A/C help

[79jasper]

In light of some recent threads, it seems to be using the "quick recharge" cans aren't exactly the preferred method.
I've seen people mentioning to pull a vacuum, using the manifold gauges, changing the drier, etc.. But it's never anything specific.
I've also seen Gary mention using a fridge/freezer compressor to pull a vacuum/use as a air pump. (My dad used to do that, but I was too young)
I've also seen people mention flushing the system.

I believe my system is basically empty, so I want to maybe use the uv dye, or replace the orings first, then use it.
I want to know more detail on those things I've seen people talk about, just didn't really explain.

My system is R134A. It's a 94.

(I know we have several serious A/C guys here that do this stuff daily)

 

[rlb245]

Before you do anything you should check the system for leaks. You should charge the system with nitrogen to 125 psi and let it sit for 24 hours. If the system loses alot of pressure over that amount of time then you have a good leak. You need to find the leak and repair it. You can bring the system back up to 125psi and use soap and water to find the leak. you see bubbles where ever there is a leak. You can check about 85% of the system this way and repair most problems. But if the leak is in the evaporator it get's ugly fast.
Note : you use nitrogen not air! Nitrogen is a drying agent and will absorb moisture. Moisture is your enemy it tunes to ice and clogs the expansion valve or capillary tube system.
If you only loser 10 to 20 psi over the testing period then put a vacum pump on the systum and pull it down to about -5 and charge the system with the correct amount of 134A. if ya got all the water out of the system you should be good for a while.

Notes : 1. if there is a leak then hope it's in the high side of the system and not in the low side. The low side operates under a vacuum. If there is a leak then air will enter the system over a period of time and the system will stop working.

2. If there's a leak in the high side and depending on it's size will determine how long the system will run before you need to recharge it.

3. Compressors are famous for leaking. O rings dye out, shrink, and break. If your system hasn't been used in a while. rebuild or replace it

4. The condenser coil in front of the radiator is another good place to find leaks

Your best beat is to ensure the system can hold a 125psi charge of nitrogen for 24 hours or a vacuum of -15 for 24hrs.
if it does then the system will cool like it should with no problems if the correct size charge is used.

I hoped this helped. I carry allot of certification in my wallet and HVAC is one of them.

PS: Harbor Freight has a cheap little vacuum pump that will pull a vacuum on the system.

 

[79jasper]

I for sure wanted to leak test first.
Best way to get ahold of some nitrogen? How much?

I would say last time it worked would of been two summers ago when she was parked due to trans issues. I haven't messed with the ac since.

 

[rlb245]

If you no some one with an nitrogen tire inflation kit you can barrow or an AC tech how will do it for you at a low coast. The only other way is buy one here

http://www.harborfreight.com/nitrogen-tire-inflation-kit-with-20-cubic-ft-tank-97061.html

 

[79jasper]

There's a tire shop near by that does nitrogen for the tires.

My boss rents nitrogen banks for testing wells, maybe I could find out where he gets them and see if I could get a 5 gal size or something.

Do you think I could take a empty propane tank and have it filled?

 

[rlb245]

Prooane tank would work but ya might run into a problem from the company that fill the tank. The are governed by state and federal regs. They may not fill the tank for you because of it's original content. Tell them your trying to purge the tank of propane and see what happens.

 

[79jasper]

Ah I see, guess I'll just have to call around and ask.

You say an ac shop may do it?

 

[rlb245]

might be worth a shot to see how much they will charge for pressure testing the system.

 

[79jasper]

To retest the pressure, could I just use the pocket sized pressure gauge?
Or will one of the quick fill adapters with the gauge built in work?

 

[rlb245]

normally you use a gauge set so you can see accurately whats going on. An air regulator gauge set up would work.

 

[79jasper]

Neither of which I have.
Is the harbor freight ac gauge set any good?

It won't be a use once and forget it tool. Will be used for family and friends cars also.

 

[rlb245]

Yes! I use it for most of my auto AC work. I have much larger units for residential and commercial AC. Beside you get your on tire inflation system (grin)

 

[79jasper]

So I need this. http://www.harborfreight.com/a-c-manifold-gauge-set-92649.html
Plus a vacuum pump. Which I was thinking of taking a pump from an old fridge/freezer.

 

[rlb245]

The smale vacuum pump is about 25 bucks but perfect for your job.

 

[79jasper]

Cheapest I saw was about $90.
Only thing I saw for $25 was the hand pump brake bleeder.