Re: coolant temp sensor

["Scott Mo." <scottmo@teleport.com>]

Phil Rose wrote:
> 
> The ACC diagnostic channel 01 ('89 100) has always produced an 09 code,
> which I have ignored until recently. According to the Bentley, the 09 code
> means a faulty "engine coolant sensor"--the one that's inserted just upside
> the large coolant hose/thermostat flange. I ran the electrical tests and
> everything appears as per specs--both the sensor resistances and the
> voltages at the connector pins. So...why does the ACC tell me there's a
> problem here?
> 
> According to the manual, the symptom of a defective coolant sensor will be
> hard cold-starts and rough running during warmup. I've never noted the
> former, but the latter symptom is sometimes present in winter. Is it
> possible that the 09 code from ACC channel 1 of '89s is not meaningful?

That does seem to be the case, the coolant temp sensor G62) they refer
to was phased in on the later 200's, the 1991 200TQ 20V has this sensor
incorporated into the heater valve at the back of the engine. The
Bentley on page D8-310-1 explains this phase in of this sensor. I
believe, this sensor is used to ensure the engine coolant is warm enough
before the interior fan is turned on. I think the earlier systems used a
standard time delay after start up to accomplish the same thing.

HTH
-- 
Scott Mo.
1989 200TQ
1988 5000TQ
1966 VW Beetle
http://www.teleport.com/~scottmo