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Discussion Starter #1
First, a request - can anyone with a Gen1 Volt start their car, turn on the AC to max, pop the hood, and tell me if BOTH radiator fans are running (see below)

Went up the local SoCal mountain today, outside temp >90 degrees and traffic at 30 mph, in mountain mode the whole trip, and about 2/3 up the steep part, I got the engine overheat warning, reduced propulsion but no CEL. Was able to pull over pretty quickly and check things out: no leaks, no radiator blockage, overflow tank only slightly low, no intermix (oil or water) and fan was running (not sure if both were). I idled it for about 15 min, then, with the steep parts mostly behind us, was able to get to our destination keeping it slow. We got back ok, but that was all downhill. Anyway, limping along with warnings does not make me feel great about taking my Volt back up the mountain.
Of note: 70k miles, No CEL, No codes in my scanner, HOLD mode went dark and was not available until I got home. Once home I did notice the upper (driver side) fan was not running, only the lower (passenger) was. Not sure if they are both supposed to run?
I searched for overheating Volt and there doesn't seem to be many such problems. I'll probably replace the thermostat, but even if the radiator fan is bad, that is an easy fix (I hope).
Thanks.
 

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Sorry for your troubles. Can you estimate the mileage on the ICE? As an example, I've driven over 122k miles with just under 95k miles with the ICE running.

Would you explain what you meant by "idled"? Was the ICE actually running or was the idling just leaving the hood open for those 15 minutes without the ICE running?

For clarity, are the levels of the coolant in the two center tanks at the top of the sticker that is on the side of the tank?

To round out the factoids, what was the month and year of manufacture. That info is on a sticker on the driver's "B" pillar. And, are you the original owner?

Hopefully, others can advise you on your fan question.
 

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Discussion Starter #3
Thanks,
I estimate ~20k miles ICE and ~55k on battery, 3/14 mfg date, original owner. The engine was running at high speed trying to charge the battery on the uphill (as expected) then we had to slow for road work when I got the overheat message so I pulled over and popped the hood to let it cool off at idle speed for a few minutes, then turned it completely off for another few minutes. The coolant I checked was the engine coolant, on the pass side but all coolant tanks were/are at correct levels.

My "hope" is that one of the fans failed on the uphill, then when I had to slow for road work there was half airflow while engine was still trying to charge the battery so it overheated. When I popped the hood I could feel the fan blowing air, but didn't think to check both.
 

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I think that your suspicion that one of the fans failed may be the root cause. No forward motion to cause airflow through the radiator when slowed/stopped. The continued running of the ICE to recharge the battery when you had pulled over seems credible. I'm not sure how to check for a failed fan.
If the thermostat had failed, wouldn't the second fan been called upon to pull additional air through the radiator to cool the fluid (or do both fans work always work together)? I'm thinking the problem is not the thermostat, IMHO. Caveat: I don't play a mechanic on TV. <grins>
 

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Hold Mode is designed to "save" some of the grid power in the battery for later use. You can’t use Hold Mode if you’ve already used all the grid power in the battery.

Is it possible your battery was fully depleted when you switched to Mountain Mode? That would account for the later lack of Hold Mode.

Is it also possible you didn’t switch to MM until you were already headed up the mountain? The manual says switch to MM ~20 minutes before heading up those roads. It takes ~15-20 minutes of driving in moderate demand conditions for Mountain Mode to recharge a Gen 1 Volt depleted battery to the ~4 bar level of power the system then maintains for use in high power demand driving conditions. You can even switch to MM with a full charge. The car will remain in Electric Mode until the charge drops to the MM-maintained level. You then won’t use extra ~0.4 gallons of gas it takes to recharge the depleted battery back up to the MM-maintained level.
 

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Discussion Starter #6
I never knew that about the hold mode. For the mountain mode, I used it the entire trip, more than an hour before getting to the mountain.
 

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Slight modification to my previous statement. The manual says: "Hold Mode is only available when the vehicle is in Electric Mode. This mode places the remaining battery charge into a reserve for the driver to use as desired. Selecting this mode transitions the vehicle to Extended Range Mode to maintain the battery charge reserve."

IOW, if the battery is fully depleted, there is no usable grid power left in the battery to "hold" on to for later use.

However, if you use Mountain Mode to recharge a depleted Gen 1 Volt battery back up to the ~4 bar level, you can then stop the car, turn it off and back on again, and the computer will recognize the state of charge is above the "switch to gas" level. When you then drive using the MM-recharged battery power, the system will record distances as Electric Miles.

If the object is to use the MM-recharged battery power to drive Electric Miles, this will work. However, since it’s not grid power, it won’t increase the kWh Used on the energy usage display. I once drove 80+ Electric Miles with only 9.8 kWh Used in my 2012 Volt by driving electric miles on MM-recharged battery power.

I’ve been driving a 2012 Volt for over 8 years now, and I have no Hold Mode, so I don’t know if you can use Hold Mode to "save" the MM-recharged battery power for later use if the battery was fully depleted when you recharged it via MM and then turned the car off and back on.

I also don’t know how the system records the use of any downhill regen obtained while driving on this MM-recharged battery power. Since the creation of the regen is not "offsetting" any use of grid power (as it does in Electric Mode), will the use of this regen be recorded as Gas Miles (as it would be if created while driving in Extended Range Mode)? Or, because the MM-recharged battery power is being recorded as Electric Miles, will this downhill regen use also be recorded as Electric Miles? I do not know, and can not test it out in my Hold-Mode-less 2012 Volt.
 

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Since only the one fan was powered I figured I dig in a little to check power and see how hard it would be to replace the unit. What I found was the drivers side fan connecter was not pushed all the way in. I plugged it in and with engine and AC running both fans are now working. Hopefully that's it.

The non OEM TYC fan has a mfg date a year after the car build date. I had a minor accident a few years ago and apparently the fan was replaced but they didn't fully seat the connector. So all this time I've been running with half air flow. Normal temps and flat land driving are not a problem, but a couple times in AZ my cabin AC was shut off when the temp was 110 degrees, and this weekend with the mountain, traffic and high temps it must have been too much.

Of note though, with the one fan disconnected, there was no CEL. You'd think there would be a code for the open circuit.
 

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Since only the one fan was powered I figured I dig in a little to check power and see how hard it would be to replace the unit. What I found was the drivers side fan connecter was not pushed all the way in. I plugged it in and with engine and AC running both fans are now working. Hopefully that's it.

The non OEM TYC fan has a mfg date a year after the car build date. I had a minor accident a few years ago and apparently the fan was replaced but they didn't fully seat the connector. So all this time I've been running with half air flow. Normal temps and flat land driving are not a problem, but a couple times in AZ my cabin AC was shut off when the temp was 110 degrees, and this weekend with the mountain, traffic and high temps it must have been too much.

Of note though, with the one fan disconnected, there was no CEL. You'd think there would be a code for the open circuit.
I gotta start lookin' for mechanics roles on TV! LOL

I'm glad that you found the problem at "NO COST" to you. Yes, the software should have caught the absence of the second fan, for sure. An oversight on the part of the coder.
 

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I'm glad that you found the problem at "NO COST" to you. Yes, the software should have caught the absence of the second fan, for sure. An oversight on the part of the coder.
It's possible that even though each fan has it's own connector they are parallel only from the harness, so one fan failure wouldn't trigger it. I'm not interested enough to take the time to mess with it further to find out :)
 

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It's possible that even though each fan has it's own connector they are parallel only from the harness, so one fan failure wouldn't trigger it. I'm not interested enough to take the time to mess with it further to find out :)
I'm thinking that the power drawn by the fan circuit could have been monitored and flagged when not in spec.
 
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