Tools / Equipment needed for A/C work ?

[gerryvz]

One of the few areas that I won't currently tackle with my cars, is A/C work. For example, a few years back when I had my 560SEC re-converted back to R-12 and had a new compressor, receiver/drier and expansion valve installed at the time it was converted.

I'm not afraid of the actual mechanical work involved with A/C stuff, I just don't have any of the specialized equipment (gauges, pump to pull vacuum on the system, and so forth).

Can anyone who does their own A/C work, provide a list of equipment needed (photos would also be helpful to illustrate each piece) for the home DIY mechanic to do their own A/C work? Approximate costs would also be appreciated, and also where to buy it. I know I would have to get the on-line certification to legally work with R-12 and that is fine.

Thanks for your help folks !

Cheers,
Gerry

 

[alabbasi]

Gerry

You probably have all the tools that you need to do a/c work , except for a vacuum pump and set of gauges. If you're trying to identify leaks, there's a couple of ways to do it and some are more sophisticated then others.

1) Leak sniffer - basically a probe that makes a sound when it sniffs refrigerant gas , kind of nice but not a critical tool. Good for finding under dash leaks that are hard to get to. - This tool is expensive new, but can usually be found cheap on ebay.
2) Spray bottle - OK you probably have one. Mix dish soap and water and spray it on connections. If you see bubbles, you have a leak.
3) Black light and yellow glasses - For detecting leaks with UV die.
4) Recovery machine . Kind of useful if you have a fleet that uses R12. Very expensive new, and very cheap used. Get one with a built in vacuum pump if you have the space and feel that you must have one.

HF makes a good vacuum pump but rubbish gauges. Get them used on CL or buy new Robinair.

For a good set of gauges, and a vacuum pump from HF (when the 25% coupon is applied) you're probably going to spend about $150 and about $25 (what it cost 12 years ago) for the test.

 

[Trae]

Hi guys,

Over the next month or two, I will be trying to identify a slow leak in the AC system in the 93' 500E.
I have a vacuum pump and set of gauges and will be using Black light and yellow glasses - For detecting leaks with UV die.

I bought a 30lb. bottle of 134a from Sam's Club for $80. With a loss rate of 4-6 oz. every three months, it should last for a LONG time, even if I don't locate the leak.

Three months ago, I replaced the low pressure shrader valve because there were bubbles coming out with the soap and water and spray method.
I also noted that there were small amounts of yellow die coming out of the high pressure shrader valve.

I charged the system and it lasted a little less than three months before the compressor would no longer engage.
This time around, I will replace the high pressure shrader valve before I move to other items.

I saw no leaks anywhere in the system with the black light. Of course, the only place I did not check is the evaporator because of its location (and my stubborn refusal to do that 20hr. job that would turn into a three month job for me)
.
Hoping the high pressure shrader valve is the culprit, but I am not holding my breath.
I will keep you posted.

In the mean time, it is cheap to recharge every three months.

 

[samiam44]

I would suggest avoiding all robinair products. I've been burned badly by their lack of quality. If you buy a new vacuum pump via amazon or gauges- there is no warrentee unless it was purchased from a robinair dealer(aka non of the discounters will get you a warrentee). The pump had porosity in the casting and would have failed any sort of visual inspection-if the company had any quality control.
Yellowjacket is much better. No parts available for robin air. I have a set of gauges and after sniffing for a while- it was defective hoses. Quality hoses cost more than the gauge set.

If you are going to do anything. You need a good thermometer, gauge set, specialized micron gauge, vacuum pump. Using a digital scale with a 30lb container to get the charge accurate. I use a disposable siring to get the cc's right for oil. Many times the leaks are at the shrader valves. They make a tool (~$40) to R&R the schrader valve without discharging freon. It screws on the fitting, then there is a ball valve and the far end has a rod w handle. You remove the schrader vale w the rod/handle, pull it back and shut the ball valve. Then unscrew the cover which hold the rod/handle on- it's slick and works well.

Trae, 4-6 oz is not a really small leak. You loose oil too with the freon. So if you are adding 6 oz 3 months X 4 months- that's 24 oz/year. The system is 1 kg, which is 2.2 lbs or 35 oz or you are replenishing 68% a year.

The micron gauge + N2 is great. Nitrogen is a dry gas(absorbs moisture) and makes finding small leaks easier (w a little freon for leak detecting). Micron gauge I evac a system and then see how many microns of vac the sytem will retain. New compressor(front seal pristine), you can get ~ 200 microns or so. Mobile system should retain 350-400 range for 30 minutes without a problem.

R-12 systems are extremely easy. I would do new hoses and a compressor, flush everything. I would re-assemble, add oil to each component per MB FSM and keep the dryer sealed till you are ready to evacuuate the system. Pull it down for a long time( 3-4 hrs is good), shoot it with dry nitrogen, stabilize pressure and then see if it leaks. If so I use the commercial blue bubble (works better than soap/water). But you should be good. Add a can of freon. You may dip the can in hot water to help vaporize the gas. Then start the car, and charge till no bubbles @ sight glass. If your gauges are accurate- you can measure the pressure and take a IR temp on the line. The difference between theoretical and measured for the freon, should be your superheat- which ~10-12 degree( I think, but you can look up the benz expansion valve in the omega catalog and see what the spec is). Note, charging inaccuracy is amplified on non critical cooling days. Ie charging doesn't work nearly as well at 70 F than 100 F.
Obviously, as charging you need to monitor high and low side gauges. Make sure things are operating normally. This is done per FSM and the rpm is 1500-2000 rpm(guess). All our pros on the list live in Hot climates- so I'm sure they will have good advice!


Michael

Michael

 

[Trae]

Wow Michael,

Great advise!
With the evac pump, we were able to retain 500 micron range for 30 minutes using nitrogen, so I did not think the leak to be very bad.
I read that the system takes 1000 cc. or 33.8 oz. That is how I charged it last time (in the summer).

Since I have lost most of my charge at this point , I am going to replace that HP shrader, charge the system (if I get a warm day) and wait for a leak again.



Where can I get this disposable siring for the oil?

 

[samiam44]

I agree.. if it held nitrogen, your leak is shrader valve. Might consider adding an ounce of oil at recharge.

Farm store or pharmacy for a syringe.

M

 

[Trae]

Thanks Michael.
I might charge it tomorrow. I'll let you know the results.
With all the "special tools" floating around, I thought is would be another special order for the syringe.

 

[gerryvz]

I ordered a pack of the syringes with the curved tips on Amazon, I think I got like 5 of them for $5-6. Amazon Prime, too !!

 

[alabbasi]

You should still be able to get an oil charge (few ounces of oil + a few ounces of R12 or R134) if you need to add oil.
You can also use these kits which are designed to add UV dye to charged systems for adding extra oil to a charged system without having to evacuate.

http://www.tooltopia.com/robinair-1...QPQsWaVPvc0n51KfMvTlPXa0kOwUA8f62waAkzr8P8HAQ

 

[samiam44]

The old days we would add oil to an empty can, evac and then pull it in the system. Autozone has 1 ounce charges you can put in the system via low pressure port. You can get freon w/ oil, but I think it comes with sealer. I don't want any sealer dye unknown oil. There are different viscosities on PAG and Ester oils. You need the correct one for our cars.

M