I have searched the other threads, but am creating a new thread because I have what I think might be a special condition. First of all I have a 98 F-150 with the V-6 engine and manual tranny. The truck has 126,000 miles on it. I notice that this summer as it gets warmer that the AC does not seem to cool off the interior as quick as it did last summer. The air just does not seem cold out of the vents. After about 10 minutes or so, as the truck cools down, then it blows cold. Now, my truck AC compressor has always cycled frequently since it was new(this was what I thought was special). about every 5 or six seconds or so. But now it cycles even more frequently than that. Of course, I took it to the dealer when it was new, thinking it was undercharged, but those dealer idiots just told me it was normal. I knew better, but what could I do, plus it cooled very well at that time. So, is a recharge in order? I have never done it before but refuse to take it to a shop that will for sure overcharge it and blow a seal just to generate more business. I can break it just fine on my own and don't need any help from the "experts". I have to admit that I am afraid to touch it myself for fear of adding too much and blowing a seal myself. How do I avoid this? I am fairly mechanically inclined and much more careful than auto mechanics. What type of kit is best for me and what type of refrigerant? I always thought that sealers create as many problems as they solve so I avoid those, but would a little oil combined with refrigerant be a problem?

 

it sounds like your under charged if it cycles every 4 sec.
go to your local parts store and get a can with the gauge on it it will cost a bout 20 bucks it is coler coded and it will tell you if your under charge or not . jus t follow the directions its easy
this is the simplest way to do it without getting into a overdrawn explanation on how the sytem works and what the pressures should be
also get some degreaser and clean the condensor coil in front of the radiator this will help with the cooling also.

 

jcc, thanks for your help. I think it just might be that simple.

BTW, I failed to mention that I did take high school auto mechanics and college level physics as well as HVAC class for my construction degree and am familiar with how an air conditioner works, so feel free to use those "big" words!

Quick update: after reading some more threads, I went out to my truck to look under hood. I understand that I am to connect to the LOW pressure side, where the larger hose exits the compressor and goes to the firewall. I traced this hose and it has no fitting on it. It goes toward the firewall, but then terminates in a medium sized canister that I believe is the reciever/dryer ,correct?, There is a fitting on the receiver/dryer. Is this the low side where I connect the recharge kit to? Also, I traced the high side just to be familiar with the system, it goes with a smaller line from the compressor toward the condenser coil, goes through a small canister which I could not identify (what is it?) and then there is a line that goes straight up to a fitting, which runs perpendicular to the line that then appears to go forward to the condenser coil. Why is the fitting that is not supposed to be used with a recharge kit the easiest to see and get to? Or do I have the fittings reversed? And, what was that little canister on the high side?

Also, I started to slowly unscrew the plastic cap on the receiver/dryer, to see if it looked like a fitting for recharging, and it started to hiss, as if gas was escaping(truck was off). I tightened it back up immediately. AC still worked after this. Should gas escape from this fitting? Isn't the plastic cap like a tire valve stem in that it just protects the inner valve? Maybe it's leaking here and some was trapped under the cap, I did not give it enough time to see if the hissing stopped.

Just trying to be as detailed as possible here, as I kknow that those who regularly work on their trucks probably know exactly what it all means. Thanks for the help. I am planning on getting a recharge kit in the morning, but would like to get some answers to my questions first and better understand what is going on before I tinker with it tomorrow.

 

the cylinder near the firewall should be the reciver. i am not familiar with that year truck so without looking at i am not sure about the other lines.
the hissing noise when the cap is off .the shrader valeve inside is leaking buy and should be replaced that is were you are loosing your ref.
regarding the r134 with the sealer it should be fine i sell something similar for residential and comercial units that my customers swear buy so dont worry to much about that

 

Thanks again jcc, I did it this morning and it's blowing very cold, of course the real test will be when I go out there again at abour 3 or 4 pm when it's close to 100 degrees, but I can tell the difference. It cycles far less than it ever did, and watching the gauge taught me something. As the compressor runs, the pressure on the low side goes down, when it drops below safe, a sensor cuts of the compressor. then when it's not running, pressure increases, and when it rises far enough, the compressor kicks back in again.

I ended up taking back the all-in-one can with the sealer, and just bought a kit for $19 and a can of straight r134a for $9. Would have been nice to add some lubricant. Should I be concerned with adding any lubricant? Also, there was a small amount left in the can, it was tough to get it all out. I had to keep shaking the can.
I think the shrader valve on the drier might be fine, because it only hissed a bit and stopped. It seems that the cap actually depresses (from it's shape) the valve in a bit, and seals the opening itself. It's the same temporary hiss that happens when I connect or disconnect the charge line tool. You say the sealer is ok? I have always been taught that sealers work by causing the seals to swell. This works great immediately, but it keeps working until it completely eats up the seals. I was taught never to use "sealers" in any component of a car. Is the HVAC different in this respect?


UPDATE: It passed the afternoon test. It was about 100 degrees today and it blew cold. Thanks for the help. Let's hope it doesn't all leak out soon. I have seen old AC systems break as soon as you touch them, I was carefull not to fill it all the way, just enough.