Yes, I knew that the recharge was not due to the supposed vacuum leak I was hearing, I was just trying to fix it because it was annoying. It's just what led me to find out that the hissing is coming from the A/C lines, evaporator area. Maybe this is just due to there being no charge in the system. What's a ballpark estimate for a recharge and leak test on a R134a system? Are there specialized shops to go to or do you just take it to any old service shop?
If you flat lined you may have air in the system now( there is no way to know unless you vaccum the system down), air will ruin the system over time. Not to sound like a stickler but charging your a/c system by lowside pressure doesnt mean anything. Its the high side pressure that is important for cooling and you need to make sure your over charged. Over charging and undercharged with air in the system can both still show 25 on the low side. You should probably be running around 225psi on the highside when setup correcly. If you were Zero and put 1/2 a can in to get 25psi on the low side, this tells me you have lots of air in the system.
If you have converted your system to R134a from the old R12 system and you did not change the hoses the smaller R134a molecules are going through the hose wall. This is normal to have to recharge it every year. new R134a systems have a barrier hose that the R134a cannot go through as easy. If you are hearing a leak with the system empty then it is not the A/C system that is leaking. It is a vacuum leak somewhere. As for overcharging the system do not do that, when R134a systems were first starting to be converted there was many formulas out there to get the right charge. don't worry about them charge it with the same amount as was OEM for R12. Put a dye in the system when you have it recharged. The most important step in servicing a A/C system is pulling a -28 inches of vacuum on the system for at least 15 min before you charge it. This will pull all the moisture out of the system so it will work properly. Then let it stand so you can monitor the vacuum for at least 10 min to see if it has a leak. if all is good then have it charged. You need to pay attention to both high and low side pressures and if you have a sight glass on your filter that will help in the charging process. Hope this helps.
Maybe he means 25 PSI, measured at the low side? I think I read that wrong too at first. I thought, "Man that thing's going to explode. Violently."
this hissing sound, does it only happen when you have the a/c on? you did not make a hole on the evaporator by any chance when you were installing your gauges? That happened to me once when I was installing the ecm under the box.
This is what I'm thinking. If there is air in the system, maybe this is causing the sound. As far as the hoses, I don't know if they were replaced or not as the conversion was done before I got the car. It sounds like vacuuming the system is a good place to start. If I end up swapping to the 5.0L with the serpentine setup, do I just use the pump off the donor car? I may just wait until I do that and have new hoses made at that point if they need upgrading.
Yep, got to be the freon going through the expansion valve. If it had trapped air, it wouldn't cool right. That's one reason to always vaccum down a system before you charge it.
Yeah what he said. The easiest way to tell if the car came from the factory with AC is the vents in the dash by the ashtray, those were only on the AC cars.
I have just tried to put a can of freon in my a/c and I did not hear or see any leaks but the can is empty and the pressure still not reading....The system, so I think, is or was empty. Any ideas on how many lbs it takes to fil it up or any other problems it could be? Thanks. Also, I just bought this car a few days ago, 73 Maverick, I use to own a 75 comet but it did not have a/c....al new problems for me. Temp-100 heat index
you have a leak. or your doing somthing wrong. an empty system will be around 3 lbs. you will want to find the leak before you put any more refrigerent in it. if you dont have the proper ac equipiment and shop air it can be very hard to find the leak. i will hook shop air to the ac system, pressureize it then close the valves. if it holds the pressure for 1/2 and hour with out droping then you can put a vaccume pump on it and suck it down. see if it holds the vac for half an hour. if so then you should be good to charge it. you will want to put a new reciver dryer in it after you do any repairs and before you charge it.
