My air conditioner works OK at highway speeds, even in hot weather. But when I come to a stop, so does the cooling. How should I troubleshoot? What are most likely causes?
More than likely either your electric fan is not running when the AC is on, and it should, or the system is just so old and worn down or the condensor is just so clogged that it can’t quite keep up.
Check the fan, make sure it is running ALL the time the AC is on, especially if the engine isn’t running hot. Check the condensor to make sure it isn’t clogged with smutz, hose towards the front of the car! If all else fails, adding a small fan to blow into the engine compartment mounted right on the condensor will help a bunch.
Thanks!
I vaguely remember hearing the fan run after the engine stopped; but I don’t remember that RECENTLY. I suspect the fan is dead, leaving the condenser with only flow-thru air.
And gunk blocking the condenser could be impairing cooling overall, and I just notice it at idle.
Does this seem the right approach?
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Clean the condenser as thoroughly as possible without breaking anything.
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Check the fan voltage.
Is the fan voltage good?
- Yes, voltage is OK
- Wire fan direct to battery.
- Does the fan move?
- Yes, fan moves: probably a bad connection near the fan; track down the discontinuity & fix it.
- No, fan dead: buy & install a replacement fan.
- No, voltage is NG
- Check the fuse
- Is the fuse conducting OK?
- Yes, fuse is OK: Poo! … probably a discontinuity SOMEWHERE hard to find. Track down & fix it; or take it to a pro.
- No, fuse is NG: replace it.
- Observe for fan movement at idle. Observe cooling while parked.
If no improvement, take it to a pro.
Yep, checking the voltage at the fan is good. However - what about the Belt tension?? If your belt tension is not good - the compressor can be being driven sufficiently when running down the road at 2K rpm - but not when idling at 750 You might just first check the belt tension and age. A worn cracked belt can also tend to slip.
I had a car that got warm at stoplights and fine on the highway. Can you hear the compressor kick on and maybe off? My problem ended up a bad variable resistor for the fan motor. There was enough circulation naturally at highway speeds, but none at low speeds or stopped.
Bring the vehicle to a shop, and have them check the state of charge of the refrigerant.
Tester
Mustangman,
Check the condensor to make sure it isn’t clogged with smutz, hose towards the front of the car!
Exactly! Both fans are OK. I hosed down the condenser with a hi-pressure hand car wash hose and … Voila! AC at idle. Thanks!
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Tester is right. The refrigerant charge should be checked. The car is well over a quarter century old and I would be stunned if it did not have any leaks.
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Check to make sure the water force from the pressure wand didn’t bend the condenser fins. If they did get bent, it is usually possible to bend them back so you can return air flow through the condenser to normal. If you’ve done that before, bent fins could be part of the problem. If so, the reason why it worked after you hosed it down might be that the hosing down cooled off the condenser enough to get it working again, but that might turn out to be temporary.
Hmmm? Thanks for the caution; I’ll check. I was actually thinking in the other direction … thinking I really didn’t clean it well because the rigid pressure wand couldn’t reach most of the condenser without disassembling stuff. I was thinking I should go at it again with a soft brush … but maybe that would put the fins at undue risk?
A soft brush should be fine, but brush the same direction of the fins- not against them. But quite honestly, the water pressure alone should be plenty.
They make foaming cleaners for this purpose. Low pressure application, the foam gets into the tight spaces and you rinse it off.
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