Guys, I'm trying to find the location to plug in a black wire coming from the thermal limiter on my compressor. I believe that since its not plugged in, it might be causing my compressor to constantly run. Below are some pictures showing what I'm talking about.
In addition, what is the correct amount of R12 to add to the sytem? I think I read somewhere that it should be 3.75 lbs. If this is correct and a can is 12oz, then I should add 5 cans on an empty system. That being said, I'm really not sure what I'm starting with. What is a typical pressure point you should reach when using R12? Thanks for the suggestions.
Usually a fuse problem won't allow the compressor clutch to engage at all. Do you mean it runs constantly when you have the selector lever in the a/c/defrost position or all the time, even when you have off or in the heater position? To answer your other questions...... It appears to me you have a VIR system.....that means "valves in receiver". I really haven't worked on too many of those, but I wouldn't add more that 5 cans to your system........and pressures vary according to the ambient temperature. In other words, on a cool day, the high side might be around 150-200, but on a hot day it might get between 200-250. Low side also varies, let's just say 28-32. But generally on a non-cycling system anything below 28 is too low and indicates a problem. When a system gets hot, the low side can climb above 32 depending on engine speed and the temp of the condenser. If you are charging with R-12, the sightglass can be useful in determining the amount of charge to a certain degree. (hc or 134 can have bubbles and still be fully charged). Again, generally speaking, foaming or bubbles are an indication of undercharge. This is not a very accurate way to do it, but after running the system for at least 5 minutes, if you shut the motor off, while watching the sightglass, the solid column of refrigerant should break away into bubbles within 15 seconds or so on a properly charged system. Less time is less charge, and more time is more charge. You'll never read that in a book, this trick I learned from experience working at Firestone many years ago.
I'm just going to guess, since I don't have my book in front of me, that it plugs into the back of the compressor where the temp sensor is.
That wire connects to a thermal switch on the rear of the compressor. If the compressor has been swapped, the switch may not be there. There will then be a plug held in with a snap ring. You can get the switch and install it, but you have to recover the refrigerant to do it. The thermal limiter is a fuse of sorts. If the head presure got too high (or too low, as in an empty system) the switch would close and blow the thermal fuse. You can leave it disconnected but you won't have the compressor protection. The compressor is designed to run any time the controls are set to AC or Defrost. It does not cycle like a modern system. If that is the original compressor, the proper charge should be shown on that sticker on the compressor. If not, use the sight glass as nailheadina67 mentioned.
Thanks for the responses. I'll try and find a post on the back of the compressor for the thermal limiter plug. To my knowledge the car is all original including compressor. It has very low mileage. A friend added the R12. Prior to adding it, it wouldn't blow cold on the AC setting. Now, if I turn it on early in the morning when its around 80 deg. F, I can feel it cool ever so slightly. It freezes up on the lines shown below. We didn't know how much was in the system when we added it, and didn't have any gauges. I was able to locate some gages and can now measure the high/low sides at a certain temperature. Is there a manual of standard pressures @ certain temperatures to refer to? However, I'm very unknowledgeable when it comes to AC's and dont know which side is the high or low. After doing some reading, I realize I should have vacuumed the system down before adding the refrigerant. At this point, what recommendation would you guys give based on the price of R12 and the circumstances I've described? Add more refrigerant to get the right pressure, or have the existing R12 captured, vacuum the system down and start over?
You'll need to have the refrigerant in the system recovered. (I see an retrofit fitting in that pic). You now probably have a mixture if r12 and R134a in there, not good. The icing may be a sign of overcharging, but could also indicate a problem with the VIR. That's the valve with the fitting on it. It can also be caused by moisture in the system. I have a hunch that the thermal switch connector was unhooked because the thermal fuse kept blowing. This would be due to a problem with the VIR causing the high side pressure to be too high. Don't ever blindly add refrigerant to a system, you can cause damage and/or personal injury. Get a proper set of gauges before you do anything else. On these systems, you can add refrigerant until the compressor locks or a line ruptures. The basic rule of thumb for MVAC systems is: 28-35psi Low, and 2.5 times the ambient temp on the High side, with the engine at 1500, doors open, MAX AC, High Blower setting. This is far from being all inclusive, but will get you in the ballpark. (You check the actual vent temps with the doors closed, but having the doors opens puts the system under maximum load).
Well, it looks like someone may have added 134a to your system :blast: . First go to a A/C repair place and ask if they have a refridgerant identifier. This will show what refridgerant is in you system, hopefully someone just put that 134a fitting to keep the dirt out (that would be great!), AL.
If the system was empty or opened before you added refrigerant and you did not evacuate the system you have air and moisture in it. The refrigerant will need to be recovered and the system evacuated and recharged. If the refrigerant is mixed you might have a problem getting it recovered. A good shop should have an identifier to protect their refrigerant from getting contaminated and to be sure they are using pure stuff in their customer's cars. So you would need to find a shop that does not ID or has a machine just for mixed stuff. I would assume there would be a fee for disposing of mix refrigerant. Or the system would somehow need to be emptied :Brow: and then evacuated. If the system had a partial charge and you just added to it then you could just add more. If it's mixed and works it should be OK, but not correct. R134 does not carry R12 oil well so that would be a concern. A6 compressors are pretty tough. You could add some R134 oil and top it off with R134. My guess is the system is not full so low side pressure are really low and this will cause the moisture in the air to condense and freeze on the low side metal. You could slowly add refrigerant until it got cold. Low side pressure should be good between 30 and 40 psi. A good rule of thumb with R12 is watch the sight glass and pressures while charging. When it's clear with the compressor running it's full. With a mix you might try stopping with a few bubbles left. Personally I only use R12 in R12 cars. HTH
