The HVAC is VERY slow to reduce heating the cabin if it is below 40 degrees upon the start of a drive. Here is how my car performs: I set the temp at 70 in auto mode, on a cold day. The car heats quickly, so that in less than ten minutes, I'm roasting, but the fan is still on high and hot air is flowing. Hence, I need to set the temp down to about 64 or 65 to avoid super-heating the cabin. BUT, if I am taking a drive of over 30 to 40 minutes, I must continue to increase the setting up to about 76. On a multi- hour drive at below 40 degrees, the final setting is 76 to 77 degrees. In other words, the system is VERY SLOW at recognizing the cabin temperature, thus, it grossly overshoots the set temperature. The most confusing aspect of this is that the problem is far less noticeable when the outdoor temp is hot and A/C is needed.
The dealer has looked at it twice and insist that it works fine. However, they gave me a CRV loaner and the HVAC worked perfectly. Also, I will add that I have driven over 10K miles in at least 9 different cars with auto HVAC (going back into the '80s) and this is the only car that has performed this poorly. Surely this can't be the way the HVAC is designed to perform? Anyone else have this problem?

 

What year accord are you driving?

 

2018 Sport 2.0T manual.

 

I don't have a shop manual for the 2018 accord. You can try stopping by a parts store to see if their scanner can read HVAC codes. Search online for self-diagnostic codes for hvac or a/c system. You can look in your owner's manual to see if the navigation system has a way to display hvac codes.

 

While I appreciate you willingness to help, it seems that you must have a VERY dim view of the competence of Honda dealership techs? I am 99.5% confident that they have correctly searched for any codes. If it were something that would through a code, I'm sure they would have found and fixed it by now.

 

I typically post assuming someone wants to DIY the fix. The hard part of modern vehicles is that you almost need to see live data from the HVAC control unit and/or the PCM to figure out what (if anything) is messing up. I'd say something is not functioning properly with your system

Have you had this issue the whole time you had the car, or something more recent? Any work done on the car before this issue happened? When dealing with hot outside temps, does the climate control properly cool the car to the set temp?

I'm not sure if something like a Bluedriver OBD2 scanner can see that data if you want to troubleshoot. I'd look at the cabin air temperature as seen by the HVAC or PCM and maybe it will show blend door operation.

 

I purchased the 2018 in January of 2021, BUT it only had 1900, yes 1900 miles on it.
Yes, from the very first winter drive, the HVAC "auto" function has been terrible, as described.
As I mentioned, the problem SEEMS to be less dramatic when cooling is required. This is one of the more confusing aspects of the issue. Having said that, cooling is very different than heating for a few reasons. For example, when getting into a sun drenched, hot car, it can easily take a full 20 minutes before the fan speed should begin to reduce. In contrast, even if it is 20 degrees, the cabin will be up to temp well before 20 minutes has passed.
While I am a very observant person, it is possible that I just have not been as perceptive during summer drives as opposed to winter drives. The heating problem is obvious and unmistakable, the cooling performance is definitely less so.
Again, the dealership has checked this out twice, and they just think I'm a nut. Regardless, I was even happy with the HVAC performance of the CRV loaner, as well as nearly a dozen other vehicles over the years, so I know it's not just me.