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2016 Model S Battery Heater Question

I recently bought a 2016 Model S 75D with 40k miles on it and everything was great until I got a BMS_W035 code with no regen and limited acceleration. I read on here everything I could find and figured it may be the battery heater. I just replaced that, disconnected the HV loop and negative numerous times to purge the air and it’s still in the same previous condition. When I precondition the car to warm the battery, the heater unit and the hoses going in and out remain very cold. I would think I’d be able to feel some warmth if the heater was working, but I don’t know how to test it. I am new to this and in need of advice. In the short time I have owned this car, I have learned a lot on here. Thanks in advance.

Adam
 

David29

Active Member
Supporting Member
Aug 1, 2015
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DEDHAM, MA
I recently bought a 2016 Model S 75D with 40k miles on it and everything was great until I got a BMS_W035 code with no regen and limited acceleration. I read on here everything I could find and figured it may be the battery heater. I just replaced that, disconnected the HV loop and negative numerous times to purge the air and it’s still in the same previous condition. When I precondition the car to warm the battery, the heater unit and the hoses going in and out remain very cold. I would think I’d be able to feel some warmth if the heater was working, but I don’t know how to test it. I am new to this and in need of advice. In the short time I have owned this car, I have learned a lot on here. Thanks in advance.

Adam
When the coolant heater on my Model S failed, the shop found that they also had to replace one of the coolant pumps as well. After they did that and told me the car would be ready shortly, they then did some post-repair test. They then said they found that some electronic module that was attached to the back of the MCU also needed to be replaced. They had to keep the car an extra day to complete the additional work.
I have an ESA, so the extra work was on their nickel once I paid the deductible, so they would not likely have replaced all three components if they hadn't needed to. So, it could be that there is something else besides your heater that is not working correctly. Good luck!
 
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I recently bought a 2016 Model S 75D with 40k miles on it and everything was great until I got a BMS_W035 code with no regen and limited acceleration. I read on here everything I could find and figured it may be the battery heater. I just replaced that, disconnected the HV loop and negative numerous times to purge the air and it’s still in the same previous condition. When I precondition the car to warm the battery, the heater unit and the hoses going in and out remain very cold. I would think I’d be able to feel some warmth if the heater was working, but I don’t know how to test it. I am new to this and in need of advice. In the short time I have owned this car, I have learned a lot on here. Thanks in advance.

Adam

I don't think a 12V coolant pump will trigger an HV isolation fault.


Did you tried to check service mode for hidden errors? Maybe this will give you more info. HV isolation could be literally any HV component although battery heater is a common failure point.

 

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