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Master of the Dark Art of Diagnostics
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basscat are you there?
====================
YES - I am here -

this is definitely a weird one - all the tests so far are inconclusive -

we know that the actuators are moving the MIX doors
because you get full heat on both driver and passenger side vents -

the issue is discharge temp is colder on the passenger side when temp is turned down to full cold -

the MOST COMMON cause of this condition is low freon charge -

the design of the system is such that air for the passenger side ducts
is blown through the first half of the evaporator core -
and air for the driver side is blown through the second half of the core -

normally - the cold liquid freon picks up heat from the cabin as it passes through the evaporator -
the freon actually boils - AFTER it leaves the evaporator -
HOWEVER -
if the freon is low - it starts to boil INSIDE the evaporator -
SO - the passenger side gets cold liquid freon
whereas the driver side gets warm gaseous freon -

we have no idea how much freon is actually in the system -
all we have is current pressure readings -

the quick test for low freon is to grab BOTH evaporator lines going through the firewall -
BOTH lines should be equally cold -

USUALLY - the discharge line will be NOTICEABLY warmer
if the freon is low enough to cause a difference in duct temps -

SO -
if the actuators ARE moving correctly - and the freon charge is NOT low -
and there are no codes pointing to any other sensor problems -
what are the other possibilities?

1) the driver side mix door is not moving to the full cold position -
or not sealing tightly -

2) debris on the evaporator core blocking/reducing airflow on the driver side -
 

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Discussion Starter #43
====================
YES - I am here -

this is definitely a weird one - all the tests so far are inconclusive -

we know that the actuators are moving the MIX doors
because you get full heat on both driver and passenger side vents -

the issue is discharge temp is colder on the passenger side when temp is turned down to full cold -

the MOST COMMON cause of this condition is low freon charge -

the design of the system is such that air for the passenger side ducts
is blown through the first half of the evaporator core -
and air for the driver side is blown through the second half of the core -

normally - the cold liquid freon picks up heat from the cabin as it passes through the evaporator -
the freon actually boils - AFTER it leaves the evaporator -
HOWEVER -
if the freon is low - it starts to boil INSIDE the evaporator -
SO - the passenger side gets cold liquid freon
whereas the driver side gets warm gaseous freon -

we have no idea how much freon is actually in the system -
all we have is current pressure readings -

the quick test for low freon is to grab BOTH evaporator lines going through the firewall -
BOTH lines should be equally cold -

USUALLY - the discharge line will be NOTICEABLY warmer
if the freon is low enough to cause a difference in duct temps -

SO -
if the actuators ARE moving correctly - and the freon charge is NOT low -
and there are no codes pointing to any other sensor problems -
what are the other possibilities?

1) the driver side mix door is not moving to the full cold position -
or not sealing tightly -

2) debris on the evaporator core blocking/reducing airflow on the driver side -
 

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Discussion Starter #44
Thank you for your response..
I fully agree with your analysis.. It only makes sense that is the mixer door was stuck or the actuator did not work the temp would not vary with the temp setting 60,,70, 80, or 90 degrees.
I have been looking at the book I received and it has the "temp vs resistance" of the sensors, if the upper left temp sensor was sending the wrong info or the connectors have resistive contacts. That could send the wrong info to the A/C control module.
How do you take off the A/C outlet vent cover off.. I could possible put a scope down there and look at the door working or not..
If I remove the side panel on the drivers side I think I could see or measure the resistance or voltage of the upper left sensor, which I believe controls the temp of the air being sent to the drivers side..
Is there a way to see the input to evaporator coil with a video probe, maybe going in through the cabin air filter inlet?
 

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Discussion Starter #45
I forgot to tell you I felt the input and outlet tubes from the evaporator they seem to be about the same temp.. I will measure them tomorrow with a infrared thermometer..
 

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How do you take off the A/C outlet vent cover off..
I doubt you'll see anything in there, but slip something thin like a butter knife blade, credit card, or such above and below the vent defuser to release the locking tabs, then pull the vent out. Some come out very easily. Others will fight you to their death.
 

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Master of the Dark Art of Diagnostics
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18,724 Posts
Thank you for your response..
I fully agree with your analysis.. It only makes sense that is the mixer door was stuck or the actuator did not work the temp would not vary with the temp setting 60,,70, 80, or 90 degrees.
I have been looking at the book I received and it has the "temp vs resistance" of the sensors, if the upper left temp sensor was sending the wrong info or the connectors have resistive contacts. That could send the wrong info to the A/C control module.
How do you take off the A/C outlet vent cover off.. I could possible put a scope down there and look at the door working or not..
If I remove the side panel on the drivers side I think I could see or measure the resistance or voltage of the upper left sensor, which I believe controls the temp of the air being sent to the drivers side..
Is there a way to see the input to evaporator coil with a video probe, maybe going in through the cabin air filter inlet?
=======================
How do you take off the A/C outlet vent cover off..
there are two little plastic tabs on opposite corners locking them into position -
SOMETIMES you can just pull them out - sometimes not -
try this:
wrap some electrical tape around the jaws of a pair of pliers so it doesn't scratch the vent -

get a firm hold in the meddle of the vent -

GENTLY - but quickly push and pull on the vent several times -
until the tabs release and the vent comes out -

IF that doesn't work -
you'll have to slip in a credit card - or something - between the vent and the housing -
BOTH on top and bottom of the vent -

wiggle the cards around side to side while pulling on the vent -
EVENTUALLY -the tabs will release and the vent will come out -
-------------------

the actuators use a stepper motor -
they have a movement "count" of 0 = fully closed to 254 = fully open -
the mix doors also have sensors that verify the actual door position -
if these do not "agree" - a code is set -
a VERY common example of this is:
B0428 - Air Mix Door #3 Inoperative Error
and/or
B0429 - Temperature Control #3 Rear Circuit Range/Performance
this points to a back seat temp control problem -
the MIX DOOR position does not match the selected temperature -

the passenger side actuator has a split shaft -
the large - square - outer shaft controls the #2 - passenger side - mix door -
the small inner shaft has a "D" shaped hole that accepts the shaft for the #3 - back seat - mix door -
this "D" shaped hole strips out - becomes a round hole -
and doesn't turn the shaft to move the #3 mix door -
SO - the actuator and the mix door are out of sync - hence the code -


other than using a TECH2 scanner - I have no idea how to do any definitive tests -
 

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Discussion Starter #48
Wow, great information.. Will have to think about it for a bit.. I am considering a Tech2 clone, below
VXDIAG VCX NANO for GM/OPEL GDS2 Tech2Win Diagnostic Tool with WIFI
Link below:
 

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Discussion Starter #49
So by not throwing a code, the mixer door is working properly. that could leave the thermistior, bad connections, something interfering with the air flow in the drivers side evaporator or the control module. The thermistor on the upper left side should be somewhat accessible from the drivers side cover, If so possibly I could measure the resistance of the thermistor vs the temperature, to rule it out..Bad connections I could plug and unplug the two connectors, check the resistance/voltage on the thermistor and the control module which could rule out the connectors.When the temperature difference in the two vents is there the amount of air flowing from the vents are about the same so that could indicate the evaporator coil is not blocked.
Does this logic make sense to you?
 

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Master of the Dark Art of Diagnostics
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Wow, great information.. Will have to think about it for a bit.. I am considering a Tech2 clone, below
VXDIAG VCX NANO for GM/OPEL GDS2 Tech2Win Diagnostic Tool with WIFI
Link below:
===========================
I bought a TECH2 clone - it is absolutely identical to the "real thing" -
EXCEPT - it uses brass electrical connectors rather than aluminum - so - it's actually BETTER -
I paid around $300 -

just be 100% positive that the unit has 2-way communications with the car -
and is not just a reader -
 

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Master of the Dark Art of Diagnostics
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18,724 Posts
So by not throwing a code, the mixer door is working properly. that could leave the thermistior, bad connections, something interfering with the air flow in the drivers side evaporator or the control module. The thermistor on the upper left side should be somewhat accessible from the drivers side cover, If so possibly I could measure the resistance of the thermistor vs the temperature, to rule it out..Bad connections I could plug and unplug the two connectors, check the resistance/voltage on the thermistor and the control module which could rule out the connectors.When the temperature difference in the two vents is there the amount of air flowing from the vents are about the same so that could indicate the evaporator coil is not blocked.
Does this logic make sense to you?
======================
Does this logic make sense to you?
like said - this is a WEIRD one -

if you have the FSM and the TECH2 - you'll have all the tools you need to test each component -
 

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Discussion Starter #52
It will communicate with the car in tech2 and GSD2 but to program it requires a subscription (SPS). Which tech2 did you purchase?
 

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Discussion Starter #54
Hi, still trying to decide which diagnostic tool I want but I was thinking.. it sounds like the drivers side is working could it be that the passengers side is pumping out cold air about what is needed so that the cabin temperature is shutting down the drivers side while the passengers side is making to much cold air? I tried to close off the left passengers side vent and it seems like the drivers side is staying cold longer.. Does this make any sense?
Like I said I am in a quandary about which diagnosis tool to buy for the following reasons.. The tech2 may go obsolete considering it was released in 1996 and slow. the mdi2 requires a display and confusing setup, the vzdiag same issue.. On the plus side the MDI2 and the vxdiag have the latest technology for cars today, faster processing and tha vxdiag is only $120.
 

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Discussion Starter #56
Really wierd I took a look at the codes again today and saw a B0429 history code, it was not there before..
As you said before:
B0429 - Temperature Control #3 Rear Circuit Range/Performance
this points to a back seat temp control problem -
the MIX DOOR position does not match the selected temperature -

the passenger side actuator has a split shaft -
the large - square - outer shaft controls the #2 - passenger side - mix door -
the small inner shaft has a "D" shaped hole that accepts the shaft for the #3 - back seat - mix door -
this "D" shaped hole strips out - becomes a round hole -
and doesn't turn the shaft to move the #3 mix door -
SO - the actuator and the mix door are out of sync - hence the code -


I don't understand why there was not a code before when I checked and this was a history code, which indicates the code is not active now..... Is this normal?
How difficult is it to get to this mix door. The book says just take out the glove compartment and it is there, sound correct? If this is bad and needs to be replaced does it require alignment before the turning on the key for recalibration?
 

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Discussion Starter #57
=====================
Which tech2 did you purchase?
just like this one -
Really wierd I took a look at the codes again today and saw a B0429 history code, it was not there before..
As you said before:
B0429 - Temperature Control #3 Rear Circuit Range/Performance
this points to a back seat temp control problem -
the MIX DOOR position does not match the selected temperature -

the passenger side actuator has a split shaft -
the large - square - outer shaft controls the #2 - passenger side - mix door -
the small inner shaft has a "D" shaped hole that accepts the shaft for the #3 - back seat - mix door -
this "D" shaped hole strips out - becomes a round hole -
and doesn't turn the shaft to move the #3 mix door -
SO - the actuator and the mix door are out of sync - hence the code -


I don't understand why there was not a code before when I checked and this was a history code, which indicates the code is not active now..... Is this normal?
How difficult is it to get to this mix door. The book says just take out the glove compartment and it is there, sound correct? If this is bad and needs to be replaced does it require alignment before the turning on the key for recalibration?
Hey Basscatt are you there??
 

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Master of the Dark Art of Diagnostics
Joined
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18,724 Posts
Really wierd I took a look at the codes again today and saw a B0429 history code, it was not there before..
As you said before:
B0429 - Temperature Control #3 Rear Circuit Range/Performance
this points to a back seat temp control problem -
the MIX DOOR position does not match the selected temperature -

the passenger side actuator has a split shaft -
the large - square - outer shaft controls the #2 - passenger side - mix door -
the small inner shaft has a "D" shaped hole that accepts the shaft for the #3 - back seat - mix door -
this "D" shaped hole strips out - becomes a round hole -
and doesn't turn the shaft to move the #3 mix door -
SO - the actuator and the mix door are out of sync - hence the code -


I don't understand why there was not a code before when I checked and this was a history code, which indicates the code is not active now..... Is this normal?
How difficult is it to get to this mix door. The book says just take out the glove compartment and it is there, sound correct? If this is bad and needs to be replaced does it require alignment before the turning on the key for recalibration?
======================
I don't understand why there was not a code before when I checked and this was a history code,
which indicates the code is not active now..... Is this normal?

NORMAL is a relative term -
it is POSSIBLE that there is still SOME control of the back seat mix door -

SOMETIMES the actual door position matches the selected position = no code -
SOMETIMES it doesn't = code set -
if they sync up again = set code goes to history -

the actuator can't heal itself - it will only get worse over time -
the solution is to replace the actuator -
ACDELCO 15-73428 - $62 - with free shipping -
 

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Discussion Starter #59
Again thanks for the information.. I have another question or two, Does this actuator also control the temperature of the passengers side air? How difficult is it to change out the right actuator? The manual says all you have to do is remove the glove compartment and the actuator is available. Last this actuator has a "D" slot correct so I do not have to worry about getting it messed up when I reinstall the new actuator?
 

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Master of the Dark Art of Diagnostics
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18,724 Posts
Again thanks for the information.. I have another question or two, Does this actuator also control the temperature of the passengers side air? How difficult is it to change out the right actuator? The manual says all you have to do is remove the glove compartment and the actuator is available. Last this actuator has a "D" slot correct so I do not have to worry about getting it messed up when I reinstall the new actuator?
=========================
YES -
VERY easy -
CORRECT -

let's make this really REALLY easy -
here is a detailed HowTo - with pics -
 
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