A/C only blows cold while driving

I have a 2004 pre runner double cab..... The a/c only blows cold while driving. When I stop at a light or slow down it doesnt blow cold.......not hot....just not cold.

What could cause this?

Thanks
Cadman

 

Charge status (have a shop check it, the DIY kits do more harm than good), also the fan not properly engaging at idle will cause this... you'd also see a climb in engine temp but it may not be obvious on the OEM temp gauge.

To function, the condensor needs to have air flowing through it. No airflow = no heat from the cab drawn off = no cooling.
It won't blow "hot", especially if you are on recirc, because the ducts are still chilled.

 

Check the AC drain (through the firewall on passenger side engine compartment) IS dripping when AC is on. If not the air box under the passenger side dash is chock FULL of water and not allowing air flow. In emergency purchase Klondike Tacos.

 

Probably not the charge IMHO. Undercharge wouldn't any better cool with increased condenser airflow. Probably a problem with the fan clutch.

 

Hmm weird mine does the same thing maybe it's normal

 

No not normal. A/C should blow cold air whether you are moving or not.

 

Check your fans. A malfunctioning fan will cause it to blow warm air when stopped because the condensor isn't getting sufficient airflow.

 

Mine does it too. Make sure recirculating inside the truck is on. Helps mine blow colder when stopped

 

the pressure is most likely shooting up due to a weak fan clutch.no airflow over the condenser will make the ac suck
mine does this too, im gonna add an extra electric fan,when im stopped my ac it horrible.
we get it alot with the chryslers and dodges i work on everyday

 

Vacuum leak

 

It's weird mine blows snow out the vents when I'm driving but when I'm stopped it's not cold it's cool

 

thats like saying the blinker fluid is low...
why would a vacuum leak cause that in any way shape or form? maybe if the blend air door was vacuum actuated? which they arent.hell a vacuum leak might help if it made it idle higher...

 

Do a leak down test, then come back and rep me when you find out I was right.

 

Two posts that are confusing. Never heard of a leakdown test for an AC system in my career! And since the actuators are all electronically controlled in th OP vehicle, no amount of vacuum leak would cause an AC issue as described.

Many good thoughts overall though. The engine fan which draws air across the condenser and radiator could be weak, also there could be blockage of the condenser. A low charge can also cause this condition, as a slightly undercharged system would be weak at idle, but the increased RPM of an engine, as well as the better airflow across the condenser at speed will improve efficiency of a weakly charged system. Check your radiator fan, and the condensor as a starting point and go from there.

 

I have had two vehicles that has the exact same symptoms that were caused by a vacuum leak.

 

Are you talking about after evacuating the system and it has a vacuum on it, see if it leaks down? (See if it holds the vacuum) If so, the OP still has refrigerant in his system. If the system is opened for a repair, then it would need to be evacuated.

 

i really appreciate all the suggestions/ideas. I'm sure we'll get to the bottom of this issue. I'm glad i'm not the only one having this problem.

OK so how would i be able to tell if the fan is weak? i mean, to me it seems normal and blows ok. i don't know if it should be stronger or not.
Also, when you say check the condenser, BamaToy1997, do you mean make sure theres no blockage? I'm not an AC kinda guy so i apologize for sounding dumb here. I don't think i would be able to find a blockage.... would i? i'd probably need to take it to an AC shop for them to check for a blockage....right?

thanks

 

Yes, you are looking for blockage, or anything that restricts airflow. Remember, right now we are doing preliminary checks. Also look in between the condenser and the radiator to be sure nothing is there blocking airflow. Checking the fan clutch is a bit more challenging. The way I do it is considered dangerous if you are not extremely careful. What I do is I hold on to one of the blades while someone else cranks the engine over. If the engine starts, and I can hold the blade from turning, the clutch is bad. The danger is that if the clutch is good, making sure that you don't get a finger hurt when it pulls from your grip. This is VERY dangerous, and I am sure there are other techs here who may have a safer method. It's just the way I have done it for years, and I know exactly how it feels when it is going to pull away. Yes dangerous, but I take the risk.

Question is, what two vehicles did you have? Were they both Tacoma trucks?

 

Does 1st gen have a dedicated A/C fan? 2nd gen do not -- they depend on the engine/radiator fan, which at idle, generally blow a low volume of air, much lower than the airflow when you are driving, but enough to remove the heat from an idling engine.

If there is no dedicated A/C fan, then described "issue" seems "normal". If it does have a dedicated A/C fan, ensure that the thing is actually working.