Automotive Air Conditioning Information Forum (Archives)

Provided by

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

New A/C System installed, input please

FordF350 on Fri April 11, 2014 1:54 AM User is offline

Year: 2003
Make: Ford
Model: F-350
Engine Size: 6.0
Refrigerant Type: 134
Ambient Temp: 74
Country of Origin: United States

Firstly, sorry for the long post!

So I just replaced everything in my A/C on ’03 F-350 6.0 turbo diesel (New evaporator, Motorcraft compressor, condenser, drier, high and low switches, red Motorcraft orifice tube and hoses). Calls for 9oz PAG 46 and 42oz r-134a.

I drained the new compressor’s oil prior to install and put fresh Ford OEM PAG 46 in. I put 4.5oz in suction side of compressor, 4.5oz in drier. Compressor clutch air gap at .025”. I used Nylog on all seals and o-rings for the whole system (seems like great stuff!).

I pulled a vacuum after install for 2 hours and down to 29.5in and let it sit for an hour (I actually hooked the whole system together in my garage before install, pulled a vacuum and let it sit for two days after chasing down a few leaks).

Before charging I spun the compressor by hand for about 10 revolutions to move oil through.

I used 12oz cans on a digital scale. I pulled a vacuum on the service hose prior to opening the cans to eliminate air (I pulled the vacuum through the upper service port with the schrader valve).

I got a little more than one can in IIRC prior to needing to start the truck (maybe ~15oz or so? I didn't write it down).

I ultimately charged the system with 42.2oz.. I had a couple of the cans that had .3oz to .4oz more than 12oz in the can.. Is that normal?

One mistake: I have no dye in the system :/

The vents feel like ice bergs could come out.. cruising at consistent speed, it is hard to keep your hand 3” from the vent because it is so cold. Unfortunately I couldn’t find my thermocouple for my multimeter over the weekend (I just found it tonight!), so I couldn't take temps, but I can tomorrow.

I do have some quirks in the system and I would like y’alls input.

Here is the behavior I have observed. I think I may have some type of engine cooling fan issue:

Static pressure: 80psi at 74* ambient

A/C on max recirculate, driver window down. All readings at idle ~750-800rpm.

When I first started the truck (already warm from driving earlier in the day) to take the pressure readings, the pressures climbed over 90-120 seconds to 52psi low side and ~440psi high side before the high pressure cut off switch did it's job… After this happened, within 30 seconds the engine fan kicked up and brought the pressures down fast (PCM controlled viscous fan clutch).

After the a/c clutch reengaged, at idle, at 74* ambient, I had 30-34psi on low side 160-180psi high side. It stays there for quite some time, then starts to rise again, but to like 300 on high side, then the engine fan kicks up and the high side goes back to down to ~200psi.

I used my laptop and ScanXL to watch the A/C clutch status via OBD2 port while driving around and this is essentially what I see:

At idle compressor clutch stays engaged most all the time, but will cycle off for 10-15 seconds every few minutes (presumably because of high pressure). During this 10-15 seconds is the only time the vents go warm.

Under quasi-hard acceleration, the compressor cycles quickly.. on for a few seconds, off. But the vents are nice and cold (hard to tell it is cycling without the PCM data logger).

It will cycle occasionally when at say 60mph, but seems to stay engaged most of the time.

Any ideas?

It is very comfortable in the cab.. A/C feels quite nice.

I can take temp readings now that I found my thermocouple, so if needed, I can take them.

I don’t *feel* I have any leaks in the system, fyi.

FYI, I replaced the viscous fan clutch with a cheap knock off a couple years ago. Seems to cool the engine perfectly well.

You can stop reading here unless you want quick back story:

Why did I replace the whole A/C to start with? 2 years ago, I had my oil changed and the mechanic broke the tab off the engine fan clutch wire retainer. A couple of days later on a road trip here in Texas during mid-summer, I stopped at the store and left the family in the truck idling. When I came back the truck was overheating and A/C was blowing hot – the fan clutch wires had fallen into the fan and disabled the fan entirely. The A/C went downhill after that and died with Teflon in the orifice tube. I decided to replace everything A/C related, just to be safe. And as stated above, I replaced the viscous fan clutch with a cheap knock off.

Again, sorry for the long post!

Thanks for the input,


Edited: Fri April 11, 2014 at 2:15 AM by FordF350

mk378 on Fri April 11, 2014 9:09 AM User is offline

Fan should be starting sooner. Can you tell when the PCM is sending the command to the fan, such as by measuring the voltage across the solenoid? If the solenoid has voltage but the fan doesn't start, there is something wrong with the clutch.

Leggie on Fri April 11, 2014 9:18 AM User is offline

If you added 9oz of oil and it calls for 9, you overdid it. New compressor should have been filled with enough for a dry system.

FordF350 on Fri April 11, 2014 10:35 AM User is offline

Leggie, please explain... if the system calls for 9oz, and has 9oz in it, how is that too much? And no, the compressor shipped with 7oz from the factory, not the 9oz required for my system. I drained the oil from the compressor, measured it to just shy of 7oz, (which by the way, that oil wasn't as clean as I would want in my system), and added back 4.5oz in the compressor and 4.5oz in the drier. How is that too much?

mk378, I will use my scan tool today and see if I can get the fan's commanded status and compare that to what the fan is actually doing. I can also take some temps if you would like; let me know. Also, do y'all see anything wrong with it cycling while accelerating?

Thanks for the input!


Leggie on Fri April 11, 2014 12:55 PM User is offline

I didn't see that part. I read it as you added 9oz on top of whatever was already in it.

Now that's behind, you don't get all the oil out. Is 9oz drain and fill capacity or total capacity?

FordF350 on Fri April 11, 2014 1:57 PM User is offline

As stated Leggie, compressor shipped with 7oz, removed and measured to just shy of 7oz. 9oz total added to system (4.5oz in compressor, 4.5oz in drier). I highly doubt there is an oil issue here.

I just took some temps, and here are the result (all in F):

Ambient: 81*

Started the truck and ran a/c for a couple minutes to settle.

Taken at center vent, truck not moving:

48.2* at 1500rpm

53.6* at idle

No cycling while in drive way and truck is cold (first start of the day).

While driving:

50* at 35mph (some cycling)

53-56* at 55mph (quite a bit of cycling)

Back in driveway, truck warm:

51* at 1500rpm

53* at idle.

mk378, I scanned the fan clutch sensors at it appears to be working properly. The fan actually has a hall effect sensor to provide fan speed feedback to the PCM. I also watched the commanded duty cycle of the fan, and when commanded, the rpms of the fan increased until the commanded duty cycle was reduced. The fan was audible at times.

One thing I will note about the install - the condenser I replaced was a tube type, while the knockoff I installed was a flat fin type, not sure what it is called.



bohica2xo on Sun April 13, 2014 12:05 AM User is offline

Your fan is running on the ECT sensor, which would check ok on a scan tool. When the coolant temp goes high enough, it works.

The 6.0 has a second refrigerant pressure switch, in addition to the standard cycling switch. It sends it's own signal back to the PCM, which can then call for increased fan speed based on refrigerant pressure.

This is a dual function switch with 4 wires connected to it - located at the front of the engine. Either the switch is bad or possibly the harness is damaged from the wiring near it getting wrapped up in the fan. The 4 wires are:


TAN/LtGRN (two of these)


This switch in on 6.0 Diesel only, and is for the electric fan clutch.

Hope that helps


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

ice-n-tropics on Sun April 13, 2014 10:29 AM User is offline

Good job over in Bakersville.

Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy. How To Air Condition Your Hot Rod

Edited: Sun April 13, 2014 at 10:38 AM by ice-n-tropics

FordF350 on Mon April 14, 2014 12:38 AM User is offline

bohica2xo, thanks for you response.

You are correct about the dual pressure switch that provides pressure reading to the PCM. Unfortunately it doesn't look like my scan tool can read the value of that sensor. I may tap the wire (TN/LG, circuit 439) and read the output with my mutli-meter directly.

I replaced both the "A/C compressor cycling switch" (low side) and the "Dual Pressure switch" (high side) when doing this job. When I bought the high side switch, it was a GPD "binary" switch. There were 2 GPD part numbers, and I chose the more expensive one (GPD Part # 1711521). I am wondering if there is a possibility that the switch is the wrong one? It looked identical and had this year/make/model listed as a direct fit. The OEM Motorcraft part (YH1705) is only $28.. wish I had spent the extra $3 and gone OEM to be sure



bohica2xo on Mon April 14, 2014 7:18 PM User is offline


It may not be the switch if the harness took a hit when that fan connector got yanked by the fan drive.

I am not near a FSM right now, but if you have one (or an alldata / Mitchell account) have a look at the switch diagram or truth table - it is two SPST switches inside. I believe the Blk/Yel in the connector should go to chassis ground.

Pull the connector & check the ground. Go through the diagram, and jumper the connector to see if you can command a fan speed change. If the connector jumpers will let you do that, it is a bad switch. Since the switch is new, it may be ok... but since it is "generic" it may simply be the wrong part.


"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

FordF350 on Mon May 12, 2014 12:26 AM User is offline

Sorry for the slow response! I was out of the country for a couple weeks (got married!).

So I am back to playing with the truck and it's a/c and after looking into the fan clutch issue, I think I may have found why the fan is not being commanded properly: EGR delete. The EGR valve, in some versions of the 6.0L PCM programming, requires the EGR valve to derive it's cooling strategy.

I have deleted the EGR cooler on my 6.0 and from what I have read on the Superduty forums is that other people have had issues with the fan not being commanded properly after removing the EGR valve.

The solution is to leave the EGR valve plugged in even though it is no longer doing anything. Unfortunately, I installed a block off plate and threw my valve away

I will buy a used one on eBay, and report my results.


FordF350 on Tue May 20, 2014 6:48 PM User is offline

Everything is finally working awesome!! First, I bought an EGR valve and hooked it up. The PCM then began commanding the fan to 100% when the high side pressure would get high, but the fan would never rise over about 230rpm, idle or not. No P codes, no CEL. No matter what, the fan would never rise as commanded. I even hard wired it to engage, and no change. So when the high pressure switch would kick on, the PCM would command 100% fan, and since the fan would not spin up, it would cycle the A/C until the pressure came down.

I began to suspect the Dorman aftermarket fan clutch I installed a while back.

So, I bought a used OEM fan clutch on e-bay, and viola! PITA to install, but now, at idle, when the high pressure switch closes the fan is commanded to 100%, the fan jumps to ~800 rpm at idle, and the high pressure switch opens (pressure has been reduced). At 1500rpm, the same thing happens and it works flawlessly!

Even better, it's 92*f today (good heat load) so high pressure cycling would be even more evident.

I drove the truck around with the scan tool, and the compressor did not cycle once in 30 minutes! Nice and cold in the cab of the truck!

Thanks to everyone here for their input, this site is invaluable!


Edited: Tue May 20, 2014 at 6:50 PM by FordF350

jed1154 on Wed August 06, 2014 1:12 PM User is offline


I'm looking at the dfps for the ac problem on my truck. I have my scangauge hooked up now and am monitoring the fan speed. When the truck is at idle and warmed up, the fan speed is exactly the same whether the AC is turned on or not. I want to say its at 850 rpm. This is not right is it? Is the fan supposed to increase a little at idle when the AC is called on this truck? Does this point to the dpfs?

Edited: Wed August 06, 2014 at 1:41 PM by jed1154

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.