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It is a thermistor. Below is the resistance curve for the ambient air sensor in case you ever need to "test" it ;) or possibly add a switched cold weather resistor (or use a test potentiometer across it's 2 circuits then look inside at the center stack to determine the intentionally skewed outside temp)
By my calcs I figure something around 40K or so might be useful in lowing Engine Run Due To Temperature under certain cooler conditions. I will do some testing to confirm tomorrow
:wink:
WOT

 

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Discussion Starter · #22 ·
It is a thermistor. Below is the resistance curve for the OAT sensor in case you ever need to "test" it (or possibly add a switched cold weather resistor or pot across it's 2 circuits) Something around 40K or so might be useful in certain conditions
:wink:
WOT

SNIP
Cool thanks that could be useful for "testing" if the 2013 temperature fix we've heard (unofficially) is coming is not a software upgrade/retrofit. Might get a replacement part to test first. but long run I'd definitely want to look at something with a remote as that location is a bugger to reach into play with (at least with my fat arms).
 

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Ha, WOT, you know how to "speak" to an engineer!
Thanks a lot for your info, it will effectively be very interesting to see what could be done to optimize certain
situations... ;-) Like a short 10 milles run in cold weather, from a garage to another heated garage.

Also, because you have this information handy, maybe you could give me another pointer:
Can you confirm to me that the 360V battery has a resistive heater so it can heat itself to stay in the
"optimal" temperature range if the ICE engine does not come on?
and is this "optimal" battery temperature measured with dedicated temperature sensors IN the battery pack?
(I just want to make sure that IF the OAT sensor would be "decalibrated", it WON'T affect the temperature where
the battery pack is meant to be kept at)

Thanks again, WOT, I appreciate your insights!

Francois & Line
B2653 C19249
 

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Cool thanks that could be useful for "testing" if the 2013 temperature fix we've heard (unofficially) is coming is not a software upgrade/retrofit. Might get a replacement part to test first. but long run I'd definitely want to look at something with a remote as that location is a bugger to reach into play with (at least with my fat arms).
Well techncially one shouldnt need to access the sensor itself in order to "test" it. It's two-wire circuit runs from the HPCM2 under the front passenger seat, through the front bulkhead pass-through and into the underhood RF area to the sensor. So techncially it could be "tested" ANYWHERE between those points.
Can you confirm to me that the 360V battery has a resistive heater so it can heat itself to stay in the
"optimal" temperature range if the ICE engine does not come on?
and is this "optimal" battery temperature measured with dedicated temperature sensors IN the battery pack?
Yes, a 360V 1.8kW PTC heater is integral to the coolant inlet fitting of the battery pack itself. There is also inlet and outlet coolant temperature sensors so their values (and delta) can be used to establish intervention levels (passive or active) necessary to regulate cell temps under varied operational conditions.

WOT
 

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WOT, thanks for those fact based answers.
I am pushing my luck here, to ask you another technically advanced question:
We know that the battery pack is thermally insulated from the outside, and the way to heat it / cool it
is by the thermal fins between each pack where coolant flows through, as a heat transfer fluid.

If the ICE does not start, and the outside air is really really cold, is there an outside air temperature where the heat loss in
the battery pack and circulating coolant fluid would not be sufficiently compensated by the 1.8kW PTC heater?
let's also assume for this question some sort of worst-case scenario: the Volt is driven at 60MPH, so cooling losses
are maximized. But we start the commute with a fully charged battery, freshly unplugged from it's EVSE.

Note that what I have in mind is to optimize the following scenario:
my commute one way is 10 milles, from home in an heated garage to work in a heated garage.
there, a 120V plug is available for the day's 8 hour charge, so the Volt is basically fully charged at each
extremity of the commute. Also, electricity is at $0.08 per kWh, with all taxes and fees taken into account (it's cheap)
while gas is at $5.60 per gallon (it's expensive)... So, using electricity is better than burning gas (In fact, it's 10x cheaper),
but I don't want to damage the battery pack in any way by running outside (lower) of it's optimal temperature range.
We just want to optimise gas usage in short commute situation in cold temps. So it would be nice to evaluate at what
lower outside air temp we should let the ICE run anyway.

Thanks in advance, WOT

Francois
B2653
 

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Just want to add an extra thank you for the tidbits of info. I'm a googler and with the data you provided I went looking for what I could find related to testing... and found some great manuals atIt even has a partial temperature table for the part being discussed.

With the diagrams there that I have a good idea where to do some testing. (Frankydude check it out!)

Related to testing questions.. any other risks we need to watch out for in testing.. e.g. a temp where the radiators or other ICE related parts might overcool?
 

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Well techncially one shouldnt need to access the sensor itself in order to "test" it. It's two-wire circuit runs from the HPCM2 under the front passenger seat, through the front bulkhead pass-through and into the underhood RF area to the sensor. So techncially it could be "tested" ANYWHERE between those points.
So if it's a simple thermistor, the only thing required to set a test value into it would be to put a ~40k resistor into parallel acros its two wires at any point in the circuit, with a simple on/off switch disabling it, right? That actually sounds pretty easy to do, once you identify the right pair of wires...
 

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in my opinion this is the most important mod we will be able to do for the Volt. keep up the investigative work!
 

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Discussion Starter · #29 · (Edited)
in my opinion this is the most important mod we will be able to do for the Volt. keep up the investigative work!
Here are a few images showing its location, the connector pin out and where it connects on the main connectors




Remove The Front Right Side Wheelhouse Front Liner (Front Wheelhouse Front Liner Replacement
Disconnect the electrical connector.
Unsnap the temperature sensor from the air deflection/baffle.



To remove the front liner:

Remove the tyre and wheel assembly. Refer to Tyre and Wheel Removal and Installation .

1 Front Wheelhouse Liner Push-In Retainer - Front (Qty: 2)

2 Front Wheelhouse Liner Screw - Front (Qty: 4) Tighten to 3 N·m (27 lb in)

3 Front Wheelhouse Liner - Front Lower Screw (Qty: 3) Tighten 3 N·m (27 lb in)

4 Front Wheelhouse Liner - Front Lower Front Screw (Qty: 5) Tighten to 3 N·m (27 lb in)

5 Front Wheelhouse Liner - Front Procedure Disengage the upper interlocking retainers.



Here is the info on the actual connector



Harness Type: Forward Lamp
OEM Connector: 13543521
Service Connector: 12101856
Description: 2-Way F Metri-Pack 150 Series, Sealed (BK)
Terminal Part Information

Terminated Lead: Service by Connector Assembly - 12101856
Release Tool: J-38125-12A
Diagnostic Test Probe: J-35616-14 (GN)


The pins run to the Hybrid Hybrid Powertrain Control Module 2 X1


Code:
Pin  Size    Color   Circuit  Function 
26   0.35   L-BU/GY  636       Outside Ambient Air Temperature Sensor Signal
40   0.35   BK/L-BU  61        Outside Ambient Temperature Sensor Low Reference

The Hybrind Powertrain Control module is under the passenger seat




Hope that helps. I'll keep digging to see what other useful stuff I can find.
 

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Extremely precise and valuable information!
Thanks, tboult and WOT,
personnaly I would prefer to add the resistor with a switch in the passenger compartment under
the passenger seat, by locating the appropriate wire pair.
Francois
B2653
 
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