PTC Heater
Thread Starter
Junior Member
Joined: Jul 2025
Posts: 20
Likes: 2
PTC Heater
My new to me 2023 C300e has been with the dealer with a HV battery charging fault (charges, throws an error and restarts every 15mins or so). After advice from Germany they changed the AC/DC controller (they could have meant the inverter) but that didn't solve the problem. Now they plan to change the PTC heater. Isn't this for cabin heating? could it be linked to a charging fault
Senior Member
Joined: Apr 2025
Posts: 484
Likes: 203
From: Lowcountry, GA
'25 S580
So for comparison on another brand's EV system - which is the field I work in,
The High Voltage system consists of HV battery, battery charging system, inverter-motor, and junction boxes linked to other accessories like PTC heater, battery heater, etc.
This HV system is separate from the regular 12V accessories system, with the HV battery and DC-DC charger converting the HV DC to 12V DC for charging the 12V battery - like the alternator on ICE cars.
When there's an issue within the HV system, such as isolation fault, it could cause all sorts of issues with charging and drivability.
Depending on what DTC/fault code or the electrical characteristics the technicians found, they might've been able to pinpoint it to the PTC heater, which is very possible.
I'd trust their diagnostics and give them the chance to fix the issue.
If the PTC is not the culprit, the issue will persist.
Hope this helps!
The High Voltage system consists of HV battery, battery charging system, inverter-motor, and junction boxes linked to other accessories like PTC heater, battery heater, etc.
This HV system is separate from the regular 12V accessories system, with the HV battery and DC-DC charger converting the HV DC to 12V DC for charging the 12V battery - like the alternator on ICE cars.
When there's an issue within the HV system, such as isolation fault, it could cause all sorts of issues with charging and drivability.
Depending on what DTC/fault code or the electrical characteristics the technicians found, they might've been able to pinpoint it to the PTC heater, which is very possible.
I'd trust their diagnostics and give them the chance to fix the issue.
If the PTC is not the culprit, the issue will persist.
Hope this helps!
Member
Joined: Nov 2018
Posts: 85
Likes: 13
From: United Kingdom
W206 C300e AMG Line Premium Plus with driver assistance package
The heater may also heat the battery or it might have a separate battery heater. If that fails it could well trigger a charging fault.
Thread Starter
Junior Member
Joined: Jul 2025
Posts: 20
Likes: 2
Got the car back today and it's fixed (touch wood) so looks like PTC heater was the issue. Tech said without using the word "common" he's done a few and merc are aware of the problem....
Thanks for the help guys
Thanks for the help guys
