Please Help Me Troubleshoot My A/C Compressor

[crawdad]

Can any of you folks give me some pointers on how to troubleshoot my A/C compressor? It want come on at all when I hit the switch in the cab. I am an absolute clutz when it comes to anything electrical. I do know that the wires are connected to the compressor. If someone could give me a basic step-by-step on what to do and/or check in order to know whether or not it's the compressor itself or the wiring, I would be most appreciative.
Thanks a bunch.

[Slonaker]

It could be that it won't come on becaue it is out of freon, or because the pressure switch (on the side of the drier/accumulator on my '86) is bad. The pressure switch, if working, prevents the compressor from turning when it is too low on freon so that it won't burn up.

Have you checked the freon level? If you are unsure, you can jumper across the pressure switch briefly with the A/C turned on in the cab. If the compressor turns, you have a bad switch or low freon. If the switch is bad, it can be replaced without opening up the system, and the part is not very expensive. It has a schraeder valve behind it so the freon won't leak out.

That is about the extent of my knowledge. As far as testing the switch in the cab, somone who knows more about electrical stuff will have to jump in.

Slonaker

[crawdad]

Ok, that may be it, because it is out of freon. When the engine was replaced, my nephew did not recharge the system. I'll check the switch as you suggested just to make sure. Thanks for the help.

[Slonaker]

If it has not been converted to R134, I would suggest you do it. The stuff is $8 a can at Wal-Mart. I have not priced R12 in a long time, but it is QUITE expensive. My R134 conversion cools well enough for the south Texas heat.

Good luck.

Slonaker

[crawdad]

What all is involved with a R134 conversion? Will parts need to be replaced, etc.? I have heard that some seals will need to be replaced, but that's coming from someone who doesn't know any more about it than me. I'd like to get this thing working before too much longer as it's already starting too get a little warm. We're not south Texas, but we get our fair share of hot around here.

[Slonaker]

They used to say you had to replace all the o-rings and hoses. They don't say that any more. There is a type of oil you can run in it that is compatible with the old oil, but I can't remember what it is called. You use it, and it mixes with the old oil left in the system from the R12.

I flushed my whole system with a $35 flush gun and some flushing solvent. I had to pull all the parts apart, so I put them back together with the proper type o-rings. This also allowed me to start fresh with PAG oil, the type usually used in R134 systems. The other advantage is that it allows you to start fresh with the proper amount of oil. Otherwise, you have to just guess how much to put in.

I replaced my compressor with a brand new one, so I wanted to make sure everything was in as good of shape as it could be. You might not want to go to so much trouble.

I would pull the orifice tube. It is in the aluminum tube coming off the bottom of the evaporator. You can identify the spot by the pinch in the tube that keeps it in place. It works like a filter, and by checking it you can judge the condition of the system. If it is full of black crud, you need to flush the system, and your compressor is probably bad. If it is clean, you are probably okay. It is about a $2 part, so you might as well check and replace it.

You will probably want to replace the drier/accumulator. It has a dessicant in it that absorbs any moisture in the system. A new one will be compatible with R134. I think they run about $35.

I forgot to add, you will also need a set of adapters for the ports. I have used the cheap ones from the auto parts stores, but they were pretty crappy. I now buy ones from an automotive A/C shop, and they seem to be much sturdier. They also use their own schraeder valves rather than trying to adapt the old ones to work. I had an old R12 schraeder valve that would not seal for anything, and I ended up doing the job twice because the system has to be evacuated and vacuumed down again so that I could install a new port adapter with an integrated valve. I won't use the cheap ones again.

Of course, before you fill the system, you need to have it vacuumed. This will pull out the moisture and air, and also let you know if it is airtight. If it will hold vacuum, it will probably hold pressure.

Slonaker

[crawdad]

Appreciate the information. That helps a lot. I don't have the tools nor the smarts to do this myself, so I'll probably have it done by someone. At least I'll now be able to converse with them in a manner that makes them "think" I know what I'm talking about.