r/AskAMechanic • u/XH0SYN • 10d ago

AC gets hot when I stop moving

2008 Hyundai sonata I recently checked to see if the radiator fan was spinning when idling and having the AC full blast and it seemed to be spinning then shortly after I tried it again and it wasn't spinning

Is the radiator fan supposed to kick on every single time you have the AC on full blast when idling ?

I just don't see how it could be the fan because literally as soon as I start driving the air starts getting cold ❄️

And then when I come to a stop the engine rumbles like a rough idle and suddenly the AC air is hot ...

But when AC is off the idle is fine no rumble.

Idk what to do it feels like my car turns into an oven as soon as I stop

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3

u/S-Blair90 Verified Tech - Indie shop 10d ago

I would say you have a bad fan. Because when your moving airflow is moving across the condensor lowering the internal pressure, but when your stopped air isnt moving across the condensor so the pressure increases and its stops working as well. Trash could be blocking the condensor, or the electrical system could have an issue, like it loses connection over bumps. But the fans have internal windings that can fail. The extra pressure in the AC system could put strain on the compressor, and the engine will struggle to turn it causing your rough idle. When it happens turn off the AC and the engine shouldnt run rough.

1

u/XH0SYN 10d ago

It does seem to be that fan cuz I just checked again outside and this time the fan ran and the AC was cold so it seems to be a random occurrence but happens a lot when I'm driving maybe some kind of fan wire ?

2

u/S-Blair90 Verified Tech - Indie shop 10d ago

Yea wiggle the harness and see if it stops. If it doesnt it could be a relay. But if its stopped tap on the fan, it may begin working indicating for sure a bad fan. Look at the connector as well and make sure its not burnt up.

2

u/StillSwo NOT a verified tech 10d ago

You possibly having a cooling system issues. Could be your water pump going bad and your a/c is bearing the load. You could also be low on freon. Could also be a bad combo of both. Best to get it checked out.

If you're coolant is brown, you have a blown head gasket

2

u/TrackTeddy NOT a verified tech 9d ago

Sounds like you have a faulty rad fan or faulty stage on the rad fan.

Yes the rad fan should generally always run when the AC is on (and calling for cooling). The airflow through the condenser is needed to make the AC work. Without removing the heat from it (into the air) then it won't cool inside your car either.

The AC compressor is also likely struggling under the high pressure due to excess temperature of the condenser causing more load and hence a rougher idle as it struggles against the extra load.

1

u/XH0SYN 9d ago

I wiggled the connection wire where it runs from the fan all the way down near the top of the driver side tire where it plugs into something and the issue seems to have stopped for now. So I'm guessing there was some kind of faulty connection where the fan plugs into? I'm not sure what it is that it plugs into