ok im unfamiliar with ac units. maybe someone can help.. I have a 92 f-350 crew cab dually with a 7.3 diesel. Compressor does not engage when i turn it on. It did work when i bought the truck but i was told there was a leak in the system. will the compressor engage with no pressure in the system? im thinking of buying the retrofit kit from r-12 to 134a and also getting the leak finder and possibly new o-rings. Any help on this would be greatly appreciated. Or any better ideas also.

 

The compressor should not engage without freon in the system because of the Low Pressure Switch. You can purchase a cheap Pressure Tester at a local autoparts store to see if you have any freon left in your system. As for the retro fit kit, you are going to have many different opinions on this issue. I've retrofitted two cars without incident, but I do not use my A/C all the time.

The leak finder kit is too expensive when you can do the "soapy water" test. mix in a spray bottle a little dish soap and water, spray over system, bubbles=leak. This test only works though if you have pressure in the system.

A "bottle of stop-leak" is never a good idea, as it does stop leaks in small areas but it also clogs up smaller passageways.

The o-rings I cannot write about as I have no experience with them.

Bottom line is that if you are a "do-it-yourself"er, you may want to purchase a cheap pressure gauge and report what you found. Many people will be willing to help.

Hope I have helped and confused you.

 

The compressor will not run if the static pressure in the system drops below ~42psi. If you were told there was a leak, and now the compressor won't engage, I'd say the system is empty. Remember, leaks in anything will only get bigger.

You can check the operation of the compressor and wiring by bypassing the Low Pressure Cycling Switch on the accumulator briefly. It's a 2 wire switch and the accumulator is the "can" near the firewall on the passenger side. Don't leave the jumper connected for more than a few seconds. Jump the connector and see if the compressor engages (engine running, AC on, of course).

Do yourself a huge favor and stay away from those retrofit kits! There is much more to conversion and repair than adding fittings, oil, and refrigerant. The parts in those kits are of very poor quality and their instructions are totally lacking There's nothing magic in those kits and you can "build" one with good parts for about the same price.

You can repair your system, but you absolutely need access to certain tools. These are:
- A manifold gauge set. Harbor Freight has a decent set for ~$40, AutoZone ~$50, many chain parts stores will rent them.
-A vacuum pump. They cost $130-500. www.ackits.com has a nice one for DIY for $135. Again, many parts stores will rent one.
- Spring Lock coupling tools. ~$15-40 depending on the type. You'll probably have to buy these. I recommend the spring loaded clamshell type.
- A can tap. ~$10. You'll probably have to but this. Don't use the cans with hoses attached. They will not attach to the gauge set and can introduce air into the system.
Investing ~$300 in tools to fix your ac might seem counter intuitive. Keep in mind that, if you have them, you'll never have to pay for an AC repair again. They will pay for themselves with the first repair job. You can also recoup some of the money by doing AC repairs for family and friends. Just something to consider.

First, you need to locate the leak. The most common area is the o-rings in the spring lock couplers or any ither line fitting. The dead giveaway of a leak is oily dirt around a fitting. On a vehicle of this age, it's recommended to replace all of the seals at all of the fittings. A seal kit is about $9. Easy to do and cheap insurance. This will fix about 80% of leaks.
Look for the same oily dirt at crimped hose connections. Also inspect the hoses and metal lines for physical damage, rust, etc.
Look closely at the condenser for rock damage and oily spots indicating a leak. Here in Ohio, I see a lot of rust damage on the tubes on the condenser. Look at the tube running down the passenger side of the condenser, at the bottom where it enters the condenser. That's where they rust.
Look for oil stains on the bottom of the compressor. This indicates a leak in the comp body seals. Also look around the compressor clutch. These leaks require a compressor replacement and are very common leak areas on older vehicles.

Once you find the leak you can assess the cost for the repair. You will need to replace the accumulator, about $35, and the orifice tube. The orifice may be a separate part ($2), or part of the liquid line (~$20). The system should also be flushed of the old oil. Lacquer thinner and lots of compressed air will do the job.

This sounds like a lot when written down, but actually it's pretty easy. If you can rent the tools, you can often fix the AC for under $100.
Ac systems need to be fixed correctly. Any shortcuts you take will usually lead to more expensive repairs later. NEVER use any kind of sealer in an AC system. They're basically snake oil 99% of the time and can badly damage your system if used improperly.

This should get you started. There's more to do after you find out what you need.
Good Luck

 

one more thing I might add is to pay close attention to your accumlator. FOr some years ford thought I would be a great idea to insulate suction side componets. Componets that while the system is running, get very cold and condensation forms on these parts. water leads to rust. Check your accumulater for this foam insulation and if it has it. just replace it. its about 35 bucks and cheap insurance. more than likely the oil oriface in the bottom of it is clogged as well.

 

thankyou i appreciate the info and i will try and give an update as soon as i find out more info or any problems, questions, etc..first im goin out to see if my compressor flips on. Also there is some sort of pressure in the lines. If i push on the valve air does exit, just dont know if there's enough pressure