Ford AC Trouble ! (Variable AC compressor)

[Music] hi everybody and welcome to new episode of diagnose Dan today were working on this 2013 Ford Fiesta and the customer complaint is the AC is not working so let's diagnose this together now let's start out by confirming the customer complained the car is running right now and the AC is on so let's get a temperature reading now that was 24 25 degrees with the AC setting on max so that's not cold enough so customer complained confirmed now there's really lots of ways to diagnose an AC problem we could connect our gauges and look at the pressures and we could go for scan data scan tool we could do a visual inspection lots of ways to approach this problem I won't be able to go through them all in this video so as you keep watching my channel if we get another AC problem I might do another approach so you guys get to see all the aspects of diagnosing an AC system now there's a couple of things I noticed about this particular AC system when I turn it on I hear the compressor clutch engaging and the cooling fan kicks in and that's actually very valuable information now just by hearing the compressor clutch engaging and the cooling fan kicking in we can draw some conclusions and we can rule some things out of being our problem I've taken the belt cover off and there isn't really a good technical reason for me to do that is just to show you guys that clutch is engaging so I'm going all the way for you guys so you better like this video I'm fine I'm fine I'm perfectly fine thank you I've got to explain it's on a Saturday I'm in the shop I'm all alone I'm shooting this video and I really got no one to talk to except for you guys but you guys don't talk back until in a couple of weeks in the comment section of this video and that's a bad base for a good conversation right now so sometimes I forget you guys are watching and I think I'm alone and I get carried away a little bit but I'm not losing my mind I'm perfectly well perfectly I'm fine so let's continue with our AC problem now let's hook up a scan tool and see if there are any code stored that could give us some more direction now let's select Ford 2013 Fiesta and on this particular model the AC is controlled by the PCM so let's go to engine and let's see if there are any code stored that could give us a better direction and there is a code store for the AC variable a C compressor control circuit fault now so far we have learned that our compressor clutch engages and our cooling fan turns on we also know we've got this variable AC circuit control fault but what is a variable AC and how is it controlled I know that most of my viewers have got a pretty good basic understanding of an AC system if you don't or if you want to be refreshed I might do a separate video on the basic operations of an AC system for this video let's concentrate on what we need to know to diagnose this car now these are the main components of a variable AC compressor I took a compressor apart for you guys to see what's inside now from brand to brand the design might vary but the basic operation stays the same let's start off with the front part of our compressor this is where normally our pulley or clutch would sit now you can find these compressors with or without a clutch that's because these types of compressors don't really need a clutch for their basic operation now let's take a closer look to what's inside these are our pistons this specific compressor has got one two three four five six seven Pistons but that number may vary now to get a better understanding of this compressor we'll focus on just one piston I get the other six Pistons out of the way to simplify things [Music] now when the compressor is assembled it looks like this but when we get it apart we can see our piston goes into a cylinder in order for the AC system to work the refrigerant has got to be pumped through the system now in order to pump the piston has got to move up and down in the cylinder now very similar to a combustion engine a compressor needs valves to let gas into and out of the cylinder now each of the seven cylinders has got an inlet and an exhaust port the cylinders have got inlet valves and exhaust valves these are the exhaust valves they cover the exhaust ports now as the piston moves up in the cylinder the exhaust valves do allow gas or refrigerant to come out of the cylinder but when the piston goes back down it doesn't allow the refrigerant to go back now the inlet valves do the same thing on the other side now in order to get some pumping action the pistons need to move up and down in the cylinders now as the belt drives our drive shaft of our compressor the drive shaft turns the swashplate and as you can see the Pistons can move freely as the swashplate turns now as this compressor is turning you can see there's no pumping action of our Pistons and that's why basically these type of compressors have no need for a clutch now in order to get a back and forth motion of our Pistons we can set the swash plate at an angle now as we turn the swash plate at an angle we can see we get this asymmetric motion the motion of the swash plate results in the back and forward motion of our Pistons we've learned we can adjust the stroke of the Pistons by adjusting the angle of the swash plate but how does the PCM adjust the angle of the swash plate that answer lies in the back of our compressor in the back of our compressor there is a solenoid by controlling this solenoid the PCM can open and close passages within our AC compressor these passages lead to the high and the low side of our AC system by switching between the high and low side the compressor can use the pressure of our refrigerant to adjust the angle of the swash blade now remember the fault cut we had it sent variable AC compressor control circuit fault and the only thing controlling our variable compressor is this solenoid so basically the PCM is telling us there is a problem in the circuit of this solenoid so let's look at the wiring diagram and do some measurements now let's take a quick look at a wiring diagram and this over here is our AC compressor control valve and we can see there are two wires one brown and white wire coming from a 7 1/2 amp fuse so that is our feed wire and the other wire must be the control side it's a white and brown wire coming from the PCM on the back of our AC compressor is our control solenoid and indeed there are two wires one brown and white and one white and brown being the power feed coming from a seven a half amp fuse and a control side coming from the PCM now let's start out by back probing that feed wire and see if there's voltage coming from that seven 1/2 amp fuse and my test light lights up so that's okay now while we're in here let's back probe the other wire and see what we've got a net wire and on that side we've got power as well we just did this test with kion and engine and AC off this way we're sure the solenoid is not controlled by the PCM yet this simple five-minute test has just provided us with some fantastic information let's draw some conclusions now the power was coming from a fuse on this side and the control side comes from the PCM on this side now the PCM flag the code for a fault in this circuit somewhere along the way now with the test we just did we confirmed there's a voltage on this side of the connector able to light up a test light so if confirmed our fuse and our wiring up to the solenoid is just fine now we also measured a voltage on the other side of our solenoid that had enough current flow to light up my test light confirming the wire integrity within the solenoid to check the rest of the wiring or circuit because we had a circuit fault is actually very simple as long the solenoid is not controlled or switched to ground by the PCM that voltage coming from the fuse should travel from the fuse through the wire through that solenoid up to the control pan of the PCM now if this circuit is okay the power should run from this fuse down to the solenoid through the solenoid up this wire through this connector up to connector a pin 41 of our PCM the PCM lives next to the battery on this model and I was able to trace down pin 41 and the wiring color matches the one of a wiring diagram I had to use a piercing tool and if the circuit up until this point is okay my test light should line up and it doesn't so let's check the test light and the test light works let's check again nothing we just connected our test light to connector a pin 41 of our PCM my test light did not light up so there's either no voltage over here or at least not enough current flow to light up my test light my test light did light up at the connector of our solenoid so somehow there's no path from the connector to pin 41 this can indicate only one thing there's a brick or very high resistance somewhere along that path we just tested in 41 of our PCM our test light did not light up now as far as the diagnosis is concerned this is a valid test we know there should be enough voltage and current flow at that pin to light up our test light but does that mean there's really nothing there there are certain things a test light cannot tell us so let's do the same test using a power probe [Music] so our power probe just learned us there's three and a half volts on that pin something our test light could not tell us now that three and a half volts we saw is called a bias voltage and a bias voltage is a voltage the PCM uses to diagnose a circuit the PCM is expecting that 12 volts going through the circuit and coming back in that pin 41 of the PCM as we have seen that 12 volts is not there this still could mean there is an open or a short to ground and that's where the bias voltage comes in as long as the bias voltage doesn't get pulled to ground the PCM knows there's no short to ground so there must be an open or how Forte's calls it a circuit fault remember a blown fuse is also an open in the circuit as we take a look at the wiring diagram we can see our wires of our control solenoid don't go directly to the PCM and to the fuse but they run through a connector this is a five wire connector and the other three wires are of the o2 sensor now what I want to do is find this connector and see if our problem lies in front of that connector or behind that connector to give us some direction this connector is located in the left side of our engine bay now it turns out to be this connector has a lot more wires than the five I thought there would be that's because this diagram is only showing us the relevant wires for this circuit I could have known there were more than five wires looking at the pin numbers since we are looking for pin three and 28 now let's see this pin 22 23 24 25 26 27 28 I back probed both sides of pin 28 on the connector if there's 12 volts coming into the connector everything in front of our connector is just fine if there's 12 volts coming out of the connector a problem lies somewhere between our connector and our PCM if there's 12 volts coming into the connector but a bias voltage on the other side our problem lies in the connector itself you well diagnose Dan fans were almost done a problem lies somewhere within that connector and the owner of the car told me that the previous shop who looked at this car wanted to replace the PCM it's a great thing he came to me for a second opinion because that would have been a very costly mistake I took the connector apart and the pins look very clean now let's isolate our problem and let's start out with this side of the connector now let's do a measurement directly on the pins since this is the side coming from the PCM we want to see that bias voltage on that pin and there is our bias voltage so nothing wrong with this side of our connector now I wanted to do the same thing on the other side of the connector but look what happened this is pin 22 23 24 25 26 27 28 but there's nothing there now somehow that pin came out of the connector but with the help of some pliers I was able to push it back into its slot now it seems to be tight now I can't get it out anymore so let's reconnect it and see if we have got a fix the moment of truth only if our circuit is completed and at 12 volts go back into the PCM only then the PCM can start pulling the voltage to ground using duty cycle now if you want to learn more about duty cycle watch one of my previous videos called how D PWM duty cycle explained if our circuit is complete and my test light lights up at the PCM the PCM should be able to energize the variable compressor solenoid again that swash plate should tilt and the interior of this car should get nice and cold again and let's start out by clearing the codes no coats present that's fantastic you I think I've got a happy customer no parts required sounds a lot better than replacing the PCM and not fixing the problem now if you liked this video and if you want to learn more please subscribe to my channel and when you hit the bell you will get a notification each time I post a new video yeah a diagnosed and fixed it again see you next time guys bye bye [Music]

Channel: DiagnoseDan

Views: 171,431

Rating: 4.9559793 out of 5

Keywords: Diagnosedan, air conditioning, AC, variable compressor, variable ac, variable air conditioning, gmto, snap-on, ford, fix, car repair, ac repair, ac fix, educational, bias voltage, circuit, electrical

Id: xwIOL7ghrnI

Length: 31min 49sec (1909 seconds)

Published: Fri Sep 07 2018