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A/C cycling on and off? by FieroCat
Started on: 05-22-2014 10:38 AM
Replies: 17 (345 views)
Last post by: TopNotch on 05-23-2014 02:17 PM
FieroCat
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Report this Post05-22-2014 10:38 AM Click Here to See the Profile for FieroCatSend a Private Message to FieroCatEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here's a new one: when I turn on the A/C, it sounds like the compressor kicks on and off every 3 to 4 seconds, and makes a clicking sound (like the vent door opening and closing) at the same time. Sounds just like a microwave that's running at 50% power level... cool air still comes out, but it cycles on and off and the engine revs up and down to compensate. What could be causing this?

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My Fiero: 1986 Pontiac Fiero GT, V6, 4-speed manual

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Patrick
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Report this Post05-22-2014 10:55 AM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post

My very limited experience with A/C would suggest your refrigerant is low. You probably need a re-charge.
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DLCLK87GT
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Report this Post05-22-2014 11:04 AM Click Here to See the Profile for DLCLK87GTSend a Private Message to DLCLK87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:
My very limited experience with A/C would suggest your refrigerant is low. You probably need a re-charge.


I second that. One of our cars was doing the same thing, I added a can and it started operating normally....for about a week then back to on/off. It leaked out apparently.

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FieroCat
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Report this Post05-22-2014 11:09 AM Click Here to See the Profile for FieroCatSend a Private Message to FieroCatEdit/Delete MessageReply w/QuoteDirect Link to This Post
Interesting, I would think that low refrigerant would only make the air less cold... I assume a 1986 model uses the R-12 refrigerant, where does one get a recharge for R-12 now? Probably just an A/C repair shop?

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My Fiero: 1986 Pontiac Fiero GT, V6, 4-speed manual

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rogergarrison
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Report this Post05-22-2014 11:16 AM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
That how I always knew mine was low too. Let me take a guess, you just started using the AC and it hasnt been on since last summer...right ? I learned a long time ago to run the AC, power windows, and convertible top at least every month to keep seals, motors, etc all working. You just need to run it for a few minutes. You prob leaked it out from a dried up clutch seal due to non use. (thats how I learned it)

[This message has been edited by rogergarrison (edited 05-22-2014).]

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FieroCat
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Report this Post05-22-2014 11:27 AM Click Here to See the Profile for FieroCatSend a Private Message to FieroCatEdit/Delete MessageReply w/QuoteDirect Link to This Post
Been using it occasionally for a few weeks now, running for more than a few minutes at a time, keeps cycling.
Bought the car in February so not sure how it was maintained before. Mechanic who inspected the belts said the belt was like new.

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My Fiero: 1986 Pontiac Fiero GT, V6, 4-speed manual

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masospaghetti
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Report this Post05-22-2014 11:31 AM Click Here to See the Profile for masospaghettiClick Here to Email masospaghettiSend a Private Message to masospaghettiEdit/Delete MessageReply w/QuoteDirect Link to This Post
Slightly low referigerant actually gives lower vent temperatures, but the capacity to remove heat is reduced. I know this sounds counter intuitive, but essentially, the lower volume of refrigerant also means lower pressures on the low side of the system (and thus lower temperatures), but the lower volume of refrigerant also cannot absorb as much heat as a fully charged system.

So what you get is a system that cycles more rapidly as the pressure drops below the threshold of the cycling switch.

As you continue to lose refrigerant, eventually the system becomes ineffective at removing heat and you'll have warm vent temperatures. As you lose even more refrigerant, the compressor won't even turn on to protect itself, since its lubricating oil is carried in the refrigerant, and an empty system provides no lubrication.
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Boostdreamer
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Report this Post05-22-2014 12:07 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
Does it damage the system to run it while it is low and cycling? Mine is doing that also. I figured it was the compressor about to go. Glad I saw this thread!
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ag9123
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Report this Post05-22-2014 12:22 PM Click Here to See the Profile for ag9123Click Here to Email ag9123Send a Private Message to ag9123Edit/Delete MessageReply w/QuoteDirect Link to This Post
I believe there is a pressure switch in the system which needs to be activated to engage the compressor. if the pressure is marginal, the compressor will cycle on and off.

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DLCLK87GT
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Report this Post05-22-2014 01:43 PM Click Here to See the Profile for DLCLK87GTSend a Private Message to DLCLK87GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Boostdreamer:

Does it damage the system to run it while it is low and cycling? Mine is doing that also. I figured it was the compressor about to go. Glad I saw this thread!


I'm no AC tech but can't imagine that constant cycling of the compresor is good for it. I'd keep it off until you get it serviced.
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Boostdreamer
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Report this Post05-22-2014 03:11 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
I took it in and had it checked. I was half a pound low. Cost me $71. Said my compressor was noisy and would not last long. Suggested I wait for it to die then change over to R134. I really like that guy! Very knowledgable and practical.
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Report this Post05-22-2014 03:24 PM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
134 is ok in a car as small as a Fiero. Otherwise the original R12 is far superior. None of my newer cars that came with 134 get cold...they just barely cool/make tolerable. For that reason I prefer just using the vents and opening the windows. I had the Astro and Magnum checked a few times by the dealer because it kept so warm...it was fine according to them. Only time I use AC is when a girl dont want her hair messed up, or maybe if I get stuck in city traffic on a 90* day. My one Fiero I had with AC was great for keeping a soft drink cold putting it in front of the vent. If I rolled up the windows and used the AC, you had to turn it halfway down to keep from freezing (R12)
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Boostdreamer
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Report this Post05-22-2014 06:48 PM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
Roger, my AC man says that the system has to be charged exactly right with the correct number pounds of pressure. Just adding a can here and there will never create the optimal system.

Also says that Gates and Goodyear belts have a higher content of nylon than other belts such as Dayco which has a higher content of rubber. More nylon than rubber makes the belt stronger and less likely to stretch. He strongly recommends Gates belts. That's what I put on after my Dayco belt broke in the first 5 minutes of use. It was my fault for not setting it tight enough, though.

[This message has been edited by Boostdreamer (edited 05-22-2014).]

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rogergarrison
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Report this Post05-23-2014 08:39 AM Click Here to See the Profile for rogergarrisonClick Here to Email rogergarrisonSend a Private Message to rogergarrisonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I never said to add a 'can' of freon anywhere ? I never do that because like you say, it never works right. I only let a garage or AC shop fix mine.
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masospaghetti
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Report this Post05-23-2014 09:23 AM Click Here to See the Profile for masospaghettiClick Here to Email masospaghettiSend a Private Message to masospaghettiEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Boostdreamer:

Roger, my AC man says that the system has to be charged exactly right with the correct number pounds of pressure. Just adding a can here and there will never create the optimal system.

Also says that Gates and Goodyear belts have a higher content of nylon than other belts such as Dayco which has a higher content of rubber. More nylon than rubber makes the belt stronger and less likely to stretch. He strongly recommends Gates belts. That's what I put on after my Dayco belt broke in the first 5 minutes of use. It was my fault for not setting it tight enough, though.



Interesting observation about Dayco, I've never been terribly impressed with their products (Belts and tensioners). Gates does seem superior.

You are absolutely right about the a/c system needing a specific amount of refrigerant, and the best way to do it is start with an empty system and add exactly how much you need, in pounds.

That being said, IMO, you can get acceptably close charging using gauge pressures. It's not always practical to empty the system and charge by weight. Especially with a small car like the Fiero, which has way more cooling capacity than it really needs. I've done refrigerant recharges using gauge pressures on a bunch of vehicles and always been happy with the result.
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Boostdreamer
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Report this Post05-23-2014 10:09 AM Click Here to See the Profile for BoostdreamerClick Here to Email BoostdreamerSend a Private Message to BoostdreamerEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by rogergarrison:

I never said to add a 'can' of freon anywhere ? I never do that because like you say, it never works right. I only let a garage or AC shop fix mine.


I was just throwing out some general information that I personalized with your name on it. Politically correct mandatory apology extended
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Lou6t4gto
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Report this Post05-23-2014 02:14 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
My Fiero is running 134, and if you leave the Fan ON, it WLL FREEZE you out ! My wife's Formula FIREBIRD was running a little warm, also (134), so I checked and it was low, so I put more in, THEN it cycled every 3-4 seconds for about 3-4 minutes, then went back to normal !
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TopNotch
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Report this Post05-23-2014 02:17 PM Click Here to See the Profile for TopNotchClick Here to visit TopNotch's HomePageSend a Private Message to TopNotchEdit/Delete MessageReply w/QuoteDirect Link to This Post
It's normal for a typical auto AC system to cycle -- that's how the pressure, and therefore the temperature, is controlled. But if it cycles rapidly, it could be low on coolant.
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