- The climate control on my 2007 works ok when it is warm outside, blowing nice cold air.
- When it is cold outside the blower motor will not come on in auto or manual to blow hot air.
All the functions on the unit and display work, just not the blower part.
I let the vehicle warm up for 5 minutes, and I can not get the blower to come on. Turning the unit off and back on does nothing either.

The only way to fix it is turn the ignition on and off, after which it comes on within a few seconds blowing nice warm air.

I came across a thread from someone with the exact same issue, but it looks like it never got resolved.
https://g35driver.com/forums/audio-v...ermittent.html

I also followed the instructions to put the unit in diagnostic mode and everything seems to be ok. That was provided in thread: https://g35driver.com/forums/g35-sed...control-3.html

The only thing I did notice when I did the diagnostic mode is that the sensor readings are as follows:

- First sensor (ambient temperature) was 17 C with the outside temp being 17C.
- Second sensor (in vehicle temp) was 33C. It was hot inside so that looked ok.
- Third sensor (intake sensor) was 14C.

I set the temp to 21 C and drove home.

When I got home I did the diagnostic again.

This time it was 16, 27, 7 with the fan blowing at a strenght of 3 out of 7 as indicated on the unit.

Now I could be wrong since I never checked this before, but I was thinking the inside temp sensor should have been reading around 21. 27 seems to be a bit high since I am telling the unit to keep it at 21.

But I think that would not fix my initial problem as I can not get the blower to come on in manual, and if have been reading the service manual correct when you put the unit in manual it should come on no matter what.

Any ideas where to look next?

 

I had issues with my old HVAC system in my car with the old bose unit. I purchased a new head unit and HVAC controller and all my problems disappeared. Maybe you have a loosening cable in the back of your car, or a system on the way out?

 

As a follow up I diagnosed it some more this morning, when it was cold again.
Self diagnosis on the unit worked fine and I checked the sensor temperatures and they were indicating 2/4/3/ so that seems ok.
However, no heat.

After some further testing I noticed the display shows the fan running at 6 out of 7, however it is actually running at 1 out of 7, super slow.
So the unit control seems to be working ok as it is trying to run the fan at almost maximum speed.

I had to stop and start the car a few times for the fan to actually come on.
Stopping it again after it came on would once in a while cause it to stop again on the next car start.
It seems to be random if it works or not.

Going by that either the control units fan output is defect, or the blower motor itself is.

I am leaning more towards the control unit because the fan does work without any issue as soon as the unit works properly.

Does anybody know how the actual speed control works? It is just a regulated output voltage coming from the control unit, or is there a seperate control unit on the fan that regulates the fan speed?

 

As an update, I ended up changing the blower motor relays and it works flawless. $32 part.

 

I to have that same problem with the blower fan especially when heat is on it works intermittently, but when it works it works very well and quiet until you turn car off and on then it wont come on until it feels like. I replace the climate controller on the console no change,i also replace the ac controller no change,now i'm heading to the relay but not sure where it is,can anyone help me to locate the relay for the hvac fan

 

It is located underneath the fuse box at the driver side, underneath the steering column area.
You have to remove 1 dash panel and 4 screws that hold the fuse box in place. There are 2 identical relays underneath the fuse box. 1 is the blower motor relays, the other one I believe is for the defroster, but don't quote me on that. I had it done at the dealership and it was less than $60 including parts and labour. I did not feel like taking a chance with wires popping out from the fuse box.

 

https://g35driver.com/forums/general...mittent-2.html

Pictures and instructions are on page #2.