SI83.70-P-0014A | Service Information: Conditions for turning heater booster on/off | 10.2.05 |
Model 211 with Engine 271.941, 628.961, 646.951 /961, 647.961, 648.961
Due to many inquiries about insufficient heat output after cold starts, the following is some information of the on/off conditions for PTC heater boosters:
"AC OFF" button:
- Vehicles up to 11/2004: If the "AC OFF" button is activated, the PTC heater booster is off (see SI83.30-P-0005A).
- Vehicles as of 11/2004: The heater booster is no longer off when "AC OFF" button is activated.
Consumer shutoff: If stage 1 or stage 2 of the consumer shutoff is active, the PTC heater booster can no longer be activated. This means that the PTC heater booster is nonfunctional.
Remedy: Drive vehicle at a higher rpm to improve alternator power output.
On-board electrical system: If several consumers (e.g. headlamps, audio system, rear window heater and heated seats) are all on at the same time while driving, the power output of the alternator is insufficient to ensure the operation of the PTC heater booster.
Remedy: Drive vehicle at higher rpm to improve alternator power output.