Ford A/C Quick Tips #7: How To Quickly Diagnose A/C Concerns

welcome back to the shop once again today we're going to go over some more AC Diagnostics for your Ford vehicle now the concern we're diagnosing today is where you turn the AC on the button lights up everything looks fine but you're getting zero cooling out the vents so then you go under the hood you look at your AC compressor it's spinning just fine pulley side but your Center clutch hub here is not engaging the compressor is not turning on today we're going to go through three easy checks that you can do on your vehicle without ever getting your hands dirty and you're going to know exactly what the concern is or be able to narrow it down to a subsystem that is a not allowing the compressor to come on now the first thing you realize is that the AC compressor is PCM control so when you press the button to turn a C on you're simply requesting AC operation the PCM is going to actually command it on and allow it to run but first it needs to do both go through a series of pre checks to make sure the engine is operating okay because it is such a load on the engine it's going to make sure the system pressures are okay II that temp is okay and of course the ambient temperature is okay to make sure that the compressor is not going to slug okay so it goes through a series of pre checks and any one of those can disable the AC operation the PCM simply will not allow it okay let's go over to the vehicle and I'll show you just how fast and easy can be to diagnose one of these on your Ford now the number one reason why the AC system will not come on is because the system pressures are simply too low what you need to realize is that inside these lines right here is refrigerant and pan oil and the refrigerant is needed to drag the pack well through the system and lubricate the compressor so when it's not coming on because the pressure too low it's simply because the PCM is protecting the compressor from lockup so the absolute first thing I do before I start busting out multimeters and everything else is get a basic manifold gauge set like this and connect it up just to the low side board on here okay and there's going to be a thicker tube like this and there's going to be a smaller port on it and there's give me a thinner tube like this you can kind of see you'll see it on your vehicle that's kind of a bigger port on that's the high side you just want to tap into the low side on here and we're going to watch the gauge okay now this gauge should read some kind of pressure at 30 40 50 psi obviously a hot baby 80 90 100 psi that's going to allow the AC clutch to actually come on now if there's lower fridge rent it's going to cycle very fast as it drops and everything else but it'll actually come on our consumer diagnosing today is where it doesn't come out at all no matter what and as you can see on this one there is no refrigerant in the system so it's simply not been a compressed refrigerant first off and it's definitely not going to carry the oil through the system so that's a darn good reason why the PCM is not allowing the compressor to come on now this is the most common and least invasive test we're going to do on an AC system like this for a no clutch engagement concern I would say 90% of time this is the concern so it's a really quick easy check that you want to do first now let's say you're AC charge level is okay but your compressor clutch is still not turning on the very next test we're going to do is even easier actually what we're going to do is a key on engine off self-test on the PCM with a scan tool now most cheap scan tools have this option the IDS has it of course and even the free four scan software has this option on it also we'll do a key on engine off self-test and what that'll do is I'll test all the outputs of the PCM commands fans actuators solenoids and of course you guessed it the AC clutch right here right now the nice thing about this is that it does a low test on the entire circuit coming down to the AC clutch and back so it'll test the PCM driver so circuitry the relay the inputs to the relay and of course the Magnetic clutch on the backside here the disc clutch on the front side here and then back on through the ground all at once why you sit here and watch alright here we go now once the self-test is started the fans will come on at the same time the clutch comes on what I like to do is grab the clutch and try to spin it to make sure that the magnet has a strong grip on it that there's no problems with the mating surface in between these two the clutch and the pulley and that it doesn't slip on there okay you should not be able to move it like this when it's engaged so we'll go ahead and start that self-test now and you'll see it and hear it suck this plate right here back there goes it's still holding it's holding it's holding it's holding and it let's go once the fans turn off it's a very good test to do it test the integrity of the clutch itself and of course the electrical circuit all at once now you may have noticed the PCM still turned on the AC compressor even though our system has zero pressure in it and the reason being is the PCM knows the engines not running and therefore no damage can occur to the AC compressor what did not test is these AC pressure inputs like the low pressure cycling switch there and the high pressure cutoff switch right there now if your AC system pressures check out okay it's 50 psi or higher and then the key on engine off clutch test also pass for you the very next thing you want to do is come back to the scan tool and look the live data stream for the PCM these are the four bids right here that you want to bring up on your screen so we can watch them live as we change inputs and of course outputs once the vehicle started the very first one you want to check is this one right here air conditioning clutch allow this will tell you if the PCM is even allowing the AC clutch to come on it can turn it off for many many reasons not just system pressures so you want to look at this one make sure it says yes the very next one here is air conditioning clutch cycling switch and that one will tell the PCM hey there's enough pressure in the system for proper safe operation of the AC system so that must say on now this next one I hear is the high pressure switch this one should be open at all times if it's closed the system pressure is too high so you want it to say open and okay like that the very next one here is the wide-open throttle AC cut-offs relay which is on some older ford vehicles is separate whereas this one they're combined with the air conditioning clutch relay so they're all the same unit on there since it is PCM controlled you want this one to say on and that'll tell you when the PCM is commanding the AC clutch on through the relay now with the key on engine off we're going to turn the AC M max okay and you can see the difference here so yes the AC is system is allowed Thank You mr. PCM the AC clutch cycling switch saying yes there's plenty of pressure go for it this next one the high-pressure ones saying it's okay as before and then of course this last one it's not turning on the AC clutch relay because the engines not started now once the vehicle started after it idles and it stabilizes it will turn on the AC clutch and you can see it changed on right here and of course you'll be able to hear it under the hood very loved AC clutch coming on now between the three tests I just had you do and the information up on the screen here - live data stream from the PCM you should be able to tell which system or sensor is not allowing the AC clutch to actually come on an AC system to operate so let's go through a few quick scenarios on here depending on what you may see reading on the boxes here now the first one let's say it says no on closed off at that point you know the high-pressure switch the circuitry or the high pressure there's too much high pressure in the system that's not allowing the AC system to operate okay now if it says no off okay off then you know the low-pressure cycling switch is what's not allowing the system to actually come on okay here's a few more pidz you want to select on the newer ford vehicles you want to go into the PCM or the climate control module depending on if the vehicle in the model year this vehicle is inside the climate control module and you want to look at the evaporator temperature there's a little sense around there like I said they get you know moisture from the evap and of course they'll corrode over time and then they'll throw like they'll show like negative 20 negative 10 or zero when obviously we know it's 7080 degrees outside so you want to check that make sure it's reading close to ambient and then the same thing the external temp sensor the Sun load and all that stuff is not a big input to the climate control but it is an input and it does tell it the conditions the vehicle is operating in now the other one that's even more important is over in the PCM on the newer vehicles you check a few more things without ever going under the hood - and these are all generic pidz so you should be able to select them on your scan tool if it's a halfway-decent scan tool so clear those we're going to look at the AC pressure and that's the low side pressure it just has a reading now and then the PCM commands it on and off and our command and request mode sure and that's about it this one right here so go and look at those okay so our AC request they call on the newer vehicles and that's the same thing is the AC button on so we'll press it on and it responds so the PCM knows it's getting the request from the club control module to turn the AC on okay and then read this right you get this AC pressure this is an actual pressure transducer built right into the system they're in a line and it'll tell it the pressure so you can tell if it's reading you know correctly or not if it's again showing you know 20 psi whereas your manual gauges say 90 then you know you've got a problem in that area so you can get a lot of information just on what the actual PCM is seeing here now on this one and the scan tool we can actually turn on and off the clutch ion and that's a good tool to to make sure it's turning on based on scan tool input so as you can see there's a lot of great information just by looking at some live data streams from the PCM not too bad right it only takes about five minutes and I bet your hands it didn't even get dirty at this point you should know which subsystem is not allowing the AC compressor to turn on and cool down your vehicle and you can just zero in that subsystem and do detailed Diagnostics now the reason why I don't get into detailed Diagnostics in these videos is because each model and year is different depending on their setup on there but at least at this point you know if it's that electrical side of the AC clutch relay it's a refrigerant problem which like a sudden 90% of time its refrigerant or hey the evap temp cent Tempah is way off it's like negative 20 with 90 degree degrees out you know exactly where to head next now if you liked this video be sure to hit like down below and if you want to see more make sure you subscribe because there's always great new content coming on the channel not to mention a library of almost 600 pair of videos showing you how to fix your Ford yourself I'll see you next time

Channel: FordTechMakuloco

Views: 826,230

Rating: 4.7441759 out of 5

Keywords: ford, f-150, how, to, repair, diy, Ford, Motor, Company, (Automobile, Company)

Id: VhU2KeumoVk

Length: 13min 8sec (788 seconds)

Published: Tue Sep 06 2016