Hey guys, this is my first post, so forgive me if I lack any etiquette common around here, I will learn I promise! I am the boyfriend/mechanic of a proud Honda Fit owner, and I am stumped on this one. Here is the issue my girlfriend is having:

Her AC is cold when we are on the freeway, but it blows "room temp" when we are on city streets or idle. My first thought was condenser fan, but it seems its just radiator fans on these cars, and they are both blowing (well... sucking) fine. So I took the car to a shop to have the freon evacuated and recharged, they also pressure and leak tested the system, and tested compressor functionality, all was well. The service adviser's conclusion was that it is summer and "These small cars take longer to cool off when it's 105* outside". This was not an issue last summer, so please tell me someone has an idea besides "its hot outside".

Additional info, it's a 2009 fit, base model. AC fan blows strong at all times, just not cold.

Thanks for your time, and any suggestions offered.

 

If you are bringing in 100% outside air with 105 deg. outside temp. normally expect about a 35-40 deg. drop in vent temperature. If you are operating in recirculation mode (just cabin air and no outside air) you should expect slightly lower temps. Have you measured the temps at the center vent and compared freeway vs city driving? Have you checked the condition of the cabin filter recently? When the car was recently recharged did they charge by weight method or pressure method ? Amount of charge is only 13.1 to 14.8 oz on this car.

 

This is both with Recirc on and with fresh air. I have not taken measurements of the air coming out, other than just the "feel" test. I suppose I could pick up a laser thermometer or something. The cabin filter was changed within the last 5000 miles (not sure her exact mileage right not, but I know it was part of her last service, and it wasnt too long ago). As for the method they used to recharge the system, I am not sure, sorry. Are both methods used by professional shops? I figured they all went based on weights, I guess I learned something new today.

 

The low speed performance on the AC is not all that great on these cars. More cooling takes more horse power. That said, if it ran cooler before then I guess something is wrong. I do not have a good guess for you. If you want to quantify your observations with numbers measure of the AC output temperature. Go to Walmart in the housewares section and buy a $10.00 digital cooking thermometer. Stick it in the center vent and you will be able to monitor what the temperature is of the air coming out of the evaporator (plus a few degrees).

45 degrees or lower is a good number running down the road. You should never go below 39 or 40 or your evaporator will freeze up. You probably will not reach those numbers idling unless it is cool outside.

Also make sure that your condenser is not plugged up with bugs and dirt.

Today most shops charge the AC system by weight. That works 90 - 95 % of the time. Occasionally you have to throw a set of gauges on one to fine tune the R-134 charge. It does not have to be off by much to cause a problem.

At an idle with the AC and fan on full, is the compressor cycling or is it on all the time? I would expect it to run almost continually at a idle.

 

That's all good advice from n9cv. I have an analog thermometer that I purchased at AutoZone for around $6 and it works fine. It has a round dial with a probe so you can insert it in the a/c vent, center vent is best. I typically get 40 deg. temps from my 09 Fit on 95 deg days and high humidity days running in recirc mode. Given the 105 deg temps that you have really taxes the a/c system for a Fit. Most pro shops use a combination unit that reclaims, vacuums, and recharges the system based on weight. These units are not cheap and small shops may not have one of these units. If the shop diagnosed your a/c problems properly and then found no leaks after pulling a vacuum and recharging correctly I can't offer any other advice.

 

Well thanks for all the great suggestions guys. I did not get a chance to check the cycling of the compressor. The mystery problem has disappeared for the past few days. So I'm hoping it stays gone (even though I know better), but it is still 100* out here, so I don't know what to think. I might go buy a thermometer for the vents just to have on hand, so I can give better info if a problem ever pops up again. I will also take a look at the condenser fins just to make sure it isn't all clogged up with debris. Thanks again for your time and assistance, and if the problem comes back, so will I.

 

My 09 does the same thing , It seems many people living in hot climates have problems with their AC's.

I have a meat thermometer that I leave in the vent and it does blow colder when the engine is at higher rpm than idling.

I just figured this was because the compressor is driven from the engine, not sure if this is correct though.

Tinting the windows seemed to help a bit in keeping the temp down and I always use a sunscreen on the windshield so the ac doesnt have to work as hard to cool the car.

 

I've had a meat thermometer in my vents for some time to monitor vent temperatures and have noticed this issue as well.

I think what it is, is that the ECU uses a higher temperature to determine when to cycle the compressor on at low idle in order to conserve fuel.

The hack I've found to get around it is put the car in neutral when stopped and idle the engine to around 1500 rpm. Vent temperatures then go back down.

 

You could also do what i did and solder a variable resistor in parallel with the evap sensor. Then you can trick the ecu into thinking the evap is hotter than it really is and fine tune the exact coldness with the variable resistors. Doing that made my idle AC very powerful.

 

Check to see if your AC fan is operating at idle, while you are at it heck your engine cooling fan for normal operation.

I recently noticed the same thing about my AC and my over temp light would come on if I was idling with a hot engine (stuck in traffic), turns out There a problem in my Main Fan Circuit (fuse 30). I am currently working on fixing the issue.

// EDIT: I just found that my radiator fan is blowing the circuit which prevents my AC Compressor fan from coming online.