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Weird HVAC blower problem


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Heuschrecke
Novice
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Aug 11, 2020, 9:04 PM

Post #1 of 12 (312 views)
Weird HVAC blower problem Sign In

 Can anyone here explain this weird problem my 2011 Charger's HVAC blower is having?—or direct me to a forum that might explain?
I just went on a 22-hour trip from Virginia to Florida and back again. As I drove, the air-conditioned airflow from the vents slowly lessened so that after a period of about an hour-and-a-half, there was no airflow at all. I could still feel coldness when I put my hand right up to the vents, but nothing was actively *blowing* out. (The trip was in 90'F+ weather, so loss of blown cold air very unpleasant.)
Here's the weird part:
If I stopped driving, to park at rest area or gas station, then over period of about 10 minutes, the airflow from vents would slowly increase until it was full-blast again. This 10-minute blower "recovery" happened regardless of whether I shut off car's engine. (On trip, we ended up stopping and parking somewhere every 90 minutes just to "recover" the airflow.)
What would cause the blower to slowly fail over ~90 minutes when driving, and then recover over ~10 minutes when engine idling or off?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Aug 12, 2020, 2:45 AM

Post #2 of 12 (301 views)
Re: Weird HVAC blower problem Sign In

Super high humidity part of the issue. That's classic for icing up you may have seen a large puddle of water under it when taking a break then would see nothing after using A/C for a while.
The reasons include:
*Low charge from a leak.
*Restricted airflow over evaporator can be clogged cabin air filter?
I'm unsure if both CCOT and X-Valve set ups were used in these the first is "Cycling Clutch" type is set to stay on too long somehow can do that the second low charge the first sign is Expansion valve types open and close a nozzle for flow to prevent that.


So: Run it now see if you see frost or ice on return lines Underhood then decide if you want to take it on or send it out highly suggested as it's not an easy thing to diagnose WHERE the exact problem is then be equipped to do it without making it worse is or can be a disaster for you,


T



Hammer Time
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Aug 12, 2020, 3:28 AM

Post #3 of 12 (295 views)
Re: Weird HVAC blower problem Sign In

Tom is right. The evaporator is icing over so no air gets through it. There are a number of things that can trigger this.
This is an expansion valve system so it has a temp sensor right in the evaporator that could be bad among other possibilities.

Some ways to try to avoid this until you find the problem is to run the blower on higher speeds and if you need to regulate the temp, do it with the temp control and not the blower speed. Lower blower speeds make the evap run colder.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Heuschrecke
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Aug 12, 2020, 11:29 PM

Post #4 of 12 (248 views)
Re: Weird HVAC blower problem Sign In

Thank you for your advice, Tom.


Tom Greenleaf
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Aug 13, 2020, 2:36 AM

Post #5 of 12 (236 views)
Re: Weird HVAC blower problem Sign In

'Welcome and good luck with fix. BTW this site can be goofy, your post showed 3 times it goes thru on 1st try despite what it said?
Problems A/C are usually a leak but not always. This smacks of low charge caused icing both performance of cold air with low flow. The job if you don't wait forever is just find and fix the leak is a job sometimes it's slow so harder to find.


If you really want and need it to work long term get help or you'll need a novel as it's a trade to do this stuff worth it now more costly later if you wait and want it to work properly - just know that.


Good luck with it IMO the common issue doesn't mean this one is an evaporator leak which is involved should seek proper help to not destroy whole dashboard in fixing one is replacing it labor more than the parts.


Clue if still working at all is finding oil evidence in the melted water if new when you shut it off or oily where it drains a dead give-a-way still better to know that ignore it,


Tom


Heuschrecke
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Aug 13, 2020, 8:33 PM

Post #6 of 12 (206 views)
Re: Weird HVAC blower problem Sign In

Yes, when I tried to post reply I kept seeing "504 Gateway Timeout" error in my browser, so I thought reply hadn't been registered; I tried 3 times.

I've found that cabin air filter is significantly clogged with debris. I'll replace filter. Also, refrigerant seems to be low, so I'll fill refrigerant. (I had brought car for "check up" at mechanic before my long trip, so I'm surprised they didn't report those problems.)

If filter and refrigerant don't permanently fix problem, I'll definitely bring car to professional mechanic so I don't destroy my dashboard (as you warn). I hope I don't have serious leak.

After your advice, I have much better ideas about what might be wrong.

Thank you again for the advice, Tom and Hammer Time.


Heuschrecke
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Aug 13, 2020, 9:13 PM

Post #7 of 12 (201 views)
Re: Weird HVAC blower problem Sign In

And yes, I did see large puddle of water whenever we stopped driving on trip.


Tom Greenleaf
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Aug 13, 2020, 9:36 PM

Post #8 of 12 (191 views)
Re: Weird HVAC blower problem Sign In

That's actually very encouraging news and do now think the filter is it and quit at that or recharge the car from a well held vacuum. Seriously, you don't want to use one of kits with gauge on can things and mess this all up if anything start over with exact amount listed on the car or best 3 listed guesses you find that match I do recall 32 ounces but don't go by me or that either.


It's makes "water" or condensate so it's probably OK just watch now for it dripping if so that's good news it's close most of the time unless remarkably dry air RH or say reads in mid 40s center vent when on for a while in realistic temps moving along.
Good luck this may be all set now!


Tom



Hammer Time
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Aug 14, 2020, 4:07 AM

Post #9 of 12 (173 views)
Re: Weird HVAC blower problem Sign In

You should never attempt to simply "top off" refrigerant. It is important to have the exact amount of charge and the only way to do that is to completely evacuate and recharge the system using a measured charge.

If it does in fact resolve the freezing problems, then you have to look for the leak or it will be happening again. The dash evaporator Tom referred to is only one possible leak source and the hardest to repair.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Heuschrecke
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Sep 1, 2020, 11:05 PM

Post #10 of 12 (108 views)
Re: Weird HVAC blower problem Sign In

Greenleaf & Hammer,

A couple weeks after I changed cabin air filter, I have not noticed any diminishing of airflow as I had before. So, again, thank you.

One thing that I do not understand and that has been puzzling me:
Why did evaporator only freeze up while I was driving? On long trip to Florida, if airflow stopped, we could park while leaving engine and A/C on, and airflow would resume. With A/C on during both driving and parking, why did evaporator freeze only during driving?

Thanks &
Best Regards,


Hammer Time
Ultimate Carjunky / Moderator
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Sep 2, 2020, 4:23 AM

Post #11 of 12 (93 views)
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Because it takes extended use for it to freeze up, especially if the blower speed is turned down once the car cools. The compressor continues to run and eventually the evaporator becomes a complete block of ice and no air gets through it.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
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Sep 2, 2020, 4:51 AM

Post #12 of 12 (87 views)
Re: Weird HVAC blower problem Sign In

Right. Thought I said to look for water dripping when humid enough. Those still cool for a while before too much ice if that. They usually leave a huge puddle when you shut it down as parked if you notice that. Look for dripping if not it's still icing just slower to quit on you, Tom






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