Cruise control light on before start and then disappears

[PLP]

A while ago I retrofitted my 2003 Bxster 2.7, MT with CC and OBC.
OBC was activated and works fine.
CC was activated via Durametric as well and it seemed to work, but only for a short time.

CC activation was done much later... just nowadays.

Initially the green light was lit when ignition on.
After starting the car it will either stay on or turns off with the switch.
It would engage and work fine.

However, at some point on the same day it stopped working.
Cruise control light on before start and then disappears within seconds once the engine is running.
I checked the clutch switch, brake switch, adjusted the brake switch travel... nothing helps.

I cannot get the light to turn on.
Why?

Also, since here.
What is the normal behaviour?

Green light shows up with ignition on, right?
The switch on the stalk will do nothing yet.
Then once the engine is running, depending on the condition of the switch on the stalk, the light will remain lit or goes away. Right?

If lit, you activate the speed control by pushing the stalk forward. Other options, cancel, resume... all typical.
It all worked, but now I get nothing.

Durametric activation was cycled, but no help.

I am confused.

Oh, the B7 fuse is OK.

[And416]

I experienced the same issue with my factory CC. I had to replace the brake switch. My brake lights functioned even though the CC did not function. Replacing this switch solved the non-functioning CC.

[PLP]

Originally Posted by And416

I experienced the same issue with my factory CC. I had to replace the brake switch. My brake lights functioned even though the CC did not function. Replacing this switch solved the non-functioning CC.

Thanks for the response.
You might be onto something as today in the morning it worked just fine...
The CC switch would activate and deactivate the light.
I drove most of the trip on CC and all was OK.

I did check brake switch. Seemed OK, adjusted it one more time.
Time will tell.
If it happens again, I will be replacing it.

[lkchris]

This is called “bulb test”. Like your check engine light.

[PLP]

Originally Posted by lkchris

This is called “bulb test”. Like your check engine light.

Not really.
CC is not part of it.
Until I added it and activated, the light would never show up.
Other lights - yes. I agree.

[KevinH1990]

I had similar symptoms to PLP's. My cruise control stopped working, but the bulb illuminated when I started the car. I traced the problem to fuse B7 which had blown. Since that fuse also controls the brake lights, I'm concerned that the problem could recur and cause a safety issue.

Are there any areas I should check to see what could have caused the fuse to blow? The only work I have done on the car recently is installing a rivnut in the windshield header. (One of the fasteners that holds the center light and associated components had come loose.) This did require that I disconnect the three electrical connectors that feed into the light assembly.

Thanks in advance for any suggestions.

[KevinH1990]

https://rennlist.com/forums/996-forum/1272957-b7-fuse-keeps-getting-blown.html

I found this thread on Rennlist. It appears to be more pertinent to my issue. I checked the wiring in the trunk and couldn't find any obvious issues.

The only visible issue I found was one of the brake light bulbs is discolored. The filament is intact, but the bulb is darkened which suggest that it may be getting hot.



I replaced the bulb and fuse B7 (again.) The light is working okay in the garage, but I need to complete a road test to see whether this resolved the issue. I need to choose a place and time with light traffic to avoid creating a hazard for myself and others.

[KevinH1990]

I think I found the problem. I disconnected both taillight assemblies and the fuse didn't blow when I used the brakes. When I reconnected the passenger-side taillight, I didn't have an issue. This suggested a problem in either the driver's side taillight assembly or the wiring.

I decided to risk "throwing parts at a problem" and replaced the driver's side taillight bulb carrier since other posts suggested that it was prone to failure. I've driven the car about 10 miles with the new bulb carrier installed and everything seems to be working.

[LoneWolfGal]

Originally Posted by KevinH1990

I decided to risk "throwing parts at a problem" and replaced the driver's side taillight bulb carrier since other posts suggested that it was prone to failure. I've driven the car about 10 miles with the new bulb carrier installed and everything seems to be working.

Good work, Kevin. That's the kind of sniggling problem that makes you pull your hair out.

[PLP]

Finally - I got it working.

I am not sure, though, which step made it work, but it has been fine since then.

Again, rear light assemblies are aftermarket.
Since the controller died on both sides, I used resistors and voltage controllers to adjust LED intensities between brake and tail lights. It works fine, but could contribute to the issue.

Also, the center lamp received LED replacements.

Durametric Pro was heavily in use.

The first error I was getting was about malfunction with the brake light switch. I thought it was due to LEDs, so I added a load resistor to assemblies (still same) and then to the center. Still same...
So I got a new switch, despite seeing the original one working OK.

I swapped it and CC worked for a while and died.
One difference though. I noticed with the old switch that the brakes would start catching, just a tiny bit, but still before the lights would light up. It was not any dangerous, but technically speaking friction would take place before the light is visible. You could see it only when slowly rolling back or forward when sitting at the lights.

Back to Durametric.
This time it says something about clutch sensor - something about "takes more than 5 seconds between gear changes".
I am like - what is that?

I pulled it out and tested.
Sure enough there is some high resistance where the circuit should terminate.
Since I ordered two switches for the brake pedal (one was clutch one was brake) I was like - whatever, lets swap it.

And since then all is good.


So in short - for sure both - brake light switch and clutch switch were replaced (not the start with clutch switch - the large, 4 pin one).
A total of 3 load resistors were added. Lights each 6 Ohm, while the center got 30 Ohm.