How to make ac better

[dakta1420]

Hey guys so on my 98 sl2 it's a fun car to drive but I hate the ac. It works. But it's not as good as the honda or the dodge truck I own. The compressor was replaced last year with a used one seems to work fine. But it just not cold enough or powerful enough. I wish it blew harder and was colder. The ac at idle is 55 degrees but while driving it goes down to 45 the honda and truck are 45 at idle and 40 when driving. How can I lower the idle temp. I know it has a variable displacement compressor. If that makes a difference I don't know.

[watkins]

Start by having someone check to make sure the system is working as designed and has enough R 134a.

General idea for temperature is that an A/C system should blow about 25-30 degrees colder than ambient when measured at the center dash vent.

[dakta1420]

The system is properly filled and has been varified. Pressures were good.

[Rope-Pusher]

Go join Tony in Siberia. You won't need AC there.

You'll already have an icy BM.

[theholycow]

For the "I wish it blew harder" issue, you may be able to transplant a fan from another vehicle. I doubt your 1998 uses the same fan setup that GM used for decades and probably quit using in the 1990s, but if it does, google it...there's threads on other forums recommending the fan from a certain year of Corvette. I may eventually do that for my car. It could also just be that your fan is starting to wear out after 15 years and putting in a new same one could help.

"but while driving it goes down to 45" makes me think a different pulley could do the job. You could test that theory by just keeping RPM up...feed it a little bit of your right foot all the time to prevent it going all the way down to idle RPM. If that helps then changing the pulley could help. You'd need a different length belt too. If this behavior is by design then you're modifying it beyond design specifications. If it's a malfunction then you're applying a hack that may fix it forever or may hasten further failure.

Variable displacement I don't know anything about other than basically how it works, conveniently described on this good reference site:
http://www.freeasestudyguides.com/varia ... ssors.html
I guess the question is, does it go all the way to full displacement when turned on at idle? I suspect that it should, so that might be a troubleshooting issue. If it doesn't and isn't supposed to by design then it's a modification issue. In a 1998 model it may be operated by a somewhat autonomous circuit, requiring some hardware work, while I would expect a more modern vehicle to control it in software. An easy and extreme hack would be to apply full power to it, but it's designed for PWM and may not be able to handle that.

One other thought: You might check the evaporator and condenser. If the condenser (looks like a radiator and is positioned in front of the engine's radiator) has junk built-up in its fins then the wind it experiences while driving would compensate, but otherwise it would struggle at a stop. If its tubes are clogged on the inside then it may load the compressor more, and higher RPM would help. This could explain the failure of your previous compressor, too. Except for wind speed, the same thoughts go for the evaporator.

Ok, that's all my brain has for now.

[watkins]

On the topic of stuff inside the evaporator; an improperly evacuated system might still have moisture in it, which damages the seals and can cause them to break apart and enter the system.

Honestly, most of the time I see either a dramatic leak in the A/C system or there is absolutely nothing wrong except for the loose nut behind the wheel.

[AHTOXA]

[bk7794]

I wish I could make my a/c stay at 45 at idle. When I am driving I can feel ice cold air though.

[AHTOXA]

Start by having someone check to make sure the system is working as designed and has enough R 134a.

General idea for temperature is that an A/C system should blow about 25-30 degrees colder than ambient when measured at the center dash vent.

Assuming you mistyped above. If my ac stayed at 30 below ambient at that means I would blow 75 degree air on most summer days. that would not keep me cool.

[watkins]

No typo. I did mean at more normal temperatures though; not Texas temperatures. There is a parabolic nature to the temperature below ambient, however. More likely than not, your A/C is blowing low-to-mid 60s with your hellish ambient temps. The difference in temperature from the ambient is what keeps you cool, not necessarily the actual temperature.

[AHTOXA]

Perhaps you're right but I have my doubts. If the car wasn't baking in the sun all day but was in a garage, then while driving through the 105* heat the a/c feels cooler than mid 60's. It's downright cold on dry skin.

[watkins]

Toss a stick thermometer in the left-center dash vent. You'll be surprised.