[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]
Climate Control Diags (&RE: Recirculate Doors) - LONG
Before I excerpt the info on the "digital" climate control diagnostics,
I had a couple of things I wanted to note based on looking at the Bentley
manual ('84-'88 5000S/CS):
1 - There was discussion about the fan motor that blows air by the interior
temperature sensor. The discussion alluded to the motor being mounted
vertically. From the manual the motor appears to be mounted horizontally
under the dash. Furthermore, there is an exploded parts diagram on page
87.80 of the manual that implies that the motor has some type of splined
drive connector for the fan. If I had one of those babies go out I would
certainly look into repairing it myself or obtaining a non-factory
replacement.
2 - It appears that there were a number of updates to the non-digital
climate control system between '85 & '86. Page 87.62 in the manual
discusses these changes.
The manual states that the digital climate control system was used start-
ing in November 1985. The control head is distinguishable from the older
system by the lack of the rear window defrost control and the addition of
a bi-level mode and override switches to set the fan at low or high. The
manual states that some faults are indicated w/o activating the fault
memory system. The LED next to the outside temperature button will flash
for ~1 min after a fault is detected or the ignition is switched on when
there is a fault. I wanted to note that the manual devotes 100 pages to
the digital climate control system. It includes detailed troubleshooting
flow charts as well as individual component tests. If you've got a real
problem it's probably best to obtain the manual. I'll include a discus-
sion of the fault check system here.
The fault system can be activated when the ignition switch is in the ON
position, the engine need not be running. The fault system is activated
by pressing the red "WARMER" button while holding down the "OUTSIDE TEMP"
button. After activating the fault system the "OUTSIDE TEMP" button can
be released. When initially activated the numeric LED displays will in-
dicate a code of `01. This value indicates the "channel" that is select-
ed for monitoring. Notice that the Climate Control system will continue
to operate in the mode it was in before the fault system was activated,
and it is possible to terminate the fault system display by pressing any
button on the head other than the "WARMER" and "COOLER" buttons.
The fault channel selection will increment when the "WARMER" button is
depressed ... there are 23 fault channels. The fault channel value is
accessed by pressing the blue "COOLER" button. Once the channel has
been accessed it is possible to check other channels by pressing the
"WARMER" button. The channel definition is:
Chan Function
======================================================================
`01 System Faults (see fault code table below)
`02 *UNUSED*
`03 Int Temp Sensor*
`04 Ext Temp Sens - Plenum*
`05 Ext Temp Sens - Radiator*
`06 *UNUSED* (But referenced on page 87.138!)
`07 Graphic Control Head Output
`08 Specified Temp Reg Flap Position
`09 Actual Temp Reg Flap Position
`10 Specified Blower Motor Voltage
`11 Vehicle Voltage <=== Useful for monitoring battery too!
`12 *UNUSED*
`13 Ambient Temperature Switch
`14 *UNUSED* (But referenced on page 87.141!)
`15 Kickdown switch (auto tranny)
`16 Engine Coolant Overheat switch
`17 *UNUSED*
`18 *UNUSED*
`19 *UNUSED*
`20 *UNUSED*
`21 AC ON signal
`22 # of low voltage occurrences
`23 *UNUSED*
* - Readings from these channels are an encoded 3 digit value that are
decoded using a table in the Bentley manual.
System Fault Codes for channel `01
======================================================================
00 - No worries mate!
`01 - Interior temp sensor open
`02 - Interior temp sensor shorted
`03 - Exterior temp sensor in plenum open
`04 - Exterior temp sensor in plenum shorted
`05 - Exterior temp sensor in front of radiator open
`06 - Exterior temp sensor in front of radiator shorted
`07 - Motor for positioning heater flaps in programmer NOT OK
`13 - Battery voltage less than 9.5v
`14 - High pressure sensor - Excess pressure in system
`15 - High pressure sensor - short circuit
__________________________________________________________
Definitions for graphic control head output - channel `07
(Imagine the 2 7-segment LED displays adjacent to each other)
H G A-Radiator Cooling Fan Stage 1
| | B-A/C Compressor ON
v v C-Temp flaps toward cooler position
==== ==== D-floor vents open
A==> / / / / <==F E-BI-LEVEL (center & floor open)
/ / / / F-center vents open
===== ===== G-A/C Recirculation door closed
B==> / / / / <==E H-Temp flap toward warmer position
/ / / /
==== ====
^ ^
| |
C D
__________________________________________________________
Testing air control doors - the diagrams on pages 87.127 & 87.128 show
the actuator connections for the climate control. If the diagram is
correct, the same line that selects outside air or recirculated air
controls the flow of coolant to the heater core. The table below shows
actuator positions for several conditions.
Function | FRESH/RECIRC | CENTER VENT | DEFR/FOOT | HEATER VALVE
===================================================================
OFF | RECIRC | CLOSED | WINDSHIELD | CLOSED
ECON 64F | FRESH(?) | FULLY OPEN | FOOTWELLS | OPEN(?)
ECON 84F | FRESH | CLOSED | FOOTWELLS | OPEN
BI-LEV 64F | FRESH(?) | HALF OPEN | FOOTWELLS | OPEN(?)
BI-LEV 84F | FRESH | HALF OPEN | FOOTWELLS | OPEN
AUTO 64F | RECIRC | FULLY OPEN | FOOTWELLS | CLOSED
AUTO 84F | FRESH | CLOSED | FOOTWELLS | OPEN
DEF | FRESH | CLOSED | WINDSHIELD | OPEN
===================================================================
Notice that I question a couple of the entries in the table in regards
to the heater valve being opened when the temperature setting is low.
I'm noting that here, because the heater valve servo and fresh air/recir-
culate servos are connected together. One important thing to note is
that the recirculate/fresh air door has only two valid positions ... if
yours appears to be somewhere in between it is an obvious fault. BTW,
the heater valve servo is open when the actuator arm protrudes from the
vacuum motor and the valve is closed when vacuum is applied to the motor.
Steve Buchholz
s_buchho@kla.com