Interesting A/C "problem"... give me your 2cents

[lostatlantis]

There's one annoying thing with my A/C... whenever it's hot outside (say 85F+) and I've driving around (city or highway, doesn't matter) for about 15 minute or so with the A/C on, the air would slowly decrease until it's very weak. It's still cold air coming out, but it's almost like the fan slowed down or something.

At this point, if I turn off the A/C and switch to vent, the air would gradually increase back to where it was. I'd say it's a pretty swift increase back.

I try to keep my air setting at "Low". By the way when the A/C air starts to decrease, I can temporarily correct it by increasing the fan setting. But it very quickly dies down and I would have to increase the fan setting more until it's maxed out.

BUT, if the outside temp isn't extremely high the A/C works perfectly.

Also, this A/C "dying" starts after 15 min or so in the heat.

Compressor issue?

[CDNFB]

Re: Interesting A/C "problem"... give me your 2cents

Your evaporator is icing up. That is caused by not enough pressure in the system, either from low refridgerent charge, or compressor failure. My FB used to do that until I got it recharged.

[lostatlantis]

Re: Interesting A/C "problem"... give me your 2cents

Your evaporator is icing up. That is caused by not enough pressure in the system, either from low refridgerent charge, or compressor failure. My FB used to do that until I got it recharged.

I am curious, can you explain how low pressure causes the evaporator to ice up? If there's not enough refrigerant in the system, wouldn't that mean a hotter evaporator and hence, less cool air produced?

How much did it cost you to recharge the system? Is an inspection for leaks usually included in the price? I am assuming there's a leak in my firebird if the refrigerant is indeed low, since the system is a closed one.

Appreciate your help!

[CDNFB]

Re: Interesting A/C "problem"... give me your 2cents

Because the pressure doesn't build up as high as it should, and the high pressure switch doesn't shut the compressor off. With the compressor always running the condensed water that collects on the evaporator starts to freeze.

With a normal running system when the pressure builds up to max, the high pressure switch kills the compressor and the system pressure then slowly bleeds down at which time the evaporator warms a bit and the water doesn't freeze, but runs off the evaporator. When the system reaches the low pressure threshold, the pressure switch re-engages the compressor and the cycle starts over again.

The evaporator will freeze if there is no compressor cycle or the cycles are extremely short because there is no time for the evaporator to warm to just above freezing.

[RAZOR Z]

Re: Interesting A/C "problem"... give me your 2cents

Just go to your local auto parts store and you can get a 1 1/2 pound canister of a/c recharger and the adapter with the gauge on it to put it in, should cost you less then $30 and you only need one can for a v6 firebird/camaro. Some of the brands also advertise that they will stop leaks too.

[CamaroJeff™]

Re: Interesting A/C "problem"... give me your 2cents

perhaps a clogged orifice tube? kind of a guess, but it could lead to problems like that.
if refrigerant level is up to par anyways.

[bah]

Re: Interesting A/C "problem"... give me your 2cents

perhaps a clogged orifice tube? kind of a guess, but it could lead to problems like that.
if refrigerant level is up to par anyways.

cant be that because he is claiming to have an airflow problem, no air flows through the ac system itself, just the evaporator

[CamaroJeff™]

Re: Interesting A/C "problem"... give me your 2cents

cant be that because he is claiming to have an airflow problem, no air flows through the ac system itself, just the evaporator

only reason i say that is if the evap is freezing up (possibly due to a clogged orifice tube) it would cause a lack of airflow. domino effect so to speak.
im no a/c tech but i know if that thing gets clogged your a/c stops working.

[CDNFB]

Re: Interesting A/C "problem"... give me your 2cents

Well, the clogged orifice tube would mean that there would be a redued rate of expansion for the evaporator, but the system high and low pressures would be normal, but the cycle would take longer, and that means the evaporator would have a chance to warm at the lower pressure, just prior to the compressor kicking in to raise the pressure (the start of the next cycle).

See, what you need to avoid here is a system that cannot create enough pressure to shut off the compressor or cause the cycles to become extremely short.

[97wht3800]

Re: Interesting A/C "problem"... give me your 2cents

its not a camaro but I was workink on this girls car and I checked the pressure and its at 100 which is way too high. How do I get the pressure out? I tryed stickin a long screw driver into the part you connect the bottle to but it didnt drop the pressure any suggestions?

[bah]

Re: Interesting A/C "problem"... give me your 2cents

97, was the car running? and you do not want to do that, dont go assuming unless you have a full gauge set, not just low side, ac isnt measured in pressure, its measured in the weight of the refrigerant

[97wht3800]

Re: Interesting A/C "problem"... give me your 2cents

Yah it was running with ac on full, I did gauge it and have done my car and my dads truck before w/o problems, but I went to measure it and it was all the way to 100 on the gauge I have, which is well into the warning area.

[bah]

Re: Interesting A/C "problem"... give me your 2cents

there are 2 pressures, you cant tell **** from just one, you need high and low side, bleeding the **** out wont help you, sounds like an expansion valve or compressor problem