Interesting new issue...erratic HVAC
Thread Starter
Member
Joined: Nov 2016
Posts: 114
Likes: 25
From: SoCal
2009 SLK 55, 2010 ML350
Interesting new issue...erratic HVAC
Well, I spoke too soon.
Started a few weeks ago as it got hotter here in SoCal. The car stalled inexplicably in a car wash, and it's never done that. First symptom.
Every once in a while, after a cold start, will surge a couple times when maneuvering in the parking lot. Mild annoyance. Second symptom.
Third symptom, AC is freezing cold, but randomly decides where the air is coming from. Generally, I leave the AC in the blow in face configuration with maybe the floor vents opened as well.
What it does now is divert all air to windshield vents and driver/passenger window vents. No center flow at all. HVAC head unit airflow Lights disappear and it just does what it wants for a bit. Eventually it will change back to regular function, (sometimes after messing with the auto feature, sometimes after driving at increased speed) but will soon revert to the weirdness ad infinitum. No stored codes.
Vacuum leak? HVAC unit having a stroke? Electrical failure? Any ideas? I searched a bit and did not find any threads with this exact problem...most had either a concurrent temperature issue or appeared to be a passenger diverter problem. This is erratic and seemingly software or vacuum correctable. Has anyone else had this specific issue?
Started a few weeks ago as it got hotter here in SoCal. The car stalled inexplicably in a car wash, and it's never done that. First symptom.
Every once in a while, after a cold start, will surge a couple times when maneuvering in the parking lot. Mild annoyance. Second symptom.
Third symptom, AC is freezing cold, but randomly decides where the air is coming from. Generally, I leave the AC in the blow in face configuration with maybe the floor vents opened as well.
What it does now is divert all air to windshield vents and driver/passenger window vents. No center flow at all. HVAC head unit airflow Lights disappear and it just does what it wants for a bit. Eventually it will change back to regular function, (sometimes after messing with the auto feature, sometimes after driving at increased speed) but will soon revert to the weirdness ad infinitum. No stored codes.
Vacuum leak? HVAC unit having a stroke? Electrical failure? Any ideas? I searched a bit and did not find any threads with this exact problem...most had either a concurrent temperature issue or appeared to be a passenger diverter problem. This is erratic and seemingly software or vacuum correctable. Has anyone else had this specific issue?
Thread Starter
Member
Joined: Nov 2016
Posts: 114
Likes: 25
From: SoCal
2009 SLK 55, 2010 ML350
You must check for codes with a scanner. If you do not have one, buy this one.
https://www.amazon.com/Autel-AP200-B...ps%2C78&sr=8-3
https://www.amazon.com/Autel-AP200-B...ps%2C78&sr=8-3
I checked all the vacuum lines and removed/dressed gaskets//replaced air cleaner assembly which helped with surging idle problem. What it appears to be is voltage related as it happens more at idle and after short trips. This makes me suspect a battery or alternator related issue. The secondary battery was recently replaced, but I believe the primary battery is the one the car was delivered with when originally purchased.
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Joined: Feb 2017
Posts: 2,325
Likes: 1,221
From: Baltimore County, MD
'13 s212 63 p30. '06 LX470
It sounds like this all started with a car wash. Where was the water shooting just prior to the stall? Time to inspect modules that control these operations. When manufacturers starting putting modules lower in the cart an in the possible path of water infiltration the incidences of this increases. Also may sound silly but check your sunroof drains and anything effected in those areas prone from a clogged drain.
good luck.
good luck.
Thread Starter
Member
Joined: Nov 2016
Posts: 114
Likes: 25
From: SoCal
2009 SLK 55, 2010 ML350
So, went to the dealer for the recall after r/r the upper engine cover/airbox and dressing the gasket with Gummi Pfledge, and had them take a look at the HVAC, battery, and vacuum systems.They were unable to recreate the problem, and of course, now I have no check engine light, but the AC still has a mind of its own. It is definitely voltage related as it is more prevalent chugging about town and in the low rpm ranges, but all systems checked out at the dealer. I am baffled.
I think I'll just replace the battery and see what happens.
I think I'll just replace the battery and see what happens.
