notaguru

This '83AT was just refreshed by Greg Brown, and is everything it should be!

However, we're trying to track down a 1-per-tire-revolution "tick" noise. I'm pretty deaf, but passengers hear it clearly. I pulled the wheels and found no interference with tires, brakes, etc.

I don't know the rate at which the speedo cable turns, but if it's close to wheel rev it could be the source. Over the decades I've encountered a similar problem on other cars, and it's usually easy to fix with lube. On some cars, however, the cable is sealed and lubed for life and can only be replaced.

Search turned up no help. So - questions:

What's the relationship between tire rotation speed and speedo cable rotation speed?

How tough is it to access and lube the cable assembly?

OR - if drive is electrical, could it be the speedo itself?

???

The Forgotten On

It's the counter for the oxygen sensor computer. It tells you when to replace the O2 sensor (around 60K miles).

It is located under a carpeted cover next to the passenger seat next to a possible optional amp. You can just unplug it as all it does is make noise and light up a light on the dash.

Nothing is wrong with your car. Just something most find annoying is still working

notaguru

What a great response. I certainly hope you're right.

The existing O2 sensor was replaced at about 35k, so has less than 35k miles on it. If there's a reset function, perhaps the PO failed to do that. If not, how does the car know the O2 sensor has been replaced?


THANKS!

The Forgotten On

It doesn't. You have to manually reset it (which your PO probably didn't realize they had to do). It's a very basic system that isn't even connected with the 02 sensor.

I hope this is your root cause of the noise

Ducman82

And there is no speedo cable. It's all electric. Have you checked the tire tread for rocks/objects?

notaguru

It WAS the replacement alert for the O2 sensor, another brilliant design by Porsche's OverEngineering Team.

Pushing the white (reset?) button made no difference.
Pushing the white button in for 30 seconds, even while facing east, made no difference.
But when the two cables were disconnected, the TICK disappeared.

If I promise to replace the O2 sensor when the car fails smog or starts running open-loop, can I just remove that device and tape off the cables?? It's easily removed, along with the upholstered cover.

Silence is golden.
Thank you, Forgotten!

The Forgotten On

It will always tick as it is counting the miles. It just turns the light off on the dash. Overengineering at its finest

Ducman82

They made that counter because they were not sure how long a sensor would last.... So just go by mileage

notaguru

Why mileage?

With good fuel and no flaky additives, there is no reason an O2 sensor should not last for a very long time. So, instead of mileage, I'll just wait for it to stop working.

And according to notes from a previous owner, the O2 sensor in the car is an inexpensive Volvo part. The thread is right and the physics are the same. Passed smog that way at least five times, too.

THANKS!

Tickless Notaguru