Automotive Air Conditioning Information Forum (Archives)

fireguywtc on Tue August 14, 2012 8:09 PM

Year: 2007
Make: Ford
Model: F350
Engine Size: 6.0
Refrigerant Type: R-134
Ambient Temp: 102
Pressure Low: 45
Pressure High: 250

Hello all, I have searched on here and tried everything I can so I need your help.

This spring I had repairs done on my F350 which involved removing the cab and of course disconnecting the AC system. Since then I have not been able to get the truck to cool like it did when it was new. I have had the refrigerant charge checked and changed three times now along with the orfice tube two of those times. I think it is important to note when the engine work was done I had the shop change out the orfice tube when they recharged it and he said the original one was plugged. I don't know how badly since I didn't see it myself. Since then it will cool going down the road ok but when I slow down in traffic it warms up.

Assuming it was a charge issue, I had it checked and the shop added some but it didn't help much.

Next the theory was that the system may have some air in it so we recovered the charge, changed the orfice tube again, pulled a vacum and recharged again to no avail. Right now the best it will do with vent temps is about 55* going down the road at 70 mph. It warms up to the mid 65-70 when in stop and go traffic. Though it is working, it does not make the cab comfortable and since I have owned the truck since new I know it is not working like it should.

I have also checked the blend door operation and cab recirculation door, replaced the heater hose shutoff valve, and cleaned the evaporator and condensor. Engine fan is electronic and works, even kicks on with high idle. Nothing seems to help. Please help, I am so frustrated and I love my truck, I just want the AC to work properly again.

Pressures were taken at ambient temp 102:

at idle: Low 45, High 250

High idle (1200 rpm) 38/225

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1970 Ford F250 4x4
2007 Ford F350

Edited: Tue August 14, 2012 at 8:11 PM by fireguywtc

mk378 on Tue August 14, 2012 10:34 PM

Is your mechanic charging it by weight?

Using the correct OT (and installed in the right direction)?

fireguywtc on Tue August 14, 2012 11:09 PM

The orfice tube is in correctly and is the right size (red). The last one we replaced was fine also so I don't think that is the problem.

No, the system is not being charged by weight, doesn't have the tools. So we are using pressures. Thanks for the reply

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1970 Ford F250 4x4
2007 Ford F350

TRB on Tue August 14, 2012 11:12 PM

Quote
Originally posted by: fireguywtc



No, the system is not being charged by weight, doesn't have the tools. So we are using pressures. Thanks for the reply

First error. Use a digital bathroom scale if you have no other option.



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Contact: ACKits.com

NickD on Wed August 15, 2012 8:30 AM

Are you using those cans with sealer in them from Floor-Mart? Could be over slugging your system with oil. Then if using standard two valve gauges, really not intended for charging, should have a four way gauge so don't have to change hoses between drawing a deep vacuum that can suck in air in a big hurry.

Some section in the FAQ how to modify your gauges to prevent switching hose. Air and extra oil don't cool very well and sure affect pressures in the wrong way.

HECAT on Thu August 16, 2012 6:59 PM

Quote
Originally posted by: fireguywtc


No, the system is not being charged by weight, doesn't have the tools. So we are using pressures. Thanks for the reply

Checked and changed 3 times?

You cannot diagnose system performance by pressures without first verifying charge. Know you put the correct charge (by weight) in first. Your pressures look decent, but pressures can be misleading if the correct charge is not there.

You can get good engine oil pressure w/ 2.5 qts. of oil, so why put 5 qts. in it?

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HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

Leggie on Sat August 18, 2012 12:03 AM

No, don't use a bathroom scale. Bathroom scales are meant to have a load placed and it will lock in on a reading. The 1/4 or 1/2 lb resolution offered is too low.

Charge scales are 1/4 to 1/10 OUNCE resolution.

If you're using a low-loss fittings, the loss between can change is negligible.
It's not had to charge precisely by weight using a good postage scale if you know what you're doing.

Standard 3-way manifold is fine, except that Harbor Freight one which has a check valve that causes vacuum to leak-in making it seem like system has a leak during leak-down test.

Pull vacuum for 10min or so. shut off both valves. and turn off the vacuum pump. Come back in 30 min or so and verify that vacuum level hasn't decayed.

(Optional: pressurize to 150 psi with dry nitrogen. Nothing else. do not use refrigerant. Refrigerant dissolves in oil and does not remain as gas as temperature changes so it will mess up the test result.
Detach low side and measure high side pressure. Check there's no pressure loss in 10 minutes.
Remove high side and attach high gauge to low side. The purpose of this is to expose the high port to rule out port leakage.

Repeat until leak is addressed. If it leaks, it's probably one of the fittings that was removed and not assembled correctly.
Pressurize with N2, chase fitting leaks with soapy water just like tire leaks. If leak is big enough to affect pressure reading in 10 minutes you will see it or hear it.
vacuum will only impose -15 psi. Nitrogen will impose +150 psi and nitrogen leaks outward so you can use bubble test )

You can then continue the remaining 45 minutes of vacuum after the system is verified tight. It's pointless to vacuum for more than 5 minutes without taking a break to check for leaks. You could vacuum for overnight against a leak and your not treading any further.

Once you get past that, charge by weight to specs and report back.

Leggie on Sat August 18, 2012 12:14 AM

Quote
Originally posted by: NickD
Are you using those cans with sealer in them from Floor-Mart? Could be over slugging your system with oil. Then if using standard two valve gauges, really not intended for charging, should have a four way gauge so don't have to change hoses between drawing a deep vacuum that can suck in air in a big hurry.



Some section in the FAQ how to modify your gauges to prevent switching hose. Air and extra oil don't cool very well and sure affect pressures in the wrong way.

2 valve manifold is fine if you know what you're doing. Charging station and fancy manifolds saves time, but you don't need either to do quality work.

1.) pull vacuum on both high and low and if so equipped, face ball valve on vacuum pump end of hose. Shut off ball valve.
Attach refrigerant and open the cylinder. Go on and charge.

If you don't have a ball valve, push out the air in center hose with 134a by opening the cylinder with center hose on manifold loose.
Pressurize manifold with refrigerant then charge away.

You won't suck any air into the system as long as you close both valves before turning off the vacuum pump.

fireguywtc on Sun August 19, 2012 7:58 PM

Thanks everyone for the replies! I got a hold of a reputable shop here to take the truck in and have it evacuated, flushed, and recharged to the proper amount by weight. The only problem is I have to wait a while for them to get my truck in. I am also having the accumulator/dryer changed out since the system was open for a while when the cab was off. Since the shop that did the engine work also recharged the system after it was worked on (by pressures), I don't know what else they did to it in the process. Perhaps added more oil, air in the system, etc.

NickD, a few years ago I did use a shelf kit that contained sealant to check and top off my system. I don't think I got much in there but I now know its not good. Since then, and the discovery of these forums I have come to realize and practice that only putting pure R-134 in the system is the way to go. Plus it is cheaper. Since that time I have only used R-134 without and extra stuff in it.

Quote
Originally posted by: HECAT
You cannot diagnose system performance by pressures without first verifying charge. Know you put the correct charge (by weight) in first. Your pressures look decent, but pressures can be misleading if the correct charge is not there.



You can get good engine oil pressure w/ 2.5 qts. of oil, so why put 5 qts. in it? Awesome discription of the importance of proper charge. This really put it into perspective for me. Thanks!

Leggie, Thanks for the description on how to charge the system, it makes good sense. I will certainly refer to it if I end up trying to fix my truck's AC system on my own.

Thanks again everyone, Bill



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1970 Ford F250 4x4
2007 Ford F350

Crude dude on Sun September 16, 2012 2:56 AM

Fireguywtc, what became of your visit to the ac shop?

fireguywtc on Sun September 16, 2012 9:12 PM

Long story short, the shop I planned on going to has fallen through and I have not had the truck worked on yet. I am currently looking a for a reputable shop in the central Texas area, anyone know of any? I live close to Killeen, Temple, Ft. Hood.

Thanks, Bill

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1970 Ford F250 4x4
2007 Ford F350

Edited: Sun September 16, 2012 at 9:54 PM by fireguywtc

fireguywtc on Fri September 28, 2012 5:37 PM

Found a nice local shop that does automotive AC. The tech couldn't come up with a clear diagnosis because the ambient air temps were relatively cool. But the truck is going into the shop on Tuesday to have the accumulator replaced along with a flush and a new OT. This is a result of having the system open with the cab was off over a week and contaminating the dessicant. So I am having it replaced to prevent future problems which could occur from having moisture in the system. Though the repair is to prevent future problems, I am hoping it helps with my low speed cooling issues as well.

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1970 Ford F250 4x4
2007 Ford F350

dolqiu on Tue October 02, 2012 11:11 PM

thanks for all the information guys

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http://www.doltuku.co
http://dir.doltuku.com

ezautoac on Thu October 04, 2012 10:48 PM

I think the first step is what everybody is saying... recover, vacuum, charge with correct weight. lets see what happens.

fireguywtc on Fri October 05, 2012 11:22 PM

Well I got all the repairs done like I mentioned in my prior post. This time I was assured the system was charged to spec by weight and pressures look good. The next two days I drove it around with mid 80's for temps and while driving down the road the vent temps hover around 50* like before. However, it seems to stay cooler when I am driving at slow speeds/idiling. But its difficult to really test the system until it gets hot again.

One thing this pro mentioned when working on my system that I found odd is that he was using a infra-red thermometer gun to check vent temps and I have a pen themometer in the vent. He claims that when my vent gauge reads 50-55 that his gun reads around 31-34 degrees. He told me my pen gauge is wrong.

Well I searched this forum and found a few threads that mention infra-red guns are an inaccurate way to take vent temps and gauges like mine are more accurate. I decided to check my guage for accuracy so I found a meat themometer and put them both in places with known temps. I used living room temp, frige, ice box, and ice water. My gauge appears as accurate as they come.

So it appears that my vent temps are accurate to the pen guage rather then the infra-red temp gun. Any thoughts on that?

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1970 Ford F250 4x4
2007 Ford F350

Dougflas on Sat October 06, 2012 10:53 AM

Place the thermometer into a crushed ice cup. Add a little water to displace any air. The reading should be at 32*.

If your vent temps are colder at idle than going down the road, monitor the battery/alternator voltage. It is possible that your voltage drops at idle thus the fan is spinning slower, therefore less airflow thru the evap. This can cause colder vent temps because the air is in contact with the evaporator a longer period of time.

Normally. at idle, the vent temps are higher because the compressor is turning slower.

Dougflas on Sat October 06, 2012 10:53 AM

Place the thermometer into a crushed ice cup. Add a little water to displace any air. The reading should be at 32*.

If your vent temps are colder at idle than going down the road, monitor the battery/alternator voltage. It is possible that your voltage drops at idle thus the fan is spinning slower, therefore less airflow thru the evap. This can cause colder vent temps because the air is in contact with the evaporator a longer period of time.

Normally. at idle, the vent temps are higher because the compressor is turning slower.

fireguywtc on Sat October 06, 2012 3:09 PM

Thanks for the reply. I checked the gauge for accuracy and it is spot on.

I messed up when I said it was blowing colder when idiling. What I was trying to say is that it seems to stay colder at idle now then it did prior to the repair work. But that is with mid 80's ambient temps. Going down the road the vent temps are about 50 and idiling goes up to about 55 at the mentioned ambient temps.

Sorry for the confusion, it is sometimes difficult to type out your thoughts correctly.

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1970 Ford F250 4x4
2007 Ford F350

ezautoac on Sat October 06, 2012 7:50 PM

Yea infrared thermometers are inaccurate for vent temps. If you point it at a vent you will notice as the lens gets colder the reading also drops event though vent temp hasn't dropped.

fireguywtc on Mon October 08, 2012 7:16 PM

I figured the infrared was probably inaccurate so it seems that good help is hard to find.

Today for giggles I tried running my AC to see how cold it would get. With an ambient temp of about 60* I could only get my vent temps down to 50* while driving. Idiling they would creep down closer to 45. Blower speed seemed to have little effect on my vent temps.

Another thing I tried today was putting my hvac setting on vent only with the dial on the coldest setting. I noticed that the air coming out of my vents are about 30-40 degrees warmer then ambient air. Perhaps I have a heating of air that is causing my AC to be warmer then normal.

I am at a loss with this whole thing now and I am not sure what to do. I am open to all suggestions of what else I should be looking for. I feel that the AC system itself is working correctly now.

Thanks in advance. Bill

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1970 Ford F250 4x4
2007 Ford F350

Edited: Mon October 08, 2012 at 7:28 PM by fireguywtc

fireguywtc on Fri October 12, 2012 6:46 PM

Looks like there is not going to be any resolution to this. Today the ambient temps got up to the high 80s with humidity, the AC system just isn't cooling like it should. Vent temps got to the low 50's for the coldest while driving.

Think I might dump this truck before next summer since I cannot get this thing fixed.

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1970 Ford F250 4x4
2007 Ford F350

HECAT on Fri October 12, 2012 7:44 PM

Quote
Originally posted by: fireguywtc
Another thing I tried today was putting my hvac setting on vent only with the dial on the coldest setting. I noticed that the air coming out of my vents are about 30-40 degrees warmer then ambient air. Perhaps I have a heating of air that is causing my AC to be warmer then normal.

That's something to look at. Try checking A/C performance with engine cold, or try pinching off a heater hose to stop flow thru the core. You may be experiencing a blend door or heater control valve issue reheating your air.

-------------------------


HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

iceman2555 on Sat October 13, 2012 10:27 AM

Assuming that the system was charged properly at the last shop....(?) and the correct orifice tube was used....there are several test that could be performed to determine the performance issue. Operational pressures would be good to have but not a necessity.
Also the ambient temps should be a bit higher than 60.
Place the vehicle in a high heat load condition....MAX AIR....HIGH BLOWER....DOORS OPEN.....ENGINE AT IDLE. Allow the system to operate app 5 minutes under these conditions. Measure the inlet and outlet temps of the evaporator....these should be equal. A slight variation is acceptable...but not more than 3-5 degrees.
If the variation is greater than the 3-5 degrees there is a charge issue. The outlet being warmer is an indication of an undercharged system a possible refrigerant flow issue.
If the charge appears to be correct....check the outlet temperature of the evap and compare this temperature to the actual vent temp. Allow for a slight difference between these temps for possible heat absorption in the dash. If there is a major difference in these temperatures, the performance issue could be within the heater core/ blend door area.
Also check the rec/max air door. This should be a visual inspection...not just the sound of the doors closing....we have experienced several calls this year concerning the lack of adequate sealing of the doors or the position of the doors this year.
However, from the posted info, this does not appear to be the issue. First thoughts are that the heater/blend doors/actuators are at fault. If not mistaken there is a potentiometer reset with this vehicle. May require the use of a scan tool.

As Hecat stated...block off the heater hoses and recheck the system...but the system must be charged correctly even for this test. It may be necessary to block off both heater hoses...and do this prior to the engine reaching operational temps.

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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

fireguywtc on Sun October 14, 2012 2:11 PM

Thanks for the post Iceman, I want to try that. I have a question though, what is the best way to measure evap temps? If you guys want, when I do the test I can take some pressure readings as well.

Also I checked the blend door yesterday and it works fine. That is all I have done so far.

Tomorrow I am going to call the guy who worked on my truck and see what he has to say about this also and to also confirm that he charged my system properly by weight. The biggest problem I am having with this so called "pro" is agreeing on vent temps since he is measuring with an infrared gun and I am using my pen thermometer.

I know that threads can be sparatic when it comes to the details so here is a list of what I have had done to this truck so far attempting to remedy this issue since the cab was taken off the truck for repairs:

1. OT replaced, system vacumed and recharged improperly by mechanic shop.

2. System recovered, OT changed again, recharged again (not by weight) but worked a bit better.

3. I took apart the HVAC system (box) to inspect and clean the blower, cleaned the evaporator, cleaned the condenser and checked everything else for proper function.

4. Replaced the hot water shut off valve that operates when the AC is on Max AC. Sometimes called "Max AC assist", but mine is the factory version.

5. Took the truck to the pro shop to have the system flushed, accumulator and OT replaced, system vac'd and recharged.

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1970 Ford F250 4x4
2007 Ford F350

fireguywtc on Tue February 19, 2013 11:07 PM

Hello everyone!

Just an update. I recently took my truck to another shop that I found by word of mouth. Was highly recommended by all that I talked to. The shop looked it all over from square one and determined that I could use a new AC compressor. The tech said there was a fluctuation on the high side pressure. So the truck got a new compressor, charged by weight, etc. Tech said the pressures looked better after the repair.

Now that I have it back, the AC seems to be functioning fine but I still cannot get the vent temps below 50 no matter what setting or ambient air temp. Most of the time the vent temps are in the mid 50's. It is fine for this time of year but I am afriad that when summer returns and the heat is on, I will be suffering again. I am quite frustrated. My last thought is to put in an adjustable low pressure cycling switch, but I cannot find one.

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1970 Ford F250 4x4
2007 Ford F350

Edited: Tue February 19, 2013 at 11:08 PM by fireguywtc