Whats up everyone, Im in a dilemma. The dilemma is whether or not I should use a vacuum pump to recharge the AC.
- Got a 2003 Mercury Grand Marquis with 98k miles (my first car!) and a mechanic said i wouldn’t need to use a vacuum pump because my AC line is absolutely bone dry. He even said it’s a bit concerning that nothing hissed out the lines when he pushed a key in it.
Do I still fork out the $80 on a vacuum pump to make sure there’s no moisture?
Nothing hissing means the pressure inside and outside the system have equalized. That means there's more than likely air inside. Manifold gauges are $52 on sale at Harbor Freight right now. Get a set and hook up to the valves, then use the vacuum pump to try to pull and hold a vacuum. If it holds, as @chucktobias said, you'll want to replace your receiver/dryer and probably the orifice tube. Vent the vacuum before disassembly. The receiver dryer has water absorbing material inside that slowly gets saturated when air is present. R-134a can deteriorate and produce hydrofluoric acid in contact with water, which will destroy the system. Be careful, this can be a dangerous job.
I’ll stop by Harbor Freight and Damn, this job got a lot more complicated.
Where can i get these parts? Why will i need to replace the orifice tube? To be honest, Im a complete novice, I don’t know what that is and i don’t know what a receiver drier is either.
The orifice tube is what the refrigerant goes through in order to get into the evaporator inside the dashboard, where it cools you off. It's basically a little screen. There are also designs with expansion valves. Ford tends to use the orifice tube layout because it's cheaper.
The receiver/dryer or accumulator/dryer is a metal can a bit larger than a soda can that is on the low pressure side. Generally they're painted black, and the low pressure port is on it.
I was a novice as well a couple years ago. My experience with A/Cs came from engineering school. No formalized HVAC training. One of the videos Chuck posted above I used when I serviced my Ranger's AC a couple years ago. It's still blowing freezing cold. Take your time, do your research and ask questions here if anything is unclear. You'll be dealing with up to 300 PSI systems on the high side.
Thanks for the answer! I will use the pump. Why should the receiver/drier be replaced? How do i find a leak without putting refrigerant in?
Aside from the fact it's nearly 20 years old the receiver/drier will have become saturated with atmospheric moisture. It needs to be open to atmosphere for as short a time as possible.
Check to see if the AC system holds vacuum when you purge it. You can also look for signs of a leak like oil around fittings or obviously bad hoses. Other than that you would need to charge in some refrigerant with UV dye and look for leaks. (Or use an electronic detector.) Pay attention to the service valves, especially the high pressure side. Might be best to just replace those before putting in refrigerant. Hopefully you don't have a leaky evaporator since the dashboard has to come out of the car to replace that.
Be sure to wear eye protection when working on air conditioning. One wrong move and you can have refrigerant spraying all over the place, and you do not want that stuff getting into your eyes.
Pulling vacuum on an empty system is really only needed if you want it to work. With no pressure it's a good bet it's been exposed to atmospheric moisture. The receiver/drier should also be replaced. On the face of it though there is a pretty bad leak that needs to be tracked down as well.
To recharge you'll need a manifold gauge set to monitor pressures as you put in the refrigerant, which needs to be the proper amount by weight. Do not use a "recharge kit" that just has a cheap low-side gauge and contains destructive sealer.
https://www.youtube.com/watch?v=0HCSsv3uYfM
https://www.youtube.com/watch?v=_IBFLMYZEzI
Thanks for the answer! I will use the pump. Why should the receiver/drier be replaced? How do i find a leak without putting refrigerant in?
To be honest, Im a complete novice, I don’t know what that is and i don’t know what a receiver drier is either.
You definitely need to do some research before tackling this. You can do a lot of damage both to the car and to yourself. A shop manual covering the AC system would be helpful. Some libraries have those available. You could also subscribe to Alldata DIY for 30 days for about $20.
It's a good idea to replace the orifice tube while you're in there, assuming it's accessible. It looks like this and only costs a few dollars:
Your receiver/drier looks like this:
