Feb 17, 2013 - Technical, Towing and Toad    8 Comments

Non-Functioning AC On My 2000 Ford Ranger

Don’t ask me how I prioritize projects. It beats me. Something told me that today was the day to troubleshoot the non-functioning AC on my 2000 Ford Ranger. It worked when I bought the truck but quit sometime in the late summer.

I thought that I might just need to add freon, so I watched a video about how to do that, and I learned that the first thing I needed to check was if the compressor is coming on.

So I went out in late afternoon and my French-Canadian neighbours from Ontario (first time I mention them) were out. We talked and I mentioned that I was about to pop the hood on my truck to check the AC compressor. The husband sprang into action to help me! OMG, I love RVers!

He knew exactly where the compressor was and how to test it. Bad news: the compressor clutch wasn’t engaging. He had me pull the fuse and test it to make sure that wasn’t the problem. Nope. So I know I need to take it to a shop. But I now have enough knowledge not to get taken.

Unfortunately, I have to get the brakes done first, so no AC for a while. At least, I know I’ve gone as far as I can with that repair.

No AC wouldn’t be so bad if I had automatic windows, but I have the arm exercise model. L has a newer Ranger with power doors and windows! He said he’d trade me those for my rear doors!

With help like that and my repair manual, I’m getting well acquainted with Moya’s engine compartment and am rather enjoying getting my hands dirty tweaking this and that and just exploring everything.

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  • When an auto AC is low in Freon, the compressor magnetic clutch is prevented from engaging by a pressure sensor. There’s a safety reason for this interlock sensor arrangement, for which an interested person can get more info on the Web. But I only mention this to say that not all is lost, if the compressor does not turn on.

    It is usually worth putting in a can of Freon, which is usually enough to bring the pressure up so that the compressor will engage. Then, as Freon is pumped by the compressor from the low side to the high side, the compressor will cut out again, and again, until there’s enough Freon added to keep it running non-stop.

    If the leak is sufficiently small, a can or two of Freon may be needed each season to keep it running.


  • I can get freon plus the tubing thingy for about $30, so it wouldn’t be a total loss to try that, then.

    But all the instructions I’ve seen say to put the freon on with the AC running and my AC isn’t running. You’re telling me I could push some in from the can with the AC on and then the clutch MIGHT engage and start circulating the stuff through the system? Or…

    Thank you for restoring my hope! 😀

  • Yep. Exactly!

    When the pressure is so low that the low-pressure cut-out switch activates, the higher pressure in the can will cause the Freon to flow into the system. When there is enough Freon in the low side, the compressor will engage, then turns off after a few seconds. Keep putting in Freon while watching the pressure gauge that comes with the can, until the compressor runs non-stop.

    If you find that there is Freon in the system, such that the Freon does not flow because there is pressure in the system, then what I describe above will not happen. Now, I usually can locate the low-pressure switch, and verify that it does activate, and can even disable or bypass it, but that is getting too complicated for a novice.

    New Freon cans that come with a pressure gauge make it so easy for anybody to add Freon. I had to buy a pressure gauge kit, which I hardly use anymore. And no, I am not a car mechanic.


  • Thank you! You’ve already more than established your credibility, so I’m trusting you on this! 😀

    I am going to try the freon. Hopefully, Walmart will have some. Otherwise, I know I can get it on Amazon.

    I’m feeling especially optimistic because the AC went from super cold then petered out over time. Sounds like a leak to me… A can of the stuff twice a year or whatever really wouldn’t be a huge deal and could end up being cheaper than getting the thing fixed.

    On Amazon, I saw freon with a leak sealant added. Thoughts on that?

  • I need to add the following caveat!

    It is not safe to add Freon into a system that has such a bad leak that the pressure is the same as atmospheric pressure. You want to see a system with some Freon left, with some pressure such that air cannot enter the system. This was the reason for the low-pressure cut-out switch, which prevents the compressor from sucking in air if the leak is on the low pressure side of the system.

    An AC properly filled with Freon will always have its low pressure side above atmospheric pressure, and air cannot enter the system. A system depleted of Freon may have its low side sufficiently evacuated by a running compressor, such that air will get sucked in through the leak. Hence the reason for the low pressure cut-out switch.

    You can verify that there is still some Freon by depressing the Schrader valve on the Freon fill port. If Freon plus some oil squirts out, then there’s still pressure in the system. Then, go ahead and hook up the can.

    Good luck!


  • Do I need special tools to test that port?

    My hopes may be dashed tomorrow, but tonight, I will dream of an icy cold truck tearing across Texas under a harsh yellow sun. 😀

  • Walmart has the best price on Freon refill cans, the ones with a gauge attached. Wonderful and ingenious stuff. Yes, I always buy the ones with a bit of sealant. It does help. All of my cars need a bit of Freon every summer.

    About the AC petering out, that is because as the Freon leak causes the pressure to drop, the compressor will keep on cycling, with more and more time off than on, until the pressure is so low that it stops altogether.

    One should strive to keep enough Freon in the system, to keep the compressor from cycling this way. It wears out the compressor clutch, and sometimes also the low-pressure switch. One can tell by paying a bit of attention. Run the AC in the morning, so that it is cooler and Freon has a lower pressure. Set the interior fan on low. That lowers the Freon temperature and its pressure. Pop the hood, wait a bit, and one can usually hear if the compressor is cutting in/out, along with the radiator cooling fan.

    By the way, I am a retired engineer who dealt with theoretical work such that my job description was “scientist”, but I am also a tinkerer and handyman since birth.


  • This is the sort of thing I wish I’d known to watch out for. My fear is that I did have a small leak, the freon all leaked out, and then I killed my compressor. I will do the check for freon tomorrow.

    I could have guessed your job and hobbyist titles. 😉 Thanks again!

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