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post #1 of 13 (permalink) Old 03-13-2015, 09:09 PM Thread Starter
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AIr Conditioning Question

I need a recommendation. I have one mechanic that will check and recharge my ac with R12 for $59.00 for the check then roughly $70.00 per pound of R12. My question is should I retrofit it for R134 now and future proof it? I have someone that will do the retrofit for about 150.00
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post #2 of 13 (permalink) Old 03-13-2015, 10:25 PM
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R134a, at this juncture, is not "future-proofing" anything. It's on the horizon to be phased out.

If the R12 system is still working and doesn't appear to be leaking it's still possible to get years out of it.

I have nothing against R134a and one of my cars was retrofitted before I bought it. It is a bit less effective than R12, but not enough for me to notice in VA. The Shadow can still freeze off various body parts with R134a. It just seems that R134a is not going to be available long term at this point. I wish I could find the US Phaseout schedule, but am not having any luck this evening.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #3 of 13 (permalink) Old 03-13-2015, 11:38 PM Thread Starter
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Thanks good info. Looks like US car makers have until 2017 to phase out R134. I think my concern was the overall cost of R12. Not sure how much it would cost to completely recharge the system. Then again it is a 79 Silver Shadow and it will probably be the cheapest thing I do all year. I am in So. cal and Phoenix, so the colder the better.
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post #4 of 13 (permalink) Old 03-14-2015, 08:03 AM
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Originally Posted by risrae View Post
I need a recommendation. I have one mechanic that will check and recharge my ac with R12 for $59.00 for the check then roughly $70.00 per pound of R12. My question is should I retrofit it for R134 now and future proof it? I have someone that will do the retrofit for about 150.00
I'd stick with R12, it's a more effective refrigerant. My own car quickly reaches ACU outlet temps of less than 2 degrees C. Most modern cars using R134 rarely get below 6 or 7.

R12 gas molecules are larger than R134 which means leakage (often due to the permeability of old hoses) is less of a problem. Even if you're happy with the the performance of R134 its likely that it will need topping up more frequently offsetting any initial saving.

An entire Shadow/Early Spirit system refill only requires a little over three pounds of refrigerant so If your system is blowing cold already then you'll only need a top-up of R12.

If you're still able to source R12 stick with it and, if you're able to, buy some to save for later use as it's becoming increasingly difficult to get hold of. Of course the other complication is finding a refrigeration engineer willing to use it as most countries forbid this.

As R134 is cheap, and works, ultimately you may find yourself having to switch to it. It's still cheap and is likely to be available for some time so once again it may be worth putting some aside for the inevitable day when it too is made illegal just as R12 was. It's replacement R1234yf is so horrifically expensive there are cases of it being stolen for resale on the black market. It's also far less efficient and has to be pumped at such high pressures that older cars will have to extensively modified.
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post #5 of 13 (permalink) Old 03-14-2015, 11:55 AM Thread Starter
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I have two garages that can do the R12 still here in So. Cal. I suppose I could always drive down to Mexico and pick some up there as well if need be. Im leaning toward the R12 and it sounds like only needing three pounds is not that bad for the benefit of colder air.

It is blowing hot now so it is most likely totally empty. It went from blowing pretty cold one minute to hot air the next. Good idea to pick up a case or three of R134 now. Ill start stock piling that now.

If anyone has a place to still source R12 Id like to get a link. I see it every so often on Ebay, but it is so expensive.
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post #6 of 13 (permalink) Old 03-14-2015, 01:13 PM
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If it's suddenly stopped it's more likely a low charge has caused the thermal fuse to blow.
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post #7 of 13 (permalink) Old 03-14-2015, 03:30 PM Thread Starter
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Where is the fuse? If I reset it will it blow cold at least to test it.
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post #8 of 13 (permalink) Old 03-15-2015, 12:47 PM
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From your earlier posts you have a '79 Shadow II in which case the thermal fuse is mounted on the alternator bracket. It's the black plastic rectangular block which as three thick cables connected to it.

It serves a dual function, Firstly it contains a fusible link that would blow instantly if the compressor clutch coil, or cable between the coil and the fuse were to short. The third connection goes to the superheat switch mounted in the back of the compressor. When this grounds, for example when the refrigerant is low, it causes a resistor mounted next to the fusible link to gradually heat up. If this happens for an extended period the heat generated melts the link cutting the supply to the compressor clutch. From your description this is possibly what has happened.

If I recall, the three connections are marked S, B & C and correspond with connections to the superheat switch, battery (supply or input) and compressor clutch.

Its purpose is to protect the compressor against a low refrigerant charge that would cause compressor damage. Under this condition it would heat for extended period as the superheat switch provides a constant ground. Transient conditions, that are not damaging to the system, however do not allow the resistor to get hot enough to melt the fuse.

The gradual heating of the resistor should differentiate between the two however there was a factory modification that involved adding yet another resistor in series with the first that extended the heating time even further.

Like all fuses it can be jumped and a plastic Littelfuse can be used to bridge between the incoming supply current to the clutch feed, B & C. This provides protection to the clutch but obviously bypasses the superheat protection.

OE thermal fuses are quite expensive and difficult to get hold of but aftermarket ones are easy to order on line and in my experience are just as reliable and only 1/10th the price.

You sometimes see cars where a new original type fuse if fitted thermal protection is made ineffective by disconnecting the round push on connector to the superheat switch on the rear of the compressor. It's a good indication that someone's trying to hide a problem.
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post #9 of 13 (permalink) Old 03-15-2015, 01:02 PM Thread Starter
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Originally Posted by byteme View Post
From your earlier posts you have a '79 Shadow II in which case the thermal fuse is mounted on the alternator bracket. It's the black plastic rectangular block which as three thick cables connected to it.

It serves a dual function, Firstly it contains a fusible link that would blow instantly if the compressor clutch coil, or cable between the coil and the fuse were to short. The third connection goes to the superheat switch mounted in the back of the compressor. When this grounds, for example when the refrigerant is low, it causes a resistor mounted next to the fusible link to gradually heat up. If this happens for an extended period the heat generated melts the link cutting the supply to the compressor clutch. From your description this is possibly what has happened.

If I recall, the three connections are marked S, B & C and correspond with connections to the superheat switch, battery (supply or input) and compressor clutch.

Its purpose is to protect the compressor against a low refrigerant charge that would cause compressor damage. Under this condition it would heat for extended period as the superheat switch provides a constant ground. Transient conditions, that are not damaging to the system, however do not allow the resistor to get hot enough to melt the fuse.

The gradual heating of the resistor should differentiate between the two however there was a factory modification that involved adding yet another resistor in series with the first that extended the heating time even further.

Like all fuses it can be jumped and a plastic Littelfuse can be used to bridge between the incoming supply current to the clutch feed, B & C. This provides protection to the clutch but obviously bypasses the superheat protection.

OE thermal fuses are quite expensive and difficult to get hold of but aftermarket ones are easy to order on line and in my experience are just as reliable and only 1/10th the price.

You sometimes see cars where a new original type fuse if fitted thermal protection is made ineffective by disconnecting the round push on connector to the superheat switch on the rear of the compressor. It's a good indication that someone's trying to hide a problem.
Thanks so much for the advice. I have it scheduled for Wednesday to get looked at, leak checked and re-charged. By chance can you provide a link to the aftermarket thermal fuse? May order it to have on hand.
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post #10 of 13 (permalink) Old 03-15-2015, 01:05 PM
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Where are you located? If in the US this would be one source -

http://www.jcwhitney.com/4-seasons-o.../p3041368.jcwx
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