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Discussion Starter · #1 ·
Is my HVAC crazy or is it just me?

Note: Auto Defog is totally not on. Checked and rechecked several times.

So I'm driving for a while on a straight road with the sun shinning and it's 76 F outside. HVAC set to Auto and 76 F and the AC light is on. Suddenly it feels noticeably warmer and the air coming out the vents is no longer as cold. AC light is definitely still on. I bump it up to 77 F and then 78 F. The AC light is still on but I've got very warm air coming out. Finally, at 79 F setting it switches over to the Heat light being on. Now I go back down. 78, 77, 76 F and the Heat light is still on. At 75 F it finally switches to AC and I get cold air. So there's this 3 degrees zone in either direction where the system is changing between Heat and AC without the indicator light matching.
I think that in this 3 degree zone it is mixing the two, which seems awfully inefficient. But it's also inconsistent because 76 F was perfectly comfortable until it decided to start using heat too and then I had to drop it to 75 F to be comfortable. Further down the road it did the same thing at 75 F and I had to drop it to 74 F.

Now... Further evidence of craziness today. Plugged in and sitting in my car in the shade. It's 82 F outside. Settings are the same, Auto and 76 F. I see that I'm getting 6kW of juice. I'm just sitting there when I suddenly notice the fan speed is kicking up and I'm only getting a net gain of 4-5 kW of juice. Fan speed keeps going up, it's getting noticeably warmer, and I see the power drop and actually go negative! Obviously the heat is cranking up, despite the display showing a light on AC only. So I set it down to 75 F, the cabin cools and the power goes back up to 6kW. About 5 minutes later I get the same fan increase, cabin temperature rise, and power drop to negative. Is this broke or is it just a crazy system that requires constantly lowering the setting to keep the heat from blasting? I can't turn the heat off because the display says the heat isn't even on.
 

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Is my HVAC crazy or is it just me?

Note: Auto Defog is totally not on. Checked and rechecked several times.

So I'm driving for a while on a straight road with the sun shinning and it's 76 F outside. HVAC set to Auto and 76 F and the AC light is on. Suddenly it feels noticeably warmer and the air coming out the vents is no longer as cold. AC light is definitely still on. I bump it up to 77 F and then 78 F. The AC light is still on but I've got very warm air coming out. Finally, at 79 F setting it switches over to the Heat light being on. Now I go back down. 78, 77, 76 F and the Heat light is still on. At 75 F it finally switches to AC and I get cold air. So there's this 3 degrees zone in either direction where the system is changing between Heat and AC without the indicator light matching.
I think that in this 3 degree zone it is mixing the two, which seems awfully inefficient. But it's also inconsistent because 76 F was perfectly comfortable until it decided to start using heat too and then I had to drop it to 75 F to be comfortable. Further down the road it did the same thing at 75 F and I had to drop it to 74 F.

Now... Further evidence of craziness today. Plugged in and sitting in my car in the shade. It's 82 F outside. Settings are the same, Auto and 76 F. I see that I'm getting 6kW of juice. I'm just sitting there when I suddenly notice the fan speed is kicking up and I'm only getting a net gain of 4-5 kW of juice. Fan speed keeps going up, it's getting noticeably warmer, and I see the power drop and actually go negative! Obviously the heat is cranking up, despite the display showing a light on AC only. So I set it down to 75 F, the cabin cools and the power goes back up to 6kW. About 5 minutes later I get the same fan increase, cabin temperature rise, and power drop to negative. Is this broke or is it just a crazy system that requires constantly lowering the setting to keep the heat from blasting? I can't turn the heat off because the display says the heat isn't even on.
With Torque Pro, I've noticed both the AC and heat running at the same time, when the HVAC is set to Auto and the Heat light is on. I wonder if it has to do with humidity? My auto defog setting is off, but maybe having the HVAC setting on Auto has the same effect?
 

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In my experience there's a "zone of confusion" between the point at which heat is needed and A/C is needed where the HVAC system goes a bit bonkers. Luckily, that range is where I can just turn off the heat button and direct air where I want it to be comfortable.
 

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Discussion Starter · #5 ·
I wonder if it has to do with humidity? My auto defog setting is off, but maybe having the HVAC setting on Auto has the same effect?
Hmmm... That's possible. I'll have to test for that.
 

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Hmmm... That's possible. I'll have to test for that.
There are long threads on here about how screwed up the HVAC system is on the Bolt. There is a humidity/temperature sensor which lives in the box behind the rearview mirror. If auto defog, or auto, are used, it is active. If you use manual temperature setting, and avoid using the windshield vent, it will mostly stay off on newer Bolts, which have separate heat and AC buttons. On older Bolts, there is no way to stop it. It is a braindead zombie, which will run AC and heat together, come he11 or high water.

 

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Discussion Starter · #7 ·
If auto defog, or auto, are used, it is active
Well, that sucks. So turning off auto defog just stops it from working when you don't have it on auto? That's screwy. I really wouldn't care if it blended it and you didn't really notice. But it's like it reaches a point where the A/C gets it just slightly too cold and it immediately blasts the heat on full in addition to keeping the A/C running, requiring you to manually adjust the temp down. But at least the A/C seems to work okay when needed. My ICE used to take about 15 minutes to get the cabin comfortable, which really sucks with a 13 minute commute.
 

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Well, that sucks. So turning off auto defog just stops it from working when you don't have it on auto? That's screwy. I really wouldn't care if it blended it and you didn't really notice. But it's like it reaches a point where the A/C gets it just slightly too cold and it immediately blasts the heat on full in addition to keeping the A/C running, requiring you to manually adjust the temp down. But at least the A/C seems to work okay when needed. My ICE used to take about 15 minutes to get the cabin comfortable, which really sucks with a 13 minute commute.
My 2020 works perfectly ! I never put it on auto !
 

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I never use auto just like I almost never use auto on any of my previous cars that had it.

If I wanted something to do unknown things behind my back, I'd use auto.
 

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Discussion Starter · #10 ·
I never use auto just like I almost never use auto on any of my previous cars that had it.
My previous car was the only one I've had with auto climate. It sucked because it would slow down the A/C or heat way before reaching the target temperature. I thought it was a German car thing. I had driven a few American rental cars that the auto climate worked perfectly so I was not expecting it to be this stupid in the Bolt. Oh well. Manual control it is then.
 

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There are long threads on here about how screwed up the HVAC system is on the Bolt. There is a humidity/temperature sensor which lives in the box behind the rearview mirror. If auto defog, or auto, are used, it is active. If you use manual temperature setting, and avoid using the windshield vent, it will mostly stay off on newer Bolts, which have separate heat and AC buttons. On older Bolts, there is no way to stop it. It is a braindead zombie, which will run AC and heat together, come he11 or high water.

On 2020 with Auto mode and heat off it will still cycle heater with AC running and temp. Set at 74.
94 outside 54% humidity.
I didn't have enough time to play with various manual settings.....so what I did is disconnected HV DC cable from heater and no lights or error codes showing up.... I have not tried using heater while HV DC cable was disconnected.
And it will be staying disconnected during the summer.... no need for cycling cabin heater.
Definitely bad design and no option for user to keep heater not running in the summer .
And auto defog is ticked off ....
 

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Discussion Starter · #12 ·
On 2020 with Auto mode and heat off it will still cycle heater with AC running and temp. Set at 74.
Yup. I added the PID for the heater and saw it come on. At least they could have had the indicator light for heat come on so you would know what it was doing. I can see the logic of trying to blend the heat with A/C to achieve the desired temperature, but you should have an option to disable that on an EV. Still doesn't explain why it would go from a steady temperature, with the car in the shade, to suddenly turning the fan and heat way up and making it much warmer all of the sudden.
 

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so what I did is disconnected HV DC cable from heater and no lights or error codes showing up.... I have not tried using heater while HV DC cable was disconnected.
And it will be staying disconnected during the summer.... no need for cycling cabin heater.

Thanks so much for doing this. I didn't want to risk throwing codes that would require a trip to the dealer. May try it now.
 

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Yup. I added the PID for the heater and saw it come on. At least they could have had the indicator light for heat come on so you would know what it was doing. I can see the logic of trying to blend the heat with A/C to achieve the desired temperature, but you should have an option to disable that on an EV. Still doesn't explain why it would go from a steady temperature, with the car in the shade, to suddenly turning the fan and heat way up and making it much warmer all of the sudden.

I agree with all this. I suspect poor sensor location, or bad software design.
 

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Thanks so much for doing this. I didn't want to risk throwing codes that would require a trip to the dealer. May try it now.
Update on disconnected HV DC cable for cabin heater..... if you turn off car and turn it on after 30-60 speedometer screen will show to service cabin heater but there will be no thrown codes or in app car status show any issues..
I would advise to cover male and female connections with plastic and rubber straps so no water can enter.
And once weather is calling for reconnecting is very easy.
Remember that there is red plastic that you have to move to the right to unlock before pushing down to disconnect.
From various tests manual.....automatic....defog on and off it seems to use cabin heater even you have only AC on.
I'm more interested putting all power from battery to ground and AC in the summer than cycling cabin heater to manage humidity.
Remember that you have to do this with car in off position and preform safety practices when handling HV DC.
There are no power to cabin heater if car is not powered on.
 

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is there no fuse for the cabin heater that can be pulled?
I am kind of laughing at JJ's experience with HVAC, because in the future that's what A.I. is going to be like. It will sense something (unreal) and it will activate the calvary. :)
That what we get for trying to automate everything, including self-driving.
 

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is there no fuse for the cabin heater that can be pulled?

in the future that's what A.I. is going to be like. It will sense something (unreal) and it will activate the calvary.
Fuse 60 under the hood. I wonder if that would do the same thing. @EV Engineering?

Isn't that what Ray Kurzweil, and the Singularity was about? ;)
 

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Discussion Starter · #18 ·
is there no fuse for the cabin heater that can be pulled?
I was just hitting auto and then hitting AC off, then AC on. Now it's in semi-auto. I don't think the heater will come on but haven't really checked.
 

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Fuse 60 under the hood. I wonder if that would do the same thing. @EV Engineering?

Isn't that what Ray Kurzweil, and the Singularity was about? ;)
That would be much more complicated removing from distribution box....beside screws on the top there are 2 more under and to remove it you have to remove entire distribution box from base....and it will require disconnecting service disconnect under the rear seats for that.... it will still trigger after every start screen message ( no error codes will be stored).
I believe that ECM is testing resistance over HV DC cables every time you start the car ( that is only way to show if I disconnected connector on cabin heater).....and if there is open loop ( no resistance from cabin heater) it will show message.....I have disassembled couple Bolts down to everything and replacing fuses inside distribution box are not quick.... they are little more complicated and require service disconnect under the rear seats to be removed for that.
Reason for removing service disconnect under the rear seats if you are removing distribution box is because this box is used as switch to various other electronic feeds even when car is off.
 

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I was just hitting auto and then hitting AC off, then AC on. Now it's in semi-auto. I don't think the heater will come on but haven't really checked.
I have tried many different methods and cabin heater will still be cycling.
If you have come up to something I didn't discover I'm open to suggestions....
Make sure you use Telek PID'S or factory scanner for testing purposes...I use factory scanner.
 
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