[bxd20]

Here's what's happening on my 2014. I've had it since new, so I know how the climate system is supposed to work and something is definitely "off" here.

If I put it in Auto/Comfort in the morning, driving on EV power, I get good solid heat and it comes out as it's supposed to on a cold morning: mostly on my feet, a little on the windshield.

Once the car is toasty and the fan speed automatically decreases to low, I lose all heat on the floor, absolutely zero coming out down there, all of it is going to the windshield. It's on 77 and my feet are freezing while I feel the air hitting my face.

If I take manual control and put it on "floor" mode, it still only blows on the windshield.

If I then manually increase fan speed to High, it's then willing to blow on the floor.

Is there a blend door in the dash that could be sticking that I can lubricate?

Or other ideas?

Thanks!

 

[TSquare]

Have you turned OFF the Auto Defog Setting that is located in the center stack settings? It sounds like "Auto Defog" could be trying to force air onto the windshield.

Or you are correct and the blend door is not working properly.

 

[bxd20]

I'll double check Auto Defog later today, though I know I haven't changed that since buying the car.

This morning I was playing with the settings further, and realized that even at a High blower setting, while a little is coming out on the floor, probably 90% of it is going to the windshield. This is in manual mode with the Floor setting chosen.

 

[Barry]

The auto defog setting is a good suggestion. If that doesn't help, you can force the HVAC to reboot, which recalibrates the blend door settings.

You do that by pulling the HVAC fuse that is in the left fuse panel (by driver's door), I think it is fuse #5, and keep it out for about 15 seconds while the car is off. You will hear the calibration happening.

My car does something similar, and this fixes it, but only for a couple of days. The dealer suggested trying to replace the heater control module, but it is expensive for an experiment.

 

[bxd20]

I confirmed, Auto Defog is off.

I pulled out fuse #5 (which is the correct fuse for HVAC), waited a minute, put it back in. Waited about a minute, I did hear some sounds. Started the car, and put it on Floor mode, and, what do you know? It's working correctly. Only getting airflow on the floor.

Now, I did break good troubleshooting protocol and change two things at one time. While the fuse was out, I also removed the cabin air filter, thinking perhaps if the system saw backpressure, it might default into a mode where it blows on windshield? I'm not sure if it's intelligent enough to do that.

While the filter looked very clean, it probably has 24,000 miles on it. I've ordered a replacement. I really don't think it's the filter, but when the new one arrives I'll install and report back.

Hopefully the problem doesn't return every couple of days.

I don't mind spending money to have it fixed, but I hate "experiments". A dealership should have a scan tool specifically for troubleshooting HVAC issues, I've seen Ford dealers use one on my cousin's escape that was exhibiting weird climate control function problems.

 

[Barry]

One other tip, if yours acts up again, is to experiment with the other vent settings. I find that the setting that blows both on the windshield and the floor at the same time works better than the floor only setting. More warm air gets to the floor with that setting. Yours may be different, of course, but for me it works well enough that I can forget about it.

 

[bxd20]

Barry,

You're a life saver. The problem came back a couple days after pulling the fuse. Contrary to what would seem like common sense, the "Floor" setting delivers almost nothing to the Floor while the "Windshield and Floor" setting pumps most of its air to the Floor, which I can live with for now.

Thinking through the cause, since it's possible for the system to blow air onto the floor, I suppose it's probably not a mechanical issue at its core such as a door. More of a control module, as your dealer stated. Do you have any further details? Exact name of the module, or even better a part number?

 

[Barry]

^ The service writer just referred to it as the "heater control module" and quoted around $700 to replace. I have no part number. This was the next step in the "diagnostic" procedure (wild guess procedure) after they already reprogrammed the module twice with only temporary improvement. If you take yours in for service, I predict they will want to follow the same procedure and charge you for a reprogramming first, and send you home with a temporary fix, before trying anything else.

 

[bxd20]

I *think* this may be the part. https://www.gmpartscenter.net/oem-p...wMTQmdD1iYXNlJmU9MS00bC1sNC1lbGVjdHJpYy1nYXM=

It's about $100 new, and there are online salvage parts stores selling it for about $50 used.

The diagram shows a manual climate control in front of it, but the part number checks out against all 2014 Volts.

Tough to know how much labor is involved, I would guess it's buried in the center stack, so maybe an hour or two of work.

If anyone has Alldata or GM service manuals and can let us know if the pic appears to be correct and where located, that would be great. Also, if this thing has to be programmed for its specific application, if so that might kill the DIY option.

 

[JuneBug]

This page from the service manual may be of some help:

https://www.autocats.ws/manual/chevrolet/tis0911/en/documents_2012/Volt/SM-R/92563315.EN.html#4711

 

[bxd20]

JuneBug, thanks for that link, it was very helpful.

Reading through the troubleshooting procedure, and considering the fact that it works correctly after a fuse pull but then goes awry, I don't think it's the HVAC Remote Control Module.

It seems far more likely to be the Mode Actuator. "The mode actuator is a 5-pin stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energises the 4 stepper motor coils with a pulsed ground signal. The stepper motor puts the mode flap into the calculated position in order to reach the selected position. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap."

I'm now trying to figure out where the mode actuator is located and therefore how hard it is to replace. I know our cars share some design with the Cruze, and if that's the case, it's buried deep in the dash behind the instrument panel.

 

[bxd20]

I wanted to update my thread, for reference to anyone else who has this problem.

I got fed up with this problem and paid for GM to flash the climate module to latest firmware, back in Nov 2019.

My feet were warm all winter!

A couple weeks ago, November 2020, I notice it’s started to act up AGAIN. So weird that it was ok for at least 4 months (maybe longer, didn’t use heat spring and summer).

I pulled the F5 fuse the other day. We will see how long that helps. I don’t drive often these days so next update might take a couple weeks.