Our first installment is the story of a
1999 SAAB 9.5
with an
inoperative heater / air
conditioning assembly. |
click on photos for enlargement |
The problem may sound simple enough, but its
not. Once you have read this story and viewed the accompanying pictures, you
should have a better understanding and appreciation for the complexity any
seemingly simple repair can take on.
Ironically, the
mechanic that submitted this story complete with pictures is a guy that I
worked with in the early 1970’s. Ken came to work in a SAAB dealership where
I was a working shop foreman.
We clicked from the beginning & formed a long lasting
professional relationship as well as a friendship. We worked together on
some of the first electronically fuel-injected, overhead camshaft imports in
this country. Ken & I, along with a guy named Jerry Smith wrote the book on
making the early SAAB automatic transmissions work. Something the factory
was unable to do with great consistency.
Here we are some thirty-five years later & we both still work
on complex machines & have remained friends. Via e-mail, we reminisce about
our success & failures as we lived through the early days when automotive
technology was taking quantum leaps. Newly introduced micro-processors,
sensors, actuators & a variety of electronics took precision control of
things that were previously operated by crude mechanical devices.
Here is Ken’s story of the
broken heater & the subsequent repair.
A 1999 SAAB 9.5 sedan, a strong, safe &
complex import from Sweden came equipped with “Automatic Climate Control”.
This system is controlled by a
micro-processor that had some diagnostic ability. That is, the climate
control’s computer had the ability to record malfunctions & store diagnostic
fault codes. This repair could apply to any of the upscale luxury European
imports.
The normal approach would have been to
attach a diagnostic scan tool to communicate with the system’s computer &
retrieve the fault codes. This procedure was omitted because pieces of the
plastic gear set inside the heater’s plenum had broken & fell out of the
heater ductwork onto the passenger compartment floor. No need for exotic
diagnosis here, just some good old common sense. The heater assembly had to
be removed for repair or replacement.
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Now the fun begins...
One of the first orders of business requires evacuation of the air
conditioner’s refrigerant gas. This requires specialized machinery operated
by licensed personnel. This is necessary because the heater core that
contains the antifreeze / coolant is housed in the same unit as the air
conditioner’s evaporator core.
click on photos to enlarge
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The hoses that carry the refrigerant gas
to & from the compressor need to be disconnected, so the refrigerant gas
must be captured before this can be done. Both of these units are like small
radiators that the air flows across to provide the selected heating or
cooling.
The engine’s heater hoses (under the hood)
must also be clamped off to avoid coolant loss. This little time saver
eliminates the need to drain the entire cooling system. You can see the
specialized clamping tools that will not damage the hoses when used
properly. The heater core is connected to the engine’s cooling system
via these heater hoses.
click on photos to
enlarge
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| With the front seats still in place, the
removal process begins. The vehicle’s battery is disconnected for obvious
safety reasons. First the driver’s side airbag, steering wheel, instrument
cluster, radio, heater controls & drivers information display are carefully
removed. Leaving the seats in affords the mechanic some comfort while
performing these tasks. |
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| Once the seats are removed, it is
virtually impossible to find a comfortable working position. Stooping &
kneeling on sheet metal floor pans is no fun when you are at it for hours. Next an assistant helps with the removal
of the molded dash pad, complete with the passenger side airbag assembly.
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| With the dash removed & the carpets pulled out, the wiring harness is snaked
out of & away from the dash support bar. The wiring is attached to the dash
support bar with clips, and care has to be taken not to create wiring
problems during disassembly. Making notes & marking locations of
components is critical to proper re-assembly. A trick I have used in the
past was to take instant pictures to use as a reference as to how harnesses
& cables were routed, and what went where. Today we have digital cameras
that make this a much easier task.
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With so many systems disconnected & so
much labor time involved, it is important that everything works & there are
no rattles or squeaks when the job is completed. If even a small detail is
overlooked, there is a distinct possibility that the mechanic would be
required to go back inside to remedy the problem. That additional time would
potentially reduce the mechanic’s productivity & earnings. Time doing things
over is time not spent on another repair procedure.
| Next Ken removes the plenum assembly from
the vehicle. There are several warning labels & these warnings must be
heeded to avoid unintentional deployment of those expensive air bags. The
bottom side of the steering wheel mounted driver’s air bag displays a
warning. Special care has to be taken not to damage any wiring or
connections. The radio controls are also integrated into the steering wheel
unit. |
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| There is also the risk of personal injury,
so the appropriate technical training is a must. For example, the ECU
(electronic control unit) for the SRS, (supplemental restraint system), is
under the center console. There is a warning here. The danger is that if the
ECU is inverted, the system may be activated. The mechanic must read & understand the
warning labels.
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As you can see as we progress through this
repair procedure, it’s not really a job for the do-it-yourselfer, or a
backyard mechanic. Even a pro needs the proper training & information when
it comes to dealing with this technology. An unintentional air bag
deployment can cost several thousand dollars to repair, create more vehicle
down time & may also cause personal injury to the individual performing the
repair.
The structural steel support for the
steering column & dash is removed & set aside.
| The heater assembly is a large box with
electric motors & servos to operate the doors and flaps inside the plenum.
There is also some mechanical linkage utilizing plastic gears to make things
work. |
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| This failure involved the plastic gears &
something as simple as changing that gear set requires approximately 15
hours of labor. The factory warranty time for this repair
is 10 hours. So it’s easy to see that a mechanic needs to work quickly &
efficiently to conform to the factory allotted time. Sometimes this can be
impossible. There is one fact you can count on & that is if an untrained,
inexperienced person were to tackle this type of complex repair, the time &
expense could easily be double that of having an experienced professional
perform the repair.
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| It’s easy to see when you look through the
rear doors or from the rear seat & all you see is the inside of the firewall
& where the heater / A/C plenum assembly fits in, that this is not a job for
the faint at heart. It seems like the engineers from SAAB thought that this
unit would never need repair, as they really built it into the vehicle
before there was anything else. Once the plenum gears are replaced & all
the systems are checked on the bench, the re-assembly process begins.
Like Ken stated in his story, ” Paying close attention to detail is critical
during the assembly procedure”.
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| With the interior of the vehicle
reassembled, the air conditioning system must be evacuated to remove any air
or moisture. Then it is recharged with the specified amount of
refrigerant charge. The cooling system also needs to be topped
off with the proper antifreeze coolant mix. Both of these operations
are critical to proper operation.
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Then the mechanic should perform a lengthy
road test to insure all systems operate in various conditions, and there are
no unwanted noises in the cabin.
A quick final check for leaks, as well as
an electronic check for diagnostic fault codes is in order before the
vehicle is released to the customer. Verifying that there are no DTC’s
(diagnostic trouble codes) assures the mechanic that all systems are
operating properly.
In a professional shop like Hyannis SAAB, the vehicle will go to the clean
up area and be returned to the customer in great shape. This type of
attention to detail is indicative of a Pro who takes pride in his or her
work. These folks are a rare breed, and getting rarer all the time.
Here is another job well done by a mechanic who knows “What It Takes Today”.
Nice work Ken!
SM
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