Ac diagnostic question

Arod1226

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So my AC works fine as long as it’s not too hot out. However once it’s 90+ it doesn’t do so well. I’m thinking to replace the compressor, and hope for the best. But before I do that, anyone have any other ideas it may be? I also just went to recharge my system, and it is not in need of refrigerant.
 

super1

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So my AC works fine as long as it’s not too hot out. However once it’s 90+ it doesn’t do so well. I’m thinking to replace the compressor, and hope for the best. But before I do that, anyone have any other ideas it may be? I also just went to recharge my system, and it is not in need of refrigerant.
You need to put gauges on the low and high side to see what kind of pressure you’re running

You can try cleaning out the condenser with a garden hose
 

gforce1108

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Both fans running OK? I had a dead fan and it acted the same. FCU thought the fan was running.
 

Genesis

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Make sure BOTH fans work on BOTH high and low. If one doesn't in either mode you'll get exactly this sort of thing and over time it will cook the compressor. There's no code for it because the system doesn't know; there is no feedback mechanism from the physical fan to the system to report RPMs, etc.

Note that there is NO WAY to know the actual charge level from system pressures alone due to the compressor being variable-displacement through the RCV. These systems work quite well for that reason even if moderately-undercharged. If low charge is suspected the CORRECT way to deal with it is to recover the refrigerant, pull a hard vacuum on the system and then recharge it with the specified amount. Assuming the system has pressure and is not opened the dryer does not need to be changed when doing this but if you're losing refrigerant it is going somewhere and unless its a very, very slow leak it will get bigger over time and eventually force you to fix it. The RCV can also fail and if it does performance will be materially impacted even though the charge level is correct and the compressor is otherwise ok.

Check the fans first on both high and low and if both ARE ok then -- and only then -- suspect the charge level or compressor itself is involved.
 

Arod1226

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You need to put gauges on the low and high side to see what kind of pressure you’re running

You can try cleaning out the condenser with a garden hose
I’ll go rent gauges today and hose off the condenser, and get back to you guys. Thanks!
 

Arod1226

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Make sure BOTH fans work on BOTH high and low. If one doesn't in either mode you'll get exactly this sort of thing and over time it will cook the compressor. There's no code for it because the system doesn't know; there is no feedback mechanism from the physical fan to the system to report RPMs, etc.
When I bought the car, the fans weren’t working and the AC was having the same issue. I fixed the fans since then and the problem persists. Possible that the damage has been done to the compressor and that’s the issue?
 

Genesis

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Yes Arod, or as noted right above, the blend door. If the blend door foam is basically "gone" then the heater core will always be "part" of the circulation which of course you absolutely do not want in the summertime! :)

Sometimes you can change the RCV (which is quite inexpensive, by the way.) The problem is that frequently when it fails the reason it failed is that there's coked-up oil in it, and if its in there its in the compressor generally, it likely damaged it, and thus it probably needs to be replaced. Any time you open the system to the atmosphere the dryer must be replaced -- no exceptions, or you're begging for trouble.
 

Windex

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What did You recharge the car with if you dont have any gauges?

How much and what kind of refrigerant did you charge it with?
 

Arod1226

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Yes Arod, or as noted right above, the blend door. If the blend door foam is basically "gone" then the heater core will always be "part" of the circulation which of course you absolutely do not want in the summertime! :)

Sometimes you can change the RCV (which is quite inexpensive, by the way.) The problem is that frequently when it fails the reason it failed is that there's coked-up oil in it, and if its in there its in the compressor generally, it likely damaged it, and thus it probably needs to be replaced. Any time you open the system to the atmosphere the dryer must be replaced -- no exceptions, or you're begging for trouble.
Silly question, is rcv remote control valve? Where can I locate it and is there a way to test it?
 

oilhammer

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There are just too many to list....
When people drive around with dead fan(s), and it is easy to do on the diesels since they don't need much engine cooling at slow speeds anyway, the compressors often suffer.

Neglected cabin filters will also allow buildup of debris on the evaporator, which will significantly impact both airflow and heat exchange.

Just a quick thing to check, and this is my quick seat-of-the-pants method to make sure the system at least works component wise: Start the engine, switch the A/C on, and get out and walk around to the side/front of the car and put your hand on the low side line*. It should be obviously cooler than ambient, and should be getting cooler by the second, cold enough like it is an aluminum soft drink can just taken out of the refrigerator. And assuming the engine is cold (just started), the fans should be pulling some warm air across them that you can easily tell is warmer than ambient.

If both those happen, you at least know the system as a whole is working and functional. From there, you can evaluate things like HVAC controls, airflow inside, etc. You can also raise the RPM some, and the compressor should still stay engaged... and if it is warm enough out, the fans may ramp up to high speed. If the clutch cuts off, or the fans remain on low speed despite it being hot out, the system is possibly low on charge, and then you can get into the gauges and such.

*low side line is the FAT one, that goes to the compressor inlet from the expansion valve. The other line gets HOT, so make sure you know and understand which is which before you start feeling things.
 

Arod1226

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What did You recharge the car with if you dont have any gauges?

How much and what kind of refrigerant did you charge it with?
i bought the refrigerant refill can with the small gauge built into the handle. I will look at the can later this evening, but I know when I bought it I was assisted in picking one based off my vehicle. If that makes sense.
 

gforce1108

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The RCV isn't readily accessible like it is on the newer, clutchless compressors. It's internal. I believe that was what was wrong with my 03. Clutch engaged, pressure was good - nothing happened when it engaged. high/low always stayed the same. Sold it before I dug deeper into it.
 

Genesis

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IF the RCV is bad (stuck open) then USUALLY the reason is coked oil which has clogged it up. While sometimes the valve fails and is clean, usually it fails because its got debris in it, and if so the compressor is not far behind it failure-wise in that the bores are probably trashed and, if that crud is all through the system unless you get it out of there it will destroy a new compressor very quickly -- or plug up the dryer which will do the same thing since nothing circulates if that happens -- as well.

The only thing that cools the compressor is the circulating refrigerant. If its not circulating to take the heat from compressing the gas away then the compressor will rapidly burn the oil, now you basically got sandpaper in there and its done.

If the high and low-side pressures are roughly equal and the compressor is engaged then its either lunched internally or the RCV is stuck open.
 

03TDICommuter

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FWIW, R-134A systems are refilled by weight, not by pressure. You cannot reliably tell if there is enough or too much refrigerant in it based on pressures alone. To do it right, it needs to be evacuated and refilled by weight.

Not saying that is exactly the cause of your problem, just some info.
 

oilhammer

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There are just too many to list....
Yep, we never evaluate the pressure of the system without confirming the charge by weight... and the only way to do that is to pull it all out, pull a vacuum, and recharge it with the proper amount.
 

John Wesley Hardin

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Yep, we never evaluate the pressure of the system without confirming the charge by weight... and the only way to do that is to pull it all out, pull a vacuum, and recharge it with the proper amount.
Thats a great idea all systems work on my a/c but no cold air. I thought a recharge would fix it but gauge says system is charged.
 

Genesis

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You need gauges on both high and low.

If the system is running and both are reading essentially the same the compressor is likely toofed. This CAN be the internal RCV stuck open (and that can be changed) but the odds are very, very good the compressor is smoked and you're going to have to evacuate the system and recharge it anyway to get to the RCV, so you choose.
 

oilhammer

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There are just too many to list....
The gauges can tell you if there is something in the system.... which is often all that you need to know that the clutch should engage at least briefly.

People misunderstand and overthink A/C systems all the time it seems. It isn't that complicated really.
 

John Wesley Hardin

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You need gauges on both high and low.

If the system is running and both are reading essentially the same the compressor is likely toofed. This CAN be the internal RCV stuck open (and that can be changed) but the odds are very, very good the compressor is smoked and you're going to have to evacuate the system and recharge it anyway to get to the RCV, so you choose.
Thought I had some cold air today. Blows cool when I start it for about 10 or 15 minutes then starts fading out . I will start with a A/C shop for a diagnosis see how that goes. Thanks
 

wonneber

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Thought I had some cold air today. Blows cool when I start it for about 10 or 15 minutes then starts fading out . I will start with a A/C shop for a diagnosis see how that goes. Thanks
Sounds like when the engine gets up to temperature and the foam on the recirculate door is gone it's warming the air coming out the dash.
Maybe?
 

Genesis

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Simple diagnostic on that one: With A/C engaged, and it "faded out", turn the dial to full HOT. Is it? If the temp dial doesn't seem to make much difference..... :)
 

SteelyTed

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"The other line gets HOT, so make sure you know and understand which is which before you start feeling things."

That's what she said 😁
 
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