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  #1  
Old 05-26-2006, 09:46 AM
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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.

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Old 05-26-2006, 12:18 PM
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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
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Old 05-26-2006, 12:25 PM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
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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.)
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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Last edited by A264172; 05-26-2006 at 12:34 PM.
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  #4  
Old 05-26-2006, 12:51 PM
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Thanks for the reply.

Is that battery voltage with engine on or off?
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  #5  
Old 05-26-2006, 02:06 PM
Ta ra ra boom de ay
 
Join Date: Jun 2004
Location: Pittsburgh
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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
__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html
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  #6  
Old 05-26-2006, 02:44 PM
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smoke gets in your eyes
 
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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
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  #7  
Old 05-26-2006, 11:40 PM
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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

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