MACS Monthly Newsletter - 2021 - MAY7

Yet another poster verified what good voltages are for Toyota compressor flow sensors (Figures 12 and 13). The tech with the Sienna
with no clutch operation then replaced the compressor (thereby getting a good flow sensor in the process) which finally corrected the
problem.

CTI

Teachable Takeaways
There are a couple of teachable takeaways with this case study.
The first (as with the Chevy Volt compressor software issue), is that
you can never have too many information sources such as friends, the
online forums, factory service websites, aftermarket service info sites,
as well as correctly worded " Google searches. "

Figure 12: Toyota Flow Sensor PID Graph 1 - Known Good: The scan tool
PID graph on a 2012 Camry shows the flow sensor with compressor shut off at around 4 volts (dashed circle) as the evaporator temperature was rising (arrow). The compressor was
then turned back on and the flow sensor voltage drops followed by the evaporator temperature dropping. Note the variable displacement compressor control solenoid going from 0
amps to around 0.5 amps at the point (dashed rectangle) just
after the refrigerant flow begins.

The second teachable takeaway is to NEVER assume there is a TSB
that applies to the exact model of vehicle you're working on. From my
research on this case study, it appears that there are numerous Toyotas using these refrigerant flow sensors having pattern failures - not
just 2012-2013 Camrys. No surprise there, right? Remember the MACS
Service Report from last year where I listed the tiny group of Chrysler
/ Dodge / Jeep models having TIPM internal relay problems? Anyone
who has been working on Stellantis (formerly FCA, Chrysler) vehicles
for very long will attest that this problem is far more widespread than
the confines of a couple of years / models within that applicable TSB.
Always consider the type of component you are working on. Are there
different models / different years of vehicles from the same OEM using
that same style of component? If so, look at TSBs and online tech tips
for those other models as well.

CTI

Replacing the ENTIRE Compressor for a $50 Part?
Do you really have to replace the compressor when a solenoid or
sensor that's attached to that compressor is diagnosed as faulty? If a
compressor clutch goes out should you replace just the clutch or the
entire compressor? We've had these discussions at MACS conventions
and tend to have as many theories as there are personalities in attendance. It really boils down to your answers to the following questions:

Figure 13: Toyota Flow Sensor PID Graph 2 - Known Good: During normal compressor run operation, the flow sensor (oval dashed
line) will vary slightly in voltage (but always UNDER 3.75 volts)
as the variable displacement solenoid keeps the evaporator
fin temperature (arrows) from down into a freeze up condition.

on and the flow sensor voltage was at 3.5 volts. His scan tool could manually turn on the compressor via a bi-directional command, however even
though the Sienna was NOT listed in the TSB for a Camry, the problem was
the same, as was the solution which was to replace the compressor assembly.

May 2021

1. Is the clutch / sensor / variable displacement solenoid
readily available?
2. Is that faulty compressor " accessory component "
time-effective to replace, or is it almost as easy to replace
the entire compressor?
3. Does the compressor's aftermarket replacement part
currently available have a great quality record from other
techs' experiences in the field?
4. Is the compressor old / high mileage therefore a candidate for replacement anyway?
5. What is the customer's budget? Noticed how I saved
that one for last? As they say, sometimes " cheap " can get
" expensive " .

In the case of this Toyota TSB, the automaker says, " replace the compressor " and backs that advice up with NO replacement compressor flow
sensors available as service parts. However, we all know the aftermarket
thrives on niches like this. If a subcomponent has a medium to high failure
rate, is easy to access & replace, and can be manufactured at a cost significantly lower than the entire assembly, the aftermarket is crazy to not jump
on that type of opportunity.

MACS Service Reports

MACS Monthly Newsletter - 2021

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