Permission to publish this article is provided generously by Robin Sun at www.p-car.com. Be sure to visit his site for loads of 993 info!
On Robin's scale of difficulty (1 to 10) I would rate this task a 2.
Much of the information is derived from Randall's investigation on the oil cooler fan. You should review this information first:
964/993 Oil Cooler Fan Operation & Troubleshooting
and these rennlist postings: Override switch for fan cooler
The difficulty really depends on where you decide to mount the switch.
Switch mounting options:
- In the dash between the tach and the oil gauge
The switch pictured here can be bought from Radio Shack, Paddle Switch
- Rear fog light switch
The rear fog light switch is the 3rd switch from the left and can be bought from your local Porsche, online sources, or from Carnewal Parts Express.
- console switch
The console switch will fit nicely in the middle position, on the bank closest to the gear shift level.
The switch is a 944 hazard switch, part number 944.613.235.00. This can be purchased from online sources or salvage places such as Parts Heaven
Note:Mounting the switch in the center console will make the wiring the easiest, but you will need to modify the switch slightly with a Dremel tool to make it fit in the slot.
- Headlight switch
This is the same paddle switch mentioned above, but mounted to the left of the headlight switch. This area was originally designed to have a headlight leveling switch installed. However, only euro spec cars have this switch installed from the factory.
Almost any switch will work, provided that it is NOT a momentary switch. Be aware that for normal fan operation, the connection will be shorted. This only matters if you decide to use the rear fog lamp switch becuase it will be pulled "OUT" for normal fan speed operation, and pushed "IN" for high speed operation.
Common switch possibilites are:
1. Double Din Stereo Removal tools ( Available at any auto parts store. They are sometimes called Ford DIN removal tools. Cost is about $5 )
OR 4 small nails OR 2 well bent pieces of coat hanger
2. Electrical Tape
3. Nylon Ties ( Optional, but cleans up the install )
4. Wire. Specs of wire that I used.
5. Wire Taps ( Some people like to solder their connections also ). You can buy wire taps from Radio Shack
6. Wire cutters
7. Wire stripper
8. Cleverly bent coat hanger. Only necessary if you are going to do the rear fog light install.
9. Jumper wire with blade terminals to test your fan operation.
10. Flashlight ( Not pictured )
For the simpliest install, it takes about 1 hour for the wiring, 30 minutes to modify the switch.
I'll cover the common parts of the installation first, then talk about specifics of mounting the switch in the console, dash, and the rear fog lamp locations. If you are planning to do the dash install, read the information about mounting the switch to the dash first!
In the driver's side footwell, you'll see two bunches of wire going up to the CCU. The CCU is the unit to the left of the stereo ( when sitting in the driver's seat). You'll see an extra "bend" in the two cable bunches held by electrical tape. This extra bend is just used to take up the extra slack of the two cable bunches. Cut this piece of electrical tape to allow more slack in the two cable bunches.
Insert the DIN removal tools into the slots on the side of the CCU. Push them in so you feel/hear a click. Then pull out the CCU. You may need to push the CCU out from the back, becuase the DIN removal tools do not always catch postively enough to pull out the CCU from the front. You can use the big end of a screwdriver if your fingers can't reach.
You can also use 4 small nails or two pieces of coat hanger wire. Either way, DO NOT PULL THE CCU OUT USING THE KNOBS. You run the risk of damaging your CCU. CCU's cost about $1000 to replace.
Pull the CCU part way out, you may need to move the steering wheel stalks a bit to get clearence.
You will see two cable connectors on the back. These connectors have a spring loaded clasp on one side. You will need to depress the spring loaded clasp and then gently work out the connector. The side of the connector with the spring loaded clasp needs to come out first! The connector will not come "straight" out. When you get one connector out, you'll understand what I mean.
On the larger connector, look for the G12 wire. It's the green/black wire. That is the wire that you want to tap into. Verify that this is the correct wire several times by looking at the connector. The wires are numbered on the connector. You don't want to cut a wire that you don't have to.
After you are sure that this is the correct wire, then cut the wire. On each end of the newly cut wire, you are going to attach your speaker wire. You can either use wire taps or solder your connections.
If you are using the dash switch, I would recommend cutting cutting/tapping into the wire about 12" from the connector to the CCU. If you are using the console or rear fog light switch, I would recommend making cutting/tapping into the wire about 4" from the connector to the CCU.
Reinstall the CCU, and attach the speaker wires to your switch ( see below )
With the key in the ignition and switched to on ( You don't need to actually start the car ), turn your switch on and wait about a minute. You should hear the high speed fan come on. If this doesn't happen, try setting the switch the other way, and wait another minute. You may have the switch upside down or something like that. Try it both ways, becuase your switch will turn the high speed fan both ON and OFF.
If the high speed fan does not come on still, then you'll need to verify that your high speed fan is operational, your CCU is operational, and double check that you have shorted the correct wire on the back of the CCU.
Assuming that your switch works properly, use the nylon ties, electrical tape,etc to clean up your installation and make sure that you do not have any loose wires in the driver footwell.
Additional Notes on Switch Locations
When mounting a dash switch, you will need to remove your dash first. To remove your dash:
- Place masking tape over the defroster vents. Remove the screws that hold the plastic defroster deflector in place.
- Remove the two other screws that were under the plastic defroster deflector. Be careful NOT to drop any screws!
- On both sides to the dash, there are black plastic covers. Gently pry that out. It is just held in by friction.
- In the "middle" hole under the black plastic cover, put a phillips screwdriver in there and fish around until you find a screw head. Unscrew that. Repeat on the other side.
- Remove the clock gauge. The clock is just held in by a LOT of friction. I used a small screwdriver gently pry the clock away from the dash, and then used LOTS of finger strength to finally get the clock out. I had worked up a good sweat after just pulling out the clock!
- With the clock removed, feel around to the right and you'll feel a small stud with a bolt on it. This is that last remaining piece holding your dash in place. I used a 10 MM socket head and carefully removed the bolt. Be careful NOT to drop anything here!
With the dash removed, look at the back side of where your gauges are. You will see two small holes next to the tach from behind. They are not visible from the front becuase the leather is covering them. Decide which one you want to use and cut the leather to expose the hole. You may need to make some small modifications to the mounting hole, depending on which switch you get. For my radio shack paddle switch, I had to slightly enlarge the mounting hole. You can use a Dremel for that. To get the wire from the top of the dash into the footwell, you will have to push the wire through a grommet using a coat hanger. Straighten out a coat hanger, put a tight loop at the end and attach the wire with plenty of electrical tape. If you are going to do the dash install, it's easier to push the wire from the TOP of the dash instead of the bottom. In other words, hook up the wires to the CCU last, if you are doing the dash install.
Console switch mounting
The center console switches are mounted on two plastic pieces that can be pulled out by hand. Pull out the bottom bank of switches first, then the top bank.
Here's a picture from EJ:
You can route your wires in from the back. There is plenty of space to feed the wires in. This is the easiest mounting position.
You will need to modify the switch slightly with a dremel tool to fit properly.
Here is a picture showing the wiring to the back of the switch.
Rear fog light mounting
I haven't done this before, but when I did my oil cooler fan switch install, I wired in the back light to my fog light switch at the same time, so I was working in the same area. I did not use the rear fog light switch becuase of the "backwards" operation of the switched mentioned earlier. However, that was just a personal perference.
You will need to remove the stereo to do this install and find an available grommet to push your wires to the switch. Use a continuity meter to determine which pins on the back of the rear fog light switch to use.
If you haven't installed your rear fog light switch yet, I'd recommend that you do this first. It takes quite a bit of cutting/shaving of the dash area to get the switch to fit right. You can make a tool out of a coat hanger to screw in the small circular faceplate of the switch. The correct size for the hole which you need to drill in the dash is 3/4".