A/C Quest.

[JJ]

i recharged my a/c the other day and it wuz workin fine at first but at idle.....the rpm jumps up to about 1.5-2rpms and it just flucuates from there. But each time it revs up and down i can hear a click near the compressor...as if it keeps turning on and off.
Im just asking yall before i get it tested for the a/c system.<p>Anyways thanx in advance,
pEAce

[Stan W.]

The "clicking" you hear most likely is the air conditioning cycling on and off. It does that in response to both the compressor discharge pressure and the idle speed. When the ambient air temp is hot, the discharge pressure is high. This in-turn causes the high-pressure switch to disengage the AC clutch. Once the pressure goes down below the switch setting, the clutch is engaged again. The hotter the air temp, the higher the pressure, the shorter the cycling interval. When the engine senses high AC discharge pressure, it increases the idle so the extra load of the AC does not kill the engine. If you overcharged the AC, the discharge pressure will be higher than normal, loading the engine at idle more that it should. Many folks out there think the more refrigerant the better. Sure, an extra ounce of R-134a often makes tha AC seem cooler, but when you load up the compressor too much (with extra refrigerant/high ambient air temp/low rpm)you will know it when the engine tries to compensate. Each AC unit was specifically designed to operate with an exact amount of refrigerant. Use that amount and the AC will work best. Hope this helps

[JJ]

thanx for the info!
It helped out alot!!!!

[JJ]

Ohhh...
When i charged my system, i put 3 15oz cans into my system. Since your explaination up there seems to say that i have overcharged it, sooo my question is can i let some of it sooo that i can see whether my system will work correctly or not??<p>Thanx in advance!
pEAce

[johnnyb]

heres a question on the A/C system. Does anyone know if the 93 came with R-12 or R-134a. Just wondering if I need to upgrade my system when the time comes

[JJ]

im guessing here but i believe you will most likely have the old system.<p>I have a 92 mx and i had the old system.

[JasonH]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by johnnyb:
heres a question on the A/C system. Does anyone know if the 93 came with R-12 or R-134a. Just wondering if I need to upgrade my system when the time comes<hr></blockquote>
It's probably R12. Yopu have a sticker on the underside of the hood on the passenger side that tells you what refrigerant it uses and how much it holds.

[guyaverage]

1993's came with R12. And he is right, you should have stickers telling you what is in yours. If or when the system is upgraded, whoever does the change should put new stickers on over the old ones to show it is changed to a R134 system. Depending where you live and who does your a/c work, it may or may not be cheaper to just have the system recharged with R12. A guy I work with just had his done, it was $100 to reseal and recharge with R12, but it was $175 to do a conversion.

[Stan W.]

When the industry switched from R-12 to R-134a in 1994 if I remember correctly, it was believed the new refrigerant was "incompatable" with the old system. Many dealerships told a lot of people that they would have to get complete new systems. However, almost 9 full years of experience has shown that if your A/C system is properly and totally purged of the old R-12 & old compressor oil, and you install new R-134a with the newer type of compressor oil all will be fine. Note that R-134a has a different temp to pressure ratio, so the amount you put in your system differs by an ounce or two then the R-12. Good A/C shops have the specific specs for all the old R-12 systems and for the conversion, so they know exactly how much to put in. When they do the conversion they are to afix a new sticker under the hood with the amount of R-134a and the nominal high (discharge) and low (suction)side pressures. However, many just write the specs with an permanant marker. In the comversion process new A/C ports are installed over the original ones. These are a different size to preclude introducing R-12 into a system now filled with R-134a. Once properly converted, the system will work great. My 92 MX-3 was converted about two years ago here in hot southern California and my output air is about 42 degrees. Since the passenger compartment of the car is relatively small, 42 degrees will chill you out real quick. So, my advise is to have a reputable A/C (not dealer) shop do the conversion work. After all, the conversion is cheaper than buying the old freon year after year. If you overcharged the system yourself, perhaps a $20 bill can get the local pro to get it down to specs. Hope this helps.

[992mmx3]

Stan, good write up thanks for taking the time to do that, very informative.

[jpwmx3]

That's weird that your RPM's flucuate with your air conditioner. Mine is rock solid all the time, even when the compressor kicks in and out.
Maybe it's something else that causing the fluctuation.?

[992mmx3]

its perfectly normal for you idle to flucuate when the a/c is turned on.

[JJ]

yuh but this flucuates bad...i mean i can understand a lil minor flucuation but this is very very noticeable. Its obvious that there is some problem but ill keep yall informed of the results i get from the a/c system check.

[Stan W.]

Once you verify that the A/C is properly charged (meaning the absolute correct amount of refrigerant and proper pressures), you could look to other sources for the idle problem. However, since the original posting said all was OK until the A/C was charged. The focus has been on the SA/C system. <p>As you can tell by other postings, the MX-3 is a very "idle sensitive" car. Almost everything you do or adjust on the engine will affect your idle.<p>I do remember when I newly purchased my 92 MX-3 in Las Vegas in August, the RPM was extreamly erratic at idle. I took it back to the dealer. After all, it was a brand new car only one day old.<p>They kept it for two days and could not locate the problem, until the A/C guy suggested to check the compressor output pressure. Once they discovered the factory had overcharged the system, they released some freon (now illegal to do) and all went well.

[Darth_Luis]

Sorry to piggy back on your post, but I have no idea where the A/c on my MX-3 is... I took it to my mechanic the other day and he said my car didn't have a compressor ... it's a 1994 MX-3 so it must have A/C right? .... damn, it's hot and humid and New York! HELP!! I'M MELTING!!!! AHHHH