What's an on/off ratio?
 

Hi all,

I'm going through the manual and reading the CFI "testing electrical components" part. For my car, '87 19E 8V, the reference column says on/off ratio.

What's that? Can I get it with a VOM?

Thanks in advance.

On/off ratio is one way to measure a frequency value, something that pulses between completely on and completely off with no essentially no intermediate status. A VOM with duty cycle mode will display on/off ratio in percent. Do a forum search on 'Craftsman' for the part number of a $20-30 VOM with duty cycle mode.

Sixto

If you only have a VOM (no duty cycle setting) you can use this formula:
Duty Cycle = [1 - (V{pin 3}/V{max})] x 100%
...to extract it.
edit: (Pin 3 is at X11 in this case and max = battery volts.)

Thanks for the reply.

Is that battery voltage with engine on or off?

I'm not 100% sure... but I would think it would be when running... since that is the voltage that you are trying to find the % 'off' of.
This link has some info as well:
http://www.landiss.com/mixture.htm

Search for 3482139 at sears.com. Once in a while it goes from regular $29 to $19.99.

http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&cat=Electrical+Shop&subcat=Multi-Meters%2C+Testers+%26+Accessories&pid=03482139000

Sixto

:eek:

So thats why I'm getting a constant ~12.5V reading between pins 2 and 3.

My on/off ratio is ~10% meaning it's either a problem with the volume airflow sensor or throttle position contact.

Now I'd like to move forward and do the tests for this particular on/off ratio. Is it possible without using the contact box tool specified in the manual?

Thanks for the info