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Any way to stop the engine from running so much in the winter?

51K views 93 replies 39 participants last post by  Fiumag 
Ambient Air Temperature Sensor Resistance
Temperature Ambient Air Temp Sensor Ambient Air Temp Sensor (Min) Ambient Air Temp Sensor (Max)
°C °F (kΩ) (kΩ) (kΩ)
-40 -40 169.4 158.46 181.19
-30 -22 88.74 83.39 94.47
-20 -4 48.58 47.19 50.02
-10 14 27.67 26.93 28.44
0 32 16.33 15.92 16.75
10 50 9.95 9.71 10.19
20 68 6.24 6.1 6.38
30 86 4.02 3.94 4.11
40 104 2.66 2.61 2.71
50 122 1.8 1.73 1.87
60 140 1.24 1.2 1.29


If lowering to 15F still doesn't cut it for you, guess you could always get ahold of the $3 AMBIENT TEMP SENSOR mounted behind the passenger's side front turn signal and hard set it for the Kohm value necessary to never drop below the point that triggers the ICE to run!
 
Welcome to the club :(

I have an early build 2012, so I only have the one setting (<26*). I could really use and appreciate the 15* setting. Also, I believe that if you use the heat in Comfort mode the ICE will cycle less often.
For those with higher threshold MY2011-2012, just need to get ahold of a Ambient Air Temp Sensor that never reads greater than 16K ohm which would equal @32F. This $3 throw away part creates more resistance as the temp drops.

Confirmed on my 2013 Volt that after disconnecting this sensor and allowing the circuit to become an "open" or max resistance causes the ICE to run immediately when you turn it on regardless of whether I had extra cold setting enabled or not (ICE came on same as if you were to have the hood opened). So simply removing the sensor to bypass running ICE in extreme cold is not an option.

BTW: Getting to the Ambient Air Temp Sensor is extremely easy and I only had to remove 1 screw from underneath the deflector or air dam underneath the front bumper so no need to even open the hood!;)


Ambient Air Temp Sensor removed


White hole on the left behind the grill and next to radiator is where the sensor mounts from inside


Sensor attached to its cable



1ea 9/32 deflector (air dam) screw I had to remove to allow enough room to reach in and disconnect the sensor while on my back
 
No the car has a separate sensor for intake air temperature.
Yes, that is correct the Mass Airflow Sensor with Inlet Air Temperature Sensor is integrated into a single sensor attached to the AIR CLEANER ASSY.

BTW: For those who disconnect the Ambient Air Temp Sensor like I did to test, when you reconnect this sensor the center display will initially read -40F on the DIC. Just disregard this as it will take several minutes for the sensor to be recalibrated prior to reading an accurate temp again!;)

Pics below are how I installed a 1/2W 15k Ohms 5% resistor in place of the Ambient Air Temp Sensor in order to prevent unwanted engine runs this winter during our periods of inversion and below 15F temps here in the valley. After putting this resistor in, the center display now displays 58F and will not drop below this even when temp does fall. If I do decide that I want engine assisted heating, I can still manually turn engine on by putting the Volt into Mountain or Hold mode! Also dropped the Config setting from Very Cold (15F) back to Cold (35F) since this setting is now bypassed anyways. Probably leave this resistor in for the duration of the winter and will reinstall the actual sensor sometime in the spring. Just left the loose sensor in the glovebox for safekeeping!:D



 
somms,

Thanks again for getting this ball rolling!
You have a workaround.
My only concern is the battery TMS and where it gets its temp sensing from.
This would be much harder to conceal when taking the car in for service. I would rather use your approach but,,,
We have to find where the battery TMS gets its air temp sensing from.

AFAIK, The battery pack has 16 temperature sensors. The temperature sensors are located on the top of the batteries. There are schematics in the Volt service manual that shows these temp sensors 1-16 to confirm this. I'm not concerned with trying to conceal the Ambient Air Temp Sensor since its primary function when it is cold is to display the current air temp on the Center console display which will force the ICE to run regardless if the cabin temp is already comfortable and the ICE was already previously running if it ever senses a resistance greater than the software ERDTLT threshold!;)
 
The AC compressor function is to provide refrigerant flow in the AC refrigerant loop to help cool down the cabin, help dehumidify the air in a defrost mode and help maintain the battery temperature. Rather than a more typical pulley, the A/C compressor uses a 3-phase alternating current, high voltage electric motor to operate. It has an on-board inverter that takes High Voltage direct current from the vehicle's High Voltage Battery and inverts it to alternating current for the motor. The AC compressor shall be activated when any of the three following events occur:

• The customer pushes the AC button
• The HVAC control, in AUTO mode, requests the electric AC compressor on to help in cooling the cabin or removing moisture in the defrost mode
• The High Voltage Battery Thermal System requests the AC compressor on to help maintain the battery temperature

The Hybrid Powertrain control module 2 uses values from the A/C refrigerant pressure transducers, A/C refrigerant thermistor, duct temperature sensors, ambient air temperature sensor, passenger compartment temperature sensor, evaporator temperature sensor, battery cell temperature sensors, battery coolant temperature sensors and battery coolant pumps to determine the speed at which the compressor will operate. This speed request message is sent from the Hybrid/EV Powertrain Control Module 2 to the A/C compressor control module via serial data message.

The ambient air temp sensor is one of nine values used by the Hybrid Powertrain control module 2 in order to determine the speed at which the 3-phase AC compressor will operate if the Air Conditioning button is pushed, in AUTO mode to remove moisture in the defrost mode or High Voltage Battery Thermal System requests the AC compressor on to help maintain the battery temperature. This is why I plan on only using the bypass during the cold winter months and reinstalling the sensor before the summer months!;)
 
All of this to prevent random condensation in the engine that will quickly evaporate on next run anyway? I suspect there will be very little condensation if any and in my mind, not running the engine with a bit of frequency might also be damaging equally or worse than condensation by letting seals get dry, cylinder walls end up with no oil on them, hard deposits forming and so on. All for the sake of burning a little bit of gas which in the long run is pretty insignificant to the overall cost of ownership. I don't mind running my ICE in the winter at all as I feel it is good for it. Also, I know that in two years I will certainly use up my oil life this way instead of pouring good oil down the drain. There are a lot of reasons to just not be worrying about it and let the engineering and technology in the volt manage it.
Exactly! I am a button push away from still having the "option" of turning on the ICE whenever I choose by either selecting Hold or Mountain mode on the fly. Now, the ICE is not being "forced" to run whenever the temp may drop slightly below a software threshold even though the cabin may already be nice and toasty which is rather silly and redundant!;)
 
somms, thanks for the super useful resistance to temperature chart!

Instead of substituting a fixed resistor I am going to calculate a series or parallel resistor (with a switch) so my 2012 will act more like a 2013 and use ERDTT only below 15 deg. F (or maybe 10). On really cold days I see (feel) the benefit but it is pretty annoying to have it come on at 24 deg. F. So I think lowering the threshold (like the 2013 does) will work better for me, and will also give me a better idea of how cold it actually is outside (with a correction factor).
Chart would be better if it were anywhere close to being accurate!:p

By the chart, 15Kohms should be @40F whereas the center console for my 2013 Volt is reading static 58F instead!;)

Maybe if I get a chance later I may experiment with various other Kohm resistors and report back what other values readback on the display. Keep in mind that the center console temperature display is NOT realtime as soon as the resistor or even the original sensor is plugged in. You will initially get the max -40F reading until the BCM consistently reads this value for several minutes. In my case, I installed the resistor at night and of course, the center console initially read -40F (and engaged the ICE immediately) but by the next morning it had registered at 58F where it has held at ever since. If you have no resistor or sensor attached and power on the Volt, the center console will display NO temperature value as well as the ICE engaging immediately upon power on.

You could get creative and put 2 10Kohm resistors in series for 20Kohm or 2 32Kohm resistors in parallel for 16Kohm resistance, ect. but I just wanted to keep it simple as possible and the way I have this installed, I am literally about a minute (1ea 9/32 screw away) from reconfiguring the original temp sensor back in if I really had to. The actual sensor will probably get reinstalled eventually in the spring!:)


Charging System Operation

The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:
• Battery Sulphation Mode
• Normal Mode
Fuel Economy Mode
• Headlamp Mode
• Voltage Reduction Mode
• Plant Assembly Mode


Fuel Economy Mode

The BCM will enter Fuel Economy Mode when the ambient air temperature is at least 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery current is greater than -8 A but less than 5 A, and the battery state of charge is greater than or equal to 85%. Its targeted accessory power module set point voltage is the open circuit voltage of the battery and can be between 12.6-13.2 V. The BCM will exit this mode and enter Normal Mode when any of the conditions described above are present.

BTW: Keep in mind that you probably shouldn't pick a fixed resistance that reads back on the center console<32F since it may possibly throw you out (or in?) of Normal mode for 12V battery charging!?:confused:
 
So what about putting a resistor in parallel or series (it's early) with the original sensor to offset ambient temp up 10° or 20°?
This offset would be easy to figure if you want to know what the real outside air temp is from the display.
10° would work for me. Canucks would need more.
If you wanted to keep the original ambient air temp sensor in circuit, the addition of a fixed resistor in parallel would be the only option since put in series the fixed resistor would then offset the center console temp reading in a more negative direction (more resistance=colder readback value) defeating the purpose...
 
Of course parallel !!

Now, what would that value be for a 10° positive offset? Or a 20° offset?
But please,,, let it not be that cold this winter that I need a 20° offset to keep that smelly gas burner from starting up!!!! Please !!
Unfortunately, you couldn't just add 1 fixed resistor in parallel to the ambient air temp sensor and have an accurate but offset new outside temp reading: http://diyaudioprojects.com/Technical/Electronics/parallel-resistor-calculator.htm

If the Ambient Air Temperature Sensor Resistance chart were correct (which it isn't), lets say you wanted to have the ambient air sensor(R1) at 14F=27Kohm resistance instead read 34F (offset of +20F) by adding a fixed resistor in parallel(R2)=39Kohm. Using the above linked calculator total resistance is now 16Kohm or offset by +20F.

Now, lets go to the other end of the scale and say the outside temp is now 104F and the Ambient Air Temperature Sensor (R1) is now only reading 2.6Kohm. Throwing the R1=2.6Kohm value into the calculator with the same fixed resistor in parallel(R2)=39Kohm shows the new total resistance value of 2.4Kohm which is now maybe only offset by+5F. It would no longer be accurate linear offset you were looking at...
 
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