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heater not working correctly

11K views 9 replies 7 participants last post by  bluebee 
#1 ·
I can only get heat to come out of the passenger side. The driver side is cool. Anyone know what I need to replace to fix this?
 
#3 ·
I little update to this. Seems like there are several issues going on. When I would idle the heat was cool as I started accelerating heat would come out the driver side again. I also noriced that that the heat would be about the same hot temp no matter what degree I put it on. As I tried to adjust the temp, I would have to go do all the way to the low 70 degree reading before it cools any. Any suggestions?
 
#9 · (Edited)
Lack of heat at idle could be the auxillary water pump inop.
This pump is designed to provide flow through the cabin heater core when the engine water pump is at idle speed & can't provide enough flow through the heater core. The pump is located on the bottom of the fan shroud, left hand side. Remove the plastic shield under the engine to gain access. The pump will be easy to see from underneath. The pump should operate with key position to "engine on/run" (engine does not have to be running) with the HVAC unit calling for heat, i.e. a high temp setting, & engine temp > 32F. If the pump is working, a slight vibration can be felt with your hand or finger. No vibration means a problem with the pump (most likely), power circuit to pump or HVAC control.

BTW, BMW's TIS recommends running this pump when bleeding the cooling system. The flow assists pushing air out to the expansion tank.
If you had good heat before & your coolant level has not dropped, it is unlikely that air in the system is your problem. In this case, I'd check the auxillary pump first.
EDIT: missed you post re low coolant. Bleed is good idea. But why is you coolant low. Time to check for leaks?

Regards your passenger side no heat symptom
You may want to have a fully BMW capable diagnostic scanner check your system. Heat is controlled by the HVAC head using a sensor reading duct air temp after the heater core. The controller then opens or closes the heater water valve to adjust temp. Each side is controlled independantly, i.e. a duplicate rt/lt system. The diagnsotic scannner can report real time values so the one can work out what is likely wrong. E.g., if the sensor incorrectly reports 100F when the duct air is actually say 35F, the HVAC will close the water valve giving no heat -> replace the sensor. OTOH, if sensor correctly reports 35F and HVAC signal to water vave is "wide open" -> probably the water valve or wiring is inop. etc. etc.

Similarly, a scanner can help determine why the HVAC wants to blow fully hot air at any setting above 70F.

Regards
RDL
 
#5 · (Edited)
Did you find the problem? Mine is doing this also. I recently replaced the fan shroud and had the fan blade and clutch out but all went back in fine. I dont see any leaks but will double check again and check level of coolant.

Drive slow i get no heat, punch it and I get lots of heat. It's like thermostat is sticking. Just strange this just happened to start after I changed the shroud.
 
#8 · (Edited)
Thanks Jimmy for the bleed suggestion! and to Bluebee for the links!! The video (#2 link) is perfect I like seeing it done its easier for me when I see it.

When I went out today i checked my coolant level and it was down. I will bleed and then see if that fixes my problem.

Not my thread so I hope this helps him as well! This forum has helped me so much Thank all of you for being there for us.
 
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