Member Since: 30 Jul 2013
Location: Waterlooville
Posts: 55
Heating problems
Hello,
For the last 2k miles I experience some issue with the heating. It starts normal and it blows front/face/foot, and I can change it from the climate control, but at some point after 20-30 minutes of driving, it literally doesn't blow anywhere. I can hear the fan is working.
I cleared the faults, but they would reappear again:
B1B74-00 (28) Front foot-defrost mode stepper actuator
B1B75-00 (28) Front foot-face mode stepper actuator
B1B76-00 (28) Front left air blend stepper actuator
B1B77-00 (28) Front right air blend stepper actuator
B1B78-84 (28) System pressure - Bus signal/message failure - signal is below allowable range
B1B82-00 (6C) Rear air distribution stepper actuator
B1B83-00 (68) Rear air blend stepper actuator
Does above clearly mean I have to replace all for stepper actuators?Thanks,
Tiho
Last edited by logche on 5th Jan 2024 5:31 pm. Edited 1 time in total
4th Jan 2024 12:08 am
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10426
Are you saying you can’t or can hear the fan after 30 mins ?
4th Jan 2024 12:13 am
HairyFool
Member Since: 04 Jan 2023
Location: Essex
Posts: 583
I would be looking for something common to all actuators such as a reference or supply voltage.
For example my memory mirrors generated a whole set of codes for the position sensors left and right, horizontal and vertical. All caused by a missing 5v rail.A visitor from the dark side, my other vehicle is an MG5 EV
4th Jan 2024 12:14 am
logche
Member Since: 30 Jul 2013
Location: Waterlooville
Posts: 55
Pete K wrote:
Are you saying you can’t or can hear the fan after 30 mins ?
Fan is working and I can hear it all the time. After 20-30 minutes, the air doesn't come neither from front, feet, or face. It looks like all the flap doors are closed.Thanks,
Tiho
4th Jan 2024 12:19 am
logche
Member Since: 30 Jul 2013
Location: Waterlooville
Posts: 55
Found this on the manual.
Click image to enlarge
If it is short circuit, how can I trace this?Thanks,
Tiho
6th Jan 2024 9:46 pm
HairyFool
Member Since: 04 Jan 2023
Location: Essex
Posts: 583
So the key error is "B1B78-84 (28) System pressure - Bus signal/message failure - signal is below allowable range"
The fact that the system works for a time then stops rather indicates it is not a simple short circuit. Also the step motors are getting a "close" signal rather than the actual LIN bus shorting out. Everything originates from the Air con control panel.A visitor from the dark side, my other vehicle is an MG5 EV
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