AC Compressor Question

[itzbinnice]

On my 95 XLT the compressor is not engaging.
Two years ago I had refrigerant added (66.00) by a local shop and the AC worked fine all summer. Last year turned the AC on in the summer and again no cold air and the compressor did not engage. This time the same shop charged me 103.00 to add refrigerant, he also checked for leaks and there were none according to him.

Yesterday I tried the AC for the first time and again compressor not engaging so no cold air. I suspect low freon again and that's why the compressor not engaging. I do know that the compressor engaged during the winter when putting in heat or defrost mode, it always does that and was designed to do so.
What stumps me is now if I put in in heat mode the compressor does not cycle.
I'm not sure if it shouldn't do that since it's 75 degrees out or because it also needs the correct amount of freon to cycle on.

The power distribution box has no fuses or relays, the only fuse I could find was fuse 18 in the fuse panel indicating AC system. Checked the fuse and that was good. I also disconnected the two wire connector to the compressor and checked with a test light, there was no power.

Does anybody know what other tests I can perform to rule out the compressor being defective and advise if the low freon will not cycle the compressor when in heat mode. Maybe a charge will solve the problem.
Either I'll find a different AC shop or bring the KY jelly with me if I go back to the shop I've been to previously.

BTW my neighbor had one of those gauges that comes with the do it yourself charge kits. I put the gauge on the low side and it showed 35 PSI, don't know how accurate that is though.

 

[crunchie_frog]

I am not sure you are dealing with a scrupulous mechanic if he charges your A/C twice and tells you there are no leaks. If he has actually charged it twice, then you have a leak(s). You can do a visual inspection for leaks of the hoses, compressor, accumulator and the condenser by looking for oily residue on these components. The evaporator could also be leaking but it cannot be seen readily like the other components. You could try adding some refrigerant that has either a red dye or a UV dye (need a black light to see the leaks). You can probably get a can for ~$20 or so. If you want to test your compressor, you can short circuit the connection that goes to your pressure switch that is on the top of the accumulator. I would only run the compressor for a few seconds if you do short circuit the pressure switch connector. You could also have a bad pressure switch, there probably is a resistance test you can find someone on the internet or on this forum.

Sounds to me like you have a leak, just the mechanic did not take the trouble to find it, which he is supposed to do by regulation. If you do have a leak, you have to decide if you want to find it and fix it yourself or pay the money for someone else. If you do it yourself, you need a set of gauges (~$50 - $100), some spring coupling removal tools (~$10-$20), a vacuum pump (~$100-$200), the leaking part(s)(~$??), 30 oz of R-134A ($20-$50) and some compressor oil (~$10 - $20). My guess is even it is a simple leak, they will charge you several hundred dollars to find it and fix it or even $500 - $1000 if it is a major part like the compressor, condenser or evaporator.

 

[itzbinnice]

Thanks for the reply crunchie_frog.
I'll try to briefly jump the pressure switch on the accumulator just to see if it goes on. Hopefully it will so I can rule out the compressor.

Although having decent gauges, vacuum pump,etc, is the proper way to check I have no desire to spend hundreds of dollars on a 20 year old vehicle.

I may just buy one of those recharge kits that my neighbor has and try charging it with that for 30.00. If it lasts me the summer it's worth it.

I still need to know if the R134A is low will the compressor still not kick in when in the heating mode. I would think it would not kick in although it did in the winter months. May be just a coincidence that it did stop cycing at one point and I just didn't notice it since the vehicle is not used often.

 

[crunchie_frog]

I am not sure why the compressor came on all winter. I can say that it could have been low already and now that it has warmed up the leak rate of the R-134a has increased and now you have insufficient pressure for the compressor to come on.

 

[itzbinnice]

This morning I went to check the pressure switch and discovered that the AC repair shop broke the locking tab on the connector to the switch. He then taped it in place with duct tape and put black electrical tape over the duct tape. Sloppy work habits, had he just used a screwdriver he could have disconnected it without breaking the locking tab.

I put a test light on the two wire connector going to the pressure switch and there was power going to it.
I then jumped the connector and the compressor immediately clicked on, I only let it run for a couple of seconds. The good news is the compressor is not defective. I think I'll just buy a refill kit and give that a shot and bring it up to 45 PSI to see if the compressor engages.

 

[crunchie_frog]

Your system refrigerant capacity should be on the labeling under the hood, I think it is 30 ounces. You probably have some in there so it will likely take two cans (12 oz each). You may want to try some with stop leak gunk in it if you are not planning on repair. You know you require a certain amount of oil in the system and if you have leaked some out over time you run the risk of compressor failure if the oil is too low.

 

[itzbinnice]

Thanks for the information, I'll buy what you suggested. I did see the refrigerant specs under the hood but have forgotten the figure, I'll check again before adding the refrigerant.

I'm still a bit uncertain of how to add the refrigerant. I know where the low side is and how to use the can with the gauge on it watching Youtube videos.
What I'm not sure of is will the freon go in without the compressor running.
I can disconnect the pressure switch and jump the connector to start the compressor then immediately press the trigger on the freon can to let it flow.
I'm nervous about doing it this way since I've bypassed the pressure switch.

Do you think I can use this method and get some freon in there, then stop the engine, reconnect the pressure switch, and hope enough went in that the compressor will now run so I can continue to add more until the correct PSI for the ambient temperature is reached.

I saw one video where the guy said the compressor must be running to add freon, he then went ahead and removed the compressor relay and jumped the appropriate pins in the relay receptacle. But my Explorer doesn't have a compressor relay.

 

[crunchie_frog]

Start your car, turn the ac on max with the windows down, connect up the R-134a to the low pressure port, add the R-134a, some may go in and the compressor will kick on by itself. If it does not, you will need to jump the pressure switch connector and continue adding and remove the switch when the compressor will cycle on and off by itself. My guess is after you add one 12 oz can the compressor will still be cycling on and off pretty quickly and you can remove the jumper, but it does take a while to empty a can ~5 minutes. And then you probably need another 12 oz can. You really needed to know how much was in the system before your started. You cannot tell by reading the gauge whether it has 30 oz in it but if the compressor was not coming on at all, you did not have very much left in there.

 

[itzbinnice]

crunchie_frog

Many thanks for the instructions. But I'm a little confused about jumping the pressure switch. When I tested to see if the compressor was working I removed the connector and jumped the wires on the two wire connector.

You stated "you will need to jump the pressure switch connector and continue adding and remove the switch when the compressor will cycle on and off by itself."
How can the compressor cycle on and off if I bypassed the pressure switch.
Do I need to leave the connector on the pressure switch and pierce the wires going into the connector to jump the switch?
Or is it that there is a temperature sensor somewhere that will cut of the power wire going to the pressure switch when a certain temp is reached.

Another concern of mine is how much oil is in the system, no way to check that.

My sister also is having AC problems and her mechanic recommended a reliable shop.
She is going there this morning. I may just wait and see what they charge her and what she thought of the shop. If it's favorable I may just have them look at my vehicle. I surely am not going back to the guy I went to two times before.
These AC systems are sensitive and I can do more damage than good if not done correctly with the proper tools and knowledge.

Edited: BTW forgot to mention I checked the AC specs on the under hood sticker and it shows maximum 134A is 30 oz and max oil to be 7 oz.

 

[crunchie_frog]

You are correct, you would need to reconnect the pressure switch after the first can to see if it will cycle on its own. A good mechanic is a good idea, finding one is the hard part. Many of us on this forum have discovered the best, most reliable, cheapest, honest, mechanic are ourselves.

 

[itzbinnice]

You are correct, you would need to reconnect the pressure switch after the first can to see if it will cycle on its own. A good mechanic is a good idea, finding one is the hard part. Many of us on this forum have discovered the best, most reliable, cheapest, honest, mechanic are ourselves.

I've decided I'll try to do it myself. Just ordered 2 cans 12 oz on Ebay of Dupont 134A for 15.00 shipped, the seller is local.

Since it's warm out I'm sure the mechanics are charging premium prices.
Why not try it myself on such an old vehicle. I'll post back after the refrigerant arrives and I give it a charge.