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Discussion Starter · #1 ·
Hi guys,

I'm trying to get Cruise Control working in my T56 inspired Jag Xj6. I have wired up the system based on the diagram below:

http://dl.dropbox.com/u/24984984/GM%...0XJS (1).pdf

This set up worked for an A4 setup, but I'm having trouble getting it to work with my new T56 setup. For my T56 setup, I haven't added the second in-line switch for the brake pedal, but I figured for testing purposes it should be essentially the same as having one switch, as the clutch anticipate release switch functions as a normally closed circuit, until the pedal is depressed just like the primary brake switch.

Here's the wiring diagram I used to confirm the correct connections in my vehicle:

http://dl.dropbox.com/u/24984984/lt1...k wiring.pdf

If anyone has the shop manual scan for this particular circuit, could you post a link to it?

since the system worked on an automatic, perhaps it is a tuning issue? or is there another additional switch that I am not taking into account? My current set up does not have a clutch "saftey" switch, ie having to start the car with the clutch down, although I don't think that should matter either, right?

Any help?
 

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Discussion Starter · #3 ·

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You need to feed the high mount stop lamps with the power at pin "g" of the cruise module. The cruise module needs to see a ground path on that circuit (through the bulbs) when the stoplanp relay is not powering it.
Run a wire to the high mounts from pin "G" Be sure the bulbs are good and that they work. If you feed the bulbs from another source other than pin "G" the off condition of the circuit wont show a ground and the cruise wont work.
 

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Discussion Starter · #5 ·
i have Terminal G hooked up to the "GP" wire which operates with the brake light switch. The GP wire feeds the "bulb failure unit" in the rear of the car, which the high mounted lamps feed from. when the brake light switch is activated (pedal depressed), i get 12v at the wire which feeds Terminal G on the cruise module.

my high mounted rear lamps currently are working fine... so i don't think that part of the circuit is the fault.

here's how i have my circuit set up for that integrated into the XJ6 diagram:

http://dl.dropbox.com/u/24984984/Brake Light XJ6 circuit.jpg
 

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All your wiring looks correct, if it is wired like your hybrid diagram shows.
The only thing I can think of is the bulb failure unit is keeping the ground signal through the high mount stop light from going low enough to signal th CC module . Try isolating it ,(circuit GP to the high mount) from the failure unit to see if you can get it to run.There has to be some voltage applied to the GP wire, so when a bul goes out it sends current to the indicator bulb on the dash VIA the failure unit.
All the rest of your wiring looks correct.
 

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Discussion Starter · #7 ·
Well, I think i might have figured out the problem -- big time stupid mistake by me.

I got so wrapped up in seeing that I had voltage at the GP wire that I didn't even consider the possibility that i might not have the "High Mounted Lights" -- and in fact, I don't. I only have regular rear tail lights. I;ve seen the arrays at the junkyard, and i guess my brain put them both together somehow.

While the stock XJ6 wiring diagram I have indeed lists the high mounted lights, I'm guessing they were an option at the factory and my car didn't get the treatment.

That being said, I guess the tail light voltage is not enough to bleed the circuit down. Now I need to figure out a way to emulate having the high mounted lights. In reading this post, it looks like people have had the same problem when they add LEDs to the high mounted array -- can cruise be functional by tweaking the voltage drop at the array? If so, could I just "fake" having the high mounted array?
 

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Just grab any high mount unit from the u pull it yard, and stuff it in the back window. Thing is , remember to have the high mounts only on the circuit in question and dont hook it to the bulb failure module. It absolutely has to see a full ground path through the 921 bulbs in the high mount. They have the same socket as a 194 you couls just hang them on somewhere and wire them for the sake of testing. Save your salvage yard trip for something bigger, or a list of stuff.
Hope it works for you tyler.
 

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Discussion Starter · #9 ·
i had an idea... using a resistor set to ground on one end and to the GP wire on the other -- 10 watt 1ohm resistor should match the 4 1ohm in paralell lights on the high mount, correct? I dont want to have a wierd looking high mounted light on back shelf. It'd be great if i could just get it to work as is. Otherwise i'll have to wait til a VDP XJ6 shows up at the junkyard... not impossible, but because the yard is a "pick n pull" type, alot of time the parts are trashed when you get to them.

what do you think about the Resistor idea?
 

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I would wire up a couple 921 bulbs as described first, to see if the theory I posed is actually correct. If it works then go to plan 'B"
Drop resistors would probably satisfy the Cruise module as far as seeing a ground path, but with the circuit live with 12 volts, it might smoke.:smash:
 

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Discussion Starter · #11 ·
Why would adding the resistor cause the system to smoke if all i'm doing is emulating the bleed down? if that was the case, wouldn't it smoke every time i pushed on the brakes in the stock system? I'll see if i can wrangle up some bulbs and just use them just after the GP wire, with a little tap in connector. I wish i just had the stupid CHML but oh well.

What if i added an in-line resistor to the GP wire? just snip snip the GP wire and solder the resistor in? that way i wouldn't have to ground it separately....the GP wire already has a ground at the rear stop lights... i think.
 

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Why would adding the resistor cause the system to smoke if all i'm doing is emulating the bleed down? if that was the case, wouldn't it smoke every time i pushed on the brakes in the stock system?
Wasnt sure if the resisitors would dissipate the heat generated by connecting them to ground (in place of a bulb). Bulbs do for sure.just sayin.
Maybe I misunderstood what you were saying.
 

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Discussion Starter · #13 ·
i guess i'm just not really understanding how the circuit works or affects the cruise module -- i dont see how having the bulbs in the circuit in addition to the rear tail lights can cause this annoying problem.
 

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Well, that circuit has power with the lights on (brakes applied) and wont allow the cruise to engage unless the circuit has a ground path while it is not powered up.
I do know that if the bulbs are blown the path to ground through them wont be there, and the sense circuit in the CC module wont allow the cruise to run because of that.
Also are you sure the CC module is recieving the VSS signal?
Have you checked it to see?
 

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I don't know if this applys here or now........ I once placed LED tail light bulbs in my Z3, cruise control stopped working due to there not being enough draw/ground ??? on the circuit, did some research, modified the flasher with an electronic fix and ..... what-do-ya-know........ cruise works fine
 
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