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Offline M Jennings

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1978 Pinto AC Compressor Cycle?
« on: July 16, 2015, 02:11:31 PM »
Does anyone know if the AC compressor on a 1978 Pinto cycles on and off? I just got my system charged after 27 years and the compressor clutch is on all of the time as long as the control is set to AC. It's a 2.8 engine if that matters.

Offline pinto_one

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #1 on: July 16, 2015, 07:03:08 PM »
It runs all the time , but only if you have factory air , if it is a dealer add on it will cycle on and off ,   
76 Pinto sedan V6 , 79 pinto cruiser wagon V6 soon to be diesel or 4.0

Offline M Jennings

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #2 on: July 16, 2015, 09:00:15 PM »
Thanks. Mine is a factory setup so it doesn't cycle. I just had the system converted to R134 and charged today. Unfortunately in about 25 miles of nice air conditioned comfort it sounds like either the compressor or clutch is ready to come apart.

Offline pinto_one

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #3 on: July 16, 2015, 09:20:48 PM »
Check the idler pulleys , they sometimes make a bunch of racket when the bearings are going bad , happens when they sit for sometime and the Greese drys out, some had an idler at the bottom to keep the belt from whipping around , that also makes a load noise
76 Pinto sedan V6 , 79 pinto cruiser wagon V6 soon to be diesel or 4.0

Offline amc49

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #4 on: July 17, 2015, 04:10:51 PM »
The rattling is because compressor is probably right on the edge of self destruction.

ALL compressors must at some time or another cycle off or they blow up.......liter ally. They will be at extreme ultimate a/c production (you will LOVE it!) just before they frazzle, you may well get ice crystals coming out of the ducts just before they blow.

The method used to control the on/off can vary but wire one up to stay on 100%? I've done it back when I was young and stupid on a MII and you could not count the parts of compressor when it happened. Some one told me I could do it and the result. After that I picked up a book to find out no, not even.

The dealer install will use a very similar or exact same compressor as the OEM and the same rule applies to both. The control function over it allows one version to seem like it never goes off but it does in some fashion I assure you. One is expansion valve and the other the complicated OEM thing, I forget the exact name of the system.

If they have charged to proper R134 pressures then the compressor should shut off more and faster since R134 uses much higher pressures than R12 ever did. Assuming your pressure controls were not changed there. At temps like now (here in Texas 95F+) R12 about 210 psi highside and R134 300-325 highside.

The systems even now seem to stay on and may indeed do so around idle but they definitely go on/off at highway speeds. The service manuals on these Pintos will clearly detail when and how often they should cycle off, it depends on several different things. The older twin popper compressor like the Pinto uses I look for proper pressures both low and high, that pretty much gets the clutch cycling on/off right at idle, maybe 30-60 seconds (expansion valve type) on before going off. The pressures are more important to hit.

Constant leak systems like orifice type will stay on much more at idle and variable leak ones like expansion valve cut on/off more but BOTH must eventually cut on/off at say highway speeds.  Why you rev to 2500 for an extended bit after charging to make sure they are properly going off.

An older compressor pushed to the higher pressures needed by R134 may well rattle anyway........ .....

Offline amc49

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #5 on: July 17, 2015, 04:25:37 PM »
FYI, the cooling systems and a/c have become so closely entwined now that I have put in LEDs for low and high rad fans and a/c clutch cycling times in all my Ford cars to quickly determine the working of things. I used to have a/c clutch cycling lights back in the old cars in the '70s to be able to tell how often the clutches were working back then too. Valuable maintenance tool.......... .

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #6 on: July 17, 2015, 09:42:12 PM »
I've noticed on mine, that after the conversion and recharge, that on acceleration, say onto a highway on ramp, the blower motor seems to weaken in output - is this a possible vacuum issue, the blower motor itself, or just normal?

Offline pinto_one

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #7 on: July 18, 2015, 09:41:44 AM »
Your vacuum check valve may be bad or have a vacuum leak , the fresh air duct along with the windshield defrost duct may be open/closing at that time when you hit the ramp , engine manifold vacuum is low at that time ,   Some leaks also happen at the vacuum can (in the fender in front of passenger door) the bottom may have rusted a hole in it , happen ot mine , 

76 Pinto sedan V6 , 79 pinto cruiser wagon V6 soon to be diesel or 4.0

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #8 on: July 18, 2015, 12:43:32 PM »
Your vacuum check valve may be bad or have a vacuum leak , the fresh air duct along with the windshield defrost duct may be open/closing at that time when you hit the ramp , engine manifold vacuum is low at that time ,   Some leaks also happen at the vacuum can (in the fender in front of passenger door) the bottom may have rusted a hole in it , happen ot mine ,

Pinto one, would the vacuum check valve be located under the dash, or behind the glovebox? What should I look for?

Offline pinto_one

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #9 on: July 18, 2015, 01:24:49 PM »
The vale is under the hood , right around the starter solonid , the hose is around 1/4 inch , it goes to the vacuum can , open the passenger door , you will see the line from the valve , trace it out from there ,



 
76 Pinto sedan V6 , 79 pinto cruiser wagon V6 soon to be diesel or 4.0

Offline joebob

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #10 on: July 18, 2015, 11:57:58 PM »
If I can be nosey, what does the conversion cost?
77 yellow Bobcat hatchback
Deuteronomy 7:9

Offline M Jennings

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #11 on: July 19, 2015, 04:57:12 PM »
I found a local guy who advised me to buy a new drier for the system since it had been open for over 20 years. The drier was $25 and he charged me $125 to convert and charge the system.

Offline joebob

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #12 on: July 20, 2015, 01:28:38 PM »
Thank you. I am sure I won't get off so cheep
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Deuteronomy 7:9

Offline pinto_one

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #13 on: July 20, 2015, 07:31:00 PM »
The conversion can be done very easy on a pinto, one it is a dry system, only the refrigerant circulated in it, newer cars , oil and the refrigerant is both circulated together to lube the compressor, so if they say you have to flush the system run don't walk , it does not ,   the small kit you can buy has the two new fittings to screw on the old ones, ( take different charging fittings so you can not mix up the other refrigerants) next is the dryer , found that they say change it when you go to the 134A but I used the old one , only if they were not open to the air for years or days on end , the compressor oil is changed to the newer oil , just dump into a container and measure and refill with the same amount, then the only thing you have to do is pull a vacuum and charge the system, did my 80 pinto wagon ten years ago and the 76 eight years ago ,
76 Pinto sedan V6 , 79 pinto cruiser wagon V6 soon to be diesel or 4.0

Offline amc49

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #14 on: July 28, 2015, 12:22:24 AM »
Uh, the oil circulates with the refrigerant on the earlier type compressors too, no way are they oil tight and the service manuals clearly say that discharging refrigerant too fast pulls oil out of compressor with it to lose track of where you are amount wise. If you use PAG oil with the R134 you MUST get every last bit of the older mineral oil out, it can react with it to bubblegum up like jello and tear up the compressor. The official industry conversion number says the mineral oil must end up being 2% or less.  If you use ester oil then you do not have to get 100% of the old oil out. The oil type can make you or break you there. There is no such thing as a 'dry' system, every a/c system I've ever worked on even back in the '60s required oil running mixed with the refrigerant. Not as much as the later ones or these with compressor turned on its' side but some oil is always in the freon, it lubes the reed valves to not overheat, the hottest parts of the compressor.

Dryer changes if left open to air 24 hrs. You CAN get by without changing but you must do a super vacuum job and a refrigerant sweep will help as well. Any o-rings are different material too but they'll go for a good while before failing. I vacuum my own stuff down using a simple 110 volt compressor out of a 5K BTU home a/c window unit. Maybe $10 worth of fittings on it to make it work.

R134 will not cool quite as well as R12 with R12 equipment used, you can make it better at idle with additional condenser cooling like an add on electric fan, the OEM generally doubles up the finning on R134 condensers to make up for  the refrigerant difference. R12 highside of say 200psi will need to be around 300 psi with R134 to get the same amount of cool, that may show up problems with older hoses. R134 systems have high pressure switches that cut out around 450 psi, a good chunk higher than R12 since the normal running pressures are higher.

A good strong blower inside car helps a conversion as well, but an act of Congress getting one of those, the available ones you get anywhere OTC are nowhere near as powerful as they could be, the industry does not care either. I've long said that someone could step in there and create a killer market selling 'high-performance' blowers, people never grasp how much a high output there can increase the cooling of cars. You can freeze the evaporator solid and if the blower does not move max air the output will still s-u-c-k.

I converted cars there for a bit and they worked very well. My Tempos were converted 20 years ago and they still cool fine now. I hate modern swivel o-ring sealed systems though, they tend to leak down faster than the positive metal-to-metal connections the older cars had. Again, all they care about there is installing the a/c lines without using a tool on the assembly line at all. All done by hand only.

Offline pinto_one

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Re: 1978 Pinto AC Compressor Cycle?
« Reply #15 on: July 28, 2015, 08:03:30 AM »
have to say the oil on the pinto compressors (York style) do not circulate though the whole system, but you are right about the compressor reed valves needing oil, but its done all inside the compressor , they are chambers in the inlet and outlet side built into the top of the compressor block, they act like oil separators , if you remove the head you will see both of them . you also will see a tiny hole in each , oil is pulled in tiny amounts on the inlet side chamber and after it runs though the valves it collets in the outlet side chamber , the hole there drains into the front clutch side bearing between the shaft seal, lubes the bearing also ,  does a good job unless you put the wrong head on a different compressor block, those you will have valve problems , these were also used in aircraft , they would never go bad , only the lines or hoses would pop or split from age , I always blow the system out with dry nitogen when I have it, the newer one as in your tempo does circulate the oil , and if you replace anything like the condenser you have to add oil for that part , they all hold a certain amount of oil to work when running , a pinto does not , you only have to check the oil level in the compressor , if you cut open a pinto dryer you will most likely not find any oil in it, the new cars you will find a few ounces , and I also like AMC49 hate the swivel o-ring  snap connectors , they are responsable for most if not all a/c compressors to go bad , low Freon means less lube for the compressor , more oil leaks out , way less lube === dead compressor and a system full of metal,  :-\
76 Pinto sedan V6 , 79 pinto cruiser wagon V6 soon to be diesel or 4.0