Cold air blowing in heater mode

[Pawan77]

Hello Guys:

Once in a while my car is blowing cold air from the center and side dashboard air vents even when I am running the fan in heater mode (with 3 red rods on the dial, compressor off and temp above 70F). Once in a while means the whole ride. This happened once in the last month and happened twice already in the last 2 days. What could possibly go wrong. I changed the resistor (The oart with spikes on it) like 1.5 yrs back and the fan speed is in control doesn't go up and down on its own, so I am thinking that this issue has nothing to do with the final stage resistor.

Please throw some light on what could be the possible culprit for blowing cold air. Thanks for reading.

[rowdy lee]

... your thermostat is failing in the stuck open position... not allowing the engine to warm up (get hot) as it should. Too much cooling because too fast water flow... not controlled/throttled by thermostat.

[Pawan77]

Does it throw any codes for this if I get a scan at Autozone?

... your thermostat is failing in the stuck open position... not allowing the engine to warm up (get hot) as it should. Too much cooling because too fast water flow... not controlled/throttled by thermostat.

Does it throw any codes if I get it scanned at an Autozone?
My engine is getting hot as normal, the temp gage is getting from the blue zone to the mid zone. No abnormality on the temp gauge!

[spunk]

Does it throw any codes for this if I get a scan at Autozone?



Does it throw any codes if I get it scanned at an Autozone?
My engine is getting hot as normal, the temp gage is getting from the blue zone to the mid zone. No abnormality on the temp gauge!

The same thing happens with my car. I always thought it was normal .. it blows hot air from the top vents and cold air from the ones facing me. It gets warmer as the car warms up.

[rowdy lee]

Does the temp needle keep going low and high between idling and driving?

Cold air output and hi-low needle is a sign of t-stat sticking open...

There is a hot water valve in the system. I think it's controlled electrically by the climate-control computer.

Your coolant level is normal in the expansion tank?

I would look in the Bentley BMW manual, read about the system and find out where the parts are located and how to check them out. Hot water may not be getting into the heater core. Hot water valve may have a problem.



Sorry... not too helpful.

[Pawan77]

Does the temp needle keep going low and high between idling and driving?

Nope. Nothing like you mentioned, everything is normal.
Cold air output and hi-low needle is a sign of t-stat sticking open...
This happened 2 yrs back and I changed the thermostat.

There is a hot water valve in the system. I think it's controlled electrically by the climate-control computer.
I will look into this.

Your coolant level is normal in the expansion tank?
Its a brand new expansion tank. Changed only 2 months back and the coolant level is normal.

I would look in the Bentley BMW manual, read about the system and find out where the parts are located and how to check them out. Hot water may not be getting into the heater core. Hot water valve may have a problem.



Sorry... not too helpful.

But this blowing cold air is happening only once in a while. Thanks for the posts Lee.

[jtsystems]

are all the vents blowing cold, if so you could have an air lock in the system.

Air locks can move around and while you engine may get a good flow of water on most occasions when the heaters are working it is possible that an air lock is forming causing the water to not pass and thus causing cold air.

That is of course only if its cold air from all vents on occasion.


Maybe worth bleeding the system and seeing if that works?

[nathancarter]

The three most likely culprits have already been mentioned.
1) Stuck-open thermostat. Might give code P0128 or maybe another code that I can't remember right now. Might or might not visibly affect thermostat. One test (if you don't have codes) is to drive around town at lower speeds till it looks fully warmed up, then get on the highway in 5th gear and 50-60mph. If the temp needle drops, thermostat is definitely sticking open.

2) Low coolant level. Check your coolant level by the floating stick gauge when the car is cold. Air pockets will naturally gravitate to the expansion tank, and will generally only move to other areas of the cooling system if the level in the tank is very low.

3) Sticking heater valve. I don't know of any way to really test this, but based on the "sometimes" description of your symptoms, this one kinda sounds most likely to me.... unless the "sometimes" is directly related to driving on the highway vs. idling around town, which would be the thermostat as mentioned above.

[the andrew]

"Sometimes" sounds like a heater valve. Little guy sits under the air cleaner box and is about a 10 minute job. OEM ones are Bosch, looks like a little metal film canister. Pull it up off the mounts, clamp hoses to minimize coolant loss, loosen the two hose clamps with 8mm socket drive, disconnect electrical, reverse install.

[DTMdan]

Recently I have had the opposite problem...

In the past couple months I usually had temp set around 70-80 and adjusted manually on the center vents above radio. But now that it's getting warmer some days I will put it on cooler, well sometimes it will blow hot air out on the cold setting, even with AC on... I think every time that it does this it's blowing hot air out at the top center vents above radio and the vents near your feet and then cool air on side vents nearest windows.

Anyone know why it would be doing this?

[nathancarter]

Recently I have had the opposite problem...

In the past couple months I usually had temp set around 70-80 and adjusted manually on the center vents above radio. But now that it's getting warmer some days I will put it on cooler, well sometimes it will blow hot air out on the cold setting, even with AC on... I think every time that it does this it's blowing hot air out at the top center vents above radio and the vents near your feet and then cool air on side vents nearest windows.

Anyone know why it would be doing this?

- Center dial set to red dots instead of blue dots.
- Low refrigerant charge.
- Heater valve sticking open
- Compressor not engaging

[DTMdan]

Thanks Nathan

[Pawan77]

Thank you all for the postings. I will do the suggested diagnosis and will post the update here. Thanks again.

[repandpresent]

I have a similar problem but it's dedicated on one side. Not until recently has my car been acting weird. When I turn the heat up I only get heat on the drivers side while all the vents on the passenger side blows out cold air. My temperature needle gets to the center in about 3 minutes and it sits there. I tried to mess with a few settings but nothing changes. Any input?

[e46RedHead]

I have a similar problem but it's dedicated on one side. Not until recently has my car been acting weird. When I turn the heat up I only get heat on the drivers side while all the vents on the passenger side blows out cold air. My temperature needle gets to the center in about 3 minutes and it sits there. I tried to mess with a few settings but nothing changes. Any input?

Were you able to find a fix to your problem? I am having the same issue but my driver side blows cold and my passenger blows hot.

[Mudnyrey]

Your problem most likely is your Heater Control Valve, or you may have a portion of your heater core that is blocked. Most likely I would lean on you Heater Control Valve.
You can simply check the output of you HVC line and see if one of the lines is hot and the other cold. Most likely there might be 3 radiator lines going to your fire wall, one is a return and the other two are a supply feeding the heater core.

[MIKYZZ4]

Check for properly operating BOWDEN CABLE#2 here:https://www.realoem.com/bmw/enUS/sho...diagId=64_0824 in addition to checking operation of heater control valve #2 here:https://www.realoem.com/bmw/enUS/sho...diagId=64_0890
Read up on your heating system in your Bentley Manual.
Don't forget to check for proper coolant levels when cold.