I did a Gen III Vortec conversion two years ago with the help of many on this forum, but especially from Frank (Manuchao), who lives nearby and gave me lots of advice as well as welding and grunt work help manuevering the drivetrain into position. He did a Vortec conversion on his rig years before me, but he never installed Cruise Control, so I helped him with that since I was successful installing CC on mine. In the two years between, I forgot a lot of stuff and didn't document what I did very carefully. Also, between the two vehicles, I encountered some common pitfalls. What should be a very easy plug-and-play can be maddeningly frustrating- if you don’t understand a couple of very important points...
So, I’m going to make it easy for you (and for myself if I ever help someone again) if you’ve already done a Gen III conversion and have yet to install cruise control, or if you’re planning a conversion, read this first and it will be even easier.
Frank and I both used a Rostra Universal Right Column Mount Switch 250-3743. You can also buy a left-hand mount if you prefer. You really only need two “momentary on” switches, but that’s up to you, and you can adapt these instructions accordingly, which are written for the Rostra switch.
You need to interface the Rostra switch with three wires from your TAC controller. A fourth wire on the TAC is needed, but it doesn’t interface with the switch.
If you haven’t built or ordered your engine harness yet, I suggest you have your vendor bring the four necessary wires from the TAC into a separate loom that you can pass through the firewall to enable the cruise control.
The four wires needed are:
Pin 4 - “Cruise Control Set/Coast Switch Signal” (DK BLU)
Pin 5 - “Cruise Control Resume/Accel Switch Signal (GRY/BLK)
Pin 6 - “CHMSL Supply Voltage” (LT BLU)
Pin 14 - “Cruise Control On Switch Signal” (GRY)
These are all on the larger of the two connectors on the TAC controller.
If your harness was already fabricated, chances are that the TAC connector is not wired for CC, meaning the above-mention pins and wires are vacant. In this case, If you still have the original harness, go ahead and remove the necessary pins and wires. It’s easy, open up the connector, remove the green cap and push the pins through from the backside, then pull the wire through with a needle-nose plier.
Install these into your working TAC connector the same way - push them in from the back, wrap them in a loom and feed through your firewall.
Pins 4, 5 and 14 connect to the Rostra Switch. Pin 6 taps into your brake light circuit. CHMSL stands for Center High Mount Stop Lamp. More on that later.
You also need to find a source for Switched Power, and a Ground. The other circuit that is critical is the TCC or Torque Converter Clutch wire. This is usually a purple wire that connects to the PCM, pin 33 on the blue PCM connector. Your harness vendor will provide this with a label and instructions to power this lead. I mention it here, because it’s critical to the functioning of the Cruise Control. If you don't have this configured correctly, cruise control will not work. It functions the opposite of the brake light - it needs to be powered normally on, and when you press the brake, the circuit opens, and the internal clutch is disengaged. There are several brake switches that you can buy that provide this functionality an a second set of spade terminals. This is well documented on other Vortec blogs.
To install the Rostra switch, pick a location on your plastic column housing and and mark it. Below is a picture of Frank’s. Also note the reinforcement on the inside of the plastic column housing. I don't trust 30 year old plastic. It wasn't designed for the stress of a Cruise Control stalk, so reinforcement is in order. There’s three layers of fiberglass impregnated with plastic epoxy, after cleaning and sanding the inside plastic to enhance the adhesion:
See posts starting with #7832
What did you do with your 60 this weekend?
Here’s how to install and wire the Rostra switch. Cut off the pins, thread the cable through the hole and replace with a standard six pin connector like this:
https://www.amazon.com/Molex-Circui...=1524955138&sr=8-1&keywords=six+pin+connector
The connections are as follows, go ahead and build the connector accordingly (The connector is only necessary so you can easily remove the column housing. You could opt to wire it directly without the connector):
Red and Blue need to be wired together to one pin, which connects to Switched Power
Black - Connect to Ground
Green - Connect to TAC pin 4
Yellow - Connect to TAC pin 5
Brown - Connect to TAC pin 14
Now for Pin 6, the CHMSL voltage supply: This is very simple if you have normal stock incadescent brake lights on your Cruiser, but if you have LEDs, you need to jump through a few more hoops. Your cruise control will not work with standard Land Cruiser wiring if you have installed LEDs. The reason is that the TAC monitors changes to resistance on this pin. My simple understanding is that the LEDs only pass current one way, so it looks like an open circuit to the TAC. The TAC wants to see some resistance in the circuit. This problem is well documented on many enthusiast forums.
Either way, you need to tap into the brake line circuit to provide voltage to TAC pin six. If you’ve already done the Vortec conversion and your TCC lock-up is working, and you don't have LED brake lights, then all you have to do is tap into the brake light circuit and wire the tap directly to TAC pin 6. You can use a Scotchlok tap, or any other method you deem appropriate and you’re done! You should now have a functioning cruise control.
If it doesn’t work, check your TCC. That’s what tripped me up when I first installed mine, and Frank also had a non-functioning TCC. Again, the TCC is opposite of the brake circuit. The TCC wire expects constant voltage to allow the lock-up to occur, and when you step on the brake, it opens the circuit so the lock-up is disengaged. In my case, I used a relay and wired it incorrectly, in Frank’s case, he used a brake switch that provides the correct normally closed set of spade connectors, but for some reason it wasn't working.
It’s easy to check all your connections with a test lamp. Remove the TAC connector and note the pin numbering and test accordingly with a test lamp. Have an assistant turn on the key after you remove the connector, put the test probe into each of pins while your assistant presses each of the buttons and steps on the brake, one at a time. You can also test the TCC, by inserting the test probe very carefully behind the PCM connector at position 33, along side the wire. Turn off the key before you re-insert the connector back into the TAC, or you may throw a code or two.
If you have previously installed LED brake lights and tail lights, you’ve probably already applied a fix for the hyper-turn signal problem by modifying your turn signal relay, but it may not have helped the cruise control problem. To make modern electronic throttle-by-wire cruise control work with LEDs, a common fix is to wire large 25W or so resistors around the LED’s, so that there’s a path to ground via the resistor (This is a common issue on many different models of cars with cruise control where the owner has upgraded to LEDs). The problem is that these resistors generate a lot of heat, so you need to be careful where to place them. They also can overtax your 30 year old Land Cruiser wiring.
Another way to solve the problem is with a relay. You create a circuit that emulates a CHMSL circuit while isolating it from the LED brake circuit. You just need a relay and a small incadescent bulb with a socket and pigtail.
Here’s how to do that with a Single Pole Single Throw (SPST) relay:
You can put the light bulb in the engine bay and ground it there as well or just stuff it somewhere under the dash where it won’t be conspicuous.
If you haven’t yet replaced the factory brake switch with one that will create the normally-on circuit for the TCC, you can do this and save yourself the time and trouble of replacing the brake switch using a “changeover relay”. This is the way Frank’s rig is currently wired:
Hopefully someone finds this useful. Frank and I spent quite a few hours troubleshooting and coming up with a workable solution.
Happy Land Cruising with Cruise Control!
So, I’m going to make it easy for you (and for myself if I ever help someone again) if you’ve already done a Gen III conversion and have yet to install cruise control, or if you’re planning a conversion, read this first and it will be even easier.
Frank and I both used a Rostra Universal Right Column Mount Switch 250-3743. You can also buy a left-hand mount if you prefer. You really only need two “momentary on” switches, but that’s up to you, and you can adapt these instructions accordingly, which are written for the Rostra switch.
You need to interface the Rostra switch with three wires from your TAC controller. A fourth wire on the TAC is needed, but it doesn’t interface with the switch.
If you haven’t built or ordered your engine harness yet, I suggest you have your vendor bring the four necessary wires from the TAC into a separate loom that you can pass through the firewall to enable the cruise control.
The four wires needed are:
Pin 4 - “Cruise Control Set/Coast Switch Signal” (DK BLU)
Pin 5 - “Cruise Control Resume/Accel Switch Signal (GRY/BLK)
Pin 6 - “CHMSL Supply Voltage” (LT BLU)
Pin 14 - “Cruise Control On Switch Signal” (GRY)
These are all on the larger of the two connectors on the TAC controller.
If your harness was already fabricated, chances are that the TAC connector is not wired for CC, meaning the above-mention pins and wires are vacant. In this case, If you still have the original harness, go ahead and remove the necessary pins and wires. It’s easy, open up the connector, remove the green cap and push the pins through from the backside, then pull the wire through with a needle-nose plier.
Install these into your working TAC connector the same way - push them in from the back, wrap them in a loom and feed through your firewall.
Pins 4, 5 and 14 connect to the Rostra Switch. Pin 6 taps into your brake light circuit. CHMSL stands for Center High Mount Stop Lamp. More on that later.
You also need to find a source for Switched Power, and a Ground. The other circuit that is critical is the TCC or Torque Converter Clutch wire. This is usually a purple wire that connects to the PCM, pin 33 on the blue PCM connector. Your harness vendor will provide this with a label and instructions to power this lead. I mention it here, because it’s critical to the functioning of the Cruise Control. If you don't have this configured correctly, cruise control will not work. It functions the opposite of the brake light - it needs to be powered normally on, and when you press the brake, the circuit opens, and the internal clutch is disengaged. There are several brake switches that you can buy that provide this functionality an a second set of spade terminals. This is well documented on other Vortec blogs.
To install the Rostra switch, pick a location on your plastic column housing and and mark it. Below is a picture of Frank’s. Also note the reinforcement on the inside of the plastic column housing. I don't trust 30 year old plastic. It wasn't designed for the stress of a Cruise Control stalk, so reinforcement is in order. There’s three layers of fiberglass impregnated with plastic epoxy, after cleaning and sanding the inside plastic to enhance the adhesion:
See posts starting with #7832
What did you do with your 60 this weekend?
Here’s how to install and wire the Rostra switch. Cut off the pins, thread the cable through the hole and replace with a standard six pin connector like this:
https://www.amazon.com/Molex-Circui...=1524955138&sr=8-1&keywords=six+pin+connector
The connections are as follows, go ahead and build the connector accordingly (The connector is only necessary so you can easily remove the column housing. You could opt to wire it directly without the connector):
Red and Blue need to be wired together to one pin, which connects to Switched Power
Black - Connect to Ground
Green - Connect to TAC pin 4
Yellow - Connect to TAC pin 5
Brown - Connect to TAC pin 14
Now for Pin 6, the CHMSL voltage supply: This is very simple if you have normal stock incadescent brake lights on your Cruiser, but if you have LEDs, you need to jump through a few more hoops. Your cruise control will not work with standard Land Cruiser wiring if you have installed LEDs. The reason is that the TAC monitors changes to resistance on this pin. My simple understanding is that the LEDs only pass current one way, so it looks like an open circuit to the TAC. The TAC wants to see some resistance in the circuit. This problem is well documented on many enthusiast forums.
Either way, you need to tap into the brake line circuit to provide voltage to TAC pin six. If you’ve already done the Vortec conversion and your TCC lock-up is working, and you don't have LED brake lights, then all you have to do is tap into the brake light circuit and wire the tap directly to TAC pin 6. You can use a Scotchlok tap, or any other method you deem appropriate and you’re done! You should now have a functioning cruise control.
If it doesn’t work, check your TCC. That’s what tripped me up when I first installed mine, and Frank also had a non-functioning TCC. Again, the TCC is opposite of the brake circuit. The TCC wire expects constant voltage to allow the lock-up to occur, and when you step on the brake, it opens the circuit so the lock-up is disengaged. In my case, I used a relay and wired it incorrectly, in Frank’s case, he used a brake switch that provides the correct normally closed set of spade connectors, but for some reason it wasn't working.
It’s easy to check all your connections with a test lamp. Remove the TAC connector and note the pin numbering and test accordingly with a test lamp. Have an assistant turn on the key after you remove the connector, put the test probe into each of pins while your assistant presses each of the buttons and steps on the brake, one at a time. You can also test the TCC, by inserting the test probe very carefully behind the PCM connector at position 33, along side the wire. Turn off the key before you re-insert the connector back into the TAC, or you may throw a code or two.
If you have previously installed LED brake lights and tail lights, you’ve probably already applied a fix for the hyper-turn signal problem by modifying your turn signal relay, but it may not have helped the cruise control problem. To make modern electronic throttle-by-wire cruise control work with LEDs, a common fix is to wire large 25W or so resistors around the LED’s, so that there’s a path to ground via the resistor (This is a common issue on many different models of cars with cruise control where the owner has upgraded to LEDs). The problem is that these resistors generate a lot of heat, so you need to be careful where to place them. They also can overtax your 30 year old Land Cruiser wiring.
Another way to solve the problem is with a relay. You create a circuit that emulates a CHMSL circuit while isolating it from the LED brake circuit. You just need a relay and a small incadescent bulb with a socket and pigtail.
Here’s how to do that with a Single Pole Single Throw (SPST) relay:
You can put the light bulb in the engine bay and ground it there as well or just stuff it somewhere under the dash where it won’t be conspicuous.
If you haven’t yet replaced the factory brake switch with one that will create the normally-on circuit for the TCC, you can do this and save yourself the time and trouble of replacing the brake switch using a “changeover relay”. This is the way Frank’s rig is currently wired:
Hopefully someone finds this useful. Frank and I spent quite a few hours troubleshooting and coming up with a workable solution.
Happy Land Cruising with Cruise Control!
)
