AC / Coolant Fan assembly issues, Im new to the group and would really appreciate some help

[Handy Andy]

This why I asked about Manual versus Auto...

The BCM...it "handles" the demand for the PCM to adjust power level in "mid-flight" so it can maximize the motors RPM torque range...


Because it also involves the Instrument cluster.

This thing is a complex mess, to start and just say replace this and that are just shots in the dark, so it sounds like everything that COULD be replaced - was - and no, it still doesn't work.

Let's see, you're getting responses thru the OBD scanner...

So it's trying to work, no cooling - one thing you did not mention I covered this in another thread in a Focus forum, that the "expansion" nozzle - the one that does the constriction to get the refrigerant to "work it's magic" - wonder if that is shot.

You have pressure, but you didn't say you had high side and low side - by my own experience you need at least 7kPa to "start" the cooling (pressurize the switch) so it rises to about 15 to as much as 30kPa - but you also have a low side that is the RETURN (vacuum to compressor) side which is the lower, the dynamics between gives you the cooling and heat is exchanged. (so it may be too high in pressure - forcing it to shut down - bypass)

You might (again I don't have your vehicle in front of me) also have a fan resistor - low speed one - designed to make the fan quieter - so the "biggest test" is to see if overheat or above range - the radiator fan will kick on to cool the motor - but the low-speed resistor might have opened preventing the low-speed side to work.

So if the clutch works...

Back probe Pin 13 of the PCM - see if the PCM can work the relay (continuity) - if the Pin 13 line can be turned on (by grounding) that wire, then the issue seems to be with the PCM.

... or ...

I've seen accident vehicles have issues, some even as simple as a broken thermometer (air-temp sensor - open line) to check the temperature of the air - so something simple is getting in the way of all this.

Did you check that section of the relay/wiring mess?

 

[Shubbs]

Ok so just probed the fuse box again. The fuse relay for my model is relay 5 and the pcm relay is relay 3. Both have power on the lower connection of the switch part of the relay. And when I test the ground side of the fan relay switch is tests out with good continuity (very low resistance) but when I test the PCM relay ground it has 1.3kohms. so if the PCM controls the fan circuits it looks like I have a bad ground on PCM relay 3 see photos. What you think? Thoughts?

Also, the compressor was bad anyway so I got new one which came with all the other stuff so either way compressor needed changed out so I'm good with that. Just need to figure the fan issue out.

 

[Shubbs]

This why I asked about Manual versus Auto...

The BCM...it "handles" the demand for the PCM to adjust power level in "mid-flight" so it can maximize the motors RPM torque range...
View attachment 6670

Because it also involves the Instrument cluster.

This thing is a complex mess, to start and just say replace this and that are just shots in the dark, so it sounds like everything that COULD be replaced - was - and no, it still doesn't work.

Let's see, you're getting responses thru the OBD scanner...

So it's trying to work, no cooling - one thing you did not mention I covered this in another thread in a Focus forum, that the "expansion" nozzle - the one that does the constriction to get the refrigerant to "work it's magic" - wonder if that is shot.

You have pressure, but you didn't say you had high side and low side - by my own experience you need at least 7kPa to "start" the cooling (pressurize the switch) so it rises to about 15 to as much as 30kPa - but you also have a low side that is the RETURN (vacuum to compressor) side which is the lower, the dynamics between gives you the cooling and heat is exchanged. (so it may be too high in pressure - forcing it to shut down - bypass)

You might (again I don't have your vehicle in front of me) also have a fan resistor - low speed one - designed to make the fan quieter - so the "biggest test" is to see if overheat or above range - the radiator fan will kick on to cool the motor - but the low-speed resistor might have opened preventing the low-speed side to work.

So if the clutch works...
View attachment 6671
Back probe Pin 13 of the PCM - see if the PCM can work the relay (continuity) - if the Pin 13 line can be turned on (by grounding) that wire, then the issue seems to be with the PCM.

... or ...

I've seen accident vehicles have issues, some even as simple as a broken thermometer (air-temp sensor - open line) to check the temperature of the air - so something simple is getting in the way of all this.

Did you check that section of the relay/wiring mess?

Also not entirely sure what you mean by manual and automatic? Thought you were referring to the transmission? It's a manual transmission. AC control panel in cabin is also attached in case you were referring to that?

 

[Shubbs]

This why I asked about Manual versus Auto...

The BCM...it "handles" the demand for the PCM to adjust power level in "mid-flight" so it can maximize the motors RPM torque range...
View attachment 6670

Because it also involves the Instrument cluster.

This thing is a complex mess, to start and just say replace this and that are just shots in the dark, so it sounds like everything that COULD be replaced - was - and no, it still doesn't work.

Let's see, you're getting responses thru the OBD scanner...

So it's trying to work, no cooling - one thing you did not mention I covered this in another thread in a Focus forum, that the "expansion" nozzle - the one that does the constriction to get the refrigerant to "work it's magic" - wonder if that is shot.

You have pressure, but you didn't say you had high side and low side - by my own experience you need at least 7kPa to "start" the cooling (pressurize the switch) so it rises to about 15 to as much as 30kPa - but you also have a low side that is the RETURN (vacuum to compressor) side which is the lower, the dynamics between gives you the cooling and heat is exchanged. (so it may be too high in pressure - forcing it to shut down - bypass)

You might (again I don't have your vehicle in front of me) also have a fan resistor - low speed one - designed to make the fan quieter - so the "biggest test" is to see if overheat or above range - the radiator fan will kick on to cool the motor - but the low-speed resistor might have opened preventing the low-speed side to work.

So if the clutch works...
View attachment 6671
Back probe Pin 13 of the PCM - see if the PCM can work the relay (continuity) - if the Pin 13 line can be turned on (by grounding) that wire, then the issue seems to be with the PCM.

... or ...

I've seen accident vehicles have issues, some even as simple as a broken thermometer (air-temp sensor - open line) to check the temperature of the air - so something simple is getting in the way of all this.

Did you check that section of the relay/wiring mess?

Also where's the PCM located will also try to probe the wires your mentioned. Have not previously tested any of the PCM wiring. So just found the high resistance on PCM relay ground literally just now.

 

[Shubbs]

This why I asked about Manual versus Auto...

The BCM...it "handles" the demand for the PCM to adjust power level in "mid-flight" so it can maximize the motors RPM torque range...
View attachment 6670

Because it also involves the Instrument cluster.

This thing is a complex mess, to start and just say replace this and that are just shots in the dark, so it sounds like everything that COULD be replaced - was - and no, it still doesn't work.

Let's see, you're getting responses thru the OBD scanner...

So it's trying to work, no cooling - one thing you did not mention I covered this in another thread in a Focus forum, that the "expansion" nozzle - the one that does the constriction to get the refrigerant to "work it's magic" - wonder if that is shot.

You have pressure, but you didn't say you had high side and low side - by my own experience you need at least 7kPa to "start" the cooling (pressurize the switch) so it rises to about 15 to as much as 30kPa - but you also have a low side that is the RETURN (vacuum to compressor) side which is the lower, the dynamics between gives you the cooling and heat is exchanged. (so it may be too high in pressure - forcing it to shut down - bypass)

You might (again I don't have your vehicle in front of me) also have a fan resistor - low speed one - designed to make the fan quieter - so the "biggest test" is to see if overheat or above range - the radiator fan will kick on to cool the motor - but the low-speed resistor might have opened preventing the low-speed side to work.

So if the clutch works...
View attachment 6671
Back probe Pin 13 of the PCM - see if the PCM can work the relay (continuity) - if the Pin 13 line can be turned on (by grounding) that wire, then the issue seems to be with the PCM.

... or ...

I've seen accident vehicles have issues, some even as simple as a broken thermometer (air-temp sensor - open line) to check the temperature of the air - so something simple is getting in the way of all this.

Did you check that section of the relay/wiring mess?

Also do you have any ideas how much refrigerant I need in this thing? I read yesterday it was like 550g and read elsewhere it was a lot less, didn't add too much so maybe I also didn't add enough refrigerant. I can't remember how much I added but wrote the qty down in my shop. Can get that later, but would be good to know what's required also. Car did have a front end collision years ago but ac was working fine for last ten years. The collision was minimal, guy reversed into my bumper at a stop light. New bumper and grill, but that was it.

 

[Handy Andy]

Also where's the PCM located will also try to probe the wires your mentioned. Have not previously tested any of the PCM wiring. So just found the high resistance on PCM relay ground literally just now.

Ok, slow down - this is where you then you turn from Ω on the meter to read for voltage VDC- and then engage AC.

What happens is; if all the things work right - the PCM will sink current from the Relay coil side, engaging the relay and completing the power circuit to the fan to turn it on.

You will see the power (Voltage) of the voltage to the RELAY (coil side) when you engage AC, the meter should show close to battery voltage. When AC is on (Thru the climate control) the PCM then turns on a transistor (or MOSFET) to drop power from the line (in this case 3) - if the meter "stays" close to 12VDC then the PCM may be the fault - or the continuity of the wiring from the Relay to PCM is bad. Why would it stay up, the wire itself is a "Dead short" to the PCM, if the wire is broken or problems with wire breaks inside - you can't see them, your voltmeter does. It will see no change in power from the relay - the voltmeter is designed to be a high impedance (no load) instrument so if the wire was good and the PCM worked - your voltage reading on that meter would go to below 1 volt (drops) and stay there as long as the AC clutch and Cooling fan worked - because the relay was consuming power and dropped current thru that wire - it's consumed by the PCM's internal switch used to turn on that fan relay.

Why ask about Manual or Automatic Climate control - you took a picture of the "Manual" side - the Automatic one uses a similar "shaped" control but there is a digital display of the temperature setting in the center of the "big" circle and has or uses a module that talks to more devices (ugh) and that includes the HEC (Instrument cluster) BCM and PCM and develops a plan on how to keep you at your selected temperature and the vehicle drives like it isn't bogged down on the loading of heavy AC demands like previous vehicles used to be.

You may have to use a short wire to check from the relay coil contact to the PCM so your Meter can measure for voltage change from the PCM trying to turn on the Fan thru that relay's coil.

The Relay has to be installed and that pigtail is from the PCM side of the coil (non-powered side) of the relay.

You check across, so the Pigtail gets the Positive Test Lead and the Black Negative lead goes to ground

IF the temperature sensor is not working - all this is moot for it has no idea on how to develop a plan to even heat or cool the car - it will just sit there, so if you get heat but no air, then we blame the BCM the PCM and pressures of High and Low side - we need to find out what's going on.

The PCM is mounted on the side of the Battery Box.

You, facing engine, Battery to the right.
The PCM is bolted to the LEFT side of the battery box in between the engine and the transmission
Locate the wires to your spark plugs, to its right, you found the PCM.

Before you go too far, the main problem with many of these is with the Fuse box corrosion issues.
The PCM may be fine, but the wiring from the Fusebox to the PCM may have corroded.
Some of the wiring from the Fusebox goes under the battery box and it's tray.

You should also check the BLOWER motor.
IT may be a part of this mess.​

 

[Shubbs]

Ok I will go and do the voltage test for relay 5 like you suggest. I think you are talking about the fan relay. The wierd reading I got earlier was from relay 3 which I don't think is actually used in my car as the wiring goes nowhere although the relay is installed. Bizarre but I did this earlier. I couldn't trace the wiring from Relay 3 (the PCM relay) because I don't have wiring diagram for color codes of wires so I pulled the fuse box apart and that relay, relay 3, PCM relay has a purple red wire for the hot and then a grey/purple for the ground side. Now here's the kicker the ground side of that relay does not go to ground. It's jumpered in the fuse box to an open half of a fuse that isn't used in my car. So if the PCM relay 3 even does click on for whatever reason it doesn't operate anything and the ground side of the relay goes to Fuse F18. See photos. So that's a dead end.

Also Earlier I pulled the PCM out and measured good continuity from pin 13 on wiring loom from PCM to relay 5 as part of the fan circuit. (Will now go do your voltage test as have not done this yet.

Will now go do the voltage test you suggested to see if PCM is not switching to sink the coil for relay 5 (fan relay)

 

[Shubbs]

Ok so I did the voltage test on RELAY 5, Fan assembly relay. The car running with ac switch off reads about 14.07V and when the ac is switched on, I also measure 14.07V measured from GREEN/BLUE wire that goes to the PCM from Relay 5 coil. The fan does not switch on.

Also for sh1ts n grins after I did the test above, i left relay 3 out and tried to start the car. The car won't start without relay three engaged but the ground side of relay 3 contacts goes nowhere. Totally boggles my mind but it's there for a reason I guess.

Ok, slow down - this is where you then you turn from Ω on the meter to read for voltage VDC- and then engage AC.

What happens is; if all the things work right - the PCM will sink current from the Relay coil side, engaging the relay and completing the power circuit to the fan to turn it on.

You will see the power (Voltage) of the voltage to the RELAY (coil side) when you engage AC, the meter should show close to battery voltage. When AC is on (Thru the climate control) the PCM then turns on a transistor (or MOSFET) to drop power from the line (in this case 3) - if the meter "stays" close to 12VDC then the PCM may be the fault - or the continuity of the wiring from the Relay to PCM is bad. Why would it stay up, the wire itself is a "Dead short" to the PCM, if the wire is broken or problems with wire breaks inside - you can't see them, your voltmeter does. It will see no change in power from the relay - the voltmeter is designed to be a high impedance (no load) instrument so if the wire was good and the PCM worked - your voltage reading on that meter would go to below 1 volt (drops) and stay there as long as the AC clutch and Cooling fan worked - because the relay was consuming power and dropped current thru that wire - it's consumed by the PCM's internal switch used to turn on that fan relay.

Why ask about Manual or Automatic Climate control - you took a picture of the "Manual" side - the Automatic one uses a similar "shaped" control but there is a digital display of the temperature setting in the center of the "big" circle and has or uses a module that talks to more devices (ugh) and that includes the HEC (Instrument cluster) BCM and PCM and develops a plan on how to keep you at your selected temperature and the vehicle drives like it isn't bogged down on the loading of heavy AC demands like previous vehicles used to be.

You may have to use a short wire to check from the relay coil contact to the PCM so your Meter can measure for voltage change from the PCM trying to turn on the Fan thru that relay's coil.

The Relay has to be installed and that pigtail is from the PCM side of the coil (non-powered side) of the relay.

You check across, so the Pigtail gets the Positive Test Lead and the Black Negative lead goes to ground

IF the temperature sensor is not working - all this is moot for it has no idea on how to develop a plan to even heat or cool the car - it will just sit there, so if you get heat but no air, then we blame the BCM the PCM and pressures of High and Low side - we need to find out what's going on.

The PCM is mounted on the side of the Battery Box.

View attachment 6677
You, facing engine, Battery to the right.
The PCM is bolted to the LEFT side of the battery box in between the engine and the transmission
Locate the wires to your spark plugs, to its right, you found the PCM.

Before you go too far, the main problem with many of these is with the Fuse box corrosion issues.
The PCM may be fine, but the wiring from the Fusebox to the PCM may have corroded.
Some of the wiring from the Fusebox goes under the battery box and it's tray.

You should also check the BLOWER motor.
IT may be a part of this mess.​

 

[Handy Andy]

The car running with ac switch off reads about 14.07V and when the ac is switched on, I also measure 14.07V measured from GREEN/BLUE wire that goes to the PCM from Relay 5 coil. The fan does not switch on.

There's the answer - the fan doesn't click on because the relay coil is not getting power it has, sent to ground thru the PCM.

Loop wires are common with Ford - they "branch off" a circuit to allow space to mount the relay or other larger part

There are two in the Manual s Posts number 16 shows Violet Green and in post number 18 shows Grey - Violet.
But the "open wire", is the jumper from a relay to power a set of other terminals - kind of like a breakout of an output function.

So in the 16 and 18 posts - the "tree" is from the PCM power relay - but loops to another portion of the fuse block to provide the power for the relay, and whatever follows - to provide room for that relay (Fan) to have it's coil monitored/switched by another one of the PCM sub-systems it grounds thru itself.

In a way, there is a hierarchy as in a structure to the relay tree - one - the PCM Relay, powers a branch from itself for the FAN as well as the Fuel pump while the Instrument Cluster "buffers" the AC and Heat request

• - the BCM monitors both because it is intertwined with the HVAC and Instrument Cluster
• - but the PCM "controls" the engine side of the mess including the AC pressure (Freon) switch so it works when it should.

While the BCM looks at the HVAC system (uses the Tell-tale lights to show status) and uses the Instrument Cluster as a monitor as well as controls to both IC and HVAC

• - F21 should be a 7.5A fuse used for the Blower motor but this is also needed to power the HVAC unit thru it's own relay that also runs the Blower

So if the blower works, the HVAC is getting power, so if it gets power...

• - the Tell-tale lights of the BCM show it as such, but the PCM needs to handle the engine side
• - so if it's not capable of tuning on a relay - in this case FAN,
  • then that loop wire DOES go to something in the fuse block
  • - it powers a set of smaller contacts and also branches off of that as a means to communicate to the BCM and Instrument Cluster
    • - does not mean it has to be fused, just a spot in which to break down more lines from it (power status mostly) to communicate to the other systems.

Tends to lean me back to a broken wire - the Fam Relay coil one - or the PCM is somehow not letting power drop thru it.

IT could be a decision it (PCM) needs to determine - might be from, it's not receiving information from the other systems to tell it that AC needs to be on so it just sits there.

 

[Shubbs]

Ok so what you are saying is, the PCM is bad because internally it's not switching to ground allowing the relay coil to energize and thus allowing power on the contact side to flow to the fan.

 

[Handy Andy]

OR the wiring to that pin is bad, and just needs a new wire jumper from the coil, to the PCM.

PCM failures although rare - usually set a fault code, so this may be a failure but have to rule out all other options first.

 

[Shubbs]

OR the wiring to that pin is bad, and just needs a new wire jumper from the coil, to the PCM.

PCM failures although rare - usually set a fault code, so this may be a failure but have to rule out all other options first.

Yeah I tested the wiring loom yesterday. It's got good continuity from pin 13 on the loom to that connection in the fuse box.......will see if I can pick up a reasonably priced PCM just to verify.

Yeah I pulled the codes again last night and pulled up these. They were all historical except think it was the oil temp sensor. Took this after I tried starting the car with the PCM relay out so most of these may be related to that or clear over the next few run cycles.

 

[Shubbs]

OR the wiring to that pin is bad, and just needs a new wire jumper from the coil, to the PCM.

PCM failures although rare - usually set a fault code, so this may be a failure but have to rule out all other options first.

So I decided to circle back and double check everything again before I went out and got a second hand PCM. So I went back and read how much refrigerant I had put back in the system. It was only about 200g and the high side was sitting at 100psi so that's a bit shy of the 550g required and the 200psi-ish on the high side. So long story short I added the remaining refrigerant and low and behold the fan kicked in about 150psi on the high side, therefore i assume the high side must have some sort of hold out for the fan or something, don't know. Either way system is absolutely working perfect now at idle AND running and fan now kicks on in under 30seconds after the compressor comes on. AC is super icy blast cold ❄️🥶 so I'm well happy with that!!

Handy Andy, I appreciate all your help with this man!!! Have a great July 4th!!!

 

[Handy Andy]

Wow!

You're welcome!

Just having you talk (write?) about it - I don't mind being a sounding board.

It's the "pressure switch" needed that extra oomph the refrigerant for pressure to make the switch engage

WHEW!

(That is what I meant by the "cutout" if there's no pressure the system doesn't kick on because it thinks it's "dry"- 200g seems small but it is the 7psi in "Static" as in no flow, engine off pump off which should be the "turn on" pressure to tell the system there is enough - but that is from older days of a different system then, for what Fiesta uses now the volume needed was lower back then - current systems use more of the oil used to lubricate and suspend the FREON the needed volume and oil changes that pressure range it develops)

So then that means about 500g (550) of the stuff - then it should be enough to work!

As far as those codes, looks like a wiring problem. Low voltages from loose wire or even corroded fuse leads in the fuse box, seems like it is just showing its age.

Found several times in my own vehicle something needs to be reset - and going over the fuses - some have "water entry" from below. Like a white powder (oxide) - like it was creeping into the fuse box from the bottom side - so it becomes a concern as the box ages.

 

[Shubbs]

Yeah I was pretty shocked when the fan kicked in as I was adding more refrigerant because I assumed that since the compressor clutch was kicking on and compressor spooling up that if the refrigerator level was too low then it would have held the compressor out as well as the fan, but that wasn't the case, compressor was working, clutch kicked in but just no fan at the lower pressure. Have to say I was pretty elated when I checked the cabin and it was cold so when that happened I knew I'd got it.

As for the codes, yeah, I may have caused some of those codes by trying to start the car with that other PCM relay 3 out, because it acted pretty wierd when I did that. And im not sure they were real faults because they weren't active and they were fine previously when I read the codes. What I'll probably do is clear those codes, leave it for a bit and then circle back and see if any of the codes come back and are active. Then start on those if need be.

Yeah I know what you mean. when I was in the fuse box yesterday i did check for corrosion etc but it was pretty clean like, no signs of water ingress or oxide etc.

Like I said man, I really appreciate the help and pointers! Super happy to have my ac back just in time for Houston's July and August heat!