AC issue - no cold air, only warm

Just got an AC refrigerant refill in my truck because it was empty and was only blowing warm air. A week later, no more cold air, only warm air as before

So I either have a leak or something has gone bad somewhere in the AC system. Except a leak, what could cause the AC to not blow cold air? Compressor is not seized, I can spin it freely with my hands.

I'd like to troubleshoot my AC, so any suggestions?


thanks

 

Could be the switch that determines whether or not it has the appropriate amount of refrigerant in it. First step is to put a set of gauges on and see if its full, if it is, then start looking for electrical issues.

 

First step is always put your manifold gauges on.

If you can spin the compressor with the clutch pulled in there is no pressure in the system

The clutch should spin when not energized and belt off.

Your system was empty just what was done to find and fix the reason why.

Once The pressure drops to low the pressure switch opens voltage to the compressor clutch is no longer present.

The hot air starts to blow!

 

Actually, first step Is to find the leak since you had it refilled a week ago.

 

maybe leaking somewhere, might have the AC experts take a look

 

I bought the truck like this, so how, why and since how long it was empty on refrigerant is unknown

I didn't mind having no AC, but I just got tired of cooking in my truck whenever I would take it for a ride

 

Cooking like 120 degrees F?

 

Most likely a leak. Below a certain pressure the AC clutch won't allow the compressor to work for safety reasons. It's the same reason (if you remember to look) you won't see it engage below certain temperatures.

Take it back. Most likely the put in a UV dye to see where a leak is coming from and they'll be able to find it quickly.

 

This has now just gotten so very expensive maybe .

New to you truck with unknown leaks and no idea of how long it may have been empty.

Check for leaks this is one of the reasons good AC shops estimate to change both the EVAP coil and the condenser and the normal drier and orifice

How much is in the AC repair Fund??

 

This is why I want to do it myself, as much as possible. Though AC is a bit unknown to me, but nothing is better than trying to fix it yourself to learn new things!

yeah, it has been quite hot over here for the past few weeks, but more like 35-40°C

 

That’s hot

 

Best thing you can do is remove your grill and check your AC lines that are the most accessible (the ones infront of the condenser) and see if you can hear or see any refrigerant coming out of those lines. I got lucky with my AC system because it was one of those lines up front and I was able to replace it with a line from the salvage yard. As you can see in the photo here, once I took the flange bolt off there was a crack right where the flange bolt goes over. That’s where I would start honestly.

 

You can get a cheap kit to add refrigerant and try some of this with dye stuff.

https://tinyurl.com/yy3xmz5v

 

If it was empty, you probably have a leak, but here's an easy thing to try. Move the hot/cold selector all the way to warm, and then all the way back to cold. If you start getting cold air again it's your blend door actuator. Mine is going bad, and after I switch it back to cold, I get ice cold air for a while.

 

I have a sight glass on mine buy the driver's side headlight. If the compressor comes on look and see if you have any bubbles. If you do that means you are low.

 

Buy or use soapy water and spray all the fittings that you can see in the engine compartment.

 

$.02 IMHO you should buy a manifold gauge set and a vacuum pump. You're going to spend $400 on everything you need but it's not hard. You'll spend 3x's that amount paying someone to do it. You will also need a digital food scale. I have done my 99 Taco twice now and my daily Honda Civic once. No issues and I live in Phx, AZ. I can guide you through the process. You could start by adding UV dye to the system. That will show you where the leak is. If you buy the vacuum pump and manifold gauges you can also put the system under vacuum to see how fast the pressure drops. Generally you're supposed to be able to hold about 30" of Mercury (28-30hg) for an hour without any pressure drop. If you have pressure drop you have a leak. Now, we can also bench test the magnet and clutch on the compressor as well. Unplug the single pin ac connector. Take another battery or any other 12v source and apply 12v to the single pin connector on the compressor. If the magnet engages and the clutch pulls in that means that part is working. I'd say at that point, fix the leak and refill system. A lot of people spend money on a new compressor when some times it's just the clutch. If you're replacing the clutch, you do need to read or watch videos about the magnet's air gap. The air gap is about a 2mm gap between the main drive pulley and clutch pulley. When the belt is turning the clutch without the magnet engaged the two pulleys can't be touching or rubbing. Conversely, you don't want the air gap too big because well, it's magnetic. It's hit or miss if the air gap is set correctly on some of these Ebay kits. Just something to make sure is right the first time. I learned that through experience. You can get full rebuild kits on Ebay. Replace everything. It is not hard. The critical part is filling the system. The system has a very small tolerance or error ratio of just 2oz. Don't quote me and you can find this info out on the web but our systems take approximately 22oz. The cans are 12oz and overfilling can contribute to heat, high pressure and ultimately destruction of compressor. This is where the food scale comes in. You need to figure out the weight of the can full + the attachment valve - the weight of the can empty to know how many oz of refrigerant you're putting in. I think 1oz of refrigerant actually weighed like .92 or something. So first you would take everything apart and there are videos and write ups on how to do this on the web for the Toyota 3.4's. Replace what you need to replace and put new gaskets on the lines and all fittings (this is where 90% of the leaks are). Definitely replace the drier, if your condenser (radiator looking thing in front of radiator) is beat to hell replace that. That is where all of the heat transfer takes place. The evaporator under the glove compartment likely doesn't need to be replaced but there is an expansion valve that you should replace while you're there included in most of the kits. Once everything is put back together you need to hook up the manifold gauges and run the vacuum pump for about an hour to get rid of any moisture in the system. You should be pulling 28-30hg under vacuum. Once the pump has run for an hour, shut it off and let the system sit under vacuum for an hour to insure that you don't have a leak. System should hold at 28-30hg for an hour. Once you have confirmed that you're holding pressure now is the time to get the food scale out and place the can of refrigerant on it while it is hooked up to the manifold gauges. Open up the blue low pressure side of the gauges and start to let in the gas. There are videos to show you how to do it, slow at first so you don't freeze the compressor and then you can fully open valve and just let the can empty. Now you'll see how much the can weighs empty and subtract that from the can weight full plus the weight of the metal valve tool to give you the weight of the gas itself. The second can is the critical can. Because again, we only need 10oz out of the second can. You'll now know how much 10oz of gas is because of the foo scale. Once you start to get the second can of gas in the AC on full blast will start to get cold. That's when you start to feel great about yourself and smile!!! This was a vague overview and by no means a how to so ask questions.

 

repairing it yourself will require a few specialized tools. as mentioned above you will need a set of gauges. O' Reilly Auto parts will loan you a set of gauges but they have to be returned in 48 hrs. The gauges from Harbor Freight are "good enough" if you are doing this once a year. You will also need a vacuum pump, which also a loaner tool from O'Reillys.

The following is a general statement.
With the gauges installed and the motor not running you should see 90 to 110 psi on both the high and low side... this depends on the outside air temperature. Start the truck and turn the AC on. A full charge will show 35ish psi on the low side with a full charge and apx 225 on the high side, again, outside air temperature dependent. Anything below 35ish on the low side when you rev the motor indicates either a low freon charge or a blockage some where in the system. If there are lots of bubble in the sight glass on the receiver/drier it is more than likely a low AC charge. The AC condenser is the crap trap in the system and there is NO cleaning it... the holes in the tubes are just too small. If there is a freon leak all I can say is good luck finding it, unless it is obvious. If you hook the vacuum pump up and watch the gauge you should see the low side gauge go into a vacuum. 30" of vacuum is a good sign, you will hear the tone of the electric motor of the pump change when you have reached its capability. Close both gauge knobs and watch the needle. You might have to come back every 15 minutes to check. If there is a leak this will show it to you 95% of the time. If it does leak, take the lines off the compressor and plug the hose ends with round tapered rubber stoppers that you can get at Lowes or Home depot or ? and repeat the leak test. If it holds vacuum for a long time, like over night, the leak is at the compressor, if it still leaks, separate the next easiest line and plug them and repeat. This is a time consuming process so...

Yes there are fancy electronic leak detectors and while all AC shops have them they replace everything that they can in an effort to prevent a come back and have an angry customer say... why is it so difficult to find the leak?

 

Everything good other than I would add most of the refrigerant through the high side and just a little on the low. You don’t want to flood the compressor with liquid.

 

#1 turn your a/c on with the engine running. Look at the compressor, is it engaged and turning? Is it cycling on and off every few seconds?
If the compressor is turning and not short cycling, touch the accumulator or suction line coming out of the cab, is the line cold to the touch? Is the high side line hot to the touch? If so, your problem could be in the blend door actuator under the dash. Our trucks are notorious for the actuator linkage binding. If you’ve not switched to heat lately, this shouldn’t be your problem but is a possibility.
If the compressor is short cycling you probably have a leak, don’t waist time or money on a sniffer, inject dye into the system and use a black light to find your leak. Most vehicles come with dye from the factory.

If you decide to add some refrigerant, DO NOT purchase a can that advertises stop leak. Trust me, that stuff is nasty and will ruin and completely contaminate a shops a/c machine.

These are all part of my visual inspection upon starting a no a/c problem. All except the dye, you don’t need any tools. Most of a/c diagnosis can be done with out any tools, just a good understanding of how air conditioning works.
Gauges come in when the compressor is not turning at all or all of the visual inspection steps have been passed.