REDZMAN

I wonder what would happen if I grounded the resistor to the body instead of to the lighting ground.

Any ideas? the "feeding power back" that someone mentioned above has been on my mind.

radu_rd2

Lighting ground should be the same thing (grounded to body), at least that's what the schematics show.

Check the cruise both with the exterior lights on and off as I mentioned above and report back..

REDZMAN

I will when i get home.

The ground wire from the light bulb goes back into the wiring harness, not to any nearby ground though.

radu_rd2

Yea, the schematic shows that all ground wires from the rear lights go together into one grounding point "center rear of trunk".

DTN

update? My guess is the bulb. Try switching the bulb from the left to the right. While you do that, check for a buildup of bulb grease inside the socket. If you have a buildup, then that may be the problem.

If that does not fix your problem, then get a higher ohm resistor. If you go to radio shack they have 50 ohm 5W resistors. I used 2 of them in series to make 100 ohms. The only thing that matters to the tiburon is that it sees VCC or not. If you have a LED blocking the path to VCC then it will be VCC - 3v A resistive load of any type will eliminate that -3V.

Basically, you could rip a resistor out of your computer and put it in there, and as long as the resistor was big enough to handle the current and it's ohms are great enough not to effect the operation of the LED it will work.

Assuming that you have the resistor installed correctly from brake + to brake -... Somehow, the path to ground is being seen from the + side of the brakelight. to the rest of the car. Make that path to ground smaller and it will become unnoticeable to the rest of the car.

radu_rd2

I don't know if it's just your choice of words, but this makes absolutely no sense to me.

REDZMAN

Yeah, I'm a bit confused too DTN.

Bulb Grease?

I'm not using resistors, but those resistor load kits, like the one in the link I put above.

radu_rd2

I hate to break it to you, but those ARE resistors.

DTN

vcc = car's voltage. It's a digital electronics term meaning Voltage Collector Current. I felt it was the best term to use in the case because of the obvious compairator in the system. It's difficult to explain without better schematics on the vehicle. We're dealing with black boxes. Lemme break it down in my own words and deductive analysis of this circuit

ok, first, a background on LEDs- there is no flow of current one direction of an LED, and the other has flow. The Voltage will be 3V higher on one side of an LED then the other at all times with no resistance. LEDs chop 3V off the ground potential when voltage goes across an LED. This is to forward bias the LED. Conversely, ground flows through a LED but it is equal to ground + 3V.

A transistor uses .6V to turn on and apply a signal to another line inside a digital device

a diode uses .7V to keep voltage flowing only one direction in a circuit.

http://hmaservice.com/data/Passenger/HY/HM...NG/E27B334A.gif
The cruise control system- From deductive reasoning, you can assume it is a digital circuit with transistors and diodes. You can also assume it is a comparator in there which is trying to pass a extremly small ammount of current through the brake at a voltage around 1.3-3V just enough to bias a transistor but nowhere near the ammount to turn on the brake light. Because of the configuration of the circuit, it should be thought of as a comparitor. If brake voltage >= ground voltage in the computer then turn off the cruise control. ref- "see cruise control system on page SD-129" it is a black box.

Ok, so we've got 1.3V-3V inside the cruise control system trying to match up to the 0V at the brakes and make the conditions possible for cruise control. But, because of the forward bias property of the LED, ground is non existant until 3V is applied to the LED.

The soloution is to bypass the LED with a resistor so that ground is felt inside the computer

The resistor load may be supplying too much current flow for the rest of the circuit or the LED bulb may be improperly made. Get a bigger resistor.


It's some good stuff. It helps the bulb slide in and out as well as keeps corrosion off the bulb and improves conductivity. It may not relate to your situation. I always use the stuff.

radu_rd2

Yes, some of us know all that, you don't have to explain what VCC is. And no need for a long winded explanation of mostly irrelevant stuff.

Basically, to say it short, the cruise control module is looking to sense the ground through the bulb, and does that by putting out a very small voltage. The LED does not allow any current to go through and the module doesn't sense the ground (thereby thinking that the break pedal is pressed).

You did say it wrong the first time, that's why it didn't make sense:
"The only thing that matters to the tiburon is that it sees VCC or not. If you have a LED blocking the path to VCC then it will be VCC - 3v "
You meant if it sees GROUND and blocking the path to GROUND..

And your advice is bogus, how can the problem be that the resistor is not big enough when his taillights light up? That is probably a wiring issue, no resistor value would make other bulbs light up...