Engine Size: 7.3 D
Refrigerant Type: 134a
Ambient Temp: 82
Pressure Low: 24
Pressure High: 175
Country of Origin: United States
My Truck sat for 4 years and when I put it back on the road- no A/C. A single can charge was enough to let the compressor cycle and pump refrigerant, but the compressor case leaked everything out overnight. I flushed the evaporator and condenser thoroughly, even though there was no sign of any debris or muck. I replaced the compressor, the accumulator, and the drier with new parts. Let it sit under vacuum overnight and then can-charged with my best guess.
I used a Variable Orifice Tube for extreme Service, in case that could score some extra cooling on a hot New Orleans day.
The clutch cycles on when the low side climbs to 45 psi, and it draws right back down to 24-26 and holds. High side is 175 idling, and creeps up to 250 @2000 rpm.
The high side of the OT housing is hot, and the low side is icy cold. The line out of the evaporator is cold, and the accumulator is cold.
So why am I blowing 60 degree air out the vents? Shouldn't it be A LOT colder? If I lived in Montana, I would think I did a great job fixing my A/C! But in New Orleans, a 20-degree drop isn't gonna cut it. I need some guidance here. Thanks in advance for your input.
If your evaporator is getting cold, then either your heater is adding heat to the air flow, or one of your diverter doors or flaps is not directing that cold air correctly.
That was the first thing I thought, so I put a ball valve in the heater line and closed it. The heater isn't bringing any heat into the system. I guess there's not enough air getting across the evaporator. This is a retired U-Haul truck, so nothing will surprise me when I open up the airbox. Could be a dead possum wedged in there.
Was the system already converted? What type of oil in the new compressor?
Get rid of the variable OT, they simply don't work. How much refrigerant did you charge in? You should be using close to the amount they specified for R-12.
Edited: Sun September 26, 2010 at 2:11 PM by mk378
It seems as if the system in undercharged. This seems to be an attempt to charge to a specific pressure and the belief that lower pressures are essential for cooling. This is far from reality....post charge rate..let's see more info. These pressures are on the low side for 12 and now the vehicle is operated with a higher pressure refrigerant. Seriously believe the system is undercharged.
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.
134a retrofit was done long ago, when it was a U-Haul truck.
The compressor came with oil in it- the instructions said it was 134a compatible and not to screw with it, so I didn't screw with it. It leaves a fluorescent green wet spot on the fittings when I pull the gauges off.
The OT hisses, loudly, like for two full minutes after shutdown. Is this normal? Replacing that fancy OT will mean having a shop recover and recharge for me, which I guess wouldn't be the end of the world. I only opened it up myself b/c it was already empty, but I don't want to blow my freon into the atmosphere on purpose...
I charged in two full cans and about 1/2 of a third, so 30 oz minus charging losses.
R12 capacity was 50 ounces on this vehicle.
See, I TOLD you I was doing something wrong! I skipped looking up the capacity and tried to charge by gauge readings. I'm still learning. I charged in another full can and now I get 50 degree air, so I'm on the right track.
How do I know when to quit? And how do I know if I've OVERcharged? This guessing game is a little harder than I thought.
One secret is to only charge by pressures when the ambient temperature exceeds 80*F, actually prefer above 85. Another secret is to make sure you are not adding any air to the system when charging. Ideal charging is to stop when your liquid line quits foaming, using the gauges as a guide. Really don't know how to explain this, but comes with years of experience.
Am told, we are too stupid to adjust wheel bearings, so have to get a second mortgage to replace hub bearings. Too stupid to adjust a carburetor and timing, so that was replaced by a computer that has more problems than cures. Dumb enough to pour windshield wiper fluid in my AT dipstick, so they got rid of that. Too stupid to know when to turn my headlamps on or off, lock the doors, or adjust the temperature in the car, so another computer for that. More problems, with all kind of safety and anti-thief devices that work wonders for keeping me from starting my own vehicle. Like anyone wants to steal it, would be doing me a favor if they did. Now spying on me if I am wearing my seat belt or not.
AC use to have sight glasses so you knew at a glance if your oil and refrigerant were correct. So you if want to be sure your oil is correct, have to completely drain and flush the system and carefully measure in the correct amount. They made refrigerant easier, just buy a charging station so you can draw a vacuum without changing hoses, measure and put in exactly the correct amount.
So if you don't want to develop those skills, just buy a charging station. But still have to be awake while using one, but nearly as awake by using other charging methods.
When retro fitting...there are NO SET PRESSURES for the system. The mere fact that one is retro fitting a vehicle is a complete change from the designed functions of the system. The system in question was never designed to work with a chemical such as 134a and it's higher operational pressures....how can one expect to be able to charge by pressures. Heck, there are not set pressures for a 134a system. There are always variances due to operational conditions. The systems must be charged to a specific amount of refrigerant. Then and only then do pressures even begin to become a diagnostic procedure.
The idea of charging to a certain pressure is as old as the hills. It does not work in a modern AC system. The recharge tolerances are too small. It seems each day we encounter a 'seasoned' tech that simply does not understand that undercharging a repaired system by a 'few' ounces to accommodate what he perceives is the 'correct' pressure for that system and of course, the result is a severe component failure and system contamination.
Encountered a tech a few weeks ago in Ft. Lauderdale. He was new to a purchasing jobber and immediately it became evident that his 'defective returns' were extremely high. I made a call with the jobber OSR and we actually did a few in shop tear downs to attempt to explain to the 'tech' why he was experiencing these problems. He, of course, basically informed us that we did not know what we were talking about and that the OE HVAC engineers did not know s*&t about AC functions. He had determined that all factory charge rates were incorrect for proper operation of the system...that often when utilizing the factory spec's that operational pressures were too high...often extremely high (perhaps a restriciton) and that by 'adjusting' his charge rate, he could improve on the pressures and also increase cooling efficiency of the system. No wonder is returns were so high. After we left, I called an associate that is the sales manager for another large AC supplier in the SFL market. Ask if he had any history with this shop.....his response....they would no longer sell to this installer......the reason...his 'warranty/defective' returns were too high. After some serious conversions with our jobber sales manager...it was decided that they would no longer sell to this shop. Thankfully many jobbers are now understanding this problem and are not longer simply pushing parts out the door.
On this vehicle...simply charge until the inlet and outlet temps of the evap are the same temperature. This is best accomplished with a high heat load on the evap...max air, high blower, doors open, engine at idle. Once the temps are the same...or within 3-5 degrees of each other....all is good. It is quite possible that at this time the system pressures may be higher or actually much higher than you would expect...do not remove refrigerant.....increase condenser cooling.....add fans...insure that all engine cooling components are functioning as designed. Removal of refrigerant will shorten expected life of components and cooling performance issues.
Good luck with your repair
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.
Thanks for the useful info. I'm with you, NickD- I'm a big fan of concepts lost in our modern world- "thinking" and "learning". I'm doing a little of both, and fixing the a/c in my shop truck as well. win-win.
A/C work seems to have a lot in common with dentistry- if you ask two experts you get three opinions. Also, there are usually several ways to do something right, and each one works most of the time. The trick is knowing which one will work right here, today, on this job!
The goal is to have proper pressures with a full charge of refrigerant. To do this you need a condenser designed to handle the added heat load of R134a. Main issue in doing this is not too many are drop in replacements. So custom hoses will need to be made.
There is only one way to do it correctly. Full charge proper pressures. How to achieve that is where you have opinions. I've stated mine.
The A/C worked great for several hot Los Angeles days when I first bought the truck January 06. It crapped out before the end of the first week (somewhere around Phoenix) and I never explored the system until a month or so ago. So I guess the truck got the 'used car for sale' fix right before I bought it. I'll probably charge a little more over the weekend- I 'get' how a sight glass works but there isn't one in this system. At this point, just blowing 50-degree air is a satisfying improvement- maybe I should quit while i'm ahead!
My next A/C adventure is a firewall-forward upgrade for my 64 Lincoln (different thread). Thanks again for the input!
For Nick D: Well, that's a fine lookin' family dog and probably well worth a check-out trip to the vet, assuming same dog as per post. Regarding your comments on R-12, I have farm equipment and couple of old hobby gonna-fix-it-up-one-of-these-days cars, with R-12 systems that will need a complete work-over at some point. I may have to do the reto-fit to 134a or, alternately, find a qualified tech with an R-12 source. Working on R-12 systems seems a tad more big-brother sensitive.
That said, what is going on with the R-12 already made that's not in hands of private hoarders or commercial shops with existing inventory? Is it being destroyed by the guv and if so, how? According to a tech book, a chlorine atom dissassociates from the freon (R-12 that is) and raises havoc with ozone layer. If chlorine- a greenish yellow gas, and R-12 both are heavier than air, how does it make the journey?- probly oversimplification but just asking. Unless all of it's retrieved and nuetralized, it would probably be better put to good use doing its intended purpose. I've heard some countries did not join the R-12 ban and the stuff is actually still being made outside the U.S.
On a more practical note/question, the old Ford has a Tecumseh / York style compressor. I remember one of these units (different car long ago) noisily lugging the motor at idle. If a person went to a newer unit (compressor only), would that definitely require 134a legally or in reality, or could R-12 be used? God bless.
Blessed are those who have not seen and believed.
Actually, that is a photo of me, LOL. That was Dok, born when this site was formed, poor guy died about five years ago from torsion, and finding a decent vet around is here crazy. Nearest one that does surgery was over four hours away, in severe pain, no way could I get him there in time, so had to put him down. Should update that photo to Derik, my latest Shepard, but have to remember how to do that. Dok was one of those way oversized Shepherds that is subject to torsion, got a German standard this time, quite healthy.
Have five vehicles, three are R-12, all working fine, you have to get a 609 certificate to be able to buy it. I personally never believed in that theory, for one thing, can't recall the name of those two UCLA guys, but there experiment was in a closed box. If R-12 does get up there, UV will break it down, it will fall to the earth and more O2 will go up there. Even NASA backed off from that theory with no real proof. But once a law is made in this country, impossible to break. Al Gore's next attempt was to get rid of R-134a, but maybe he is history now with his recent sex scandal.
R-134a is great in an R-134a system, believe it or not, my wife is after me to get rid of my three R-12 vehicles and buy a new one. Probably will, if I can find something half way decent.
Suspect drcliff topped his R-12 system with R-134a, just to get rid of it, very common among used car dealers. Never asked him about his fittings and accumulator that had to be changed.
Nick, the truck looks like a professional retrofit. there's a (faded) blue sticker, and and R-12 ports had been replaced with 134a ports. It was a UHaul truck its whole life until me, so it was done by a UHaul fleet mechanic. "Professional" is a relative term.
My Lincoln, on the other hand, looks to have been converted by some doofus in his backyard. The York was full of slightly-burned mineral oil, and the lines are lined with some grey filmy gunk- layers of stop-leak, i presume. this one gets a compressor and condenser upgrade, all-new hard parts and custom hoses.
Can still stick with R-12 with the 64 Lincoln, but may have problems finding leaded high octane fuel. Kept a 70 Buick 455 for awhile that required leaded fuel, problem with unleaded is it burns a lot hotter burning out your exhaust valves. I addressed the high compression problem by installing Canadian head gaskets, Canada never sold high octane fuel, so Buick was making thicker head gaskets for them.
Found a 73 intake manifold with the new carburetor and the EGR valve to solve high combustion chamber temperature problems and also installed an HEI distributor from it. It worked, to my amazement, really didn't change the fuel economy and not much in the line of performance. Said the heck with adding dual catalytic converters. Ha, would still like to say the heck with those, but the fine is rather stiff. Didn't have to for a 70.
When you could buy high octane leaded fuel, say even in 1985, the price was $1.55 per gallon as opposed to paying about 75 cents a gallon for standard unleaded. But you weren't getting your moneys worth, as the EPA was quietly decreasing the lead content from 100% down to 10%, so people were still having lots of burnt out exhaust problems.
Another trick was to regrind your camshaft so that about 20% of your exhaust fumes were left in the cylinders that served the same purpose of the EGR, but that can get hairy. Guys that were disconnecting their vacuum line to the EGR were bragging about the drastic increase in HP, but were out 600-1000 bucks soon after to get a new valve job. High temperature valves helped a little, but would end up with holes in your pistons.
Lead in gas affects people in different ways depending on the amount of their exposure and the degree of their barrier in that blood brain barrier thing. Some become very aggressive and stupid which I feel explains our current lot of politicians, with especially with all these stupid attack ads on TV and our current laws.
Your could have traded in your Lincoln in for a Ford Focus and received 4,000 bucks for it. I couldn't help but notice at my Ford dealer, the price of the Focus jumped from $14,000 to $18,000 during that time period. Sure worked, Ford dealer was able to empty his lot, but afterwards, the Focus price tag dropped to $15,000. So exactly whose pocket this all this tax money end up in, certainly not the consumers. GM was selling at list prices, but afterwards, started to offer as high as $5,000.00 in rebates, and that was without a trade in.
Really difficult to find a bargain when dealing with stupid fellow Americans and crooked politicians. Same with the real estate market, if someone was dumb enough to pay $400,000 for a $150,000 home, that money wasn't lost, $250,000 of that ended up in someones pocket. Damn house was only worth $150,000 in the first place if even that much.
They say for a democracy to work, the citizens have to be intelligent, sure won't find any intelligence in the way our public school system has deteriorated.
Getting back on topic, not only problems in keeping your vehicles running, but plenty of government interference as well. Since I can't completely drain my blocks anymore, latest problem is finding 100% anti-freeze. All this 50-50 crap, and even at that, I need a 60-40. If its not one damn thing, its another.
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