In my short tenure in the service department of my Honda dealership, I have learned that outside air temperature and HUMIDITY play a great part on the performance of the A/C. In very humid weather the condensation will rob the evaporator of "cold" by washing it down the drain tube and the water will insulate the air passing through the evaporator not allowing it to get a good dose of "cold". The hotter the incoming air a greater amount of "cold" is required to cool down the air. So if it is very hot and very humid, the performance of the A/C will suffer.

This could explain why the guys from AZ are having good luck with their A/Cs.

just my $0.02!

fredjeep

 

the previous 2 posts by homerwinzlow & fredjeep about humidity's effects on auto a/c are definitely very informative, i'm going to reread these several times. many thanks for presenting these views about how this can cause differences in the vent temps-auto a/c is really complicated for the layman. when i was told that 42 degs at vent is ideal, i left without asking "will this always hold true", now i know why my temps aren't quite that good. and as fredjeep mentioned AZ has low humidity & high temps so a/c's are working better there.

 

I just thought of another thing that will effect the performance of your A/C. When you are moving along at speed more air goes over the condenser and the "colder" the refrigerant will get. When you are sitting in traffic or just idling in the driveway, not much air will pass over the condenser. Honda adds an electric fan to their cars to assist when the car is not moving fast enough to make the "cold" cold enough. Not yet having my F-150, I am not sure if they have an assist fan like honda does.

My first question to one of my techs who explained how the A/C system works was "why not just put in a bigger more powerful A/C system?" Well that would be the obvious thing to do. Unfortunately, if the system cools to much it will freeze the condensation on the evaporator, clogging it and no air will pass through and the A/C will not cool any longer. Remember the A/C must dehumidfy the air when using the defroster in winter too. Trying to get the perfect balance between not enough "cold" and too much "cold" is hard to do. Especially in our great country, where we get it all, sub zero temps to scorching desert heat to sub-tropical jungle is a tough thing to do.

So if it is very hot, very humid and you are stuck in traffic, your A/C will not perform it's best. Just be thankful you are not in the Plymouth Sundance in the next lane with all 4 windows down, a/c that broke 3 years ago sweating like a...well a Plymouth owner.

Just my $0.02

fredjeep

 

I dont know if this will be the case for anyone else out there, but today I had an 04 F150 come in for poor AC performance, and I noticed upon opening the hood that the compressor was not staying on more than 35 seconds and shutting off with a hard snap to the compressor clutch, very hard and noticeable. So I hooked up the guages and found the high pressure was rapidly building up to 450 PSI and the compressor was cycling off with the high pressure switch. Upon inspection I found the fan clutch was barely spinning the cooling fan and no or little air flow was being provided across the condenser. I recommend that you check your cooling fans to see if they are drawing air across the condenser and throwing off lots of air behind it, especially those whom are getting very poor cooling at Idle.

 

what did the fix amount to on this, homer. sounds like your our a/c tech-do you work for a dealer?

 

All this talk about humidity is quite interesting. BUT.....Ringking lives in a desert state at an altitude where the air is very dry. So, how do you explain that? (Unless he's in Dixie where it's a lot more humid and less than 3,000 feet above sea level.)

I work for a large well known store chain and tend to the refrigeration systems for the produce and frozen foods warehouses. Our condensors (Baltimore Air Coils) are water bathed twenty-four/seven in addition to having six huge 8 foot fans to move air over them. This extracts a lot of heat.

But ringking says he gets 39 at the evap vent. Only thing I can think of is outside air is being mixed in somehow. (I was joking about the windows, RK)

 

Ive ordered a fan clutch for it. Ill let you know how it works out, and yes I am a dealer tech.

 

Pops, I appreciate your humor. Just had a bad day and the a/c topped it off.

I really think that this post has been the most informative that I have read so far dealing with a/c problems. I really understand the a/c unit much better now.

I drove on the freeway today (90 deg. outside) and my a/c about froze me out. That, to me, proves what everyone is saying about it working much better when you are traveling faster. One other thing that I have noticed, now that I have been driving the last few days with a thermometer stuck in my center vent, is that when the a/c is on a higher blower setting it tend to raise the temperature of the a/c output. When set to a lower blower speed such as #1 or #2 it cools down a couple degrees. I think my a/c temperature the last couple of days, in 90+ degrees, has been anywhere from 52 to as low as 38 degrees. I don't know if that helps any of you, who like me, turn it on full blast when you get in your truck after it has been sitting in the sun. Maybe try full blast for a couple of minutes and then set it to a lower blower setting.

Thanks to everyone for your posts.

This website/forum is awesome, keep all the info. coming.

 

i asked the a/c tech at my dealer about what control settings were best or if it made any difference when starting the truck. he said any of them that didn't have the recirqulation- such as max a/c because this would reuse the hot cab air at start and thus prolong the cool down . so if i understood him correctly, if the cab is hot don't start with max a/c since that uses recirq. automatically and on other setting don't push recirq button until cab is cooler. i guess everyone has noticed the recirq. mode goes off when you move off of max a/c and then you have repush that button to get to come on again-this is on the manual a/c unit.

 

Actually , the best thing to do when the cab is hot is to roll down the windows and purge the hot air for a bit. That can blow out as much as 40 degrees your a/c won't have to absorb and exchange.

Max a/c does recirculate the cabin air, and it's also the most efficient setting since it's re-cooling cooler air than that which is outside.

 

I agree with rljphx. I live in Tucson and you have no choice but to run AC all the time. Mine is cold and cools the truck in rapid fashion. In fact, often I have to turn it down. Bottom line is your AC is broken and the warranty covers you for a fix. There is no excuse for your dealer not to make it right. On a side note, I'm now getting 15.3mpg and am very happy. This is while running AC!!! I wonder what mpg I'll be getting when winter time comes around?

 

Thats what I do. I jumped in my truck yesterday and it was about 150 inside, so down went all the windows for a couple minutes.

Also bear in mind all those interior components have been absorbing heat all that time and they will be disappating heating for some time while your cabin air is being cooled, so the time to get stable interior temps will be directly proportional to how large the cabin space, amount of interior seating, carpeting, and interior trim, and how long it has been absorbing direct sunlight. Even color of material and its composition will affect your cool down times.

 

Yup, that's why I LOVE my white truck! I never thought it would make such a big difference, and I never thought I could appreciate white paint. Easier to keep clean, too.

I had my windows tinted in Salt Lake county, too. That's worth the money I paid. Now when I cruise back and forth between SLC and LA, most of which is scorching desert highways, I don't bake on one side and freeze on the other!

You can see those highways I drive. I shot these photos:http://community.webshots.com/album/39701976CnOkbE

 

I think the point about the trucks interior absorbing and retaining heat is an important. My FX4 with the black interior is still hot after driving 10 miles into the sun even though there is cold AC. I liked the idea of tinting the windows, but I'm only leasing right now.

This isn't saying that you don't have a problem. You have said that the temp coming out of the vent is cold, but what about the volume of air. Try comparing with a friends F-150.

Doc Holliday
400 miles and counting

 

I will try rolling down the windows and purging the hot air out and see what happens. The interior color is something I never thought about, mine of course is black so that certainly doesn't help.


Hey Pops, where did you get your windows tinted, what percentage of tint, and how much did they charge you? I had a 1997 F-250 LD and had the windows tinted. The problem was I always had trouble at inspection time. The tint shop said that they did it within state laws. I don't want to run into that trouble at inspection time again, so does anyone know that legal tint limit in Utah? Thanks again for all your helpful info.