the dash take the dimmer wire from the power connector harness and splice it into the green/red or grey wire on your headlight switch harness. This is the wire that activates the dimming circuit on the control unit when it receives a +12V signal from the parking light circuit.

Reconnect the battery cables, positive first followed by the negative/ground.

Connect the 4 wire connector to the respective 4 wire connector going to the Control Unit and reconnect the blue and green connectors to the back of the cluster. Do not try to completely reinstall your cluster yet because you need to calibrate the "zero" setting on the boost gauge and set the night dimmer level. Reconnect the headlight switch. Put you key in the ignition and turn the key to the "On" position without starting the car. Turn the headlight switch to the full headlight setting. With a very small flat blade screwdriver turn the "calibration" screw on the control unit clockwise until a few of the LEDs light up... the more the better. Then turn the "dimmer" screw either direction to set the brightness to an appropriate level for night time viewing. Turn the head light switch off. Now turn the "calibration" screw counter clockwise just until no LEDs light, then turn it an additional 45° (or 1/8th of a turn):

Your unit is now calibrated, ready to be reinstalled back into the dash and your car can be re assembled.

Once it's all back together give yourself a pat on the back and go for a nice long drive to admire your handy work... but watch the road too!

Step 10a - Alternate Setup & Calibration

Calibrating the Control Board

Calibration is really simple. Simple adjustments can be done before you even wire up the LEDs. It is best to check some basic voltages. All voltages are respect to the control board’s ground.

Here is what we did:

·        There should be about 1.8v on Pin 5 of the Input/Output (I/O) Bank on pins on the PCB. Or between the car’s stock pressure sensor output pin (Pin 101 on the ECU) and ground, assuming it is connected to the Boost Control Unit PCB.

·        There should be about 1.7v on Pin 4 of IC1. This can be adjusted using the Zero Adjustment P1. Turn P1 Anti-Clockwise to increase the voltage and Clockwise to decrease it.

IMPORTANT NOTE: If the voltage on Pin 4 of IC1 is above 2.5v, very erratic and inaccurate readings will result. It is best to set this first to about 1.7v.

When you first power the unit on with the LEDS connected, some of them may be on. Simply turn the 25 turn adjustment trim pot P1 Ant-Clockwise until the first LED is the only LED that is on. Remember Anti-Clockwise Turns the lights off and Clockwise turns them on. If you are in doubt, simply turn P1 Clockwise for a few turns until the lights come on. Then turn the adjustment trim pot Anti-Clockwise until LED 1 just goes out + about 1/8” of a turn. That’s it, you’re done!

Setting up the Dimmer for Night Time

This adjustment is also really simple. You may need to wait until dark to do this. Simply apply +12v to pin 2 of the I/O bank of pins, or just turn on your lights if you have wired it up to the car’s light switch. When in operation the lamps will be noticeably dimmer. You may want to adjust Zero Calibration (P1), with the ignition on but with the engine off, Clockwise to turn some lights on, (only a few of the lower LEDS will be able to be turned on) so a few indicators are on. You can then adjust the dimmer’s night setting adjustment (P2) Clockwise to set them dimmer or Anti-Clockwise to set them brighter, until you get the desired brightness. Once this is complete you may have to re-do the Zero Calibration of P1 as mentioned earlier.

Step 11 - Admiring the Finished Product

The following photos show various close ups of the dash after re-installation into the car.

We hope you find this article interesting. If you would like more information on this great mod, please email us or go to our Gauges For Sale pages.

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