A/c pumps hot air intermittently
Thread Starter
Newbie
Joined: Jul 2025
Posts: 11
Likes: 0
2013 A207
A/c pumps hot air intermittently
2013 E350 cab....Took it to a MBZ 3 rd party service shop and they could not find the issue. No codes and worked fine when hooked up to ac test. Was suggested it might be a pressure sw. or the compressor is on the way out. Spent a lot of money on diagnostics to get a non answer. Has anyone else experienced this problem?
thanks
Colin
thanks
Colin
Senior Member
Joined: Mar 2022
Posts: 267
Likes: 61
From: Chicago
Bi-Turbo E550 Coupe (W207)
Google Gemini AI Overview
A car AC blowing hot air can stem from several issues, with a low refrigerant level being the most common. Other potential causes include a faulty compressor, problems with the condenser, or electrical issues.
Here's a more detailed breakdown:
1. Refrigerant Issues: Refrigerant Leak: Leaks are a frequent culprit, causing the system to lose refrigerant over time and struggle to cool the air effectively.
Low Refrigerant Levels: Even without a leak, refrigerant levels can naturally drop, impacting the AC's cooling performance.
2. Compressor Problems: Faulty Compressor: The compressor is vital for circulating refrigerant. If it malfunctions, the refrigerant can't move through the system, resulting in warm air.
3. Condenser Issues: Blocked Condenser: Debris, dirt, or leaves can accumulate on the condenser, hindering its ability to dissipate heat and leading to warm air.
4. Electrical Issues: Blown Fuse, Faulty Wiring, or Relays: Electrical components play a crucial role in the AC system. Problems with these can prevent the AC from functioning correctly.
5. Other Potential Issues:
Clogged Air Filter: While less common, a dirty air filter can restrict airflow, making it feel like the AC is blowing hot air.
Thermostat Settings: Ensure the thermostat is set to "cool" and "auto".
Broken Cooling Fans: Fans help cool the condenser and evaporator; if they're broken, it can affect cooling performance.
Clogged Expansion Valve: This valve regulates refrigerant flow, and a clog can disrupt the cooling process.
A car AC blowing hot air can stem from several issues, with a low refrigerant level being the most common. Other potential causes include a faulty compressor, problems with the condenser, or electrical issues.
Here's a more detailed breakdown:
1. Refrigerant Issues: Refrigerant Leak: Leaks are a frequent culprit, causing the system to lose refrigerant over time and struggle to cool the air effectively.
Low Refrigerant Levels: Even without a leak, refrigerant levels can naturally drop, impacting the AC's cooling performance.
2. Compressor Problems: Faulty Compressor: The compressor is vital for circulating refrigerant. If it malfunctions, the refrigerant can't move through the system, resulting in warm air.
3. Condenser Issues: Blocked Condenser: Debris, dirt, or leaves can accumulate on the condenser, hindering its ability to dissipate heat and leading to warm air.
4. Electrical Issues: Blown Fuse, Faulty Wiring, or Relays: Electrical components play a crucial role in the AC system. Problems with these can prevent the AC from functioning correctly.
5. Other Potential Issues:
Clogged Air Filter: While less common, a dirty air filter can restrict airflow, making it feel like the AC is blowing hot air.
Thermostat Settings: Ensure the thermostat is set to "cool" and "auto".
Broken Cooling Fans: Fans help cool the condenser and evaporator; if they're broken, it can affect cooling performance.
Clogged Expansion Valve: This valve regulates refrigerant flow, and a clog can disrupt the cooling process.
Senior Member
Joined: Mar 2022
Posts: 267
Likes: 61
From: Chicago
Bi-Turbo E550 Coupe (W207)
Now that I gave you AI feedback, here's my personal feedback from having AC issues with my E550. It could be that the refrigerant is slowly leaking. I had to have my AC system "sealed" through one of the car ac sealant cans then recharged with refrigerant and has worked fine ever since. Also check that the compressor isnt freezing, I think mine might need replacing soon. I noticed so much water underneath my vehicle after I drive it so probably means the compressor is getting frozen however I am still getting AC so I'm just basically living on borrowed time.
Last edited by ibbij; Jul 30, 2025 at 10:17 AM.
Super Member
Joined: Sep 2017
Posts: 738
Likes: 163
From: Orlando, FL
2016 E400 Coupe (C207)
You didn't give any indication as to how you define "intermittent" (e.g., every other day, twice a week, once a month, etc.). For several years now, my AC has intermittently blown hot air for about 10-15 seconds and then the output turns cold again. This only happens once every few months, so maybe once or twice each summer. I took it to the dealer the first time it happened (the car was then still under CPO warranty), and they found no codes and no other apparent cause.
Thread Starter
Newbie
Joined: Jul 2025
Posts: 11
Likes: 0
2013 A207
sometimes when turning ac on blows hot for 5 min to 1 hour or longer , turning eng off, ac off , auto off selecting full hot then full cold sometimes resets system...happens about 20 % of the time...no leaks , no codes shown, no elect issues found nor clogged filters???
thanks
Colin
thanks
Colin
Junior Member
Joined: Mar 2012
Posts: 35
Likes: 6
From: Treasure Island, Florida
2011 E550 Cabriolet
I had a similar problem with my 2004 CLK500 convertible, which I later traded for an 2011 E550 cabriolet. Don't know if MB used a similar bit on the A207, but here's a link about that. It was maddening to figure out.
https://www.benzworld.org/threads/th.../#post-5249126
https://www.benzworld.org/threads/th.../#post-5249126
Last edited by RealDonn; Jul 31, 2025 at 10:29 AM.
Member
Joined: Nov 2024
Posts: 152
Likes: 43
From: New Jersey/Philly
2010 E350 Coupe
I had this problem for the 1st 6 months or so when I 1st got my coupe. No faults, electrical issues, etc at the time. I bought a can of refrigerant (the A/C Pro) & it showed the system had no loss via the pressure tester built in to the cap of the refrigerant can.
I returned the can & did 2 things that worked.
1.) Short term fix was to wait until the car reached operating temp before switching the A/C on. It always blew cold this way.
2.) I started cleaning the system with Kool-It evaporator & system cleaner once a yr towards the end of summer. Was it actually that simple? Well, the notorious musty smell was gone (which the car had when I 1st bought it) & my A/C hasn't blown hot in over 4 yrs now. I also can put the A/C on right away & it still blows cold which it never did the 1st spring & summer I had the car.
I returned the can & did 2 things that worked.
1.) Short term fix was to wait until the car reached operating temp before switching the A/C on. It always blew cold this way.
2.) I started cleaning the system with Kool-It evaporator & system cleaner once a yr towards the end of summer. Was it actually that simple? Well, the notorious musty smell was gone (which the car had when I 1st bought it) & my A/C hasn't blown hot in over 4 yrs now. I also can put the A/C on right away & it still blows cold which it never did the 1st spring & summer I had the car.
Trending Topics
Senior Member
Joined: Jul 2008
Posts: 296
Likes: 65
2015 E400
You didn't give any indication as to how you define "intermittent" (e.g., every other day, twice a week, once a month, etc.). For several years now, my AC has intermittently blown hot air for about 10-15 seconds and then the output turns cold again. This only happens once every few months, so maybe once or twice each summer. I took it to the dealer the first time it happened (the car was then still under CPO warranty), and they found no codes and no other apparent cause.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Thread Starter
Newbie
Joined: Jul 2025
Posts: 11
Likes: 0
2013 A207
Thanks everyone, summer is almost over in canada so not an issue now but manual calls for a coolant replace soon so will get them to check again at that service. Does not happen often but is inconvenient when it does happen and am going out for a nice drive on a sunny hot day when I leave the top up. Hope I can get to the bottom of it.
cheers , happy motoring
Colin
cheers , happy motoring
Colin
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
