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AC GURUS!... AC problems


ptt

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My 1990 coupe AC seems to stop cooling intermittantly. I disconnect the battery for a few minutes and reconnect and it starts cooling again. I put my gauges on it and with ambiant temp at 82F, the low side is at 45 and the high side is at 245 after reaching normal engine operating temperature. With the thermometer in the center vent and the fan on high it is showing in the mid 40s. It may cool for a day or a week and then it stops cooling. Could the system be getting shut down by the pressure sensor(s) for some reason? Is the low side pressure of 45 be too high? Thoughts appreciated! Thanks.

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Check you compressor clutch. On both my Dodge trucks,it would cool for a while and then once it got hot the clutch would not hold a no more cooling.

You can test this by catching it when its not cooling. Lightly hit the clutch with a hammer. If it catches and starts cooling again, you have found your issue.

Clutches are available on ebay for under $100 for most compressors.

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ptt,

I had a situation the other day similar to Bill's but different. The AC on my '89 was working flawlessly since I performed a major, major "tune-up" on it. Last week, I did a brake inspection on the car due to some noises coming from the rear. Come to find out that it as a failing exhaust hanger causing the pipe to occasionally bump the rear suspension. Installed a new rubber hanger then drove it to the gas station. On the return trip found that the air coming out of the vent was warm and getting warmer. So now I'm wondering what the h*ll I did to cause that to happen. I checked the code and found a B04XX (will look it up later) The code describes issues of the blend door. After performing some of the diagnostics I come to the conclusion that it's an intermittent.

Still doesn't explain the current condition. I hook up the gauges and while I doing that, I think (play) "what else could it be". I decide to check the AC relay. Swap with a known good one. No dice. Then, for whatever reason, I decide to check the connector at the compressor. It doesn't look any different than the last time I looked at it. But, while the engine is running ( Don't try this at home. I'm a trained daredevil. School of Hard Knocks. Majored in Danger and minor injuries) Doing things in an unsafe manner is as close to living on the edge as I get at my age) Anyway...

While the engine is running a take a 1/4" x 3' metal rod and snaking it past the serpentine belt, I bump the connector. And viola! the compressor kicks on and all is right with the world once again.

John F.

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Guest Mc_Reatta

With engine off. disconnect compressor connector and inspect connector and wires. Clean both socket on compressor clutch and contacts in plug. If wires look or feel damaged, get a pigtail and splice it in. If contacts appear burnt or otherwise damaged, light filing with a jeweler's file may help.

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ptt,

I put my gauges on it and with ambiant temp at 82F, the low side is at 45 and the high side is at 245 after reaching normal engine operating temperature.

I wasn't able to include this, this morning because I ran out of time but these numbers are good at that ambient. They are at the high end of the range but still in. So, I'd say that your problem lies elsewhere.

John F.

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Guest Richard D

Also, have you converted to 134a, or are using R-12. For R-12 the low side is a bit high, for 134a with ambient temp. at 80 to 85 degrees it should be ok. Do both fans come on when A/C is on?

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The previous owner has converted the system from R-12 to R134a. As with this senerio...knowing if it was converted properly is a crap shoot! Since disconnecting/re-connecting the battery more than a week ago the AC has since performed well and shows 35F-40F on my super-scientific pizza thermometer in the center vent in bumper to bumper rush hour traffic. It must have a very slow leak as I only got a partial can of R-134a w/Dye into it after last time it stopped cooling. If I recall correctly it stopped cooling last Fall and had a fairly good pressures at that time. Thats what made me think it was a pressure sensor problem back then. Obviously I need to note pressures and watch them closely this season and maybe I can narrow it down to the cause of the intermittant gremlin. Thanks all!

Edited by ptt (see edit history)
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Yeah...I always keep that R134a lower amount of refridgerant being nessesary in mind when charging empty systems by temperature. Its hard to know what a previous owner has done though. I have had systemsflushed/ evacuated and vacuumed if theres any question or hint of a problem. As the old adage goes..."It only hurts once to do it correctly but painful many times if you dont." Thanks everyone!

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