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I have a Honda Odyssey 2019. The a/c blows ice cold… as long as I am actively driving. Once I come to a stop and begin idling, the air is no longer cold. Of note, I can get the air to be a bit cooler if I rev my engine while idling… but it’s only coolER, definitely not ice cold like it is when actively driving.

Dealership doesn’t have a clue what could be wrong and wants $500+ to do an evac and recharge w/ UV dye to look for leaks. I guess this is their starting point in their diagnostic process.

I am very aware that my knowledge base on engines and a/cs, etc is extremely limited, but I am a very logical thinker and it just seems that gathering more data first is warranted… like measuring the ??coolant?? ??level?? (I don’t know if I’m using correct terms) and comparing current measurements to what should be expected might reduce some variables when it comes to narrowing down potential causes. Especially considering the issue seems (to me, at least) to be fairly specific (compared to just a vague “air not cold” complaint).

Any guidance, advice, knowledge, recommendations, etc etc is greatly appreciated! Thank you for your time! :) :)

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  • Welcome to Motor Vehicle Maintenance & Repair! Sep 8, 2023 at 10:09
  • Dealership doesn’t have a clue what could be wrong and wants $500+ says "take it somewhere else." Presumably the vehicle is out of warranty. Sep 8, 2023 at 14:26
  • Unscrupulous dealers and repair shops take advantage of almost every vehicle owner unfamiliar with vehicle ac systems, deliberately using any method to pad a repair bill for the greatest profit. Some make repairs that never correct the problem and milk an owner for more money until the second repair results in ac cooling. Others simply don't have expertise and throw parts at the problem while profiting. Refrigeration isn't rocket science but does require knowledge of refrigeration basics before becoming experienced in refrigeration diagnosis, troubleshooting and repair.
    – F Dryer
    Sep 8, 2023 at 18:18
  • 2
    @FDryer escpecially main agents whose main customers are well-heeled and can afford to buy a new car every few years. My local agent twice tried to skin me: a) "Oh Sir! One of the cooling fans sounds just a little bit noisy, would you like up to replace it for your peace of mind, in case you break down?" b) when I needed a new control unit in the DSG gearbox (about £2000 in all), "Sometimes it is better just to replace the whole gearbox!" (about £6000 in all). Sep 8, 2023 at 19:10

3 Answers 3

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The AC often relies on the the electric fan near the radiator at the front of the engine bay running to cool the refrigerant. If the fan isn’t running while stationary there won’t be sufficient air flow to keep the AC working correctly. Do you ever hear this fan running?

Please be careful with your fingers when working around this area, because the fan could switch on unexpectedly, even when the engine is off.

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    "Be careful with your fingers around this area, because the fan could switch on unexpectedly." Even when the engine is off. Sep 8, 2023 at 18:22
  • I might add that if the fan is working fine, it might be that OP needs to clean the radiator. It might be that the fan pressure isn't enough to get good airflow through a dirty rad but the pressure while driving is enough. I'm no expert in this area though, just a suggestion.
    – ttbek
    Sep 11, 2023 at 12:13
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You are right to ask questions about this. The very first thing a mechanic should do is a pressure check of the AC system, if the pressure is low then it makes sense to look for leaks. If the pressure is good then there's no leak and an evac-refill is a waste of your money.

In any case $500 for an evac and refill on your AC system sounds like a massive overcharge to me, I'd expect to pay half that at most. I suggest you take it to a reputable independent mechanic instead.

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    If it's charged and fan works the next step would be to check the condenser fins need cleaning.
    – Jupiter
    Sep 8, 2023 at 15:38
  • Actually, anyone familiar with vehicle ac systems can assess in one of two directions; is ac running or not? If ac runs then the first thing to check for; are cooling fans running or not? Next would be inserting a temperature gauge into the center vents to measure outlet temps. A knowledgeable mechanic/technician will determine if gauges are needed or if a known dye is factory installed (GM) and search for the leak with a uv blacklight.
    – F Dryer
    Sep 8, 2023 at 18:08
  • @Jupiter That was my thought as well. Maybe the fan doesn't have enough pressure to force air through a dirty rad but driving is enough to push it through.
    – ttbek
    Sep 11, 2023 at 12:14
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Poor AC performance when idling could be caused by the compressor not performing well at low RPM, or by heat buildup around the condensor due to lack of air flow when the vehicle is not moving. You can roughly distinguish these two conditions by revving the engine in park/neutral and seeing if the air gets cooler.

If it does get cooler, you have a problem with cooling performance which may be caused by insufficient charge of refrigerant (possibly due to a leak) but might also have other causes.

If it does not get cooler, you have a problem shedding heat from the condenser. This could be due to a failing fan, the fan not switching on when it should, severe dirt on the condenser fins, general engine compartment overheating possibly from poor engine cooling system performance, or a number of other things.

Before even considering spending money on evac and refill, you need to figure out if it's plausible that doing so could fix anything.

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  • Virtually every vehicle ac system runs cooling fan(s) for one reason; the compressed refrigerant is hot, entering the condenser coils to cool down before turning into a liquid. Heat from the condenser coil flows into the radiator and must be dealt with by running one or both cooling fans immediately. Some vehicles with one fan runs at one speed while dual fans may have up to three speeds depending on ac pressures and/or coolant temps.
    – F Dryer
    Sep 8, 2023 at 17:59
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    It's either low or the fan isn't running, and you told us how to figure out which, +1. ("ice cold", I'd be leaning towards it's low - coil should be like 40f, not 33f.)
    – Mazura
    Sep 10, 2023 at 20:15

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