DIY-WB warmup

[bcroe at juno.com]

Wayne, 

That flickering is very likely an indication of too little 
voltage (at idle) to keep the WB circuit enabled.  A 
cig lighter may not be good enough; you could run 
a 12 V and ground pair of 16 gauge or heavier 
almost directly to the battery or alternator to get the 
maximum voltage available.  If the alternator can't 
keep up at idle, this may not be enough.

Check the WB voltage at the junction of D5 pin 3
(LM431) and D1 pin 2 (1N4148), relative to the WB 
ground (J4-1).  This should be rock solid at close 
to 10 volts; if it starts bouncing around (in unison 
to LED flickering), you are dropping out of heater 
voltage regulation and sensor operation.

Latching the circuit would complicate it and risk 
WB sensor damage if a long voltage reduction 
were to occur.  Better to fix the wiring.  

Bruce Roe 

On Thu, 3 Jan 2002 15:34:40 +1100 "Wayne Macdonald"
<wmcdonal at optushome.com.au> writes:
> I have noticed that once the heater has warmed 
> up that the LED flickers on and off at idle, does 
> this mean that the IP is also switching on and 
> off ?  The reason I ask is that I was thinking it 
> may be good to latch the signal to the LED so 
> that once switched on the IP stayed on. After all 
> once the heater is up to temp I would assume 
> that even when the LED and IP go off that the 
> sensor is still hot enough to work correctly.
> Or am I way off base on this.

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