"surging" HVAC fan and random heat...

Post by **clarkerussell** » 10 May 2019, 14:56

Hey guys,

My HVAC has started behaving badly... After running fine for a while the fan will slow down, then go up 100%, possibly blow some hot air, and then drop back down to normal, all in a span of about 5 seconds. Any thoughts on what could be causing this?

Post by **abscate** » 10 May 2019, 22:16

Two things to explore

If the cabin temp sensors get clogged ECC will be erratic

Sommerfeldt · Post by **Sommerfeldt** » 11 May 2019, 03:43

abscate wrote: ↑10 May 2019, 22:16 If the fangordses k

Covfefe?

- S

Post by **abscate** » 11 May 2019, 05:38

abscate wrote: ↑10 May 2019, 22:16 Two things to explore

If the cabin temp sensors get clogged ECC will be erratic

If the fangordses k

THis is what happens when you post after being up for 36 hours post red eye flight..

If the fan motor is giving up the ghost and dying, it will get erratic, too. Sometimes you will notice it changing as you brake and accelerate the car

Post by **clarkerussell** » 13 May 2019, 14:47

abscate wrote: ↑11 May 2019, 05:38
abscate wrote: ↑10 May 2019, 22:16 Two things to explore

If the cabin temp sensors get clogged ECC will be erratic

If the fangordses k
THis is what happens when you post after being up for 36 hours post red eye flight..

If the fan motor is giving up the ghost and dying, it will get erratic, too. Sometimes you will notice it changing as you brake and accelerate the car

Thanks goodness, I thought you had stroked out our something...

The fan is a noticeable item, but I'm equally confused by the surge in heat when it's been set to cool. I'm going to have to test the cabin temp sensor...

Post by **abscate** » 13 May 2019, 18:25

Try vacuuming it out first. The sensor has a tiny fan that pulls in cabin air to feedback to the ECC control unit. It often clogs up with pet hair and other detritus.

markone · Post by **markone** » 14 May 2019, 15:19

Where is the sensor located?

Post by **abscate** » 14 May 2019, 15:46

In a 1997, up near the grab handles on each side of the car near your ears

In 1998-1999 , it transitioned to a dash position , next to the heated third rear seat button to right of steering wheel,

Post by **clarkerussell** » 11 Sep 2023, 13:52

abscate wrote: ↑13 May 2019, 18:25 Try vacuuming it out first. The sensor has a tiny fan that pulls in cabin air to feedback to the ECC control unit. It often clogs up with pet hair and other detritus.

Following up on this... 4 years later...

I am still having the issue after cleaning the interior temp sensor. And the "surging" of the fan is not like the fan motor failing, but more like the HVAC controls changing it to high speed like it was trying to defrost or something.

yanga001 · Post by **yanga001** » 11 Sep 2023, 18:12

clarkerussell wrote: ↑11 Sep 2023, 13:52
abscate wrote: ↑13 May 2019, 18:25 Try vacuuming it out first. The sensor has a tiny fan that pulls in cabin air to feedback to the ECC control unit. It often clogs up with pet hair and other detritus.
Following up on this... 4 years later...

I am still having the issue after cleaning the interior temp sensor. And the "surging" of the fan is not like the fan motor failing, but more like the HVAC controls changing it to high speed like it was trying to defrost or something.

was about to say 2019 cant be 4 years ago but...

I once had HVAC controls in a manual climate control system begin to switch between AC, defrost, and other positions as a result of cold solder joints over 20 years. I reflowed the main joints to the control connector which rectified the issue.