Subject: Re: coolant temp sensor

[C1J1Miller@aol.com]

- -----Original Message-----

From: Phil Rose <pjrose@servtech.com>

Subject: coolant temp sensor



>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?

>

>Phil

>

>Phil Rose Rochester, NY
-----------

Fred Munro replied:


Hi Phil;



    You may have a bad connection which the A/C control head interprets as a

defective coolant sensor. I just had a problem with the A/C head setting 07

and 15 trouble codes - defective temperature control flap motor and/or

feedback potentiometer. Also had physical evidence of a problem - the unit

wouldn't maintain temperature. I followed the Bentley troubleshooting

procedure and it identified the temp flap motor as defective. Hmmm, that

motor looks awful expensive. Put the magical Stabilant 22A on the A/C head

connector pins and the temp flap motor connector - problem solved! It now

works like a charm and no more trouble codes.

--------
Fred and Phil:
I posted similar results a couple months back on my '91 200q.  Same symptoms
as Fred: sometimes heat stayed on full (temp flap motor would move to full
heat, then stop, and report to the control head that the position was wrong).
Pulled the black plastic cover over the air intake, pulled the wiper motor,
and pulled the temp flap motor.  Looked new, no play, etc. etc.  Cleaned the
electrical contact with DeOxit D5 spray; been fine for several months.  Total
time for fix: about 20 minutes; half hour counting the time to remove all the
leaves, etc. from under the plastic plenum with the shop vac. 
Chris Miller, Windham NH, c1j1miller@aol.com
http://members.aol.com/c1j1miller/index.html
('91 200q web site)