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rfmaster · 10-01-2009, 11:59 PM

AC-Delco AFS-75 wire - functional chart

BLUE SIGNAL + ( D7 )
WHITE SIGNAL - ( D6 )
BLACK HEATER
BLACK HEATER

O2 heater draws about 3-4 Amps when cold and drops down as O2 reaches 300C operating temperature. I set up a simple relay circuit that energizes heater whenever ignition is ON. FWIW in modern cars PCM monitors current drawn by the heater circuit. Once current reaches a certain lower limit (some) PCM will shut down heater circuit as PCM logic deems O2 is fully functional, only periodically checking to make certain. PCM will also shut it down at WOT. I have seen numerous explanations why it is done, but for the sake of our application keeping heater circuit that is always ON solves cold header problem that otherwise plagues single wire O2s.

//RF

10-01-2009, 11:59 PM	#301
rfmaster Registered User Join Date: Oct 2003 Location: OC CA Posts: 1,374	Re: Tbi swap build thread AC-Delco AFS-75 wire - functional chart BLUE SIGNAL + ( D7 ) WHITE SIGNAL - ( D6 ) BLACK HEATER BLACK HEATER O2 heater draws about 3-4 Amps when cold and drops down as O2 reaches 300C operating temperature. I set up a simple relay circuit that energizes heater whenever ignition is ON. FWIW in modern cars PCM monitors current drawn by the heater circuit. Once current reaches a certain lower limit (some) PCM will shut down heater circuit as PCM logic deems O2 is fully functional, only periodically checking to make certain. PCM will also shut it down at WOT. I have seen numerous explanations why it is done, but for the sake of our application keeping heater circuit that is always ON solves cold header problem that otherwise plagues single wire O2s. //RF __________________ "The Beast" 1975 Chevrolet C20 longbed 350/700R4! with 3inch body lift Dual Flowmasters Super 40's! TBI retrofit completed (2007-07-29) New 383CID (+030) 08-304-8 9.5:1CR x36,005 (2012-12-17)