I'm thinking of selling my rig so I need to fix some things. The AC has never worked and I never really cared but now I should try to fix it for resale. How should I start the diagnosis? Basically the switch light comes on but the temperature doesn't change. Whats the first thing to look at?

 

check to see if there is refridgerant in the system. if its too low the compressor will not come on. may have a leak.

 

Whats the best way to do this?

 

add some in you can go buy a can at your autopart store. get the one that come with the hose and remember to put it in the low side line

 

This 134A seems to leak out of the tightest system. The best thing I am told is to recharge every year.

Is the belt even on the pulley if it didn`t work why would you still have the belt on??

You might be having a clutch issue you need to see if that pulls in before trying to recharge..

If this has a major leak and has been exposed to the air for some time you could be looking at a lot of time and $$$ to get up and running.

 

Always start with the simplest things first. Make sure the belt is tight, the fuses are good and the clutch is engaging. I don't really trust the "do it yourself" recharge kits they sell at the parts store, but since you're selling the truck...Put some refrigerant in and see what happens. If the compressor comes on you have found the problem, now you have to find the leak (if you want to go that far). To find the leak you're going to have to put some dye in the system and use a UV light. Common leak points are o-rings and the service ports. Good luck and post what you find!

 

Not to get off topic but as the great Colonel Potter would say, horse hockey.

I have a 01 4runner and it has never needed to have any 134a added to it EVER and it's A/C blows 39F on the highway in 90f+ weather.

The main reason car a/c systems start to leak is the seals dry up because of lack of use in the winter and milder months. The trick to preventing this is during mild and winter months drive a day or two every week with the A/C compressor on with the heater or defroster. It will circulate the oil through the system and keep the seals nice and plump.


FOG

 

Is adding refrigerant easy? What are the steps? I know my way around my truck but the AC system is an area I've never tackled.

 

THANK YOU THANK YOU a million times over! I hate when a customer says "I think I just need a top off" Refrigerant is not like gasoline folks! It does not burn or get used up but rather it recycles itself over millions of times until there is a leak. In a proper shop you do not "top off" or recharge the refrigerant. Usually you recover, vacuum, add oil and dye, then recharge so it's not exactly a 5 minute deal. I do realize there are shops that top them off but it's not a proper method unless you know exactly what was lost and know how to use a pressure/temperature/humidity chart to know how much to add before you overcharge it.

To the OP: to answer your question. Like someone already said check the basic. Check fuses and relays. Then check to see if the compressor is engaging. If it isn't then there it's probably low on refrigerant, an electrical problem, or the cut out switch is bad, or other factors that's too early in the A.M. for me to think of. A/C work honestly isn't too hard but you do need to know what you are doing. You can buy a manifold gauge to check and see what pressures you have on both the high and low sides. Pressures can usually tell you a lot of what's wrong and pinpoint you in the right area if you know how to read them.