Quote:
Originally Posted by gbalthrop
"Defogging" or removing condensate from the inside of the windshield does NOT require heat, but rather evaporation by high air flow of "de-humidified" air that has had water vapor removed by the cold A/C Evaporator coil. Assuming your IHKA Module is controlling the "Flaps" and blower motor correctly, what happens when you press "Defrost" button on top-right of A/C Control Panel is:
1) the Blower goes to High Speed;
2) the Windscreen Flaps are opened and Footwell Flaps are closed; and
3) air is directed through the Heater Core.
If your "Snowflake" button below the Defrost Button is NOT lit, then your Compressor Valve is NOT active and you are getting NO cooling of the Evaporator coil, and hence NO de-humidification of the air. In warm, moist climates or conditions, if the Compressor is NOT pumping and cooling the Evaporator, you will NOT get quick "defogging" of the windshield. Heat of the air is irrelevant in those conditions. HEAT is only needed in cold conditions to prevent or remove ice formation.
You don't say how long the engine operated to, at and from the bus stop, but it takes 3 to 5 minutes for a cold engine to warm sufficiently to produce heat at the heater core. If you get NO warm air from the Defrost vents when the engine has run for 10 minutes, post back and someone can suggest "next steps" to address that issue. If you have INPA, ISTA, or a BMW-specific Scan Tool, let us know what you have and we can suggest specific tests.
Assuming you have a 2008 335i, here is the TIS Procedure for Bleeding the Cooling system. Ignore ALL the pages BEFORE the last page, as they deal with the "Vacuum Filling System":
https://www.newtis.info/tisv2/a/en/e...check/CNCeB76L
Most US E9x models do NOT have either a Water Valve or Auxiliary Water Pump, so I don't see any reason for step (4) related to A/C Control Panel settings for heat & blower -- the main water pump is sending water through the heater core REGARDLESS of Control Panel Settings on those models, so no settings are needed to remove trapped air from the heater core.
George |
while all these statements are generally correct there is always some corrections from bmw by design
1. bmw e9x climate control can defog windshield without compressor valve enabled, this is very easy to check if car have working condensation(fog) sensor under windshield mirror cover assembly
if windshiled was ever replaced in aftermarket shop this sensor can absent, glued incorrectly or have wiring damaged
2. n51, n52, n53,n54 and n55 engines do not have auxiliary water pump because it's main pump has variable performance, and during inital engine warmup it's performance set to minimum to faster achieve warmup and required emissions level