2010 Honda Fit. A/C not blowing very cold..,.

[Hokiefyd]

I was mistaken. Our MDX has a 19,000 BTU HVAC system.

I disagree that a BTU rating on an automotive HVAC system is not helpful information. It gives a general idea of a system's performance. It won't tell you everything, but it at least tells you something. Like an engine's rated horsepower. One could make the argument that people don't need to know the horsepower, they just expect the car to accelerate sufficiently. Well...true. But a horsepower figure still gives one a general idea about a car's performance...and indicates how much reserve an engine might have when operated under heavier loads.

If you live in a hot area, and are looking at two cars, and one has a 15,000 BTU HVAC system and one has a 9,500 BTU HVAC system, it at least might give you a clue that the one with the larger system would perform better under severe conditions. That may not may not help make a purchase decision, but at least you are more informed going in.

 

[KrisZ]

My House has a 90,000 BTU furnace for heat, while a 24,000 BTU AC system is plenty enough to keep my house cool even on the hottest days.
Heating and cooling are two different animals.

 

[DBMaster]

24,000 BTU's would be called 2 tons in A/C parlance. For this area, that would be enough for a tiny house (1,000 sf max).

I didn't really say that the information wasn't helpful, just that I didn't care to know. Some of the cars I tested prior to the Mazda had more powerful A/C, but the Mazda's driving behavior was more to my liking. I guess you have to sometimes sacrifice, but I do plan to keep this in mind next time I buy a car.

Perhaps that is why my fuel economy does not seem to suffer noticeably when using the air. The compressor doesn't put as much load on the engine compared with one that has higher cooling capacity.

 

[DBMaster]

Using some knowledge I gained about variable speed blower motors on newer residential A/C units I realized something about how to maximize the effectiveness of my car's A/C. The faster you blow air across the evaporator coil the less heat and moisture will be extracted in one pass. I have actually been finding that, on hot, humid days, I can be more comfortable in the car keeping the fan speed on 2 (rather than 3 or 4). That's good because 3 gets pretty noisy and 4 is simply too loud and annoying.

 

[SteveSRT8]

Originally Posted By: DBMaster
Some of the cars I tested prior to the Mazda had more powerful A/C, but the Mazda's driving behavior was more to my liking. I guess you have to sometimes sacrifice, but I do plan to keep this in mind next time I buy a car.


I am sorry to tell you that not every car has this problem. My buddy Neil has a 2012 Malibu 4 banger that will grow icicles on your face in 95 degree Florida heat and humidity. And you cannot even detect the AC compressor engagement at idle outside the car when listening for it!

I've had plenty of small engined cars from the 80's and 90's in my stable when my kids were young and there is no need to think they can't have a blasting cool AC.

I don't even think that is typical of your Mazda...

 

[Hokiefyd]

Originally Posted By: DBMaster
The faster you blow air across the evaporator coil the less heat and moisture will be extracted in one pass. I have actually been finding that, on hot, humid days, I can be more comfortable in the car keeping the fan speed on 2 (rather than 3 or 4).


This is absolutely the case. I find the air conditioning to be most effective when run in recirculation mode and with only a moderate fan speed.

 

[DBMaster]

Steve, I know that not every car (or, even small car) has this problem. In fact, most of the cars I tested, with the exception of the Chevy Sonic, had more powerful A/C than my Mazda. I made the sacrifice for the overall driving experience. And, most people would find my A/C adequate. I live in Texas and keep my house 70-72 in the summer. Almost nobody does that. 78-80 is the norm. I have a weird metabolism that causes me to be quite "exothermic." Terms like "freezing," "cold," "hang meat," etc. as they relate to A/C performance are highly subjective. My vent temps are perfectly normal for a modern car A/C. I am just harder to please than the average person. Most people wrap themselves in blankets at my house, including my kids. My dad is the same way so it appears to be genetic.

I once visited NYC on business. I walked down the block from my hotel to pick up a sandwich. It was a brisk April evening, temp in the mid 40's. The natives wore winter coats, some hats, scarves. I was in a short sleeved golf shirt and perfectly comfortable. I know I'm not THAT unique, but that is weird.

 

[sciphi]

When was the cabin filter replaced last? I replaced the one in the Cruze, and gained a noticeable bit of airflow back. The old one didn't look bad, but was restrictive. The HVAC was noticeably better today than yesterday.

 

[DBMaster]

My car is only a year old and it has spent the vast majority of its time either in my garage, or the parking garage at work. With only 15K miles on the clock I don't think CAF is the issue. It is my need for chill v. the overall capacity of the system.

 

[JamesBond]

The '04 and '05 Hondas that I work on have a blue cable that runs from under the dash to under the hood and controls the heater control valve. This cable can stretch and cause hot coolant to enter the heater core at all times even when the temp is set to its coldest setting.

Measure the temp at the vents with AC off, fan on, and temp set to cool and see if its warmer than outside air when the car is warmed up. Or just pop the cable end off of the heater control valve under the hood and work the valve by hand to see if its moving its full range.

Adjusting the cable on my Civic made my AC performance go from so-so to great.

 

[gregoron]

Check the air coming out of the center vent with a kitchen thermometer. Stick it in the vent. Regardless of how hot it is outside it should be blowing between 50 to 60F at max setting. If not, have it checked at an AC shop since they use the proper gauge. Do not add a can of refrigerant in there as the amount matters. It should not be overfilled. Have them add refrigerant if necessary.

If it's blowing cold air and it's just underwhelmed, have your car tinted.

 

[SOHCman]

It's worth mentioning in any AC thread...

Use straight r-134a, no stop leak junk.

And when you just pump in a can from walmart, you are introducing air and moisture. The proper way would to first purge and apply a vacuum to the line by using a manifold Gage set with valves connected to a vac pump. You dont have to evacuate the whole system, just the lines if you are topping off.

 

[Hokiefyd]

Originally Posted By: DBMaster
I once visited NYC on business. I walked down the block from my hotel to pick up a sandwich. It was a brisk April evening, temp in the mid 40's. The natives wore winter coats, some hats, scarves. I was in a short sleeved golf shirt and perfectly comfortable. I know I'm not THAT unique, but that is weird.


I wear shorts all year. Even if it's in the 30s outside, I'm in shorts. Even in North Carolina, I stand out in a crowd during the "winter".

 

[Tosh]

Originally Posted By: DBMaster
Using some knowledge I gained about variable speed blower motors on newer residential A/C units I realized something about how to maximize the effectiveness of my car's A/C. The faster you blow air across the evaporator coil the less heat and moisture will be extracted in one pass. I have actually been finding that, on hot, humid days, I can be more comfortable in the car keeping the fan speed on 2 (rather than 3 or 4). That's good because 3 gets pretty noisy and 4 is simply too loud and annoying.

You are juggling the effects of three separate phenomena, and in effect prioritizing them in this order: wind chill effect on your skin, fan noise spectrum, and last, maximum cooling system efficiency. So, you are doing the opposite of "maximize the effectiveness of my car's A/C" from a technical pov in order to improve your overall personal comfort. Just keeping you honest.

 

[jrustles]

What happened to the OP?

Heres a story DBMaster you and others with not-cold-enough AC might appreciate:
I picked up a 95 Mazda 323 a few months back, and once warm enough, have been figuring this AC system out. It had sufficient charge of original 134 to keep the low pressure switch closed, but the evap was hissing. Classic sign of being low on charge (on TX valve systems). I love my non-halogenated refrigerants, and so I bought a can of RedTek alkane refrigerant. Dropped 3/4can inside, low-side pressure checks out, system cycling fine. Problem, doesn't get as cold as I'd like on heatwave days. Noticing that the compressor is cycling on and off, it appears that this high evap temperature is by design! I'm starting to notice that smaller cars seem to be programmed for warmer evap temps. bla bla bla f.fwd days later and I have the dash out and try opening up the EVAP box to clean it. After removing what seemed like a bushel of leaves, pine needles, sticks and boxwood maple seeds, finally get the evap cleaned up. Continue to poke around and spot the evap temp sensor. The Evap Temp Sensor simply tells the ECU when to shut the compressor off to prevent icing over. Most other cars, the sensor probe is clipped onto the evap directly in front of it (like a Honda Accord). In my Mazda, the probe was inserted right into the evap fins. I pulled it out and located it flat downstream, instead of inserted. The AC now blows a bit colder (still well above freezing).

So, the placement of the evap temp probe might have something to do with poor AC performance.



My remedy was not just relocate the sensor, but I'm now using a 3-stage electronic headlight leveling switch (option not available here), with the resistors changed to appropriate values and wired in with the Evap temperature sensor. Now I can choose three levels of "cold" for the evap, depending on if I want economical passive defogging, or heavy duty proactive cooling during heatwaves! Plus people will think I have electronic leveling headlights!

If you ever have a chance to get into the HVAC system, find out where your probe is