I'm hoping the group here can help me sort through an issue I'm having. I've got a decent working knowledge of mechanics but the problem at hand has multiple possibilities and I'm hoping to avoid having to throw parts at this. As always, thanks in advance for any input provided.

After experiencing a loss of AC the other day and discovering that the compressor clutch wasn't engaging and appeared to be misaligned, I replaced my compressor on Monday with a new Motorcraft unit. I also replaced the orifice tube for good measure (old one didn't look bad, especially for 180,000 miles and certainly doesn't lead me to believe the system is full of trash and plugged up). After this job I noticed my high side pressure climbs slowly but steadily to about 350psi before the pressure switch temporarily cuts off the compressor and pressure drops again. Compressor then cycles back on and the process repeats. AC blows nice and cold, only ceasing temporarily when the compressor cycles off. I should also point out that unfortunately I did NOT check system pressures prior to changing out this compressor, which in hindsight would have been good to know. When I got the old compressor off, the clutch literally fell apart!

Here is where my questions begin, primarily due to my lack of knowledge on the workings of the electric fan clutches on these trucks. Once I saw the high side pressure issue, I took a shop fan and placed it in front of the grille of my truck and the pressures instantly went down to about 200-210 psi and everything works beautifully. Thinking logically I would assume this means I have an issue with airflow across the condenser but I have no way to quantify the performance of my fan. Additionally, the guys in the shop here at work have thrown additional thoughts in my head about maybe this new compressor being bad (not sure I buy that because the AC is nice and cold and when I'm moving it doesn't ever get warm which tells me the high pressure issue is gone while driving due to airflow across the condenser). They are also telling me the system may indeed be plugged up and that the fan in front of the truck trick is overcoming that issue, but I'm also not so sure about that.

So, how do I determine if my engine fan is moving enough air to properly cool the condenser? Additionally, what should my fan be doing at different operating conditions? I will say that occasionally I do see a fan circuit fault in my Edge Insight- is this a clue? Just to give you all the facts, I do have a BPD oil cooler mounted behind the condenser but that's been there since 2011 so that shouldn't be contributing to this. Is there a way to jump a connector or something and command the fan to "full speed" and see if that airflow increase fixes my issue? I know the old "spin the fan and check for resistance" trick but something tells me this won't work with this style fan clutch.

The truck has 180k on it so I can see where the clutch could be bad but I'd really prefer to properly diagnose this issue instead of just throwing parts at it. I just need a little help understanding what this fan should be doing and how to confirm that it is properly working. Any diagnostic tips or suggestions would be appreciated. After working so hard to replace this compressor the other day I'm a little bummed that I've got another issue, but I want to handle it ASAP.

Again, thanks for any help offered.

 

You can ground a wire in fan connector and it should lock it in 100%:
https://www.ford-trucks.com/forums/1...hich-wire.html
GROUND it, don't power it.

It would probably better to buy Torque Pro to actually read the FSS and clutch DC PIDs. It's really very embarrassing for Edge that their $400+ monitoring system can't do what that app does for five whole dollars.

 

I just replaced my AC system and just went through this.

First, did you replace your accumulator?

When I changed my engine I tried to get away with not replacing anything and just capping off each component... clearly it didn't work.

The motorcraft accumulator is not very expensive ($53 at rock auto) and should be replaced any time the system is opened.

Second, which condenser do you have? If it had been replaced after ford updated the part then you have the good one. One easy way to tell is if the fins are continuous from top to bottom it's the old one, or if there are fins all the way to the top.

The newer motorcraft condenser is a plate and micro tube, copper, parallel condenser. It is much more efficient but the down side is it cannot be flushed if you have a compressor failure.

Lastly, did you flush the evaporator and lines with the proper fluid?

With any kind of compressor or accumulator failure this is critical. I think it's important anyway but with a compressor failure it is even more so.

Going to your pressures. pressures will vary based on ambient temperatures (how hot is it).

Also, as the clutch cycles, what is the low side pressure. High and low should be checked together because one is linked to the other along with ambient temps.

When you said the orifice tube "wasn't bad" what does that mean? did it have any debris at all? if so describe it.

another thing to look at is the refrigerant that was put in... make sure it was just refrigerant with no additives like stop leak. UV dye is ok but anything else will likely cause problems.

My guess is that your condenser is clogged and your accumulator is coming apart (they tend to do that around 150-200k miles). But that is like assuming a hpo leak for a no restart... just a guess based on limited data.

Richard

 

Thanks for the information- I will give that a try, hopefully later today.

 

Thank you for your detailed response. See my answers to your questions above.

On the other hand, wouldn't the fact that the high side goes down as soon as I put a fan in front of the condenser point to an airflow issue or am I missing something here? I would just think that if there was an obstruction in the refrigerant circuit that the high side would always be high and that it couldn't be lowered by the fan test.

 

That black debris is bad. Sounds like some of the internal seals were coming apart on the compressor. that is likely what caused the already old compressor clutch to come apart.

the clutch likely acted as a fuse and prevented really bad stuff like this from happening.


Skip to 4:10 and ignore the rest

I would replace the rest of the system. the orifice tube likely saved the evaporator.

remove the lines from the vehicle (hopefully you saved the cap that came on the compressor) to flush them... it makes it a lot less of a mess.

Use this:
and this:
there may be other flush canisters, just be sure it has the wide rubber tip because you want to back flush the evaporator so the fluid comes out from the pipe where the orifice tube goes.

Try to get what oil you can out of the compressor by turning it over by hand and trying catch the oil that comes out of the ports.

I used about half to 2/3rds of the can on the evaporator and the rest on the three hoses.

Do be warned, the flush fluid will damage your paint extremely quickly.

richard

EDT: also here is the new condenser: http://www.rockauto.com/en/parts/mot...condenser,6708
they have the cheapest pricing. I also have a 5% off code you can have too. get the accumulator from there too.

 

this should also help. it's from my snapon ac training manual



Richard

 

Question- if my issues were due to a physical blockage in the refrigerant circuit wouldn't it be true that putting the extra fan in front of the truck would NOT get my high side pressure down to where it's supposed to be? Maybe my logic is flawed, but a blockage is a blockage and raises pressure because of a flow restriction in the circuit and that pressure wouldn't be relieved by any means other than removing the obstruction, correct? If this is the case, then the fact that my high side pressure goes down when I put a fan in front of the truck should indicate that I have an airflow problem and not a blockage in the refrigerant circuit.

Mind you, although I know my way around an automobile fairly well I am not a HVAC expert so I am only asking for clarification based upon my common-sense approach to this issue.

 

I may of missed some of the PDFs if you need others let me know
and I can post them later tonight for you.

Any hardware that you are not replacing will need to be flushed and have
the correct amount of oil placed back into the system and there is a PDF
that has the amounts for replacing oil lost in a flush.

 

I missed that... Yes, if the fan is not working correctly or if the evap has crap in it reducing air flow then that can be an issue. I think even the original condenser is a parrelel flow so it could still have some clogged areas. If you have a non-contact pyrometer you can check for sections that are not as hot as others which would indicate clogs (jut like a radiator).

Richard

 

Thanks for the reply- I think I'll grab one of the guys' laser thermometers tomorrow and look for hot spots in the condenser. Good idea.

Do you have any idea how to confirm if my fan clutch is doing what it's supposed to do and providing the proper amount of fan speed? I've got no idea how to ensure that my fan is moving enough air and I'm suspicious of the fan clutch because the extra fan I put in front of the truck cured this high pressure problem.

 

Did you use a vacuum pump to draw a vacuum on the system to evacuate all air before you charged? If not you will see excessive high side pressures.

 

you can try grounding it as suggested... if you have the ability to see live data you can bring up the pids to see fan rpm and duty cycle. It will vary based on engine rpm and need (ie oil/coolant temp).

Others are more knowledgeable about the fan function.

Richard

 

Yes i did.

 

Watch the fan speed sensor (FSS)
Also if you have access to a scan tool that can do
Active Command (Ford Word) and kick the fan speed
up and watch the FSS to see if it does what it should.

Active Command is used in IDS and a few other tools
may have something like that by some other name.