MACS Monthly Newsletter - 2017 - DEC4

never exceed the coolant's boiling point so a surge
tank has a non-pressurized cap with an overflow
tube vented to the atmosphere. Don't confuse these
big high voltage PTCs with the little 'chill reducers'
in the lower ductwork of many Prius models that
run off 12-volts.

service manual procedure?) make sure when putting the meter on a high voltage circuit that you
press the meter 's range button repeatedly to determine if the meter is really showing 0 (or at least below 12-volts) and not simply stuck in a range below
the voltage available on that circuit. I've actually
had numerous experiences where my Fluke meter
with auto ranging applied, did not auto range up
to the high voltage being measured. The meter
showed 0 when in actuality the voltage present was
276 volts!

Cold Leaf Complaints
Nissan Leaf owner complaints regarding their
vehicle's heating performance are not uncommon.
Their HV PTCs can fail due to internal problems, a
fuse that can blow and the DC-DC converter connections that pass along the main battery pack's 392
volts. Before diving into any HEV, EV or PHEV's
high voltage compressor or PTC heater problems,
make sure you've had sufficient training for working on high voltage systems and you use the proper
PPE (Personal Protection Equipment). In this case,
a pair of Class 0 / 1,000 volt gloves (test prior to
each use and send out for professional testing every 6 months) should be worn prior to working on
/ verifying high voltage circuits have been shut
down. A category III / 1,000 volt meter (and similar
rated leads / probes) should also be used. Another similarly trained technician in the bay with you
along with an insulated safety hook (for rescuing
an electrocution victim) is another sensible safety
precaution as well. Smart people don't go hunting
/ swimming / scuba diving alone, why would you
want to work alone on high voltage systems?

Leaf Customer Training
The Leaf 's owner forums / newsgroups are full of
customer experiences than can be helpful to us as
we educated ourselves prior to helping our customers. The presence of a dedicated heater button (Fig.
11 & 12) popped up around the 2013 model year
on the Leaf and is essential to maximizing either
range (heat / A/C off or limited) or HVAC comfort.
With a short range EV the little things add up pretty
quick. Having the shifter in 'Eco' mode effects either range or HVAC comfort as well.

The Future of Heating is Efficient Electric Heat!

Dave Hobbs

Webasto is one company that has been around
for years producing fuel fired coolant heaters helping diesel applications (both over the road semis
and passenger models) to keep vehicle occupants
warm. Commonly called 'parking heaters' (Fig. 13)

Figures 11 and 12: Early Leaf HVAC control heads (Fig 11 left) had an auto HVAC option but no manual heat on / off function like (Fig. 12 right) 2013
models had as standard equipment.

Live-Dead-Live?

you may have seen a fuel burning coolant heater on
a HD or even LD diesel in your repair shop. Now
Webasto is promoting a new technology they refer
to as a HVH (high-voltage heater). (Fig. 14) Since
there is still no uniform battery voltage for electric
vehicles, the device has been designed so that it can
be used in ranges between 250 and 450 V without a
loss in power. With an efficiency of 99%, the highvoltage heater converts electricity into heat with
virtually no loss. This is made possible using thin

To keep yourself alive, another sensible practice is
the method of verifying (twice for safety) that your
meter is working (the live part) before and after you
check a circuit that normally carries high voltage
(orange cables / conduit). Checking a nearby 12volt source (the EV's 12-volt battery would be fine)
to ensure your meter is working correctly satisfies
the live part. For the dead part (did you indeed get
the high voltage system powered down per OEM

December 2017

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017