When I'm at a red light or in drive through, my AC blows only a little cool air. In fact, sometimes it blows kind of warm. When I'm on road and air blowing across radiator, it blows nice and cool. What's up with that?

Dr. B

Mine has been doing the same thing, I figured with it being +100* heat index it was struggling just like everything else In this heat...

Sounds to me like it only blows cold when you're driving.


Thanks folks I'll be here all week!

evaporator coils might be dirty

When is the last time you changed the oil?

I don't know what if I'm wording this right, but when mine started doing that it was the Idler advance something or other

wHAT KIND OF TRUCK? I ask cause some trucks like the toyota my friend had you had to be revving 1500 rpms for the ac to cool. It was a newer truck a mid 90's model 4x4. We would take his truck to lunch and he'd run in the store and he'd say hold the gas down so the ac will kick in.

I was thinking the same thing. The ole '04 Z-71 ain't what she used to be. Bet those folks driving those 2015 F1-150s and Z-71's are sitting in a fridge at the red lights.

Dr. B

if it has electric fans the auxiliary fan could be not kicking on when at idle, If it has a mechanical fan the fan clutch could need to be replaced.

https://www.youtube.com/watch?v=GJD3-Zi9seQ

found this

Well I'm driving a 2008 F-150 and mine's doing the same thing. It did it last summer but it would go from blowing cold to blowing outside temp air. That ended up being a bad coil pack causing it to compensate by dropping power to the compressor. Now it's more like you describe. It fluctuates between cool and cold.

With the high heat and humidity your vent temp will rise while at a stop but should still be fairly cold. If while driving the vent temp gets colder then you could have debris clogged in the fins of the a/c condenser that is mounted in front of the radiator or the fan clutch is going bad and not locking up at idle to pull enough air across condenser. Those are the 2 most probable causes. if there is debris in the condenser you can use a hose pipe with a regular garden sprayer to rinse out by spraying from the radiator towards grille{engine not running}. If the fan clutch is bad then replace it.

2 Things raise the hood and see if the cooling fan is running at Idle. Some trucks turn the compressor off when the idle get too low. Cleaning the throttle body and disconnecting the battery for a few mins. will allow the ECM to relearn idle.

I was also only referencing the '04 Z71 since it only came from the factory with a fan driven by the belt. if it has electric cooling fans they would be aftermarket add-on's on the Z71.

thats what i ment to say, i figured as dry as its been the cond. coils had a lot of dust and bugs in it

+1

Early in morning and at night when it's cooler outside, the AC works about normal. I will check the fan today. Probably wouldn't hurt to spray the Lowndes county dirt off the engine anyway! Thanks for the advice fellas!

Dr. B

My wife's Toyota did the exact same thing and it turned out to just be low on coolant. Topped it off and haven't had a problem since. that was a couple of years ago I guess.

sounds like it could be the clutch on the compressor.