Speedo output "A"
 

Hi,

while trying to track down the problem that keeps the cruise control of my '80 SC from working I found that the signal "A" from the speedometer to the cruise control brain (and the OXS milage counter) looks odd. Actually, the doesn't seem to be a meaningful signal.

http://forums.pelicanparts.com/uploa...1376232722.jpg

Before I finally conclude that the speedo is shot, I would like to ask the following:

- What is the output configuration of "A"? is it a relay contact, a transistor, or what?

- How would a valid signal look like? I assume it would be some kind of frequency related to how fast the wheels turn. Is it a voltage (rectangular between 0 and 12 V)?

- Any other idea how I can check the "A" signal?

The speedometer is a VDO model 437.201/1/20

Thank you, Manfred

Manfred, I can't answer your question because my car is in the shop and I can't stick a scope on the A terminal. However, I never realised the A terminal was output for the OXS sensor - so you've explained why I've never had to reset mine in 30,000 miles (it's not connected)...

I'd expect it would have a good chance of being a 5V square wave output though - that's what you get from the transmission sensor.

I'm glad I could help you. ;) Hopefully I will find an answer for my questions, too. SmileWavy

Bump...

I can't believe that no one has an answer for me SmileWavy