Heat is Too Hot!

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I am having trouble with the temp control in my 2002 325xi.

Let's say I go to start my car and its cold outside. I set my heater in side to 72 degrees on the floor vents only. What happens is when the car warms up the heater vents on the floor blow very very hot air all the time like the temp was set at 91 degrees and will run you out of the car. In fact you can turn the temp down to 65 degrees and it's still as hot as if it was set on 91. The only time it gradually becomes cooler is if you set it all the way to 59 degrees then it's cool air. If you set it on 60 then its slightly in between but if you bump it up to 61 or 62 its all the way hot again like its set on 91. I think this guy was having the same problem but I never could find what the fix is.

http://forum.e46fanatics.com/showthr...t=temp+setting

Thanks for any help. I'm going crazy sweating all the time

Could be your heater control valve aka Water Valve.


Symptoms would be hot air blowing out of the vents, regardless of setting w/ exception of AC, which seems to override in my experience.

Not exactly what you have described, but figured I would mention it.

have you checked these? sometimes when its set to red it it will blow hot air no matter what. try setting it to the middle setting.

Do you have it set to "Automatic" Control? it should warm up to around the temperature you have it set for and then maintain that temperature. Definitely a bit colder there in Ohio then in SE PA, but should still regulate itself when a temperature is set. Have you but a thermometer in the car to see just what the temperature is that is blowing out? Are you positive that your cooling system is full with a 50/50 mix? Does it take a long period of time for the engine to warm up to operating temperature before this happens? Are you throwing any codes? A bad thermostat will throw codes and/or set off the Service Engine Soon Light, a sticking open thermostat will warm up slower and will have a too rich fuel setting (and lower fuel mileage) and a sticking closed thermostat will overheat and have a leaner fuel setting. I never use the "Automatic" setting, and actually run my A/C all year long and adjust the temperature for the weather conditions outside. There are several pluses to doing this; always keeps the refrigerate and lubricating oil circulating in the A/C system keeping seals soft (longer times between refills) and it removes moisture from the cabin air continuously (note, when ever you turn the windshield defroster on, the A/C runs). Your water control valve could be acting up, not closing off and hanging wide open so as not to regulate the amount of coolant passing through.

Thanks guys. I do not anticipate anything wrong with the thermostat. No codes are tripped and no slow heating or overheating are happening to the engine. I also have the dial on the panel vents on 3 blue dots. Any other ideas?

Final stage resistor? That affects the fan control speed...not sure about the temperature though. You might have a faulty AC control unit, know any friends with an E46 you can swap their AC control with to diagnose?

not very familir with the bmw hvac system, but it sounds like a blend door problem (if there is one on the bmw). Its probably stuck and not operating properly. Check into that, had the same issue on my other car a few yrs back, where the blend door (the gate that goes between cold and hot) was stock open on the hot side, so no matter what i did it was always blowing hot air. Final solution replaced the motor that moves the blend door.

I have the same problem and a theory. Is it possible that the supply and return heater hoses are switched at the heater valve in the engine bay. My car also blows very hot air all the time. I may have switched the hoses by accident when I moved them out of the way doing a starter replacement. Maybe someone knows if this could cause these symptoms.

Originally Posted by 325xittt

I have the same problem and a theory. Is it possible that the supply and return heater hoses are switched at the heater valve in the engine bay. My car also blows very hot air all the time. I may have switched the hoses by accident when I moved them out of the way doing a starter replacement. Maybe someone knows if this could cause these symptoms.

Not sure, but its either the Water Valve, or the blend control in the dash. Water valve, being the easier of the two replace.

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