2000 Ford Taurus Sedan A/C not getting cold

Im sure there are alot of messages on here about A/C not working so here is another. 2000 Taurus Sedan 131,000 on it. A/C working fine last summer and a couple weeks ago. Most recently the A/C didn't get cold. I filled with a tall can of Freon. 2 days later not cold. Filled it up again and watched the compressor click on while I was filling it. Got cold but just for a day or so. Need help, please before I take into the shop the diagnosis. Why isn't it getting or staying cold? Is this an easy or hard fix? Please, please help. thanks.

Chances are you've got a pretty good sized leak in the system somewhere.

Were you taking pressure readings while charging the system? The R-134a system is actually pretty sensitive to overcharging. If you've overcharged the system, it won't cool effectively either and the clutch will cycle more often than it should.

You're probably better off taking it to the shop for diagnosis if you don't have the gauges to do the job right and you don't know how to check for leaks.

-Rod

You should read around the posts on AC and the ones I have done recently in the Taurus and Escort Forums to help you decide what you have or if you even want to tackle this. If you want, you can use the advanced search cross referencing AC terms with my username. If you have a leak, which is very likely what you have, do you think you really want to tackle possibly a big job that you won't have the right tools to do it right? Repairing AC systems is more technical and picky than changing a belt, if you do it right.

You can try to troubleshoot this if you feel you can check for voltage, continuity and system pressures. Without any of that, you are operating blind. I wouldn't want to try anything without at least knowing the low side pressure while running it. Then measure the cold air and watch how the clutch goes on and off. You say you put two tall cans in it. If they went into it in about 10 minutes or less and done according to the directions, you probably didn't overcharge it and most likely have a substantial leak. Locating the leak isn't always easy, even with special dye. If you're lucky, it's just the o-rings, but they are no picnic to change depending on which or how many you do. Technically, after repairing it, to properly recharge the system, you first would need to pump out the system and hold a vacuum for 30 minutes or more.

Oh, and BTW, an undercharged system will cause the clutch to come on and off frequently to very rapidly. I discussed this in greater detail in the posts I already mentioned. I have also seen very severly discharged sytems that will come on but immediately turn off and will stay off much longer than on. My thinking here, is that this system will not come on until it is 80 deg F, a temperature high enough to increase the system pressure high enough for it to barely come on. But, it will immediately shut off when the compressor pulls the pressure down to the cutoff pressure, because there is so little refrigerant in the system to compress.

Sorry Rod, I tried, but I could not find anything that goes along with cycling too often caused by an overcharged system. Did you mean short or very short cycling? Because, that is most commonly a symptom of an undercharged system. I looked and looked in that really, really nice Ford SM, :D, but they didn't list overcharged for that in their AC troubleshooting chart, just undercharged. I suppose it could be possible to have a substantially overcharged system that would cause it to short cycle when the high side pressure exceeds the high side cut-out pressure and will come back on when it drops to the high side cut-in pressure. I think I've heard of poor cooling and definitely other significant problems with an overcharged system, but for me to understand what you mean, I would need you to elaborate on it more. I tried, I really did. But, no dice. Sorry. :disappoin :shakehead

Since you've now added two cans of R-134a to the system, I'd also be concerned that you may be running low on oil in the system. You really would be best served in the long run to take the car to a shop that has the proper equipment to diagnose and repair your system. Plus, it's the responsible thing to do. I know DuPont originally marketed R-134a as a more environmentally friendly version of refrigerant, but surprise, suprise, recent research doesn't fully support that. I won't go in to the possible coincidence that R-134a became the refrigerant of choice right around the same time that DuPont's patent rights to R-12 (aka Freon) were running out....

As for the cycling due to being overcharged, I'm going off recall here (which isn't the greatest anymore) to a 1995 Pathfinder I had that I inadvertantly overcharged. I remember that it got to a point where it stopped cooling as well as it had before I started. I hadn't trusted the gauge I was using (I know, dumb) so I forced more R-134a in, and my recall is that I realized I was probably overcharging it because as I was standing there with the engine running, I noticed the clutch cycling more as I continued to add refrigerant. That's when I knew it wasn't just that I had a big leak, but should have trusted the gauge.

-Rod

Did a little Googling to see if I could find anything to justify my recollection. Nothing scientific to explain it, but there are other people who have noticed similar clutch cycling (http://www.ford-trucks.com/forums/136021-what-could-go-wrong-if-i-overcharged-the-r134.html) apparently due to an overcharge (http://www.aircondition.com/wwwboard/2005Q1/23226.html) condition.

I also stumbled across this article (http://www.asashop.org/autoinc/march2003/mech.htm) which I found interesting. I have been suggesting people inspect their lines and fittings for evidence of oil residue when they suspect they have a leak in the refrigeration system. According to the article, the common PAG oil used in many R-134a systems will not leave such an oily residue. Interesting....

-Rod

That would explain a lot for my situation, as I'm also not seeing any oil leaks expecting to find one where the refrigerant is leaking. I installed dye, but at that time, I was not able to see any leaks yet, so I have to look again.

But this business of Rod making a mistake?!? :disappoin :nono:
OMG!!! :yikes: Tell me it isn't so!?! :shakehead I don't think I can believe it!?! :headshake :rofl: Sorry, I couldn't help myself :slap: :twak: :bricks1:

So, Rod, I guess you added refrigerant since it wasn't adequately cooling? Did it not get cold enough, like 40 to 50 deg F? Or, you didn't check? :lol2 Gotta check its temp. So, you then followed the old adage of "more is better" and found that is not true. :loser: :shakehead I believe you when you say it went to shorter cycles with too much refrigerant and less cooling. The only question I have, is did you ever get real long cycles at some point, ONE indication of a properly or near so charged system? Did you see the low side pressure gauge go back and forth between 25 psi and 45 psi? But, with long cycles? That's what it's supposed to do. As far as I know, the only way to get an overcharged system with a low side pressure cycle of 25 to 45 psi, is the high side cutout pressure is reached. That could create such a scenario as you and others had. I've heard of it too. The reason you have decreased cooling with an overcharged system, is the ENTIRE system's pressure has been raised too high. There's no room for things to expand and contract enough from phase to phase, and there's not enough pressure drop across the evaporator core orifice, resulting in diminished cooling capacity.

To think, all of that education and this is all I have to show for it. :disappoin :shakehead Finally, I'm putting my thermo to work! :shakehead :banghead:

Back then I only had a single gauge that I would either connect to the low side or the high side. Then if I wanted to charge the system, I had to remove the gauge and connect the can adapater to the hose to charge through the low side. No valved tee to allow me to have the can attached AND the gauge at the same time. I tried to charge the system because in the middle of humid summers here in Iowa I didn't think it was cooling effectively. This was also my first vehicle with R-134a. My car at the time was the '93 Taurus SHO with R-12, that car A/C got COOOOLD. So, I was probably starting with a properly charged R-134a system in the Pathfinder to begin with, and I was going off of feel for the temp out of the vent.

Since that time I've joined this forum and learned A LOT!!!

-Rod

Back then I only had a single gauge that I would either connect to the low side or the high side. Then if I wanted to charge the system, I had to remove the gauge and connect the can adapater to the hose to charge through the low side. No valved tee to allow me to have the can attached AND the gauge at the same time. I tried to charge the system because in the middle of humid summers here in Iowa I didn't think it was cooling effectively. This was also my first vehicle with R-134a. My car at the time was the '93 Taurus SHO with R-12, that car A/C got COOOOLD. So, I was probably starting with a properly charged R-134a system in the Pathfinder to begin with, and I was going off of feel for the temp out of the vent.

Since that time I've joined this forum and learned A LOT!!!

-Rod
You had two adapters for the high and low ports? I was only aware of them being different sizes. Not even the R-12 system uses the same port sizes. One gauge? I'm just surprised that would be done as I wouldn't think one could get the accurate low readings needed on the low side for something that also needs to handle 500+ psi. On a typical ac gauge set, the high and low gauges are different pressure ranges. I too have to switch back and forth between a fill hose and a gauge hose, but the refrigerant goes in so slow, it's my patience that suffers more than the accuracy of the charge. :iceslolan :headshake

In addition, as part of a proper charging procedure, especially if you are only topping off a system, as opposed to filling a totally depleted system and don't have a high pressure gauge, you need to measure the cold air discharge inside the car at the center vent at max fan speed. It needs to be between 35 deg F to 55 deg F, with the higher temperatures only when exceeding 100 deg F outside.

Rod, with your Pathfinder, that was a very fair comparison to make to your SHO's ac discharge temp, even though they use different refrigerants. They both are limited to the freezing temperature of water. Any lower, you will start frosting things up to the point the refrigerant will eventually remain liquified when it returns to the compressor, leading to compressing an incompressible (or is that screwing an incompressible? :iceslolan :screwy:) No, I think you're screwed at that point!?!:banghead: You have achieved catastrophic failure of your compressor. Anyway, either you had a few too many while charging it (we'll give you the benefit of that :iceslolan :headshake ) and somehow overshot the optimum charge, or there was something interfering with it so it couldn't cool properly.

So, were you able to correct the overcharged situation and get it nealy as cold as your SHO? Ever figure out why it didn't cool adequately? I don't blame you for letting ac techs do it and steering others that way as well. Among other things, I worked for two outfits that serviced refrigeration systems, and even with a mind numbing amount of thermo theory, I found my head hurting and spinning trying to apply theory with practice performing repairs. :confused: :runaround: :screwy: Two different animals.

I was able to get the Pathfinder to cool adequately when I got the charge lowered back to the correct amount. I still believe it was a bit undercharged before I started, but it could have all been in my head too. I have yet to find an R-134a system though that gets as cold as quickly as an R-12 system. Well, with the possible exception of my Infiniti. That car gets very cold in a hurry, especially considering that it has black interior.

-Rod

I'd think your head was fine other than the humid heat :iceslolan , but I think you were right in suspecting your Pathfinder was probably lacking adequate cooling and possibly charge. I forgot to mention that the system in the Pathfinder may have been undersized, had a design flaw, deficiency or other limiting factor that occured from use. If that evaporator coil gets too dirty, the heat transfer is diminished. If something reduced air flow through the evaporator, again you will have reduced cooling.

I think you may have hit on why R-12 was such a popular refrigerant and hard for the industry to give up. It was great to design systems around. Now, without consulting the specs on R-12 vs, R-134a, the R-12 may have a higher heat absorbing capacity or requirement than R-134a. This is known as the latent heat of vaporization, which is the amount of heat needed to change something from a liquid to a gaseous state, without changing its temperature. This phase change occurs in the evaporator, where the hot air has its heat removed, making the liquid refrigerant change into a gas. This is only useful to a cooling system because the system is maintained at a critical pressure range on the low side of the expansion valve, which is found just before entering the evaporator coil. Offhand, I can't recall how much, if any significant amount, of a pressure drop occurs through the coil before reaching the low side pressure port and cycling switch. On the theoretical side, as long the correct pressure drop occurs, the liquid goes to gas from the absorbed heat at the necessary pressure, the compressor raises the pressure high enough, the condensor cool it enough to go back to a liquid state at a pressure not too high to go through the expansion valve resulting at the necessary lower pressure. In automotive systems, it seems the R-134a systems have a fixed orifice type expansion valve.

So, Rod, do you still have that R-134a charging setup? You didn't mention how it was arranged to do both high and low sides and if there was just one gauge. If it was under $20, that's a pretty good deal if it was a decent set. I can't bring myself to buy the full gauge set when I can get by with what I have. I'd also need to have specs for the high end for there to be a point in having a gauge for it.

I do still have that setup, but have since purchased a full gauge set that allows me to charge (or evacuate) while still monitoring the high and low sides. I also have a diaphragm pump to evacuate, but fortunately haven't had a reason to try it out yet. I try to go on the theory that if I have the tool to do it, I will never need the tool. So far I've been pretty successful with that theory. The Genisys scan tool gets more use by co-workers and friends than for my own vehicles. I end up just scanning the systems in my cars looking for early signs of a problem than actually finding problems.

-Rod

:headshake :runaround:
Well, I can see I'm not getting any further on those questions. Have you considered going into politics? :naughty:

Hmm, I haven't had so much luck with the theory of buying tools in advance to prevent needing them. Maybe, I don't have a large enough expense account for tools. :iceslolan I do buy tools in anticipation of needing them or might find useful, but usually I have a pretty good idea I'll need it. One of these days I'll splurge on a scanner and a compressed (here we go again:slap:) air operated ac vacuum pump. Is that what you have? Those stand alone units are really pricey. What do you use to evacuate the refrigerant into? I guess I'd have to ask an ac repairman for one of his spent 30 lb tanks to use.

Now that we have totally run off with this thread, I wonder how things turned out for tleeburks' ac?

This wound up being a lesson in the complexities of the repair, operation, theory and design of the automotive ac system.

tleeburks, did you get your car's ac fixed? What did it need? What was wrong with it? Your response is appreciated as us regulars like to hear and learn how things turn out for our and other's benefit. Thanks.

:headshake :runaround:
One of these days I'll splurge on a scanner and a compressed (here we go again:slap:) air operated ac vacuum pump. Is that what you have? Those stand alone units are really pricey. What do you use to evacuate the refrigerant into?

Yep, that's what I have. And I haven't had to use it yet (see how that works). The expectation is I won't use it except on a system that is already empty (like my friend's Civic that has a big leak, but no obvious signs of oil which I now understand doesn't mean an evap core). I hope to be able to use the pump in such a situation to be confident there are no leaks in the system prior to installing the R-134a.

-Rod

Yep, that's what I have. And I haven't had to use it yet (see how that works). The expectation is I won't use it except on a system that is already empty (like my friend's Civic that has a big leak, but no obvious signs of oil which I now understand doesn't mean an evap core). I hope to be able to use the pump in such a situation to be confident there are no leaks in the system prior to installing the R-134a.

-Rod

Yup, that's what you're supposed to do. I think it needs to hold vacuum for around 30 minutes to prove that the system doesn't leak and also pumped out enough to eliminate all moisture. What do you use to evacuate (pump down the system) the refrigerant into? I know from the ac trade, some aren't too wild about contaminating their equipment pumping out a compromised system. Whatever gets pumped out can't be reused and has to be discarded, I assume to a recovery outfit. You'd think with a big leak you could hear it hissing when under pressure from inside or sucking air with a vacuum on it. Have you tried putting dye in? Unfortunately, you need a charged system to do that. I need to followup on my leak for dye.

That's quite the ability to ward off repairs by buying the tools for it. It does seem to have a fatal flaw of attracting other people's repairs, or is that just you? :iceslolan Now, I can make you a onetime offer of something that will work for you AND your friends. I will give it to you for just a penny, but charge $20 for s/h. I got that idea from ebay. I have a very special, no an extraordinary repellant for keeping away elephants!!! To date, I have not had a single elephant come after me or even visit my house. It's great!!! I bet you are skeptical and would rather spend your money on another preventative tool. Fine. But, don't come running to me when you are stuck under an elephant!?!:loser: :rofl:

Thanks, but evidently my cat scares the elephants away. Or maybe it's the dead chipmunks that he scatters around.

I don't have any means of capturing refrigerant, which is why, should I actually have an opportunity to use the pump, I can only use it on a system that's completely empty. Also, since I don't have the capability to capture refrigerant, I don't have to worry about contamination since all I should be getting is air and moisture.

I do have the leak detection kit, and it seems that some of the cans for R-134a include dye (even if it doesn't mention that on the can) so finding the leaks without the telltale oil stains has not been too difficult (or prevalent) to date. I do have a friend that said his system is completely dry and he could hear the leak just before it went dry, so it sounds like I may have an opportunity to use the pump afterall. I'll let you know if it's worth the $10. Helping out friends an co-workers is therapy for me. After a stressful day at work, a long bike ride or quick car project helps me relax.

-Rod