98 GrandPrix GTP AC "issue"

My 98 Grand Prix started blowing heated air when the AC is on the other
day. The clutch on the compressor is wroking and the line leading into
the evaproator (core) is getting icy cold (so the AC system is
working). However it's blowing warm/heated air with the AC on. Is
there a valve in the dash that controls heated water flow through the
heating core when the AC is on? It seems as though this is stuck
"open" letting the core get hot the same time the AC core gets cold.
Anyone have a similar problem? How do I fix it? Does nayone have a
schematic/diagram of the area in question and how to go about fixing
it.

-Thanks!
Mike

Do you have the "automatic" HVAC system or the "manual" version?


"GTPOwnerMDA" <maudette (AT) net1plus (DOT) com> wrote

My 98 Grand Prix started blowing heated air when the AC is on the other
day. The clutch on the compressor is wroking and the line leading into
the evaproator (core) is getting icy cold (so the AC system is
working). However it's blowing warm/heated air with the AC on. Is
there a valve in the dash that controls heated water flow through the
heating core when the AC is on? It seems as though this is stuck
"open" letting the core get hot the same time the AC core gets cold.
Anyone have a similar problem? How do I fix it? Does nayone have a
schematic/diagram of the area in question and how to go about fixing
it.

-Thanks!
Mike

I have the same issue with my 98 GT. Has anyone replied with
resolution ?
-=Dann

A resolution depends a great deal on what type of system your vehicle has.
The automatic HVAC controller uses electrical actuators to control
temperature. The manual HVAC controller uses vacuum motors. More info
needed from your end.

"Nine0fnine" <Nine0fnine (AT) yahoo (DOT) com> wrote

I have the same issue with my 98 GT. Has anyone replied with
resolution ?
-=Dann

Silver Surfer wrote:

A resolution depends a great deal on what type of system your vehicle has.
The automatic HVAC controller uses electrical actuators to control
temperature. The manual HVAC controller uses vacuum motors. More info
needed from your end.

Surfer my '98 GrandPrix GT is an automatic. I found the external temp
sensor for 15 bucks and I replaced it. I was sure that it was the
solution. The temp gauge is good in the cold but will not report temps
greater than 45 degrees. I had the AC unit checked and I was told that
I'm AOK. Their advice was to replace the HVAC controller. And I did,
but it was with one I picked up at the bone yard. No change... It was
99 in Chicago today. > : - ( <
If I disconnected the battery for a while would it reboot or reset
something?
-Dann

"Nine0fnine" <Nine0fnine (AT) yahoo (DOT) com> wrote in message
news:1154378385.114329.155330 (AT) 75g2000cwc (DOT) googlegroups.com...

I have the same issue with my 98 GT. Has anyone replied with
resolution ?
-=Dann

I have the auto controls. I plled apart the dash a little and can see
the servos moving for the heat/ac on both the drivers and passengers
zone. Cnat'tell or locate where the hot/cold mixer is (or if there is
a seperate one).




Silver Surfer wrote:

Do you have the "automatic" HVAC system or the "manual" version?


"GTPOwnerMDA" <maudette (AT) net1plus (DOT) com> wrote in message
news:1154104785.055876.244190 (AT) m79g2000cwm (DOT) googlegroups.com...
My 98 Grand Prix started blowing heated air when the AC is on the other
day. The clutch on the compressor is wroking and the line leading into
the evaproator (core) is getting icy cold (so the AC system is
working). However it's blowing warm/heated air with the AC on. Is
there a valve in the dash that controls heated water flow through the
heating core when the AC is on? It seems as though this is stuck
"open" letting the core get hot the same time the AC core gets cold.
Anyone have a similar problem? How do I fix it? Does nayone have a
schematic/diagram of the area in question and how to go about fixing
it.

-Thanks!
Mike

My external temp sensor is dead-nuts on. I'm wondering if I don't just
need a recharge? It is almost 8 years old and has never been in for
any service (other than a cracked fuel pump resistor (TSB on that one)
and regular oil changes. All I know s it was working fine two weeks
ago..it sat in my driveway for two weeks during the super heat and then
stopped blowing cold.




Nine0fnine wrote:

Silver Surfer wrote:
A resolution depends a great deal on what type of system your vehicle has.
The automatic HVAC controller uses electrical actuators to control
temperature. The manual HVAC controller uses vacuum motors. More info
needed from your end.

Surfer my '98 GrandPrix GT is an automatic. I found the external temp
sensor for 15 bucks and I replaced it. I was sure that it was the
solution. The temp gauge is good in the cold but will not report temps
greater than 45 degrees. I had the AC unit checked and I was told that
I'm AOK. Their advice was to replace the HVAC controller. And I did,
but it was with one I picked up at the bone yard. No change... It was
99 in Chicago today. > : - (
If I disconnected the battery for a while would it reboot or reset
something?
-Dann


"Nine0fnine" <Nine0fnine (AT) yahoo (DOT) com> wrote in message
news:1154378385.114329.155330 (AT) 75g2000cwc (DOT) googlegroups.com...

I have the same issue with my 98 GT. Has anyone replied with
resolution ?
-=Dann

Take a look at this description and see if it shines any light on the
subject:

Document ID# 515748
1998 Pontiac Grand Prix
--------------------------------------------------------------------------------
HVAC Air Delivery/Temperature Control Circuit Description

The air doors that control the flow of air through the A/C module are
operated by vacuum actuators. Solenoid valves located in the vacuum/electric
solenoid apply vacuum to the actuators or vent the actuators. The solenoids
are controlled by solid state circuits in the heater-A/C control. Push
buttons in the heater-A/C control determine the A/C operating mode.
Depending on the mode selected, the heater-A/C control determines which air
doors should be operated.

Two air temperature sensors are used by the heater-A/C control. Their
resistance decreases as the temperature increases. The inside air
temperature sensor measures the inside air temperature. The ambient outside
temperature sensor measures the outside air temperature. The difference
between the two sensor measurements is used by the control circuits in order
to determine whether the incoming air should be cooled or warmed, and to
what degree. This is determined in order to bring the inside air temperature
to the selected temperature as quickly as possible. If a malfunction should
occur in either the inside air or ambient outside temperature sensor
circuits, the heater-A/C control will set a trouble code. It will also
substitute a temperature value of 75°F (24°C) if the inside air temperature
sensor circuit is at fault or 49°F (9°C) if the ambient outside temperature
sensor circuit is at fault. The substitute temperature value(s) allow the
system to continue operations.

The sun load temperature sensor determines the amount of sunlight produced
by the sun. As the sunlight increases, the sensors current increases. This
sensor is used in order to program the blower speed and the auto/bi-level
modes.

Air Inlet Valve
The air inlet valve is closed in most of the operating modes, permitting
outside air to enter the A/C module. It is opened only in the A/C modes and
at a temperature setting of 65°F (18°C) or higher. When the air inlet valve
is open, air from inside the vehicle is recirculated in order to get maximum
cooling.

Air Temperature Valves
The air temperature valves are positioned by the left and right electric
actuators. When the door is in the cool position, air is prevented from
passing through the heater core. The door can be placed by the actuator in
any position between cool and warm in order to provide any degree of warming
to the air after it has passed through the A/C evaporator core.

Defroster Valve
The defroster valve can be moved to 1 of 3 positions. The defroster valve
actuator consists of 2 chambers operated by 2 vacuum actuators. When the
A/C system is operated in the bi-level of the DEFOG mode, neither vacuum
chamber is evacuated and the door is in position B. Air flow is then
directed to both the defrost outlets and heater outlets. If the heater
solenoid is activated, the actuator moves the valve to position C. Position
C directs air flow to the heater outlets (lower mode). If the defrost
solenoid is activated, the valve moves to the defrost outlets. This is the
position the valve is in when operating the defrost mode.

Inner and Outer Mode Valve
The inner and outer mode valve is in position B when the air conditioning is
activated, or when the bi-level or upper modes are selected. In this
position, air flow is directed out of the A/C outlets. If the OFF, LOWER,
DEFROST, or DEFOG mode is selected, the bi-level solenoid is de-energized.
This will vent the vacuum from the inner and outer mode valve actuator,
allowing the door to move to position A. The air flow will now be directed
toward the heater and defrost outlets.

Outer Mode Valve
The outer mode valve performs the following functions:

Diverting air-conditioned air through the A/C outlets
Preventing air flow through the heater and defrost outlets.
The outer mode valve is in position B when the system is in the maximum A/C
or normal A/C modes. The outer mode valve is in position A in all other
modes.

Delay Mode
The delay mode is used in order to prevent the vehicle occupants breath from
fogging the windshield when the outside temperature is low and the engine is
cold. The heater-A/C control will set the doors so that air flow is directed
to the windshield with low blower operation. The system will stay in the
delay mode until the engine coolant temperature reaches 49°C (120°F) or
after 4 minutes, whichever comes first. The system will then operate
normally in the selected mode.


"GTPOwnerMDA" <maudette (AT) net1plus (DOT) com> wrote

My external temp sensor is dead-nuts on. I'm wondering if I don't just
need a recharge? It is almost 8 years old and has never been in for
any service (other than a cracked fuel pump resistor (TSB on that one)
and regular oil changes. All I know s it was working fine two weeks
ago..it sat in my driveway for two weeks during the super heat and then
stopped blowing cold.




Nine0fnine wrote:
Silver Surfer wrote:
A resolution depends a great deal on what type of system your vehicle
has.
The automatic HVAC controller uses electrical actuators to control
temperature. The manual HVAC controller uses vacuum motors. More info
needed from your end.

Surfer my '98 GrandPrix GT is an automatic. I found the external temp
sensor for 15 bucks and I replaced it. I was sure that it was the
solution. The temp gauge is good in the cold but will not report temps
greater than 45 degrees. I had the AC unit checked and I was told that
I'm AOK. Their advice was to replace the HVAC controller. And I did,
but it was with one I picked up at the bone yard. No change... It was
99 in Chicago today. > : - (
If I disconnected the battery for a while would it reboot or reset
something?
-Dann


"Nine0fnine" <Nine0fnine (AT) yahoo (DOT) com> wrote in message
news:1154378385.114329.155330 (AT) 75g2000cwc (DOT) googlegroups.com...

I have the same issue with my 98 GT. Has anyone replied with
resolution ?
-=Dann

If you can get someone to put a scanner on your vehicle the following
trouble codes might point you in the right direction any of them are set.

DTC Table
TROUBLE CODE
DESCRIPTION

00
No System Fault

01 or 101
DTC 01 Inside Air Temp Sensor Circuit Shorted

02 or 102
DTC 02 Inside Air Temp Sensor Circuit Open

03 or 103
DTC 03 Outside Air Temp Sensor Circuit Shorted

04 or 104
DTC 04 Outside Air Temp Sensor Circuit Open

05 or 105
DTC 05 LH air Door Motor Circuit Open or Shorted

06 or 106
DTC 06 RH air Door Motor Circuit Open or Shorted

07 or 107
DTC 07 UART Serial Data Line Fault

08 or 108
DTC 08 Sun Load Temp Sensor Open


"Silver Surfer" <h.mcguffinspamouflage (AT) comcast (DOT) net> wrote

Take a look at this description and see if it shines any light on the
subject:

Document ID# 515748
1998 Pontiac Grand Prix
--------------------------------------------------------------------------------
HVAC Air Delivery/Temperature Control Circuit Description

The air doors that control the flow of air through the A/C module are
operated by vacuum actuators. Solenoid valves located in the
vacuum/electric solenoid apply vacuum to the actuators or vent the
actuators. The solenoids are controlled by solid state circuits in the
heater-A/C control. Push buttons in the heater-A/C control determine the
A/C operating mode. Depending on the mode selected, the heater-A/C control
determines which air doors should be operated.

Two air temperature sensors are used by the heater-A/C control. Their
resistance decreases as the temperature increases. The inside air
temperature sensor measures the inside air temperature. The ambient
outside temperature sensor measures the outside air temperature. The
difference between the two sensor measurements is used by the control
circuits in order to determine whether the incoming air should be cooled
or warmed, and to what degree. This is determined in order to bring the
inside air temperature to the selected temperature as quickly as possible.
If a malfunction should occur in either the inside air or ambient outside
temperature sensor circuits, the heater-A/C control will set a trouble
code. It will also substitute a temperature value of 75°F (24°C) if the
inside air temperature sensor circuit is at fault or 49°F (9°C) if the
ambient outside temperature sensor circuit is at fault. The substitute
temperature value(s) allow the system to continue operations.

The sun load temperature sensor determines the amount of sunlight produced
by the sun. As the sunlight increases, the sensors current increases. This
sensor is used in order to program the blower speed and the auto/bi-level
modes.

Air Inlet Valve
The air inlet valve is closed in most of the operating modes, permitting
outside air to enter the A/C module. It is opened only in the A/C modes
and at a temperature setting of 65°F (18°C) or higher. When the air inlet
valve is open, air from inside the vehicle is recirculated in order to get
maximum cooling.

Air Temperature Valves
The air temperature valves are positioned by the left and right electric
actuators. When the door is in the cool position, air is prevented from
passing through the heater core. The door can be placed by the actuator in
any position between cool and warm in order to provide any degree of
warming to the air after it has passed through the A/C evaporator core.

Defroster Valve
The defroster valve can be moved to 1 of 3 positions. The defroster valve
actuator consists of 2 chambers operated by 2 vacuum actuators. When the
A/C system is operated in the bi-level of the DEFOG mode, neither vacuum
chamber is evacuated and the door is in position B. Air flow is then
directed to both the defrost outlets and heater outlets. If the heater
solenoid is activated, the actuator moves the valve to position C.
Position C directs air flow to the heater outlets (lower mode). If the
defrost solenoid is activated, the valve moves to the defrost outlets.
This is the position the valve is in when operating the defrost mode.

Inner and Outer Mode Valve
The inner and outer mode valve is in position B when the air conditioning
is activated, or when the bi-level or upper modes are selected. In this
position, air flow is directed out of the A/C outlets. If the OFF, LOWER,
DEFROST, or DEFOG mode is selected, the bi-level solenoid is de-energized.
This will vent the vacuum from the inner and outer mode valve actuator,
allowing the door to move to position A. The air flow will now be directed
toward the heater and defrost outlets.

Outer Mode Valve
The outer mode valve performs the following functions:

Diverting air-conditioned air through the A/C outlets
Preventing air flow through the heater and defrost outlets.
The outer mode valve is in position B when the system is in the maximum
A/C or normal A/C modes. The outer mode valve is in position A in all
other modes.

Delay Mode
The delay mode is used in order to prevent the vehicle occupants breath
from fogging the windshield when the outside temperature is low and the
engine is cold. The heater-A/C control will set the doors so that air flow
is directed to the windshield with low blower operation. The system will
stay in the delay mode until the engine coolant temperature reaches 49°C
(120°F) or after 4 minutes, whichever comes first. The system will then
operate normally in the selected mode.


"GTPOwnerMDA" <maudette (AT) net1plus (DOT) com> wrote in message
news:1154451996.204595.237800 (AT) m73g2000cwd (DOT) googlegroups.com...
My external temp sensor is dead-nuts on. I'm wondering if I don't just
need a recharge? It is almost 8 years old and has never been in for
any service (other than a cracked fuel pump resistor (TSB on that one)
and regular oil changes. All I know s it was working fine two weeks
ago..it sat in my driveway for two weeks during the super heat and then
stopped blowing cold.




Nine0fnine wrote:
Silver Surfer wrote:
A resolution depends a great deal on what type of system your vehicle
has.
The automatic HVAC controller uses electrical actuators to control
temperature. The manual HVAC controller uses vacuum motors. More
info
needed from your end.

Surfer my '98 GrandPrix GT is an automatic. I found the external temp
sensor for 15 bucks and I replaced it. I was sure that it was the
solution. The temp gauge is good in the cold but will not report temps
greater than 45 degrees. I had the AC unit checked and I was told that
I'm AOK. Their advice was to replace the HVAC controller. And I did,
but it was with one I picked up at the bone yard. No change... It was
99 in Chicago today. > : - (
If I disconnected the battery for a while would it reboot or reset
something?
-Dann


"Nine0fnine" <Nine0fnine (AT) yahoo (DOT) com> wrote in message
news:1154378385.114329.155330 (AT) 75g2000cwc (DOT) googlegroups.com...

I have the same issue with my 98 GT. Has anyone replied with
resolution ?
-=Dann

Good news for the home team. When I got in my car today the temp
readout for 103. good for me. I didn't have far to go today so I
really couldn't test it but the system did seam to be blowing colder
air. I think I might need more lbs's of R-whatever. I think the new
ambiant air sensor fixed my problem. We'll see in the days to come.
It jives with what the surfer published. Good luck to the rest.......

For future where did you find that info ? Please pass along the url is
found on the web... PLEASE -Dann