AC temp oddity

Like most AC geeks, I have a round dial thermometer in my duct outlet.
It usually sits happily in the blue arc. Lately, with the warmer temps, I have
Noticed that the AC duct temp will rise. It only rises when I’m at a standstill in traffic.
As soon as I’m moving again, the temp drops into the frosty zone.

Is my clutch fan wearing out? Still seems to roar on startup.

 

I thought that was was typical of all cars? AC works better when moving

 

How long does it take when sitting in traffic?

Mine was immediately warming up at a stop and I found it about 1/2lb low on freon. Now takes 15-20 minutes at a stop to heat soak the condenser.

 

I’m a Reefer geek, and I don’t carry a dial thermometer, but 2 points for not using a IR gun to read air temps!
Most likely your hitting your hi pressure switch at a stop, then it cools down when you start moving. I’m a full evac and recharge by weight kinda guy. Usually it’s leaking from the stupid automotive style shraders cores

 

There is also a clutch fan relay to check out.

 

A big, round, analog gauge sticking out of my center duct. Usually hovers around 45F depending on environmental conditions. Original to the truck and has never been serviced, or needed any repair.

 

My kinda guy, big giant dial that makes girls ask questions as to why it’s there….

 

Mine dies the exact same thing. Sub’d for a possible solution