A/C in my truck blows mildly cool air, but nothing like it should. In cold weather, the compressor cycles on and off like it's supposed to. It warm weather like today, it kicks on and stays on.

I still don't see any water dripping under the truck and today was 87 and somewhat humid.

I can hear a hissing sound in the lines while it's running and for ~15 seconds after I shut the engine off. High pressure line is hot and low pressure is cold.

Today I bought a recharge kit. It was a 20oz bottle. The sticker says the system capacity is 34 oz. I ended up putting the whole bottle in and the needle on the low pressure side stayed right at 35 PSI. The compressor ran the whole time.

After driving around for a bit, the A/C got cooler, occasionally very cold. Sorry, not thermometer.

I bought this truck used and so this is my first summer. I wonder if it was nearly empty and I should try to add up to another 14 oz? Or, could it be leaking out as fast as I put it in? I would think if that were the case, it would all quickly leak out and it wouldn't work at all.

Thoughts?

 

To do it right, take it to a pro who can test it for leaks and actually measure the charge. Low side pressure is just one of many factors.

 

I was thinking about getting a manifold set. I'm fairly mechanically inclined. I've rebuilt engines, etc. I have geothermal heat in my house so a manifold gauge set will help me maintain that too. Any recommendation on a good set/brand, hopefully available on Amazon?

 

Forgot to add, passenger side carpet is dry; I know about that issue.

 

Okay, if you are going to try to do this yourself, go get a set of manifold gauges, a vacuum pump, a keg of refrigerant, and a scale.

Evacuate the system with the vacuum pump, turn the pump off, and make sure it continues to hold vacuum for a couple hours. If it holds, put the keg on the scale and charge it with the specified amount of refrigerant. If it doesn't hold, you have a leak, get yourself a leak detector kit.

By the time you get done buying all this stuff, you will save by letting a pro who already has all this stuff do it.

 

I hear ya, but I have 3 cars out of warranty and a geothermal system. It's $100 just to have the HVAC guy come out and check it.

Local farm supply store sells containers of r134a for $99 (think propane tank size). I see vacuum pump / manifold gauge sets on Amazon for well under $200. Besides, I like learning how to do new things. I impacted all 8 of my plugs out on a hot engine with nary a problem. Fun fun...

 

I agree with GLC. You can't take a rifle, blindfold you and spin you around and expect to pull the trigger and hit the one apple still hanging on the tree. What you (and many others) are doing is close to that. I used to do AC recharging (after collision work) and was once told by a shop foreman (who occasionally "dumped" on a system). (that's just dumping the refrigerant into the system without any of the steps GLC listed). I was charging a Toyota PU that, if I remember correctly, called for 1.4 lbs of freon. He said "Oh, I just put 3 lbs. in EVERYTHING!" People like that scare me! You have a low pressure shut-off sensor in the system that shuts the compressor down if the pressure gets too low (loss of refrigerant) in order to protect the compressor. If the compressor is running all the time, it may be low but you HAVE to have the correct amount in the system (within reason, meaning NOT too much) or it won't be able to expand at the expansion valve to carry the interior heat away at the evaporator, like it is supposed to. It's not a case of "if a little is good, more must be better" any more than if 7 qts. of oil is good for your engine, 11 must be better!
The answer to your last question is NO! IF you insist on doing yoiur own AC work, for goodness sake learn more about just how to do it properly.

 

I'm pretty sure that's what I was asking. I even went so far as to ask about recommended brands of manifold gauge sets. I'm willing to learn. Not sure why I'm getting all this attitude. I never said anything about dumping so much refrigerant in the system that it would be overcharged. That's specifically what I wanted to avoid. Maybe you should go back and read the thread again.

 

I don't doubt that you can properly service your AC if you have the right tools and read up on how to use them - HVAC isn't rocket science. However, as with anything mechanical, there are precautions you need to take and there are things that you should never do. It wouldn't hurt to go to the library and see if they have any books on this subject.

Moisture is the worst enemy of an AC system. This is why any time you actually open the system, it must be pumped down for hours with a vacuum pump before recharging. Before you do anything on yours, you may want to pay a pro to check it for leaks, or you need to buy a leak detector kit. I wouldn't go through the hassle of recharging it until it's verified leak-free.

 

you would be best to take it to a pro. house hold a/c systems use a different type of refrigerant not r-134a that is used in cars and trucks. also doesn't geothermal work off of a water tube system? ( i could be wrong on that) any way you need a different gauge set and equipment for each type of freon. a good refrigerant recovery machine for r-134a is going to cost you about $3,000-4,000 bucks and to get a 30lbs can of freon you have to have proper ase or similar certification.

 

I'll have to check, but I'm fairly sure my geothermal uses r134a. The freon loop is separate from the water loop, obviously. Mine is a closed loop 4 ton system. Climatemaster Tranquility 27.

As for the truck, if it's low on charge, especially as low as I think it is, then I just need to find the leak. Once I do that I will have it professionally evacuated so I can replace the parts and then have the shop recharge the system. I don't mind spending money on tools that let me diagnose the problem. I can get factory new parts cheaper than the dealer will sell them to me and save the labor installing them. I realize there are some things I can't do from home, but there is a lot I can do. I think I'll get some dye in the system and try to locate the leak.

 

Dye injection needs a UV light to find the leak, and if the leak is buried somewhere that you can't see, it may be inconclusive. There are also electronic "sniffer" type leak detectors. They cost more than dye kits, but you may be able to rent one.

 

Trust me, I did read the post and it read the same when I went back and re-read. There was strong indication that you were about as knowledgeable as most people who buy the can with the guage at the parts store. It's not the easiest thing to train an AC tech in posts on a forum. I have heard more stories of AC disasters than you can imagine, most of the time with a 20oz. can in their hand. I didn't set out to offend but I didn't want you to be the next story.
A set of guages will tell you SOMETHING about the charge at this point but the only way to know for sure where the charge stands is to evacuate and see what was in there currently. There's a lot more to the story.

 

35 Psi on low side is close to where it needs to be. You need to read the high side to diagnose the system. Go clean the condenser first.

 

I've never worked on a R134 system, but when I used to do R12 systems, I'd go for 30 on the low and 150 on the high, NEVER more than 180. I also used a thermometer in the dash vents and looked for about 40. I miss the old sight glasses - that made it easy, charge till the bubbles stop.