No Heat

Phil Rose pjrose at
Thu Mar 29 14:17:08 EDT 2007

At 9:04 AM -0400 3/29/07, Peter Schulz wrote:
>Check the CC codes, but there are other visual cues to look at too,
>the heater valve behind the head on the firewall, and the heater flap
>position motor external to the heater box...
>the CC codes in Bentley should be able to tell you what the issue is.

What Peter said.  A quick look at the value in CC channel 01 should 
show a "OO" when all is OK with the climate control system. But if 
channel 01 presents a value of "07", then something's wrong.

Assuming you've got hot water and the heater control valve is working 
properly, then you can get a quick diagnosis if there's a problem 
with the heater's flap-positioning potentiometer by doing the 
following. Set the temperature to some desired value (e.g., 68 F, 
where it probably isn't heating properly). Then, after driving for 
minute or two with the CC in "econ" mode, (assuming engine is warmed 
up), compare the reading in CC channel 08 with that in channel 09. 
They ought to have pretty close to the same value (channel 08 value 
is the "target"position for the flap motor/potentiometer while 
channel 09 shows its "actual" position. If not identical values (with 
a few units) or jumping wildly up and down, then replace the 
heater-flap's motor/potentiometer unit, as your problem is a 
worn/noisy potentiometer. Some people have allegedly been successful 
in simply removing the unit, disassembling and cleaning the 
potentiometer. That's a lot of work if it doesn't work-- and it 
didn't help at all when I tried it. Replacing the flap positioning 
motor/potentiometer immediately restored the heat.

*  Phil & Judy Rose           Rochester, NY  *      
*        mailto:pjrose at       *

More information about the 200q20v mailing list