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This would be the mode I'm most interested in. Would you be able to take some temperature measurements and reply back? I think we're to the point where we don't need pics, although please add those if you can. However it would be good if at least some discussion of how the measurement was taken, what was the measurement device, and waiting long enough so the seat has time to stabilize at its max temperature.
I don’t have the right thermometer to measure this (maybe this is a good exusue to get one!). But more importantly, it’s unlikely to get cold enough to get a good test here is Virginia. It’s nearly March and has only dipped below freezing a few times in the last couple of weeks. All that said, I’ll see what I can do.
 

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Discussion Starter #62
2017 Premier on 3 dots. Measured after ~15 mins. Ambient temp was about 28°F.
Seat back = 108°F (42°C)
Seat bottom = 100°F (38°C)
...
Thank you.

This is beginning to get interesting. Already there is a wide distribution in the reported temps. The design might just be such that there is large standard distribution in the temperature control range and some of us get the lower end of the distribution.
 

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Discussion Starter #63
I don’t have the right thermometer to measure this (maybe this is a good exusue to get one!). But more importantly, it’s unlikely to get cold enough to get a good test here is Virginia. It’s nearly March and has only dipped below freezing a few times in the last couple of weeks. All that said, I’ll see what I can do.
If you can, please do. Also, it shouldn't matter if the ambient temps are cold or not. The system should regulate itself independent of ambient temps. Although the driver might get uncomfortable :)
 

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Thank you.

This is beginning to get interesting. Already there is a wide distribution in the reported temps. The design might just be such that there is large standard distribution in the temperature control range and some of us get the lower end of the distribution.

Trying to remember my engineering stats from 40+ years ago: Would that be a "Low Q" distribution curve?
 

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Ok, I drove home from work, about 20mi and stoped at Harbor Freight, about half way, and picked up an infrared thermometer. Temp in car set to 73. Left the car running at home with seat set to 3. After 20min the temperature read from 73 to 83 deg. To me this means "barely functioning". At this point I'm wondering if this is worth a warranty visit to the dealer. BTW, I pointed new thermometer at one in the house and they read the same within 1deg, so I don't the thermo' is miss calibrated. Outside air temp about 45.
 

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Ok, I drove home from work, about 20mi and stoped at Harbor Freight, about half way, and picked up an infrared thermometer. Temp in car set to 73. Left the car running at home with seat set to 3. After 20min the temperature read from 73 to 83 deg. To me this means "barely functioning". At this point I'm wondering if this is worth a warranty visit to the dealer. BTW, I pointed new thermometer at one in the house and they read the same within 1deg, so I don't the thermo' is miss calibrated. Outside air temp about 45.
73 to 83 is way too low. How does the seat feel when you're sitting in it and the heated seats are at 3? If it's not at least = body temp, then I'd go to the dealer.
What might be happening is that the surface of the seat is loosing heat to the interior of the cabin, so it reads more or less the same as cabin temp. If you sat on it (ie, insulated it), it might get warmer. Just a thought.
 

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Discussion Starter #67
Ok, I drove home from work, about 20mi and stoped at Harbor Freight, about half way, and picked up an infrared thermometer. Temp in car set to 73. Left the car running at home with seat set to 3. After 20min the temperature read from 73 to 83 deg. To me this means "barely functioning". At this point I'm wondering if this is worth a warranty visit to the dealer. BTW, I pointed new thermometer at one in the house and they read the same within 1deg, so I don't the thermo' is miss calibrated. Outside air temp about 45.
Thanks, but for this to be accurate you will need to be sitting in the seat with the seat heater running for likely 10+ minutes. At least my car seems to stabilize in that amount of time.

It won't get up to temp if you are not sitting in the seat.

Easiest way to get a good measurement is to have the seat heater on while you're driving somewhere and then test the seat when you get there (quickly, because the seat temp cools off rapidly when you get out of the seat). Or if you have a thermometer probe like has been shown by a couple of us you can just place the probe between you and the seat and watch the probe temp rise until it stabilizes. The thermometer probe only measures one spot, but can be moved around. A thermal camera shows heat contours and the thermal gun can be moved around and give a quick measurement of various areas.
 

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Here are my results in our 2018 LT using a temperature probe from a digital kitchen thermometer. I will try to verify the accuracy of the probe by comparing it to an IR thermometer later this week. I was sitting on the temperature probe with it under my right thigh.
- Starting temperature - 23°C (73°F).
- after 5 minutes - 35°C (95°F).
- after 10 minutes - 37°C (98°F).
- after 15 minutes - 38°C (100°F).
- after 20 minutes - 39°C (102°F).
- after 25 minutes - 40°C (104°F).

I then moved to temperature probe the seat back, a little above the small of my back. So at this point the seat had been on for twenty-five minutes. After five minutes of stabilizing the seat back temperature seemed to be 40°C (104°F). The same as the seat bottom.

My question after this is: what size resistors should I use if I want to increase the max temperature from 104°F to closer to 120°F?
 

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I have a 19 LT. I would describe it as:
3 dots - eventually too warm (~20 mins)
2 dots - can be left on indefinitely, most of the time
1 dot - the only indication it's working is the dot on the screen

I would agree the seat heaters are the weakest I've experienced, but I can understand Chevy backing them off.
The above is with wearing jeans in temperatures 0F and colder.
If people are expecting to start shivering and be wearing insulated coveralls that are chilled from being outside, then get into the car and get warmed up just from the seat heaters in a couple of minutes, that isn't going to be successful.

I would like to see an "arctic heater" option that has more oomph, but I don't think most people need it and I'm in MN and we had -30F. Eventually the seat heater got hot enough that I needed to turn it down. Soldering in resistors is a good workaround, but not a change I'm fond of.

Also, if you go beyond 3 settings, you will then need different UI, cycling through one button would have to be replaced with up/down or something, eating valuable screen real estate.
 

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Discussion Starter #70
Here are my results in our 2018 LT using a temperature probe from a digital kitchen thermometer. I will try to verify the accuracy of the probe by comparing it to an IR thermometer later this week. I was sitting on the temperature probe with it under my right thigh.
- Starting temperature - 23°C (73°F).
- after 5 minutes - 35°C (95°F).
- after 10 minutes - 37°C (98°F).
- after 15 minutes - 38°C (100°F).
- after 20 minutes - 39°C (102°F).
- after 25 minutes - 40°C (104°F).

I then moved to temperature probe the seat back, a little above the small of my back. So at this point the seat had been on for twenty-five minutes. After five minutes of stabilizing the seat back temperature seemed to be 40°C (104°F). The same as the seat bottom.

My question after this is: what size resistors should I use if I want to increase the max temperature from 104°F to closer to 120°F?
Thanks for doing this.

If you want to be precise, measure the thermistor value from the seat heater module after the interior temp has stabilized for 2 different temps (the farther apart the better). That would give you the slope for the negative temperature coefficient of your individual thermistors. You can then plot the line and project to the 104F point where your seats stabilize, and to the desired final temp of 120F. The delta R between 104 and 120 would be the amount of additional resistance you'd want to add.

Here's a good quick read on NTC thermistors and shows some example curves for a ~10K NTC thermistor and would show the kind of graph I'm talking about above.

https://components101.com/ntc-thermistor-10k

If you want a quick "projection" from my results, which may not work precisely for you as we may have variations in our thermistor behaviors... your seats are getting about 9-10F hotter than mine were. The 2.2k took mine from ~95 to ~120 on High, or a 25 deg delta. If you want to go from ~104 to ~120, or a 16 deg delta, I'd estimate 16/25*2.2k-> 1.4k would get you close. Larger values will shift it hotter.
 

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Discussion Starter #71
...
Also, if you go beyond 3 settings, you will then need different UI, cycling through one button would have to be replaced with up/down or something, eating valuable screen real estate.
We could wire in external potentiometers instead of the internal R's and then have lots of control range, and independent control of the seat bottom and back :)
 

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Ok, I drove home from work, about 20mi and stoped at Harbor Freight, about half way, and picked up an infrared thermometer. Temp in car set to 73. Left the car running at home with seat set to 3. After 20min the temperature read from 73 to 83 deg.
In my experience the seat never reaches it's full operating temperature unless you're actually sitting in it. And once it does, it's too hot for comfort on the "3 dot" setting.
 

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In my experience the seat never reaches it's full operating temperature unless you're actually sitting in it. And once it does, it's too hot for comfort on the "3 dot" setting.
This is diffinately true in my Cruze and the wife’s Volt. But not my Bolt. After 20 min or so it starts to feel warm, never hot. I suppose it’s a personal preference about how warm one likes the seat, but I’m rather sensitive to cold and prefer things warmer. I’ve driven the entire 45min commute on 3 and never got uncomfortably warm. In the Cruze I’d feel like my backside was on fire if I did this.

With the Volt precondition makes the seats feel warm when you get into the car, enough to want turn them down or off. If the Bolt they don’t even feel warm to the touch, just not ice cube like.

The bottom line for me is that Bolt seat heat, at least in my car is inadequate. It would be nice to know if this is just the way the Bolt is designed for if there are grounds to get it serviced.
 

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Tangentially on topic. I deliberately cold started my car on the way home tonight (no preconditioning) and within 3 mins I could feel noticeable warmth from the seats. I was actually surprised at how quick the seat got warm.
 

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hey @TDIwyse any updates on this? make it through the winter fine and recommend it? I'm thinking of doing this myself over the weekend as it's beginning to get cold again and I find the seat heater to be quite lacking. Anything you would do differently?
 

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I ended up going for it, using the same rated resistors as OP, and I added them for both Driver and Passenger seats. So far, I'm incredibly happy with the results in my 2019 Premier. On full, the seats get borderline uncomfortably hot, which I love, and at 2 or 1 they are no longer useless. I decided to go for it due to the relative ease of modification and definite ease of replacement if something goes wrong. No bad side effects yet however and everything is working great with Very warm seats. Wife and I are both pleased. The seat gets very hot and the back gets very warm. I never had too much of a problem with the seat's bottom heat before, but the extra heat in the back is a God-send. I definitely recommend the mod to anyone finding the heated seats to be lacking. Worst case scenario you're out $50 on a new controller if you screw something up, and replacing that part is dead-simple; it's single bolt that is readily accessible under the passenger seat.
 

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In my 19m Premiere and the 17 Premiere before it, the seat heaters are the most feeble of any car I've ever owned. Ordering the parts for this tweak today.
Thanks!
 

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I ended up going for it, using the same rated resistors as OP, and I added them for both Driver and Passenger seats. So far, I'm incredibly happy with the results in my 2019 Premier. On full, the seats get borderline uncomfortably hot, which I love, and at 2 or 1 they are no longer useless. I decided to go for it due to the relative ease of modification and definite ease of replacement if something goes wrong. No bad side effects yet however and everything is working great with Very warm seats. Wife and I are both pleased. The seat gets very hot and the back gets very warm. I never had too much of a problem with the seat's bottom heat before, but the extra heat in the back is a God-send. I definitely recommend the mod to anyone finding the heated seats to be lacking. Worst case scenario you're out $50 on a new controller if you screw something up, and replacing that part is dead-simple; it's single bolt that is readily accessible under the passenger seat.
Did you disconnect the 12 volt battery before removing the controller?
 
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