View original topic: Complete how-to: Factory cruise control into MK3
leecat Thu Aug 15, 2019 5:14 pm

This week I decided to add complete MK3 factory cruise control to our non-cruise standard transmission Cabrio. I've benefited tremendously from many, many 'how-to' guides on TheSamba, so I thought I would try to do a complete start-to-finish writeup on this little addition with plenty of pictures and maybe help someone else out.

While air conditioning is for Jacobites and anarchists, I do adore cruise control. It's just not fair that I see other people zipping down the road at a constant speed without a care in the world while I suffer gas-pedal-leg cramps and blood clots, all at wildly varying highway speeds of 40 to 80 mph. Hopefully this little writeup helps out those who, like me, suffer from longtime cruise envy.

I cannot believe VW would sell me a car that has the most awful, annoying alarm system ever as standard equipment - and yet no cruise control that I would actually use daily. I guess though to be fair no one has ever stolen my 8-pound 1995 VW tape deck. Mit Dolby!!!

It can seem daunting but it's actually a very easy install - doable in a full day or less by anyone with very basic mechanical and electrical knowledge - you will of course curse the fact throughout that Volkswagen thinks giving you an extra millimeter ANYWHERE to work would invite sloth and sin and lead to the damnation of mankind.

As a quick aside, be aware that there is about a 95% chance that any cruise control computer you buy from a wrecker is garbage and will need to be repaired - they were junky from the get-go on the MK3's. If you have basic soldering skills and a soldering gun, it's doable. The second unit of two that I repaired worked, and I call that good odds. Here is a link to the repair procedure:

Once that link goes dead in the distant future - when giant mutant bees rule the world so it probably won't matter - simply search "VW Mk3 cruise control repair" and that should set you up.

Spelunking under that dash is an adventure in itself, but with determination and four-jointed fingers it's manageable. If you have an assistant who is 18 inches or shorter in height that would also help. The base car is set up to take cruise control, you just need to find a donor car and pull the components listed below. The real upside? To a wrecker it's just a pile of little crap, so it should be dirt cheap.

Be precise with your verbiage when buying - don't say "Cruise computer", but rather "Cruise module" or "Cruise relay". If the wrecker counter-person hears 'computer' the price often goes up.

Of course all the usual safety precautions apply - disconnect the battery, be careful during the steering wheel airbag removal, etc. If you stab yourself with a screwdriver or get trampled by rogue elephants, well, please don't blame me.

The Donor: I had a 1997 Jetta parts car on hand from my ABA Vanagon swap, and it had a complete cruise setup. While troubleshooting another Cabrio cruise install I had tested all the components so I knew they were good.

The Recipient: Our lovely little 1995 Cabrio. Reliable, thrifty, and slow - yet so very fun.

Things to get from a donor:

-Gas pedal actuator vacuum pod, with bracket (13mm nut)
-Cruise Control wiring harness (pictured below)
-Vacuum pump (located under the front windshield washer reservoir)
-Cruise control module (behind left-most front air vent/headlight switch)
-Clutch and brake vacuum switches
-Column switch assembly (you can get by with just the signal/cruise half)
-Soft vacuum hoses/T-connector (usually in great shape, being inside car)

Possibly required:

-Accelerator pedal (my '95 did not have the ball for the cruise actuator pod)
-Pedal-assembly-mounted Grommets for the clutch and brake vac switches (these are NLA from the dealer)

It's SO MUCH EASIER to pull the components if you can remove the dash from the donor. There are some great dash-pull writeups out there, it doesn't take long to pull the dash out of a wreck and will save you a LOT of heartache and cursing to do so. Save that for the actual install.

I'll break this down into steps, tho you can do them pretty much in any order, as long as you do them all! :) I just love distinct, numbered steps when I'm tackling something - seems to make everything much more manageable if you can break it down into an easily verifiable checklist.

Here is a pic of the harness and components - (you can actually do the install just from this one picture, if you are familiar with VW wiring and cruise pieces).

Here is an illustration of the entire cruise system as well to make sense of the harness and connections:

TIP: Print the above picture(s) and take them to the wrecker, to make sure you get all the pieces. Don't forget the vacuum pod bracket, not shown above but pictured separately below.

PULL THE FRONT DRIVER'S SEAT and lay thick mats, carpet, foam, etc. on the floor to save your back from the spine-destroying seat mount. You'll be working upside down for hours, and I can't imagine doing this with the seat in.

1. Flip up white fuse-panel-retaining clips and lift the fuse panel down - you DID remember to disconnect the battery, right? The right-hand fuse panel bracket has a terrible tendency to touch the back of the power leads on the fuse panel while you're fiddling. ZAP!!

2. Remove green wiring plug 'W' from the back of the fuse panel and replace it with the one from the cruise-equipped car. REMEMBER to use the pull-out tab on the side of the fuse panel to release the plugs (pictured)!!! The new plug contains the power feed for the cruise system. Full credit to A2Resource for their fuse panel diagram.

Plug the blue/white single-wire plug from the 'W' green plug into the blue box on the top of the fuse panel. On some later MK3's ('97 and up) the blue and green boxes mentioned here are not attached to the fuse block, but are larger and sit above it (second picture).


3. Make sure your accelerator pedal has the ball stud at the very top for the cruise actuator pod. You can feel/see it up there (with a flashlight) - you're ahead of the game if it's already on the pedal.

3a. If you have to change the pedal out, remove the accelerator cable (simple snap-in) from the very upper tip of the pedal, then remove the pivot rod circlip halfway down the pedal arm, tucked between the console kick and the pedal arm. Curse-lubricant may be required, it's a pain. Then slide the pin out the left side - installation is reverse of removal. Note that it IS possible to break the tip of the pin while removing the circlip - you are not authorized to ask me how I know. If you get the cruise-type pedal, take the pin and circlip too. Just in case.

4. Install the vacuum pod - attach the bracket (pic below) to the pod with a 13mm nut BEFORE installing. If you enjoy frustration a lot though, by all means try installing the bracket first, then the pod. The bracket is held to the dash frame with its own 13mm nut. The green rod on the pod clips to the ball at the top of the gas pedal arm. It's tight working in there, but it all does fit. You can test the vacuum pod before installation by pushing the rod in and holding your finger over the vacuum port - if it holds vacuum, it's good. The green rod IS on my pod pic below, just hard to see because of the angle - sorry.

5. Insert the vacuum switch grommets (see below) and switches for clutch and brake into the pedal assembly. In case your assembly does not have the grommets, and you pulled them and now forgot which holes they came out of, here's a pic with handy arrows:

Before you can install those brake and clutch vacuum switches though, lets talk about these push-in metal vacuum-switch grommets. If your pedal assembly is not already equipped with these grommets (that the switches thread into) and has just bare holes, be prepared for anguish. Specially designed by VW engineers with your frustration in mind, these Grommets from Hell are viciously hard to remove intact. AND no longer available from the dealer. Grab spares from the wrecker if you can salvage them. These savage little technological woodticks are the worst part of the whole swap, hands down.

NOTE: The switches have to be threaded in far enough to be fully closed when the pedal is at rest. When you depress either clutch or brake, the switch disengages and breaks vacuum.

6. Column switch! Now that the grommet nightmare is just a bad memory, like that overly-touchy counselor at summer camp, you're almost on the home stretch! Remove the steering wheel airbag (hex screws on some, push-pins on later models - there are many good threads/videos on this), plastic upper column surround (two screws from underneath) and carefully unplug the airbag wire. A 15/16 socket works to remove the steering wheel nut, and VW steering wheels are generally pretty easy to remove.

Pull the three screws from the cruise-equipped column switch, unplug the wiring plug, and remove.

You can disassemble the switch itself and replace just the signal arm with the new signal/cruise switch arm, but it's fiddly and prone to the little plastic tabs that hold the two halves together breaking and/or little springs going SPROING under the workbench. It can be done pretty easily with care and attention though. Go slow and careful if you have to go this route. Then reinstall the new switch onto the column.

And put the steering wheel back on securely. If you forget this step, handling could be adversely affected.

7. Start plugging stuff in! Brown ground wire running right off the cruise module goes to the ground tree on the driver's left kick panel up under the dash...the remaining blue plug (blue/white wire) and green plug (yellow/black wire) plug to the blue and green boxes, respectively, above the fuse panel. When plugging yellow/black to the green box, connect to the portion of the box that already has TWO wires (black/blue stripe & black/white stripe) incoming to it. Diagram below ('TV5' is the green box you're plugging into).

Then the thick rubber vacuum lines can be reinstalled - orientation is below. Far right one runs to gas pedal vacuum one to brake vacuum switch, then to clutch vacuum switch. The longer one will run to the vacuum pump in a moment.

When plugging the harness into the vacuum switches, here is a handy little rhyme: "Blue for Brake and Clear for Clutch"! That matches the wiring ends to the correct switch.

You can mount the cruise module in the factory location, on the same bracket that holds the alarm module. I removed my vent surround and headlight switch to make it easier (well, 'Volkswagen easier', which means it's all relative) to work from the front.

Now route the column switch plug up below the instrument cluster and to the switch, and plug that in. There is also an additional black/red wire with a green plug (running from that 'W' plug connector on the fusebox) that can now be plugged in, if you haven't already. It's the only unconnected wire left, so I'm sure you'll find it. It's pictured in the photo just below the 'Central Electric 2' diagram, above. Re-hang the fuse box.

8. Vacuum Pump: The final step is the vacuum pump. Personally I'm going to diverge from canon here because no way was I going to run the pump back to the stock location under the washer reservoir and have to run a line through the firewall. If you look at the cheap tiny plastic line that VW used to run from the interior out along the frame rail to the pump, it's no wonder that no MK3 VW's have working cruise control:

To boot, that line runs under the battery tray and - if you have ABS - right under a mountain of ABS crap.

Accordingly I mounted my vacuum pump to the rear of the fuse panel, left of the clutch pedal - if you pull the backing plate off the pump (just 3 rubber fittings, no bolts), it will zip-tie securely to and above the white trim clip on the firewall. This also has two advantages - the thick rubber vacuum line reaches right to it, without any intermediary piping to fail, and you can hear the vacuum pump engage when cruise kicks in. If you can't hear the pump and get no cruise, it's an electrical problem. If you CAN hear the pump and get no cruise, it's a vacuum issue.

By all means though, if you want to go stock and just replace the hard plastic line outside the firewall with something newer and more durable (like stainless brake line, perhaps), go for it.

I really hope this helps anyone thinking of adding cruise - it's a very simple system and it's just great to have it added very economically. If I've missed anything or stated something in error, please let me know!!

For more information on the cruise control system, including diagrams, diagnostics and troubleshooting, see the Bentley manual, section 96-8.

Thank you and good luck!

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