Background

The early XJ-S has electric door locks are controlled by a rocker switch on the console. The boot lid lock is manually operated only. The goal of this project was to fit the car with a remote, keyless entry system allowing doors to be locked and unlocked, and the boot lid to be unlocked, with a key-fob remote.

Parts

The Valiant Model 2RTA Keyless Entry System, made by I.C Dynamics (www.icdynamics.com) is ideal for this project. It is available from J. C Whitney (http://www.jcwhitney.com/) for $30. The electronics are housed in a molded plastic case, called the Receive Module. It comes with a wiring harness fitted with a 10-pin connector that connects to the Receive Module, and two key fob remotes. No relays are needed, as they are built into the unit. However, as a precaution I did use a standard Radio Shack automotive relay for the boot lid solenoid since it looked like it draws a lot of power.

With the 2RTA alone you can achieve keyless door lock control. However, to automate boot lid unlocking you will also need a solenoid. I pulled one off a 70-something Chevy Caprice at a junkyard. Although some modifications were required, the installation was not difficult and it works fine.

Here is a complete list of what you will need:

1. Valiant Model 2RTA Keyless Entry System (J. C. Whitney)
2. Trunk lid solenoid from a 1976 Chevrolet Caprice. I’m not sure this is the exact year, but I expect anything close will use the same solenoid. Omit if you don’t do the boot lid. (junkyard)
3. Automotive relay. Omit if you don’t do the boot lid. (Radio Shack)
4. About 15 feet of 18 gauge stranded wire—enough to reach from under dash on drivers side to opposite side of boot, then back along boot lid to lock. Omit if you don’t do the boot lid. (Radio Shack)
5. Inline fuse holder and 14A fuse, if you do the boot lid. (Radio Shack)
6. Miscellaneous connectors. (Radio Shack)
7. A few inches of 1/16" x 1 aluminum flat stock. (hardware store)
8. 6-32 machine screws, 2. (hardware store)
9. 4-40 machine screw. (hardware store)

Preparation

You will need to remove the left dash underscuttle cover and the console cover.

Installation of the Electronic Module

The electronic module can be mounted under the left dash after removal of the underscuttle. There are tabs on the case that appear to be made for cable ties, so I tied it to the steering column. It’s not what you would call firmly mounted, but I don’t think that is necessary. Align the short black antenna wire horizontal and tie it down with a cable tie to keep it that way.

Wiring

The 2RTA installation instructions are thorough and easy to follow. Since the system is intended to work in a variety of vehicles, there are some wires you don’t use at all. For the XJ-S, you will need to connect the harness wires as indicated below. See also the circuit diagram.

For door control only:

1. White (Polarity): To +12 volts, pin 4 on the rocker switch
2. Red: To +12 volts, pin 4 on the rocker switch
3. Black: To ground. I fitted a ground lug to the black and attached to one of the bolts fastening the shift lever tower to the car body, under the center console, but it could also be grounded under the dash somewhere.
4. Green: Door unlock, pin 1 on rocker switch.
5. Yellow: Door lock, pin 6 on rocker switch.
6. Purple: Ignition, if you want the doors to lock/unlock in response to the ignition switch. I picked this up from the ignition relay that is mounted up under the left side dash, approximate center. I believe I hooked it to C1. Check with a voltmeter--- should be 12+ only when ignition is on. (Note: perhaps I should have looked for some place with a fused ignition 12 volts, but this works)

1. Brown (Polarity): to +12 volts. Connect with Red harness wire. I used an inline splice connection to do this.)
2. Orange: Pin 86 of relay that drives the boot release solenoid.

Since you will be attaching to pins on the rocker switch that already have connectors you have the choice of either cutting off the existing connectors and attaching new ones with the added wires jammed in, or using "splitter" connectors. I started out trying to use splitter connectors. However, the problem is the splitters add length to the connection, and there is not enough vertical clearance between the rocker switch pins and the transmission tunnel when the console panel is in place. This caused me to revert to new connectors, bringing 2 or 3 wires together. I soldered after crimping, just to be sure.

Figure 1 shows the connections to existing switches and relays. This looks complex because I am showing a lot of the existing stuff. The changes are really very minor.

Note that I put a 14 amp fuse in the wire to the boot solenoid. The 2RTA unit has a built-in relay, so this is not absolutely necessary. I put it in because the solenoid draws a lot of current, and I could not find a rating for the built-in relay. Also, that let me run a 18 gauge wire from the front of the car, whereas I would have gone to a larger wire if it was to carry the solenoid current.

                                                                                    Figure 1. Circuit diagram.
Routing the Boot Release Wire

I followed the wire put in by Circuit City when I had a new antenna installed a few years ago. It runs under the left driver’s footwell cover, under the lip of the plastic carpet edge strip, under the back seat, then up and into the boot on the left side through a hole drilled in the parcel shelf. Inside the boot, it is routed over to the right side underneath the parcel shelf, and back under the lip of the boot lid to where I mounted the new relay using the screw for an existing cable tie-down. I used a splitter connector on the fuel pump relay pin 30 to get power to the solenoid relay contact circuit, pin 30.

Boot Lid Solenoid Modification

My strategy was to mount the Chevy solenoid on the underside of the boot lid, right over the lock mechanism so that it would directly operate the existing lock release lever. To make this work, some modifications were necessary. You may want to go to the junkyard and pick up the solenoid before you try to understand this, as it’s hard to explain if you’re not looking at the part.

The Chevy solenoid armature pulls on one end of a pivoting arm mounted on the solenoid housing. The other end of the pivoting arm is bent at a 90 degree angle and extends about ½"; this is what strikes the lock lever to open the lock. The only problem is the angled leg of the pivoting arm is not long enough to reach the XJ-S boot lock release lever when the solenoid is mounted on the boot lid. To fix this problem I removed the pivoting arm from the solenoid housing and fitted an extension to the angles arm. This was not an easy job, but not a difficult one either.

The arm pivots on a shoulder pin that is peened onto solenoid housing. To remove it, simply center punch the peened end on the outside of the housing and drill it out using a 1/8" drill bit. Be careful not to drill too deep, as you will need some of the metal there to reattach it later.

Next, cut a piece of 1/16" aluminum flat stock the width of the arm (3/8") and 1 1/8" long. Clamp it to the pivot arm in a vise and drill two holes for clearance of 6-32 machine screws.

To reattach the pivot arm, drill through the shoulder pin with a #43 drill and tap 4-40. You can then reassemble the unit, holding the shoulder pin in place with a 1/4" 4-40 machine screw. Lube with lithium grease or other suitable lubrication.

Figures 1 and 2 show the modified solenoid.

Boot Lid Solenoid Installation

The Chevy solenoid mounts onto the XJ-S boot lid over the locking mechanism. The pivoting arm described above must be positioned below the lock lever arm, so that when the solenoid is activated the extended pivoting arm strikes the lever. You will find that you need to position it at about a 45 degree angle over the lower left corner of the cutout. Figure 3 shows it in place. The solenoid mounting flange is under the edge of the cutout in the boot lid.

The solenoid is mounted on the Chevy with a single sheet metal screw. I slipped a C-nut over the hole for this screw in the solenoid mounting flange, and drilled a hole in the boot lid to match up. For additional stability I drilled another hole in the solenoid mounting flange. A metal strap is attached with another sheet metal screw through this hole. The edge of the cutout in the boot lid is sandwiched between the solenoid mounting flange and the strap.

Note: Getting the solenoid properly positioned is obviously critical. Before I drilled the hole in the boot lid I clamped the solenoid in place with the strap alone. This allowed me to jockey it around until I was sure the solenoid pivot arm was striking the lock lever properly and actually opening the lock when 12+ volts was applied. I then marked the hole for drilling and it came out perfectly.

Problems

Having the keyless entry takes some getting used to. Most notably, if you have elected to hook up the tie-in to the ignition relay, you will be surprised by the doors locking when you turn on the ignition to start the car. They also snap open when you turn it off. Nothing wrong here, just strange new noises.

The only other minor problem I’ve had is that if the battery is low the boot lid solenoid won’t fire. That’s when I drag out my battery charger!