Cruise Control won't set

Hi - I've added a 1999 996 Cab to my collection, and there is one thing that doesn't work on it (yet?). The cruise control won't set. When I push the button on the CC stalk, the light on the dash comes on, and I've checked the fuse for that as well and it seems OK. I replaced both the clutch and brake switches today, but still it won't set the CC. After searching here a bunch, I did check the brake lights. They all seem to work (both the set on the car and the set on the wing). But, I notice that all of the bulbs are 3 watt (W3W notation on the bulbs). I've seen posts that seem to indicate that perhaps the bulbs on the car should be 5W, and I think that is what the manual says. And I think the manual says the wing bulbs should be 3W. Would having the smaller wattage bulbs in the car set of bulbs cause the cruise to not set? I think the previous owner tried to replace these with LEDs, and perhaps just replaced them all with 3W when the LEDs didn't work? Thanks for any help!

I assume you are pushing the control lever forward to activate cruise control at the appropriate speed... That's the way it works in a 2002 model. The button turns on the system and illuminates the green light, and you activate cruise by pushing the lever forward. Is this the same for the 1999 model?

It is on my 99.

Yes, I've been setting the switch, then pushing the stalk away from me to set it (which is what the manual and "instructions" on the stalk seem to say. Pulling it back towards me should cancel it. This is the same as my 993.

Interesting. I wonder if you've got a defective controller. If that's the case, they have to replace the entire unit with all the control levers. I had mine done this year at my dealer - I think it was $450ish.

Thanks Dennis - That may well be true. The previous owner had said that it did work, but that may have been 6 months ago since he tried it. Since my mechanic or the dealer are 80 miles away, I was trying to check whatever I could now. But, it looks like a trip over there is in my near future. I am going to drive this car to Rennsport Reunion in less than a month, might just have to do without the CC.

Your CC has a "keep alive" circuit that detects the brake lights being on or OPEN. Normal dual filament brake light bulbs are 12/18 watts. I converted all my tail/brake lights to LEDs and had to simulate a low resistive load on the brake light circuit in order for CC to work. I used a 50W halogen bulb with a relay. The bulb filament load is only in the brake light circuit with the actual brake voltage off.

Thanks for the information about the brake light power. I do have some additional information! Good News - I found a broken wire to the clutch switch! I connected this back up and the CC will set and work now. I suspect the previous owner did this when replacing the electrical part of the key. Don't know why I didn't see it before, probably need new glasses! Bad News - If I hit the brakes the CC will switch off, the light on the dash goes off and it can't be reset until I turn the key off and back on. Even by trying the switch on the stalk. I put the original switch back on, but there is no difference. The previous owner did recently put brake pads and rotors on the car, and the brake pedal doesn't have much travel. I wonder if it needs more travel (open the switch more?) in order to work right? Is there an adjustment for either the brake pedal or the brake light switch? Thanks!

Quotes source post: 8882732

Kind sir...Please PM me or post instructions/diagram on your solution. I have the same issue since the LED tail light switch. Thanks in advance

Simple. A small 12 volt relay from radio shack and a 50 watt bi-pin bulb. The relay pickup coil is wired across the brake light circuit, picks up when you apply the brakes. The bulb is wired via the NC, normally closed relay contacts, to only have the brake circuit connected when the brake lights are OFF. All diodes, even with a very small current flow available, have a minimum voltage drop, usually 0.6 to 0.8 volts. LED diodes might have a minimum drop as high as 3 volts. If you check you will notice that the high mounted led light has more than ~1 volts applied even with the brake lights off. sometimes in a dark area you can even see a faint glow from the LEDs as a result. It is that low residual voltage that makes the CC ECU "think" the brakes are applied.

Staying with the Cruise Control theme, can someone tell me where the actual CC module is located in '99 996?

Hi - I wanted to report that I got the CC to work! A combination of perseverance and stupidity caused the problems. As mentioned by others, the brake switch actually does 2 things - brake lights on and CC off. Well, the switch can come apart when you take it out of the car, and if you put it back together again 180 degrees off, weird things happen. Thought about it last night, looked at the photo at Pelican, and put it back together again the right way. And it all works again! My thanks for all the responses. Hal - The CC module is actually under the dash on the 996s. It attaches to the accelerator pedal via a cable and actually pulls the accel pedal to maintain the speed. So, just follow the little cable from the accel pedal up and under the dash and you'll find it. I have no idea how to get it out of there though! I'll post some photos of the car later today.

Thanks Steve!

I hope I am on the correct thread. Has anyone had trouble with the inside courtesy light and inside kerb light not coming on as either door is opened? I have checked and the fuse and all bulbs are working. I removed the inside cluster above the mirror and bridged across a couple of contacts and all bulbs are working ok. Can anyone tell me where to locate the actual door switch which brings on theses lights. I have a 1999 C2 Cabriolet.. Everything else on the car is working as it was intended to work. Any suggestions greatly appreciated. BTW my cruise control works same as other Carreras mentioned. Theres a push button on the end of the arm which starts it up then push arm forward to set. Pull back or brake to release.

Quotes source post: 8882732

I had installed the Depo LED 997 MK2 sytle tail lights and now added the smoked LED third brake lights and while everything seemed to work normally at first, I actually learned that I lost my cruise functionality. It seems to be common since what I am reading is that in addition to the 50w 6ohm resistors for the tail-lights, you would also need the resistor for the 3rd brake light. The issue is do I need one for the recessed one as well as the one in the electric spoiler? If so, how did you mount your resistor for the lights in the spoiler when you should not attach it to plastic because of the heat generated? Any input would be appreciated.