Jeep CJ Digital Makeover
A few months back, we did an installation of a 6 gauge system in an ’86 Jeep CJ Scrambler. The package included a complete instrumentation system for displaying fuel, voltage, water, oil pressure, speedometer, and tachometer. The system also includes indicators for turn signal, high beam, check engine, parking brake, cruise control, 4x4 (when equipped), wait to start (when equipped), automatic transmission gear indicator(requires optional sending unit), not to mention several performance calculations which include: 0-60 MPH (0-100 KPH) timer, ¼ mile timer, ¼ mile speed display, high speed recall and high RPM recall.
You may think adding all of this additional functionality would make for a complex installation, but this is not the case; we decided to give you an overview of the system installation including an additional ambient temperature gauge, and a tire pressure gauge system to demonstrate how straightforward the installation process actually is.
One of the first things you should do is unpack the package, check the contents, and then disconnect the vehicle battery connections before proceeding. Once you have the battery disconnected you can start by determining the placement for the sending units. The system comes with a new oil pressure, water temperature, and speed signal generator that need to be installed. In addition to the standard 6 gauge system, we are installing an ambient air gauge and a tire pressure gauge monitoring system. The tire pressure system has remote sensors that are mounted on the wheels inside the tires so we had the tires removed at a local tire shop, mounted the sensors and had the tires remounted and balanced. This system will allow the owner the ability to monitor all 4 tire pressures and temperatures from inside the vehicle.
After taking a mental note of which gauges currently worked in the Jeep and which ones didn’t, we looked at installing the speed signal generator. This device takes a mechanical signal from the speedometer cable and transforms it into an electronic pulse the digital gauge system will recognize.
As you may be able to tell by this picture, Mother Nature played into our installation just a little. The speedometer cable appeared rusted into the transfer case, so we decided this may not be the best location to install the signal generator. Instead we opted to install it up by the speedometer itself, and we’ll look at that in a few minutes.
The next item we looked at installing was the water temp sending unit. Although the Jeep had an existing water temp gauge, the instrument system required the existing one be replaced by the sending unit included in the system. This is easily accomplished by unscrewing the existing unit and screwing the new one in tight. It’s no problem if your vehicle does not have a water temp gauge, the new sending unit has a 1/8” NPT thread size and includes a bushing kit that allows it to be used in a hole size up to 1/2” which will accommodate multiple locations on the manifold. Note: The threads are tapered and the sender gets its electrical ground connection through the case, so don’t use any type of sealant on it.
At this point, you can either choose to run a new wire for the sending unit installation, or you can use the existing wire (when applicable). If you use the existing wire, you will want to note the color code so you can easily locate it in the O.E.M. speedometer wiring harness later. Next on the list is the oil pressure sending unit. This sender is installed in the same fashion as the water temp, and once again no sealant is required.
The next connection we’ll make under the hood is for the tachometer connection.
We located the tachometer connector at the distributor and made the connection using a female spade connector. The location you make for tach will vary depending on application.
Since this vehicle is getting an optional ambient air temperature gauge we need to run the wire with sender under the hood as well. This was easily accomplished by cable tying the sensor to an O.E.M. harness behind the grill area.
After this connection was made, we found a suitable location to take our wires into the vehicle and used cable ties to secure the wires to the existing wire loom.
Once inside the vehicle, we needed to remove the old instrument cluster. First, we unplugged the instrument cluster electrical and speedometer connections, and then the radio connections.
Next, we unbolted the radio and moved it out of the way.
The Jeep instrument cluster was mounted from behind on 4 studs. 3 were relatively easy to get off but the last one required some additional work. To get at it meant the heater defrost duct had to be removed. That required the dash pad be removed, which in turn required the windshield to be dropped down so screws on the top of the dash pad could be removed. The Jeep’s windshield is hinged so we removed a few screws to drop it down out of the way. Once that was accomplished, the defrost duct could be disconnected and then we had plenty of room to get at the last nut that held on the instrument cluster.
After the speedometer cluster was removed, we started pulling out the existing voltage and oil pressure gauges. The Dakota Digital instrument system has the voltage and oil pressure gauges housed within the main speedometer unit, so these locations will be used for the ambient air temp gauge and remote tire pressure monitoring gauge.
The next step was connecting the signal generator to the speedometer cable. The signal generator is threaded to accept the connections for the speedometer cable so the two just screw together.
Now it was time to find a location for the control module. The location we decided on was directly behind the existing speedometer location. This allowed us a central location for wire runs and kept the unit out of the path of water and other obstacles.
We temporarily set the control module aside and concentrated on locating the rest of the wire connections. Most of the remaining connections we needed were in the factory speedometer wiring harness. We used a digital multimeter and located the wires in the harness for left and right turn signals, high beam indicator, 4 wheel drive indicator, and fuel sending unit.
The system accepts input from several different styles of fuel sending units, such as GM, Ford, VDO, and Stewart Warner, and can also be programmed for a custom setting for other type of senders.
Next, we connected and ran a 12 volt accessory power wire from the fuse box, a ground wire from the steering column area, mounted two push button control switches for the system under the dash, and ran all the wires to the control module mounting location area.
We were now ready to wire and mount the control module. The connections are clearly labeled and are easily terminated using the screw in terminal strip on the control module.
Once this was complete, we connected the instrument system, mounted and connected the ambient air temp gauge, the receiver for the remote tire pressure gauge, mounted all the gauges in there respective locations, and remounted the radio.
The final step was programming the system. We stepped through the programming using the pushbuttons we installed, and entered information about the type of fuel sender we connected, and the number of cylinders the Jeep had so the tachometer would read correctly. To set up the speedometer to read correctly, we drove the jeep to a location that had mile markers. While in speedometer mode, we pushed the programming button at the first mile marker and then once again at the next mile marker. The system was then able to calculate the distance and properly calibrate the speedometer reading. That was it, we were all set. The old discolored and inoperative Jeep gauges were upgraded to a full compliment of digital gauges that also had the capability to monitor the outside temperature and all 4 tire pressures and tire temperatures from the dash. The cost for the complete system including the additional gauges was under $1100.
