AC Issue when Idle - Compressor or secondary fan? (1 Viewer)

[dstewart3ss]

After idling for a few minutes, my AC starts blowing hot air. Once I start driving again, it cools back off......called my local mechanic and described the issue. He seemed to think that it’s either the compressor going bad or the secondary air fan. Said I will know if it’s the compressor if I rev the engine when idling and the air will start blowing cold again.

For those of you experts (I certainly am not, esp when it comes to AC systems) does it sound like one of these two issues? Or could it be something else, possibly more simple like low Freon?

Thanks!!!

 

[BullElk]

Many more mudders know more than I in this regard but I would say it is not the secondary fan because some LC/LX don't have one at all. Perhaps the fan clutch not engaging as it should when idling. @flintknapper will have good info on this when he gets back from pig hunting.

 

[flintknapper]

Stewart, it could be a number of things. Some of what you describe would be quite normal.

Without benefit of putting gauges on the system I would be leery of a mechanic suggesting the compressor is the issue.

It is helpful to know what year model your vehicle is. We encourage folks to put that info in your signature line so that we always know what we are dealing with right from the start.

You will always see decreased performance from your A/C system at idle or low speeds. This is owing to the fact that the compressor is not turning as fast *less refrigerant being circulated* and less air being drawn *or forced* through/across the Condenser which is the larger of two heat exchangers in your system.

First and foremost....you'll want to be sure the system is properly charged with refrigerant. Next you'll want to check and see that your fan clutch *for the engine fan* is working properly. Last....I would see if your condenser fan *if so equipped* is working. It helps move air through the condenser at low speeds.

Any one of these things *or in combination* would cause your issue.

Low speed and idle are the most challenging conditions for an A/C system. It needs to be in tip-top shape to handle the heat load. Simply revving your engine increases compressor speed and hopefully air flow across the condenser....so I would not use that as a diagnostic tool to determine the condition of your compressor. Often when I hear that from mechanics I am led to believe they don't fully understand the system or are trying to sell you extra work.

 

[dstewart3ss]

Stewart, it could be a number of things. Some of what you describe would be quite normal.

Without benefit of putting gauges on the system I would be leery of a mechanic suggesting the compressor is the issue.

It is helpful to know what year model your vehicle is. We encourage folks to put that info in your signature line so that we always know what we are dealing with right from the start.

You will always see decreased performance from your A/C system at idle or low speeds. This is owing to the fact that the compressor is not turning as fast *less refrigerant being circulated* and less air being drawn *or forced* through/across the Condenser which is the larger of two heat exchangers in your system.

First and foremost....you'll want to be sure the system is properly charged with refrigerant. Next you'll want to check and see that your fan clutch *for the engine fan* is working properly. Last....I would see if your condenser fan *if so equipped* is working. It helps move air through the condenser at low speeds.

Any one of these things *or in combination* would cause your issue.

Low speed and idle are the most challenging conditions for an A/C system. It needs to be in tip-top shape to handle the heat load. Simply revving your engine increases compressor speed and hopefully air flow across the condenser....so I would not use that as a diagnostic tool to determine the condition of your compressor. Often when I hear that from mechanics I am led to believe they don't fully understand the system or are trying to sell you extra work.

I have a 2004 LX with 115k miles.....I’ve owned it for a little over a year and just recently noticed the “hot” air when idling on a recent trip when we got stuck in traffic....never noticed it doing the same in the past. Then my wife had it in the Chick Fil A drive through for 5-10 minutes and said it got almost unbearable.

Does the fact that I have an ‘04 tell you anything different? Thanks for the help!!!

 

[BullElk]

Make sure radiator, condenser and area in between are clean.

 

[flintknapper]

I have a 2004 LX with 115k miles.....I’ve owned it for a little over a year and just recently noticed the “hot” air when idling on a recent trip when we got stuck in traffic....never noticed it doing the same in the past. Then my wife had it in the Chick Fil A drive through for 5-10 minutes and said it got almost unbearable.

Does the fact that I have an ‘04 tell you anything different? Thanks for the help!!!

Only that from the factory....it would not have a 'Condenser Fan' to aid in low speed cooling. Though one can be installed.

All of the rest of my previous reply still applies. It's possible you could just be low on refrigerant. Putting a set of gauges on it would reveal that. It could also detect a problem with your compressor and certain other issues that might be present in your system (I.E. restrictions, etc).

You can check the operation of your fan clutch *engine fan* yourself if you like.

 

[dstewart3ss]

So I went out to do some visual investigating under the hood today. Saw that my engine coolant level was well below ‘LOW’ almost empty. Filled it up to full so I’m hoping that was the culprit for my AC not blowing cold when idle (makes sense that could be the cause, right?). I can’t see any leaks and don’t smell anything abnormal so I’m honestly not sure how the coolant level got so low.....I’ve had the truck just over a year.....TB and WP were replaced right before I bought it. We shall see if adding coolant fixes the AC at idle.....curious though if anyone has experienced AC issues with low coolant level.

 

[flintknapper]

So I went out to do some visual investigating under the hood today. Saw that my engine coolant level was well below ‘LOW’ almost empty. Filled it up to full so I’m hoping that was the culprit for my AC not blowing cold when idle (makes sense that could be the cause, right?). I can’t see any leaks and don’t smell anything abnormal so I’m honestly not sure how the coolant level got so low.....I’ve had the truck just over a year.....TB and WP were replaced right before I bought it. We shall see if adding coolant fixes the AC at idle.....curious though if anyone has experienced AC issues with low coolant level.

Certainly your coolant level is important....but unlikely to affect the poor performance of your A/C system. Let me explain what I mean by that.

• The cooling 'system' in your vehicle *engine cooling* is unrelated to the refrigerant system for your A/C in a direct way. But...an engine that is running hot *well beyond normal operating temps* can decrease A/C efficiency in that the engine compartment becomes heat soaked. This 'can' effect the heat transfer of the A/C components. But I don't think this is your issue.
• IF you checked your coolant level via the radiator overflow bottle, then you still need to remove the radiator cap *engine cool* and see that the radiator itself is completely filled. When your radiator is filled and the overflow bottle filled to the full mark *engine cool overnight*, take a permanent marker and make a mark on the bottle where the coolant level is. That way you can easily check the fluctuations later. The level will rise when the engine is heated and fall again when it cools off. This is normal. You will lose some small amount of coolant due to evaporation over time. But significant loss over a short period of time *say a week or so* indicates a leak somewhere.
• Your A/C system without doubt needs to have a set of manifold gauges put on it and the High and Low pressures checked.
• Additionally, your Fan Clutch *engine cooling fan* needs to be checked for proper operation. It is critical it be working well in order to keep your engine cool at low speeds and to draw air through the A/C condenser. The more air moved through/across the condenser the better the heat exchange will be *assuming it isn't dirty*.
• It is important to remember that the A/C in your vehicle is a 'SYSTEM' and all parts and functions must be working properly for best performance. An engine at Idle or traveling at low speed presents the most challenge for any A/C system not equipped with an electric condenser or engine fan to mitigate the air flow issue.

 

[dstewart3ss]

Certainly your coolant level is important....but unlikely to affect the poor performance of your A/C system. Let me explain what I mean by that.

• The cooling 'system' in your vehicle *engine cooling* is unrelated to the refrigerant system for your A/C in a direct way. But...an engine that is running hot *well beyond normal operating temps* can decrease A/C efficiency in that the engine compartment becomes heat soaked. This 'can' effect the heat transfer of the A/C components. But I don't think this is your issue.
• IF you checked your coolant level via the radiator overflow bottle, then you still need to remove the radiator cap *engine cool* and see that the radiator itself is completely filled. When your radiator is filled and the overflow bottle filled to the full mark *engine cool overnight*, take a permanent marker and make a mark on the bottle where the coolant level is. That way you can easily check the fluctuations later. The level will rise when the engine is heated and fall again when it cools off. This is normal. You will lose some small amount of coolant due to evaporation over time. But significant loss over a short period of time *say a week or so* indicates a leak somewhere.
• Your A/C system without doubt needs to have a set of manifold gauges put on it and the High and Low pressures checked.
• Additionally, your Fan Clutch *engine cooling fan* needs to be checked for proper operation. It is critical it be working well in order to keep your engine cool at low speeds and to draw air through the A/C condenser. The more air moved through/across the condenser the better the heat exchange will be *assuming it isn't dirty*.
• It is important to remember that the A/C in your vehicle is a 'SYSTEM' and all parts and functions must be working properly for best performance. An engine at Idle or traveling at low speed presents the most challenge for any A/C system not equipped with an electric condenser or engine fan to mitigate the air flow issue.

Thanks for the detailed feedback....here’s a current state picture of my overflow bottle and inside the radiator. I haven’t driven it since yesterday afternoon and it’s only been cranked for ~5 minutes earlier today. Should I just add coolant directly into the radiator until it’s full?

 

[flintknapper]

Thanks for the detailed feedback....here’s a current state picture of my overflow bottle and inside the radiator. I haven’t driven it since yesterday afternoon and it’s only been cranked for ~5 minutes earlier today. Should I just add coolant directly into the radiator until it’s full?

View attachment 2743937

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Yes.....! Your radiator should be completely full and some coolant in the overflow bottle SHOULD have been drawn back into the radiator as the engine cooled. I would recommend you replace the radiator cap with OEM cap and check to see that the line from the radiator to the overflow bottle is not restricted. Also the hose from the overflow cap down into the overflow bottle, they become soft over time and degrade from the inside out.

Edit to add: You radiator cap, besides sealing the radiator is also a two-way valve that allows coolant to flow to and from your overflow reservoir. As your engine warms up...the coolant expands slightly and needs someplace to go. So it flows to the overflow bottle/reservoir. Upon shut down....as the engine cools, the coolant in the engine contracts and creates a vacuum on the system...drawing some back into the radiator and keeping it full *or nearly so*.

If your radiator cap is not working properly, or if you have an issue with the hoses or cap on the reservoir...then the fluid exchange can not happen. The common result is that your radiator coolant level *if not checked regularly* will fall below the necessary level to keep the engine cool.

 

[Rio Sunset]

Inspect your compressor pulley/clutch.

 

[dstewart3ss]

Ok so I filled up the radiator and overflow tank on Wednesday. Wife drove it 2 miles earlier this morning. I went to get in it this afternoon and the coolant level in the radiator appeared to have gone down just slightly. But the level in the overflow tank came down noticeably to the level in the picture below. I drove it about 5 miles not getting above 50 mph and checked again when I got home. Level in the overflow is the same.

I can’t see any leaks anywhere. No smells. No drips anywhere that I can see (looking around from the top with my flashlight only).

Seems like I definitely have a leak though somewhere, right?

 

[flintknapper]

Ok so I filled up the radiator and overflow tank on Wednesday. Wife drove it 2 miles earlier this morning. I went to get in it this afternoon and the coolant level in the radiator appeared to have gone down just slightly. But the level in the overflow tank came down noticeably to the level in the picture below. I drove it about 5 miles not getting above 50 mph and checked again when I got home. Level in the overflow is the same.

I can’t see any leaks anywhere. No smells. No drips anywhere that I can see (looking around from the top with my flashlight only).

Seems like I definitely have a leak though somewhere, right?

^^^^

No....lets not jump to that conclusion yet. Continue to fill the radiator and overflow. IF they continue to both go down then let's look for leaks or vapor from your tailpipe. But its perfectly normal to have to refill once or twice before making any judgments. A couple of warm up and cool down cycles should stabilize the system if you have no leaks, so don't worry just yet.