Peter Young

I have a 5.3l/4L60 combo in an 84 LandCruiser and I'm trying to get Cruise Control to work. I eventually figured out that Howell changed the color code on 2 of the 4 wires required for Cruise and I believe I have Cruise On, Set and Resume now wired correctly to a switch and two buttons. I confirmed those wires are on the correct pins on C2 at the TAC. But still no joy. I have not actually toned them them out to make sure what I have in the dash has continuity to C2 at the TAC.

I have not wired the brake wire up yet (light blue going to the TAC), but from my reading of the diagram, having it float is not a problem and should not prevent Cruise from engaging. I'm curious what else might be preventing Cruise from engage.

Purple is currently connected to a relay coming off the brake switch to supply GND to the TCM to disable TCC lockup. I'm assuming that has nothing to do with it.

And yes, the truck runs fine and speedometer works, OBD II gauges show speed correctly and everything else appears to be operational.

ls1nova71

iTrader: (4)

You have to have the light blue wire hooked to the cold side of the brake light switch, meaning it's hot when the brakes are applied for the cruise to function. The TAC module has to see a ground through the brake lights on that circuit.

Peter Young

That's interesting. There wouldn't normally be a ground on the cold side of a brake light switch, it would just be floating. I'm not saying your wrong, but I've never heard that. So, simply grounding that wire would get me going? It always says +12 from the brake switch when brakes applied.

ls1nova71

iTrader: (4)

If you ground it, youll be sending 12v straight to ground and that wont work. The ground would be the third brake light on the original truck. You can follow the ground from the ground on the brake light, through the bulb, and then to the cold side of the switch and therefore to the TAC module. If you dont have brake lights or even if you have LED brake lights, the cruise won't work.

Peter Young

Okay, I'm not following at all. If I hook the light blue directly to ground, that will be connecting +12 to ground? I need to see a schematic to understand. The ground for my brake lights is on the frame at the brake lights, no where near the instrument cluster where all this is going on. I'm not sure we are using the same terms.

The light blue is an input to the TAC, isn't it? It is either looking for +12 or GND. My understanding it was looking for +12 when the brakes are engage to disengage the Cruise Control - is that wrong?

Peter

Peter Young

I've been thinking about what you said. So, if you ran the single brake switch to a relay, I could run the light blue cruise control out one side, GND when no brake, +12 when brake. And the torque converter out the other side with just the opposite voltage. Right? Do know where I can find a wiring diagram for the pair?

Peter Young

After a lot of searching , finally found this image at ChevyTrucks that said that exact same thing and this diagram shows it the way you says it works. I found a lot of drawings that showed the gnd side floating on the relay, but this one has it so that the TAC is either getting +12 or GND all the time.

Thanks for the help. Now I have to figure out how to get what I need for the torque converter lock up onto the same relay - DPDT automotive relay? Also realized that even if I had it wired right without a relay, because I have LEDs in the tail lights, it still might not have worked.

Peter Young

How does that give ground to the TAC when the pedal is up or ground the purple wire when the pedal is down. What am I not getting? Don't you need GND on 87A?

ls1nova71

iTrader: (4)

You are correct, your LED taillights wouldn't have let the cruise work either. As for how to wire the TCC, cruise and make the LEDs work with one relay, just wire it up like my quick t. The relay will run the TCC part of it, and the TAC will see a ground through the coil part of the relay so your LEDs won't be an issue.

ls1nova71

iTrader: (4)

Sorry, I had to modify my sketch. .. Does it make sense now? The ground to the TAC with the brakes not applied will come from the ground through the relay coil.

Peter Young

Ahhhh - that's a neat trick. What's 87 attached to?

What am I going to do with the DPDT relay I just ordered?

Peter Young

Does this work too? Or am I not getting this.

ls1nova71

iTrader: (4)

87 doesn't go to anything. The TCC input needs 12v when the brakes are NOT applied and nothing with them applied.

Peter Young

I've heard from several sources that TCC needs to see GND when the brake pedal is pressed. (but that was to correct people sending +12 on pedal press).

What you're saying is it needs to lose it's +12 on pedal press - like it's using that +12 to power the lockup relay/solenoid.

ls1nova71

iTrader: (4)

That is correct.

workingdog

It's all wired up correctly, I have the light blue brake to GND permanently right now - and it's not working. I double check the wires and that +12 is available at the switch and the buttons but no joy.

What do I look at next?

Peter

ls1nova71

iTrader: (4)

I wouldn't call that wired up correctly. The light blue wire needs to have 12v when the brakes are applied. Just grounding it permanently won't do that. There are two brake wires to the TAC for cruise, one hot with the brakes applied and ont hot with the brakes not applied, they both need to work. It has to have a 12v input on that wire once every ignition cycle, so when you are hitting the brakes it is only seeing the one and is not letting it work, it's a safety redundancy thing. Hook both of them up and try ot. What kind of brake light switch are you using?

jeremytap

[QUOTE=ls1nova71;19328536]There are two brake wires to the TAC for cruise, /QUOTE]

There is only one wire to the TAC for cruise. The other one goes to the ecu. However, the do both need to be hooked up. The one to the ecu needs 0V when brakes are pressed and 12V when brakes not pressed. And the one to the TAC needs 12V when brakes are pressed and 0V when brakes are not pressed.

ls1nova71

iTrader: (4)

[QUOTE=jeremytap;19329326]Ok, thats what I meant. But they both need to be hooked up for it to work, I think that part was clear.