About to replace the A/C compressor

[was28]

I have been troubleshooting the A/C system on my '94 Explorer XLT and think my problem is the compressor but would like to confirm this. With the engine running, the A/C on max and my gauges attached I am getting a vacuum on the low side and no pressure (zero) on the high side. I have bypassed the low pressure cut-off switch and the clutch is ingaged. With the engine stopped, I evacuated the system and pulled a vacuum to about 28 inches. After 6 hours the vacuum held, so I don't think I have a leak. I also replaced the accumulator and orfice tube. I'm thinking that the compressor is providing the suction but not the high pressure. I tried charging the system after I vacuumed it and found that the high side pressure went to about 30psi as long as R134A was flowing from the can. As soon as I stopped adding refrigerant, the high side pressure went back to zero. Am I right in changing the compressor? Thanks, Wayne

 

[vidfix55]

if you are adding R134 to the system you should show some kind of pressure, engine and compressor running or not even with a bad compressor. How may cans are you adding? When adding freon, the system with full vacuum should take 1 can w/o any engine assistance.(if you liquid charge low side) gas charging you should get half a can. From there depending on ambient temps you should be showing around 75psi (this time of year) on the low and high side engine off after everything has stabilized. if your getting 0psi both sides engine off you got a monster leak that seals itself when you pull vacuum. Front seals on compressors will do that sometimes. The vacuum on the system will suck the seal back but that only with small slow leaks. If your showing 0 right after adding a can, you got a major leak. I don't know your experience with AC and gauges but do you have them on right? also what kind of gauges do you have? Some gauges have a secondary shut off so if your adding freon the gauges will show pressure, but that from the can, not the car. Can you hear anything going into the system. You may hear some expansion in the system as the pressures increase. Why did you replace the accumulator and valve anyway?

 

[was28]

Update

Thank you vidfix55 for your comments. Three days ago I went ahead and replaced the compressor. I evacuated the system and recharged with two cans of R134. With the engine off, I added the first can as a liquid at the low side. I started the engine and added the second can as a gas. My low side pressure went to 24 psi and the high side to 218 psi. I shut the engine off and waited for the system to stabilize. After a short time, both low and high pressures read 75, as you stated. I restarted the engine and checked my vent temperature. I am getting 43 degrees with an outside temperature of 76.
I should probably add a little more R134 as my pressure readings are a little low. I'm also going to borrow an electronic leak detector and go over the entire system.

My next project is to determine if the old compressor really was the problem and then rebuild it and keep it as a spare. Thanks again, Wayne

 

[Cobraguy]

I'm not sure what a 94 holds for Freon, but a 2nd gen holds 30 oz. That's two and a half cans.

Now, what did you do about oil when you changed compressors? Did the new one come with a complete charge? Any oil at all? Did you add any if necessary? Did you check the orifice tube for debris and clean/flush the entire system if needed? Lots of work to do here yet...

 

[vidfix55]

94's hold 32oz of 134a but since it technically still a R12 system. (they didn't really change anything from 93 to 94 except the fittings) you need to be careful when you get around 30. If you have to much in the system even an ounce you risk over pressurizing and blowing off out the relief valve. it will scare the hell out of ya, you'll think your engine is on fire when you get that puff of white smoke from the valve. Been there done that in my 92, happened in a drive through, the lady in front of me came out of her seat it scared her so bad.
If your holding pressures now an before it held nothing even after adding freon its a safe bet the the compressor had a trashed seal. more then likely the front seal b/c they are known for leaking under pressure but not under vacuum. O rings on the back leak but they generally leak no matter what.

 

[was28]

Looks like I need to add another 1/2 can of R-134. To answer Cobraguy's questions: I replaced the orifice tube because I wanted to see if there was any debris in the system. It looked OK (no gunk or metal filings). I also replaced the accumulator and added 2 ounces of PAG 46 to it. I drained the oil from the new compressor (actually rebuilt) and refilled it with 5 ounces of PAG 46. I also installed new o-rings at the rear of the compressor. Because I didn't find any debris at the orifice tube I did not flush the system (Time will tell if this was a mistake!)

 

[TexasBlonde]

I need help/advice re replace 1997 a/c compressor

A few years ago the pulley on the a/c compressor clutch went out and we bypassed it with the serpentine belt made to fit w/o the clutch pulley. I think we now have enough money to replace the pulley, but I told my husband I wanted to go ahead and replace the compressor too since it is almost two decades old. I could not find where you could buy the compressor w/o the pulley assembly. I could not see paying $100 for the pulley and a short time later paying $174 for the compressor with the pulley assembly.

Now all of a sudden he is trying to tell me we have to replace about 200-400 dollars worth of additional parts if we replace the compressor. What is the real deal?

Keep in mind the only part that had failed was the bearing in the pulley. It was operating just fine with cold air prior to the bearing going out. We do have the new serpentine belt for it.

Another question I have is who do I need to take it to to get the old freon removed before we replace it with a new compressor.

I do have two sons who are capable of taking the old compressor out and installing the new one. I just need to know what does HAVE to be replaced at the same time the compressor is replaced.

I am an older woman who has an even older hubby (64-76 respectively) who just cannot take this Texas heat and humidity and I need my a/c fixed.

Addendum: We do have a person who will clean, vacuum to remove any particles and or rust in the system. Also while looking to order the new compressor it stated we needed a new expansion tube and accumulator. I did add those to my list of parts. Is there anything else that will be necessary, other than new freon, to replace the compressor?

Help!?!

 

[Cobraguy]

if you mean flush the system when you say "clean", then you will need a flushing agent. I assume your friend has all the tools necessary...such as a vacuum pump, flushing tools, etc. When you say "rust", that throws a huge flag. If there is rust in your system, then I wouldn't bother with your plans. Whatever is rusted MUST be replaced prior to charging your a/c system. Fortunately, there aren't a lot of places that can rust as most of it is aluminum...but you MUST find it and replace it. You should also install a new orifice tube...but that is only a couple of dollars. Just match up the one you have. Again, special tools may be required to remove it. Hopefully it will come out with a pair of needle nose pliers.

Finally, one huge misconception is evacuating (vacuum) an a/c system will clean any type of dust, particles, dirt, etc. Nothing could be further from the truth. Placing a vacuum on the system does one thing and one thing only...it removes any moisture in the a/c system. That's it. When you put appx 29 inches of vacuum on the system, it lowers the boiling point of water to appx 59°...give or take. This means any moisture in the system will turn to vapor...and can then be evacuated through the vacuum pump. If there are ANY solid contaminates in your a/c system, flushing or component replacement is the only way to get rid of them. Let's hope you won't have any of those problems. I can tell you that if all you lost was the pulley, and your system still has a good charge of Freon, then chances are good you will be safe and can get away with a recovery, replace components, evacuate, recharge.

Be sure and double check...hell, triple check...that your new compressor comes with a full oil charge.

Nothing wrong with older women!!!

 

[TexasBlonde]

Fantastic information!

Yes, one part is the orifice which is about $2.00 and the other part is the accumulator or drier.

I believe they said the compressor is shipped with oil in it and that oil has to be drained out and a different type of oil added.

My son has had the parts guy include the oil and freon that is needed for the new compressor. As far as I know the old compressor is still tight and probably still has a full charge of freon. Plus I have seen nothing around it or anywhere else that has rust at all.

I believe there is a video somewhere here that goes through the process of replacing the compressor and clutch. I am going to watch it. I do like to research repairs and make sure I understand the process as well.

We had a 70' tree fall on our house when a storm's straight line winds hit in the wee hours of Mother's Day this year. We had people telling us it was going to take a crane and more likely two cranes plus someone who knew how to remove a tree of its size. They were throwing out 10K and even 15K to get it removed. That was not going to happen. It did not cost even close to that amount but there were people who were trying to push to see how far they thought they could dupe you into letting them charge. The young man who removed it did get ten more jobs from others for removing or topping out trees.

I appreciate all of your good information. Thank you.