Forgot more than I know

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Forgot more than I know

Postby bevis » Thu Jul 30, 2020 12:31 pm

Im a new user and would appreciate it if someone could help me understand what this cars ac system is telling me.
This is a 2005 ford focus that belongs to my girlfriend. It was owned by her and her dad and he's since passed so there's no
way she wants to part with the car. I just keep fixing everything that goes wrong with it. Its a money pit.

The compressor went south last year so I decided to do a wholesale change out of everything I could easily get to
other than the lines. I changed out the compressor / condenser / accumulator / RCD ( I don't know what the hell its called in a car. the restrictive device that goes inside the line, it was an orange one. this car does not have a TXV ) and all new seals anywhere I took anything apart that had seals.
This car has always had a slow leak that I've never been able to find with the sniffer. Ive tried under the dash and the vents, the schrader valves, all connections and anywhere else I could think of. The sniffer never went off. I did test the sniffer with refrigerant and it works.

Heres the crazy thing to me. I can pull it into 29in of vacuum and it holds overnight . Thats crazy considering that I know for a fact that there is a leak. Im thinking there is a leak somewhere on the high side while under operating pressure. At least twice a year I have to add refrigerant.

So this time I pulled it into a vacuum for an hour and then let it sit for 30 mins to make sure it didn't drop. It didn't so I dropped some UV dye in and weighed the charge at 26oz per the Ford spec. The problem is that I have no idea what changes in the accumulator / condenser / compressor may or may not have been made by the aftermarket supplier. The dropped charge did not seem to be enough.

According to the ambient T/P chart the car seems off on the published numbers. Thats not to say that those numbers are correct and are maybe just ball park numbers. I was an HVAC tech for 15 years but that was over 30 years ago in the days of ambient +30 for R22 systems. I know next to nothing about R134a auto systems. It just seems that the vent temp should be colder than it is. But maybe I'm wrong.
Here are my numbers that I came up with that netted me the lowest vent temp.

Ambient - 91.4
Humidity - 75%
AC control on max and blower on 3 of 4 with recirculate on.
24" fan on high blowing directly into the grill of the car
Car idling at 1000 RPM - Suction pressure 45 PSIG ----- High side 225 PSIG - vent temp with digital gauge and HVAC thermometer in vent - 63
Car idling at 1800-2000 RPM - Suction pressure 30 PSIG -----High side 260 PSIG - Vent temp in vent 58
At all times during this test, condensate was just pouring out of the drain and the accumulator was sweating.

Are these numbers correct or do you think I have a high side restriction somewhere ? That restrictive metering device is what I would think could present a restriction.
Any help would be appreciated.

Heres the ambient T/P chart that I found online for R143a
Also I have no idea if you should be looking at your pressures at idle or at 1800-2000 RPM.
I have googled it and there seems to be no rock solid answer.
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Re: Forgot more than I know

Postby tbirdtbird » Thu Jul 30, 2020 2:37 pm

When all the other components were replaced after the compressor died, ( the metering device you are referring to is called an orifice tube, it is a fixed orifice), it would have been a really good plan to have flushed the evap and hoses. An exploded compressor tends to shower the rest of the system with lots of crud. We don't pay a whole lot of attention to those charts, except you would like the liquid line from the condenser not more than 30° hotter than ambient. Any published charts are only rough guidelines. You did not say how replenishing the oil was done.
Your pressures at 1800 actually look pretty good and the condenser seems to be doing its job, since the liquid line from the condenser is very close to ambient.

Some leaks are under vacuum, some are under pressure. No way to predict. Recall that a vacuum is holding back only 14.7 psi, and once running the system is holding back easily up to 300 psi.
Dye is a good idea, but we have never had a leak that a sniffer could not pick up. Sniff the evap drain also.

Testing and charging should be done at about 1800 rpm. Idle speed of 800-1000 doesn't tell you much because the comp has to spool up to 1200 rpm to really do anything.

Right now I am thinking a re-heat condition with a blend door not closing all the way. This can really fool you.
See what the vent temps are when you first start up and the engine is cold, since at that time there can be no reheating.

Other comments welcome. There are some smart guys here.

I do HVAC and MVAC and I find MVAC to be much more of a challenge
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Re: Forgot more than I know

Postby bevis » Thu Jul 30, 2020 3:43 pm

you bring up some excellent points. I did not flush the system as I should have. im wondering if theres a lot of crap in the orifice tube.
I just took it out for a drive and I can feel the temp from the vent relating to the compressor shutting off and then back on in light to light traffic and hard acceleration. at highway speeds of 65 and 2300-2500 rpm, it seems to work as good as its going to but I also felt the compressor shut off under those conditions also. since I cant see the pressures, I have no idea if it shutting off on low suction pressure to too much head. I checked the operation of the blend doors because I had to replace both those junk cable devices that controls the doors in that focus. a quick google search tells you that its a very common problem. I can't imagine how much money ford has made on those parts. I changed those yesterday. now im wondering if I have that big cam on the side of the blower compartment out of sync. it appeared that you could not put those cable wheel heads on the side of the blower box in a way other then just one way. but never say never. I had to take that gearbox off the side of the blower compartment and take it apart as someone had turned the controls too far and got the gears out of sync. what I do not know is if those doors are in correct sync. a cold start would tell the story. I used to flush systems with R11 while I was doing compressor change outs when I did HVAC for a living. What is the recommended thing to flush R134a systems ? I bought the orifice tube at auto zone I think. im considering dumping the charge and buying an orifice tube that comes in a FORD box. if I go to the trouble of pulling it back apart to change the orfice tube, I really need to flush it. This car hates me and I hate it so the feeling is mutual. You cant charge an MVAC system with superheat / sub cooling because of changing drive systems and compressor design correct ?
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Re: Forgot more than I know

Postby Dougflas » Thu Jul 30, 2020 4:17 pm

Sometimes to find a leak you have to be inventive. Remove the belt and place a shower cap ( usually the GF or wife's) around the front of the compressor. Came back four of five hours and place your sniffer in there and see if it goes off. Sometimes when you can not find a leak it is the shaft seal. Putting a sniffer through a leak test on a drum of refrigerant des not work very well. As mentioned, you may have a reheat problem so eliminate the heater ore by by-passing it. Start thinking out of the box.
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Re: Forgot more than I know

Postby JohnHere » Thu Jul 30, 2020 4:22 pm

In your second test at 1800-2000 RPM, the low-side pressure looks good but the high side is somewhat elevated. It should be around 200-220 at that ambient. Did you still have the same auxiliary fan blowing through the grille or just the vehicle's fan? If the latter, you might have an airflow, fan, and condensing issue.

That being said, with a low side of 30 PSI, I would expect to see a center vent temp in the low 40's. So I agree with the previous comment that you might also have a reheat issue.
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Re: Forgot more than I know

Postby bevis » Thu Jul 30, 2020 4:53 pm

yes the 24" fan blew through the grill the entire time of testing and adjusting the charge. the fans on the car only came on a couple of times. Good idea on bypassing the heater core to eliminate it as an issue. I thought the head was too high for the suction pressure thats why I mentioned a high side restriction and if there is one, I would think it would be in that orifice tube.
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Re: Forgot more than I know

Postby tbirdtbird » Thu Jul 30, 2020 5:16 pm

If you go to a different orifice tube (OT) then "buying an orifice tube that comes in a FORD box" is the only way. Whether the OT is all covered with crud will be interesting. There is a small filter screen on it to collect junk before the actual orifice.
Superheat and subcooling are not emphasized in mobile.

As far as flushing goes, ya, R11, the good ol' days when you could really get something accomplished. There is nothing quite like it.
Be careful of the parts store products, many of those are petroleum based and that is what you don't want.
I have used Rx11 from Johnstone (or Baker or whatever) which is intended for residential/commercial but is also fine for mobile. It is made for the purpose of flushing.
Last edited by tbirdtbird on Thu Jul 30, 2020 10:55 pm, edited 3 times in total.
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Re: Forgot more than I know

Postby Tim » Thu Jul 30, 2020 7:45 pm

Zero of the regulars that support this forum ever suggest using propane or anything similar. That includes any home recipe you want to come up with. They may address someone in a different country that allows other refrigerants. But will not directly suggest anything but approved refrigerants.
Please support for your Auto A/C Parts and Tool needs.
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Re: Forgot more than I know

Postby Al9 » Fri Jul 31, 2020 1:19 am

I'd say anything that is able to evaporate fast (hexane/heptane, isopropyl alcohol or a mix of both) is an exceptional flush solvent in my honest opinion. I flushed an evaporator (plus a set of hoses) with quick drying contact cleaner (based upon both chemicals according to the SDS) myself and it did its job pretty good.
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Re: Forgot more than I know

Postby bevis » Fri Jul 31, 2020 10:20 am

went to the ford dealer today and bought a ford branded orifice tube. I just want to get a look at it to see if its got a bunch of crap on it causing a restriction. it would be crazy to go to the trouble of getting it out and not just replacing it. its not an easy access place. there will be some cursing involved. I have to wait for them to get me the oring at that fitting where the orifice tube goes in. I don't want to use a china green one. its too hard to get to to use inferior parts and especially a seal. it will also give me a chance to see if there's any metal there left over from the old compressor or coming from the new one. right now its going to have to take a backseat to the hurricane that may directly hit us here in Florida. I have to get ready for that.

As soon as I get the orifice tube changed, I'll update with pics.
I appreciate all the input and help...

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