Why is air conditioning not as cold at idle

I have noticed that while stopped the air does not blow as cold as when at speed,is this a sign of a problem with the system, low refrigerant.
I live in Dallas, At speed it blows very cold. Is there a way to check the system is there a viewing glass to check for air bubbles, I was under the impression that if bubbles were present it had a leak and needed refrigerant.

What year NSX?

With the newer refrigerant, you can buy a can of it for $10 -$15 in Pep Boys that includes a charging gauge. As long as the car is simply a little low on refrigerant (vs a major leak or air in the system), that's an inexpensive way to check and top up the refrigerant.

I too have notice this in my 1993 model, even after topping off the system. I agree with the prior response that you can easily top it off by using a can of refrigerant and a simple pressue gage that you can buy at your auto parts store. The gage shows the required pressue in lay-mans terms (green/yellow/red). I too live in texas and understand the need for air-cond, windshield sun screens, and car covers. The sun is brutal on a red exterior (fading) with a black interior (cracking).

It also may be due to the thermal efficiency of the condensers. When you are stopped, the only airflow over the condenser fins is provided by the electric fans. At speed, you have a steady and strong airflow, which carries more heat away from the fins, giving you cooler air temps. I replaced my compressor last year and recharged full with R134 and my car does the same thing as yours. Less cool (but still cold) when stopped, ice cubes when rolling.

Check your condenser fans, too. I think blowing the fuses has been mentioned before.

There are multiple reasons for this and it applies to most cars.

First there is no air flow over the condenser coils so the heat of rejection is minimized. In other words, the A/C system can't reject enough heat so it becomes less efficient.

Secondly, your compressors are driven by your engine. If you are idling then the compressors are not being driven hard. You can rev your engine up to higher RPMs and see if you notice the air get slightly cooler.

Low freon will manifest itself across all operational conditions so if you have a leak or are running low you'll notice decreased overall performance both at idle and at speed. Again, this is inherent to most all vehicles.

rbirling said:

Check your condenser fans, too. I think blowing the fuses has been mentioned before.

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+1 there are two fuses up front for the fans, check both of them.

instead of opening the hood, pulling the cover off the fuse box housing finding which fuse it is then pulling it checking it, put the fuse back, put cover back on close hood.

all you have to do is turn car on turn on AC, put your head near each front wheel( driver/pass) and hear the fans going, if they are turning the fuses are fine. I am all about less work. LOL

Thanks for all the responses, The car is a 91 but was converted to 134 refrigerant which is a good thing, I think I'll pick up a can this weekend

Check the condensor fans before you do anything else.

And you mention 134 being a good thing , not really since r12 is colder.

angus said:

And you mention 134 being a good thing , not really since r12 is colder.

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I believe he means because R-134a is a HFC refrigerant, rather than R-12 which is a CFC. That would make R-134a a "environmentally friendlier" refrigerant than R-12. R-134a has a near 0 ozone depletion potential (ODP), and global warming potential (GWP) of about 1,320 (100 yr values). Compared to R-12 which has an ODP of 1.0 and GWP of about 10,720. Also, since CFC's (like R-12 and R-22) are no longer being produced, the availability of it will eventually diminish and get harder and harder to find.

I just checked both condenser fans in the front of the car only one is running at idle. Are they set up to kick in at different points? speed, temp. I assume they are not on the same breaker do they each have a dedicated breaker, and where is it located there are breaker boxes everywhere.

Edresh said:

I just checked both condenser fans in the front of the car only one is running at idle. Are they set up to kick in at different points? speed, temp. I assume they are not on the same breaker do they each have a dedicated breaker, and where is it located there are breaker boxes everywhere.

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No, they should both run at idle. There are two fuses under the hood in front that control these fans. Lots of people (myself included) have had one blow and go undiagnosed for long periods of time.

This is the thread should help you

Both fuses are OK, and only one fan runs when i jump the green and white lead on the relay to ground. next step is to see if there is power to the fan.
to be continued tomorrow,

the fan may be bad to. they should spin with a touch of your hand. if the one that is not spinning if you try and turn it and it doesnt move much then the motor may be bad, or

if you hit somthing like a speed bump to fast you might have bent the under cariage so now the fan isnt balanced and will not spin till you bend the housing back so the blade is now balanced.

but check the Voltage and consult your Service manual to see what it should be at Idle,

another thing get that can and try topping off the refrid.

hope this helped

HEY!!! Both fans are working, I haven't a clue what was wrong, removed the fender liner and plastic shroud behind the condenser fan in order to access the fan plug, there must be a plug under the hood that allows easier access than removing all the wheel well liners??? If there is I gave up looking for it and went to the source. Anyhow it was either a loose connection or part of the shroud was impeading the fan ??? Bottom line both fans work fine. Thanks for everyones help, I'll monitor the fans this summer:smile:

glad we could help.

Edresh said:

HEY!!! Both fans are working, I haven't a clue what was wrong, removed the fender liner and plastic shroud behind the condenser fan in order to access the fan plug, there must be a plug under the hood that allows easier access than removing all the wheel well liners??? If there is I gave up looking for it and went to the source. Anyhow it was either a loose connection or part of the shroud was impeading the fan ??? Bottom line both fans work fine. Thanks for everyones help, I'll monitor the fans this summer:smile:

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Nice! :biggrin:

Vega$ NSX said:

I believe he means because R-134a is a HFC refrigerant, rather than R-12 which is a CFC. That would make R-134a a "environmentally friendlier" refrigerant than R-12. R-134a has a near 0 ozone depletion potential (ODP), and global warming potential (GWP) of about 1,320 (100 yr values). Compared to R-12 which has an ODP of 1.0 and GWP of about 10,720. Also, since CFC's (like R-12 and R-22) are no longer being produced, the availability of it will eventually diminish and get harder and harder to find.

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I think still running R-12 is a good thing. My car is now 18 years old and still the A/C works fine, it is a closed sealed system, so if it doesn't leak, it can't hurt the environment. I've never had a fridge need charging, I've never had my home air conditioner need charging. I think our government went overboard banning CFC's. I agree with the ban of using it as a propellant in spray cans, but sealed systems I think should have been left alone.

nsx4fun said:

I think still running R-12 is a good thing. My car is now 18 years old and still the A/C works fine, it is a closed sealed system, so if it doesn't leak, it can't hurt the environment. I've never had a fridge need charging, I've never had my home air conditioner need charging. I think our government went overboard banning CFC's. I agree with the ban of using it as a propellant in spray cans, but sealed systems I think should have been left alone.

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No real argument here. Just pointing out the factual numbers.

However, I can see the impetus behind the government's thinking. Think macroscopically rather than microscopically. When refrigerators are junked, very rarely is the refrigerant properly recovered and is just released into the atmosphere. Same with cars. Then multiply it by hundreds of thousands of junked A/C systems per year and that is a lot of released refrigerant. Not to mention, I just got out of a 35,000 ton central plant that uses several tons (not pounds) of refrigerant. A "leak" in that system will spew several thousands pounds of refrigerant into the atmosphere. Now multiply that by a couple dozen buildings in just Vegas alone and you can get a scale of just how much refrigeration is used. Refrigerants used by the automotive industry is literally a grain of sand in a bucket as compared to all of the other industries. The move was driven by the other larger consumers of refrigerant and the auto industry was just swept up in the move.

Air flow through the condenser, Most cars ac work better when your moving.

Anyone tried using an uprated fan for better cooling during traffic jam ?

I have not noticed to much of a difference between r12 and r134a. I have been able to get both to about 34 degrees on numerous cars and you really don't want to let the system go below 36 degrees because the evaporator can freeze

Wowow said:

Anyone tried using an uprated fan for better cooling during traffic jam ?

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I am not sure how your would up date the condenser fans with the limited space available.