Hello, I have a problem with my a/c system. It has not worked in a while so I figured I had a leak. I vac the system and filled it to see what would happen. It held pressure fine but I could not get the low pressure switch to kick the compressor on, so I shorted it with a paper clip. At that point my perfect pressure reading went from about 35 psi to near zero. Does this mean I have a leak somewhere?? But when I remove the paper clip the pressure rises back to normal. Even when I "trick" the compressor I don't really have cold air. Has anyone herd or had this problem before? Do I have an electrical problem, I asked myself but when I turn the control switch inside that controls the fan speed "with the paper clip inserted" I can get the compressor to turn off and on normally. Is my low pressure switch bad?? blocked line? Block in condenser? bad orphis? please help,
Jordan

 

I'm thinking a restriction on the low side .. perhaps a plugged orifice/H-block.

Replace your receiver/accumulator and your orifice/H-block and see if that works. How does the "touch" method work? Do the lines get cold after your controlled restriction (aka, orifice tube)? Are the lines going into the compressor hot, and the condenser hot? What about the cooling fans, to they kick on?

 

Thank you, I will try that to see. I have not tried the touch method but I will and get back to the forum. To answer your questions: it does not have any cooling fans (just an engine cooling fan) I also am thinking a block somewhere. I can get the compressor to run if I short the low pressure switch but then no pressure reading. I have never seen anything like this before. Thank you for your response. Its nice to get a second or third opinion on things. I am kind of new to automotive stuff and eager to learn as much as I can.

 

orifice/H-block? Do you mean orifice tube or the expan. valve orifice?

 

Yes, exactly. Orifice tube and expansion valve. I'm unsure what device these trucks use most commonly, as my own truck is not A/C equipped.

 

I thought all a/c systems have an expansion valve. So some have ex. valve and some have an orifice tube? I bought an accumulator yesterday as I knew I would be replacing it anyway. I also bought an orifice tube for it.

 

Hello, I have a quick question about charging my A/C system. The system calls for 2.0 pounds. Does that mean I need 32oz. for a full charge? That seems a bit high to me. Does anyone have a conversion chart for pounds to oz or a mathematical wrap up of conversion (pounds to oz)?

 

https://www.google.com/webhp?sourcei...w=1680&bih=925

Yes, you need 32oz. If that's what it calls for, put it in. Make sure to vacuum the system after it's been discharged, worked on, and you're almost ready to charge it again. Vacuuming the system actually boils the water moisture out of the air inside the A/C system. This is very important, because you can have ice accumulate on your controlled restriction (the orifice tube, or expansion valve) and you'll have intermittent cooling of your evaporator. So, my advice to you is to make sure to vacuum the system for at least 30 minutes. Coat all O-rings that you see in fresh refrigerant oil (I'd replace them if you have new ones available).

Remember, venting refrigerant into the atmosphere is illegal and harms the environment! Use a refrigerant recovery machine to recover any remaining refrigerant in the system. (These machines can usually vacuum as well)

 

Hello again, This may be a dumb question but am I correct on saying I need to add 1/2 oil to compressor and 1/2 to the accumulator? And also another question. How much oil does each component of my system take, and what type eg."visc" do I need to get

 

Honestly, you got me on the viscosity thing. Personally, there's always a bottle of universal PAG oil setting around whenever I do A/C work. I just use that. So here's what I'd use:
Looks like total, you get 8oz of oil for the whole system. I honestly don't know how much oil goes in each component, but drain it out of the compressor and measure it. Add that same amount back into your new compressor. Same for the accumulator. If nothing is in the accumulator, just add that 1/2-1.0oz of oil and charge it up.