MACS Monthly Newsletter - 2021 - JUN7

fail may not be cheap to replace, but they are still often
worth the investment, including $4000 or more for an engine, perhaps $1000 for major A/C work, vs. a new car at
$30,000 and up. What a technician has to hope for is that
these higher-dollar replacements more than compensate
for the no-profit " headache " jobs that could take more to
diagnose and repair than he can get adequately paid for.
The Audi A4 was a 2006 model with the 2.0-liter engine
and cars 15 years old are still in wide use. And when they're
premium models like an A4, they keep going through several owners as long as the body is presentable and there
are no major failures. However, at this age and greater,
they are subject to the kind of electrical issues that you
never are sure will stay fixed. So, when this particular one
came into the shop with an A/C failure - wouldn't come
on, the technician probably was pleased to identify the
issue seemed to be with the radiator fan module. He replaced it, and happily it seemed, the problem appeared to
be fixed. As soon as the coolant temperature went up, the
fans came on and then, when the A/C was turned on, the
system worked.
However, the repair failed to " hold up. " A couple of
months after the module replacement, the customer
called to say that a couple of times the battery would go
dead when the vehicle sat overnight and had to be booststarted. In addition, the customer noted that when she visited friends on a couple of occasions, she heard the fans
running when she left the car. But in both cases, the car
restarted as the battery apparently had enough charge to
last through the visits. She brought the car into the shop
and left it overnight. It had shut off when she left it, but by
the next morning the battery was dead. The technician recharged the battery and after running the A/C for a while,
turned it off. The car sat for a time and soon after the technician heard the fans come on and run at high speed, then
drop to low speed. He disconnected and replaced the fan
module (got a replacement at no charge). However, the
problem returned, this time with the fan remaining on high
speed. His service information system didn't list a relay,
but the wiring diagram showed it, and he found it under
the hood, under the powertrain computer. Enough moisture had been leaking into the relay to periodically short it
out. He was able to confirm the issue by temporarily substituting it with another, identical relay mounted close by,
and happily, it was a standard part he was able to obtain
at an auto parts store.

tion system were the condenser and hoses. The problem,
of course, was poor cooling and the technician facing the
problem had serviced the system a year earlier and the
car left his shop with temperature readings of 42°F from
the A/C registers with the system on MAX cooling.
He did a recovery with his R/R/R machine and pulled
out 20 ounces, which was exactly what his shop records
showed was what he charged into the system that year
ago. That amount is just a fraction of an ounce over the
19.4 oz factory specification of 500-550 grams (17.6-19.4
oz) and as the line goes, " close enough " if his machine
is accurate. Apparently, there were no leaks. So, he recharged the system to the 20 oz amount and rechecked
the register outlet temperature, which was 60°F with the
system set for maximum cooling. This time he checked
the passenger's side register, also set for maximum cooling and it produced air at 42°F.
So, where does he go from there. The heater coolant
control valve operated normally. The clutch engaged normally, which indicated nothing new had happened to the
refrigeration system. So, the technician's attention shifted to the air handling system. He performed a self-test
to confirm there were no codes. It was unlikely that the
almost new evaporator had failed or had accumulated a
buildup of debris on the driver's side, but in desperation
he removed the evaporator (yes, it was fine) to get a close
look at the air handling doors. They seemed to be moving
normally in both directions, so he reinstalled the evaporator and with his borescope, he just looked, hoping that
some idea would hit him, and one thought did: air seemed
to be blowing through from around one of the sides of the
evaporator. Bad evaporator sealing results as the foam
seals deteriorate and shrink away from the perimeter of
the heat exchanger. This issue is often not identified, as
a loss of cooling is attributed to failure of the flap doors
to move all the way and their own foam seals deteriorate.
In this case the technician had to take the blame, as he
should have installed new, thick foam seals when (once
more) he removed and reinstalled the evaporator. He had
more than one chance to get this right, first when he replaced the evaporator a year before, and then when he
did the R&R during his diagnosis of the comeback.
NOT-AS-OLD CAR (JUST 10 YEARS OLD)
Here's another cooler-on-one-side issue, and this time
one of the usual problems didn't apply. No low charge, no
debris on the evaporator, no defective flap door or bad
actuator on one side, no air leakage around an evaporator,
but vehicle age turns out to be a likely factor.
The car is a 2011 Cadillac SRX and the air from the driver's side A/C register was about 20° warmer than the passenger's side. Hey, it's a 10-year-old car; must be low on
refrigerant, right? No, because if it were that obvious, we
wouldn't be talking about it. How about debris packed on
one side of the evaporator? No; let's keep going. Leaking evaporator perimeter seal? No. Then it has to be a
bad actuator or door on one side. Still the answer is no.

ANOTHER 15-YEAR-OLD CAR WITH ANOTHER OLD CAR PROBLEM
As the previous item notes, when cars get to be around
15 years old, even when they have the reputation for reliability that Honda enjoyed for so many years, things do
happen, even if somewhat earlier on lower quality makes.
Truth be told, however, the air conditioning on this 2006
Honda Accord (3.0-liter V6 with ATC dual zone) had needed a lot of work over the years, including the compressor,
evaporator, receiver-drier, expansion valve and a complete
O-ring seal kit. About the only survivors on the refrigera-

June 2021

MACS Service Reports

MACS Monthly Newsletter - 2021

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