2004 330xi Heat Problem

Hi everybody!

My 330xi has been having some weird heat behavior, and I wanted to see if anybody here had any great ideas. The local BMW mechanic (not a dealer) seemed a bit stumped by the symptoms.

- Starting a couple weeks ago I was having issues where there wouldn't be heat if the car was stopped. As long as I was moving it was OK. I tried to take to show the mechanic, but it was cranking out heat when they tried it.

- This week I've had several occasions where there will be no heat at all under any circumstances (moving or stopped), but other times there will be heat.

- The temp gauge shot all the way up into the red twice this week and then quickly came back down to normal. There was no heat even when the temp gauge was in the red.

- While the heat isn't working, if the climate control is set to Auto, it seems to act strangely. The fan will occasionally rapidly speed up and slow down.

My first thought was an intermittently sticking thermostat, but I'm not sure if that tracks for a several reasons. First of all, the temp gauge is normally right in the middle, even when there's no heat. Secondly, there are no error codes being thrown indicating any kind of problem with the thermostat. Thirdly, as I mentioned, even when the temp gauge was in the red, there was no heat in the car.

I was wondering if there could be some other kind of temperature sensor involved. The fact that the gauge shot up into the red very quickly, and also came down very quickly (like 3 or 4 seconds from in the red to straight in the middle) made me wonder if the engine isn't really overheated.

Anybody have any thoughts on what could be the underlying cause of the heat problems? I'd love to get this solved before Iowa winter really kicks in.

Thanks,
Forrest

Originally Posted by TheLoo

- While the heat isn't working, if the climate control is set to Auto, it seems to act strangely. The fan will occasionally rapidly speed up and slow down.

I would only be guessing if I voice my thoughts on all of your symptoms, but as long as you mean the fan *speed* (read the rate at which it blows, not just the lights that indicate the "fan speed"), then you likely have a bad FSR. FSR = Final Stage Resistor.

http://www.bimmerfest.com/forums/sho...&highlight=fsr

I'd find another indy.

Thanks for the quick replies!

jmanscotch - if I run the climate control on manual then the blower works OK in terms of fan speed. There's just no heat. Does that rule out the FSR?

Scott ZHP - To be fair, I think the mechanic is good and competent. I'm just trying to make sure I get as much info as I can before I sign up for a bunch of hours of diagnostic tests. Sometimes with problems that are intermittent you can get in for a lot more $$$ than you bargained for.

I'm not sure to be honest. The symptoms of a bad FSR are easily the erratic fan speeds...hence my suggestion, beyond that is a guess for me .

How is your outside temperature sensor doing, is it reading correctly or on the fritz? (I say this because I recall the idea that it might be tied to several HVAC functions.)

Here we go, a read on the FSR, outside temp sensor and some more random thoughts - http://forum.e46fanatics.com/showthr...t=fsr+symptoms

Random overheating issue: If not the thermostat, then maybe some air got in you system? You could try a coolant flush (since it is likely needed anyways) and see if bleeding the system helps at all.