HVAC Fan issue, some troubleshooting done.

[evan_calgary]

Lurked here for a while and not reaching out to see if I can get some thoughts.

Definitely a somewhat known issue but i've done some of the steps to rectify and gotten stuck.

New battery, new fan motor.

Heater fan works only on defrost when its less than -10c. It was up to -40 here in the last week. I had no heat other than defrost until we hit -8 today. I do get the battery discharge warning when its cold. Turn off the car and restart and it goes away. To ensure its not the battery I left the trickle charger on overnight and the heater still did not work in the morning.

Any ideas? My next step is to replace the Final Stage Resistor on the fan motor but i'm not sure if I am just throwing money at an unfixable situation.

The 35i is a great vehicle but its been a constant maintenance headache.

Would an alternator with a sticky bearing cause this issue? I've had some minor squeeks from under the hood which seems to be more common when cold. Pulleys/belt/tensioner are all new in last 10k. I was getting low battery warnings some time back but they've gone away since replacing the battery.

Any ideas would be appreciated.

[Portly]

Originally Posted by evan_calgary

Lurked here for a while and not reaching out to see if I can get some thoughts.

Definitely a somewhat known issue but i've done some of the steps to rectify and gotten stuck.

New battery, new fan motor.

Heater fan works only on defrost when its less than -10c. It was up to -40 here in the last week. I had no heat other than defrost until we hit -8 today. I do get the battery discharge warning when its cold. Turn off the car and restart and it goes away. To ensure its not the battery I left the trickle charger on overnight and the heater still did not work in the morning.

Any ideas? My next step is to replace the Final Stage Resistor on the fan motor but i'm not sure if I am just throwing money at an unfixable situation.

The 35i is a great vehicle but its been a constant maintenance headache.

Would an alternator with a sticky bearing cause this issue? I've had some minor squeeks from under the hood which seems to be more common when cold. Pulleys/belt/tensioner are all new in last 10k. I was getting low battery warnings some time back but they've gone away since replacing the battery.

Any ideas would be appreciated.

The fact that you've tried a trickle charger indicates this might not be the issue, but: When the battery level is low, one of the first things the car will do is disable the HVAC fans, with the exception of the "full blast" defroster option (when you hit the dedicated "defrost" button.) My car seems to decide to do the same thing whenever it gets really cold - I'm dealing with it currently.

_Jeff

[evan_calgary]

Originally Posted by Portly

The fact that you've tried a trickle charger indicates this might not be the issue, but: When the battery level is low, one of the first things the car will do is disable the HVAC fans, with the exception of the "full blast" defroster option (when you hit the dedicated "defrost" button.) My car seems to decide to do the same thing whenever it gets really cold - I'm dealing with it currently.

_Jeff

Thanks for the reply Jeff. Sounds similar to my issues.

Is this just a fact of living with a BMW N55 in cold weather? Anyone know the conditions required for the car to disable the HVAC fans? Is this a given battery draw or a % of battery life remaining? I should have been at 100% battery or darn close but it was also mighty cold outside.

I am trying to decide if I should replace the fuse and potentially an alternator which are expenses I will avoid if this is just another "its a BMW" thing....

[maxwmiller]

evan_calgary, does this happen when the car is warm / has been driven recently?

With a new battery and a trickle charger, I don't see why the car would disable the cabin heater for energy reasons. However, I could see how this could be some sort of emissions or safety protocol for extreme cold. By disabling the cabin heater and keeping heat in the engine, the time required to reach operating temperature (or at least get near it) would be reduced.

[Portly]

Originally Posted by evan_calgary

Anyone know the conditions required for the car to disable the HVAC fans? Is this a given battery draw or a % of battery life remaining? I should have been at 100% battery or darn close but it was also mighty cold outside.

First, a side note: My car is an N20 engine, and acts the same, so the issue is not specific to the engine.

I believe (but do not know for certain) that the system does this once the battery drops below a certain capacity, which my experience implies is somewhere in the 45% - 50% range. I've monitored this using the Bimmerlink app, which is a handle tool to have.

Now, if you're thinking, "That can't be it - my battery is brand new!" - lead-acid batteries lose a lot of capacity at colder temps. My research is far from exhaustive, but some charts indicate that an AGM lead acid battery has less than 25% of its rated capacity when the temps are down at -40 (F or C - they're the same temperature at -40). So even a brand new battery might trigger this issue when the temps get so cold.

I can't begin to speculate why BMW thinks this sort of response is acceptable, when most cars just ignore the situation and assume the alternator will put out more than enough power to handle all the electrical loads - but for whatever reason, they do. I find it very annoying, but after dealing with it every time it gets fairly cold, I've come to the conclusion that this is just how it is with these cars, and there really isn't anything to be done about it.

_Jeff

[evan_calgary]

Originally Posted by maxwmiller

evan_calgary, does this happen when the car is warm / has been driven recently?

With a new battery and a trickle charger, I don't see why the car would disable the cabin heater for energy reasons. However, I could see how this could be some sort of emissions or safety protocol for extreme cold. By disabling the cabin heater and keeping heat in the engine, the time required to reach operating temperature (or at least get near it) would be reduced.

So yes, this seems to happen under most conditions BUT I can't confirm the oil temp is above the 80c range. I often let the car sit and idle for 20 min as it takes that long to warm up using just the defrost fan in those super cold temps.

We are past the -30c+ and in the last 3 days i've had the following:
-8: heater works
-15: heater works
-18: defrost only.

This is with a freeway drive so the car is definitely up to temps.

One final question: If I kill the car after I get the high battery discharge warning and start again, the warning goes away in the dash. Is it possible it is still triggering the system. In the one case, this was after the car was on trickle for 10 hours so the battery had to be full.

This thing is awesome in the winter but if this is a BMW-designed factory problem the car is getting sold in the spring. I can't use the vehicle if I don't have proper heat. I was ready to pull over at a coffee shop my toes were so cold the other day.

[wheela]

Originally Posted by evan_calgary

So yes, this seems to happen under most conditions BUT I can't confirm the oil temp is above the 80c range. I often let the car sit and idle for 20 min as it takes that long to warm up using just the defrost fan in those super cold temps.

We are past the -30c+ and in the last 3 days i've had the following:
-8: heater works
-15: heater works
-18: defrost only.

This is with a freeway drive so the car is definitely up to temps.

One final question: If I kill the car after I get the high battery discharge warning and start again, the warning goes away in the dash. Is it possible it is still triggering the system. In the one case, this was after the car was on trickle for 10 hours so the battery had to be full.

This thing is awesome in the winter but if this is a BMW-designed factory problem the car is getting sold in the spring. I can't use the vehicle if I don't have proper heat. I was ready to pull over at a coffee shop my toes were so cold the other day.

I'm not sure what why your car is doing that, but I don't think it's a designed feature. I've had my 2015 X1 35i since 2017 and live in Minnesota, drive it all year, and have never had a problem. I don't think I've had a -40 day yet, but it's definitely had its share of days below -18C. So I think there's hope for this issue. Hope you get it figured out, good luck!

[evan_calgary]

Originally Posted by wheela

I'm not sure what why your car is doing that, but I don't think it's a designed feature. I've had my 2015 X1 35i since 2017 and live in Minnesota, drive it all year, and have never had a problem. I don't think I've had a -40 day yet, but it's definitely had its share of days below -18C. So I think there's hope for this issue. Hope you get it figured out, good luck!

Does your car sit in a heated or attached garage overnight? This would make a big difference in overnight battery temps. Mine is outside so it gets the full brunt of the temps.

[wheela]

Originally Posted by evan_calgary

Does your car sit in a heated or attached garage overnight? This would make a big difference in overnight battery temps. Mine is outside so it gets the full brunt of the temps.

That's a good point, I do keep it in a heated garage overnight. But there are days at work where the high temp never rises above 0F, and last winter I had a short drive to the point where my temp needle wouldn't even move by the time I got there all winter. Going home on those days where the temp stayed sub-0F you can tell the car was NOT happy about it, but I've never noticed an issue with the heater not warming up in a reasonable amount of time. The worst was I had to leave it in an outdoor airport parking ramp for a week last January for a work trip. It was during a minus 0F cold spell like described above and I was worried it wouldn't start but it did. Took a while to warm up, but I don't recall it taking an unreasonable amount of time given the conditions? At least no worse than any other car I've owned.

[evan_calgary]

Originally Posted by wheela

That's a good point, I do keep it in a heated garage overnight. But there are days at work where the high temp never rises above 0F, and last winter I had a short drive to the point where my temp needle wouldn't even move by the time I got there all winter. Going home on those days where the temp stayed sub-0F you can tell the car was NOT happy about it, but I've never noticed an issue with the heater not warming up in a reasonable amount of time. The worst was I had to leave it in an outdoor airport parking ramp for a week last January for a work trip. It was during a minus 0F cold spell like described above and I was worried it wouldn't start but it did. Took a while to warm up, but I don't recall it taking an unreasonable amount of time given the conditions? At least no worse than any other car I've owned.

After talking to an engineering friend about the reduced cold weather battery capacity posting made by another member that info seems to check out. The overnight battery temp is potentially the issue. The car runs great in the winter weather and, although it oil temp needle hangs around the 1/3 mark vs. the 1/2 mark once full warmed, there is no reduced performance. With Hakka tires its quite the traction beast in the winter. Performs amazing. Minus the heating issue.

Anyone else out there with a similar issue that has actually found a resolution other than a battery replacement? Is it reasonable for that Final Stage Resistor to malfunction in extreme cold if its on its way out? Searching for any other possible solutions here other than throwing money at the car!

Does the E84 have the coolant/heater bypass on some other BMWs and does this disable the heater fan? If so, could this be malfunctioning?

I think I would likely move my issue threshold to -20c as the heater was function in -18c last night but it seems to be close to the threshold and had been warmer (-15c) during the day.