Automatic climate control acting wonky

[mclasser]

This is on my Pilot.

I noticed something funny with my ACC this winter. I leave it on 73 AUTO and normally, it would blow hot and fast during the first few miles to warm up the cabin, then gradually slow down/increase as needed to maintain the 73 set point. That's the whole point of automatic CC, right?

But now, it keeps blowing hot and fast and 'forgets' to drop down. I've driven on 30 min trips where it kept blowing hot & fast the whole time. As you can imagine, the cabin gets uncomfortably warm and I have to manually turn it down to like 70 to get some cooler air.

I've had this car since new and never had this sort of issue. What could be going on here? Is there a way to 'reset' the ACC?

 

[BMWTurboDzl]

Clean the cabin temp sensor with rubbing alcohol?

 

[Wolf359]

Yeah, I'm going to guess temperature sensor. My car has the dual climate control and it actually has several sensors so I'm guessing one of them is bad. Mine showed up with a car specific scanner. Probably won't show up with a regular scanner that only does engine and emissions codes.

 

[MCompact]

BMW's have a blower motor resistor which can cause similar issues when it fails. I'd scan the system as Wolf359 recommends before you start throwing parts at it.

 

[LazyDog]

Also check or replace cabin filter!

 

[Lolvoguy]

Why not simply use the manual climate control controls?

 

[Wolf359]

Originally Posted by Lolvoguy
Why not simply use the manual climate control controls?

I don't think you understand how you're supposed to use automatic climate control.

 

[14Accent]

Easy enough to grab a can of compressed air and blow it into the in-car sensor. It's mounted to the driver's lower panel, on the far left. Looks like you just pull the left side dash trim (where the door closes), then take out a screw and the panel pops out. Clean the sensor, try the system and see what happens now.

Also, if you want to test the sensor, the specs are as follows, using a meter between pins 3 and 4 of the sensor. 3 and 4 are the 3rd and 4th from the left, with the connector tab facing up.

14 degrees - 7k ohms
32 - 5k ohms
50 - 3.5k ohms
68 - 2.2k ohms
86 - 1.5k ohms
104 - 1k ohms

 

[Lolvoguy]

Originally Posted by Wolf359
Originally Posted by Lolvoguy
Why not simply use the manual climate control controls?

I don't think you understand how you're supposed to use automatic climate control.

Oh I understand alright, I have them on the Lexus and I use the manual function instead.

 

[GMBoy]

Originally Posted by MCompact
BMW's have a blower motor resistor which can cause similar issues when it fails. I'd scan the system as Wolf359 recommends before you start throwing parts at it.


This. ^^^^^

The fan is controlled by either a resister or a small module near the HVAC box. Auto CC usually has the module and manual systems a resister pack. I had the same symptom in my 2006 Denali which was the module near the blower. Also did it on a 2011 Lincoln. Check Rock Auto for the part.

 

[Wolf359]

Originally Posted by Lolvoguy
Originally Posted by Wolf359
Originally Posted by Lolvoguy
Why not simply use the manual climate control controls?

I don't think you understand how you're supposed to use automatic climate control.

Oh I understand alright, I have them on the Lexus and I use the manual function instead.


It's pretty clear you don't. It's automatic so you just set it and forget it. If you're using the manual controls, that defeats the point of the automatic. You mind as well walk when you have a car that you can drive places.

Basically the point was that if you have to use the manual controls because the automatic one is broken, then you should fix the automatic one. Otherwise that's like turning up the radio so you don't hear the noise that the car is making.

 

[mclasser]

Originally Posted by 14Accent
Easy enough to grab a can of compressed air and blow it into the in-car sensor. It's mounted to the driver's lower panel, on the far left. Looks like you just pull the left side dash trim (where the door closes), then take out a screw and the panel pops out. Clean the sensor, try the system and see what happens now.

Also, if you want to test the sensor, the specs are as follows, using a meter between pins 3 and 4 of the sensor. 3 and 4 are the 3rd and 4th from the left, with the connector tab facing up.

14 degrees - 7k ohms
32 - 5k ohms
50 - 3.5k ohms
68 - 2.2k ohms
86 - 1.5k ohms
104 - 1k ohms

I appreciate this info. Took a quick look and there is no dust at least on the outside slits. Shined a light and didn't see any visible dust behind the slits either. I'm gonna wait until it warms up to see if it behaves the same during A/C season. If it does, I'll open everything up for testing/cleanup.

Cabin filter is clean. Some peeps mentioned the blower motor resistor. When I turn the temp down, the fan speed also slows down. Wouldn't a bad resistor not respond/keep blowing on high?