1993 6.5 Td Gmc A/c

[HGM]

Where is he best source of information for the A/C system concerning dash controls for opening vents for dash, defrost and heater? Has anyone seen info on conversion to 134a. The condenser conserns me. Does it have the capacity needed for the conversion? I have a 1993 GMC 6.5 TD. thanks

[kaylabryn]

If you are mechanically inclined and want to do it yourself, I would check out ackits.com. They are a company here in Phoenix that sells about everything you need to convert and they are a wealth of info. They have a forum just for A/C systems with a FAQ.

Mike

[More Power]

Your condenser has plenty of heat exchanging capacity for an R-134a conversion. That's what I'm using in Lil Red (1989 Chevy K1500), which was converted to R-134a. :)

Jim

[Robyn]

I have done several conversions from 12 to 134 and to a couple other refrigerants too.

The secret is to be sure to flush out the condenser and the evaporator well with a suitable solvent to get rid of all the old oil and any other crud that has accumulated inside these two items.

Once the system is clean you will also need to replace the accumulator assembly. (Silver canister on the RH side of the truck near the firewall)

Be sure to replace the orifice tube also. This will be located in the inlet side of the evaporator. (Its about the size of a pencil and has a small screen and a little tube in it)

Be sure your hoses are in good shape and replace any and all O rings at the connections.
Install the access port conversion valves and then you can staer the recharge sequence.

You will first need to hook up a vacuum pump (refrigeration) to the system and suck it down to 30"hg for about 30 minutes to remove any and all air and moisture that can and will be present while the system was open to the air.

Once the system is fully evacuated you can install the refrigerant.

Now the system needs a specific type and amount of oil. Many times the oil can be dumped directly into the accumulator inlet port before installing it. Placing 1/2 the oil amount directly into the compressor inlet and then turning it slowly by hand is a good idea.

The oil volume for the typical compressor and system used on your rig is 8oz.
There are two types of oil, ESTER and PAG use Ester as it is best compatible with any residual mineral oil left from the use of R12

Once you have flushed the system all the old oil is gone so new has to be added.

*** The compressor also can harbor some old oil too so be sure to remove and drain any oil from it before doing the recharge.

With all the oil issues taken care of you can install the R134.

The amount needed depends on the size of the system but generally its about 3-4 pounds.

To do a first rate job you will need a compound HVAC gauge/hose set but you can do it with a small low pressure charging hose and the little 1 pound cans.

I use a 30 pound pail and invert it on a scale and then open the valve and allow the liquid to charge into the low side port.

Tou can get a fair amouint in this way but you will need to run the thing and suck in the final amount.

********* Caution**********

And this is a biggy BIGGGGGGGGGGGY
Dont ever open the valve on the highside of the gauge set with the AC running and the 134 source tank valve open too.

The tank can be over pressured by the AC pump and EXPLODE causing injury or worse.


Once you have some 134 in the system you need to run the thing and let the AC cycle and observe the operation.

The unit will cycle on and off as the pressure drops in the low side and the switch turns the compressor off and on.

At first until you have the charge just right the system may cycle rapidly but as the thing fills to optimal levels this will even out and a normal cycle rate will follow.
Observe the air temp at the vents in the cab, the temp should be around 40-45 F with blower on MAX.

If need be depending on the outside temp you may need to run the engine on a fast idle to keep the fan pulling enough air through the condenser.

Once you have it all working right a trip around any and all joints with a "Sniffer" is a great idea to be sure you dont have any leaks. Be sure to check areas around "crimps" on hoses too.

******************NOTE*************
Always wear safety glasses when handling refrigerant as it is very cold and can freeze skin, eyes and such on contact.

EPA regs require that all used refrigerant be captured by a suitable flushing and recovery unit and not vented directly to atmosphere.

Just so you know this.


Hope this helps

Robyn

[Kenneth]

I just recharged my R-134a system in my truck in my HVAC class here at school and it was 2 lbs even. I do have an extended cab, if that makes any difference in the A/C capacity size.

Robyn is right. Make sure you flush everything out really good and change ALL the o-rings. We have done some conversions in my class and so far everything has gone great. I do have to say it is nice to have all the top of the line Robinair equipment, with dyes, and oils all in stock. It makes A/C repairs much easier.

I know Car Quest and Napa have conversion kits as well, but they are probably more expensive. Good luck with your conversion.

[trbankii]

Bringing this back to the top. The R12 system on my '93 has finally given up the ghost entirely. Last summer it sorta cooled the air if you had it on, but it certainly wasn't cold. This summer there is no difference between the AC and vent.

I also read through Jim's article in the Members' Section: http://www.thedieselpage.com/members/archive/airconditioning.htm

I don't have the tools, so I'm somewhat leaning toward just taking it in to have someone do it. But I'm not opposed to having a shop evacuate out any remaining R12, do the cleaning and conversion myself, and filling it up with R134a if that is likely to give me a better end result.

I'm not quite clear on whether the cleaning/flushing is something you do with the equipment or if it is something that you're disassembling and physically cleaning stuff. The article mentions the evacuation and flushing, but isn't too clear on the details. If it is physical disassembly and cleaning, I'm figuring that it might be worth my time as I'm liable to be more meticulous than the random flunky at the shop. But I get the impression it would be evacuate the R12, flush/clean the system, evacuate that, and then refill with R134a.

Also saw http://www.ackits.com/ mentioned a few places. Looked their under the vehicle specific stuff and they have either a few parts for my '93 or a complete AC system for about $900. If they have conversion kits, I must be missing them.

Looks like I can get the accumulator mentioned in the article from RockAuto (http://www.rockauto.com/catalog/x,carcode,1052514,parttype,6972) and the Interdynamics kit from Amazon (http://amzn.com/B0002JMDLI) for under $100 for both items.

I'm still sort of thinking that it would be best to have a shop do the work so it can be properly evacuated and flushed, but I'd like to go into it being knowledgable - and likely furnishing the accumulator and the best kit for the task so I know what is being put into it rather than "Joe-Jim-Bob's Gen-u-wine AC Retrofit Kit" - although it looks like the Interdynamics kit is the primary one that comes up in search results.

[trbankii]

Bumping to see if anyone has any input.

[More Power]

Best recommendations include replacing the accumulator with a new unit at the time of conversion. The old accumulator will contain a quantity of the old compressor oil and any debris. New accumulators aren't all that expensive.

Otherwise, it wouldn't be a bad idea to flush the remainder of the system to remove the old (incompatible) oil and any debris.

Drove Lil Red the other day after a few months of sitting.... A/C still works great, after 9 years. Jim

[okadoc]

Best recommendations include replacing the accumulator with a new unit at the time of conversion. The old accumulator will contain a quantity of the old compressor oil and any debris. New accumulators aren't all that expensive.

Otherwise, it wouldn't be a bad idea to flush the remainder of the system to remove the old (incompatible) oil and any debris.

Drove Lil Red the other day after a few months of sitting.... A/C still works great, after 9 years. Jim

Hi guys, the best refrigerant for automotive air is hydrocarbon M 30 made by Engas. R134a was banned in Europe back in 2010, testicular cancer we believe was the driver. The largest single killer of men in Oz is testicular cancer. Ovarian and other female disorders are rising dramatically here as we'll and its a don't spare the horses James approach to establish a link and vaccine .
The HC refrigerants are compatible with all oils and materials used in an a/c system. Change the receiver drier and vacuum the system to 250 microns, the use of a digital vacuum stat to confirm this vacuum level is the only way to be sure of the dehydration level which is the most critical procedure when servicing A/C systems. Once the 250 microns is reached isolate the vacuum pump from the system and monitor the level and if it does not rise above 500 microns within 30 min then the system is only then completely dehydrated with the removal of all non condensable gases and the leak proof integrity of the system is ratified.Note it is not remotely possible to establish this critical criteria by way of analog compound gauges they simply aren't sensitive enough. The dehydration of the system does not properly commence until the system reaches 900 microns and is considered wet until 500 microns is reached and when the system is then isolated and the microns don't rise above 500. If they do then it either requires more dehydration or the system has no leak proof integrity. WARNING.If this procedure is not followed there is a 99% chance that moisture is left in the system and it will hydrolyse under temp and pressure and then you have PACMAN disguised as hydrochloric acid rampaging throughout your expensive much loved system. The flexible lines will undergo chemical composition changes that are very detrimental to the health of the system . Outgassing will occur ( refrigerant loss through the flexible lines) and the interior surfaces turn into a hard plastic type plaque and dislodge into the system blocking condensers, valve plates and orifices and restricting refrigerant flow and system capacity, the acid also attacks all vulnerable materials present and there's too many to list here suffice to say that the words PAIR SHAPED explain everything. We have been using hydrocarbon refrigerants in O z for some 15 years and they are well on their way to dominating the market over the whole refrigeration industry. They are a refrigeration trades persons dream come true. M 30 flashes 10 times faster than 134A and evaporates 7 degrees c colder at the same pressure as 134A.So at 30 PSI suction pressure the swept volume of the system = 134A volumes of course , so volumetric efficiency is the same with the added bonus of a 7 deg lower evaporator temp which intern equates to more heat rejection overall. The compressor operates with a cool sweat to the touch and much cooler discharge temperatures . The refrig charge is 30% of the system 134a charge max. most 4x4 require around the 250 grams .Happy to reply to any questions you may have.

[DmaxMaverick]

Hydrocarbon refrigerants work very well, and much better in most cases, than many flouro/chloro's. Very well, that it, until you have a leak. Most leaks are so slow they don't pose a problem, but a blow-out can be rather eventful (dude...where's my hood?). Propane (LPG) is very popular, inexpensive, commonly available, and works as well as R12. Most (R12 compatible) refrigerants imported from Mexico are part or mostly propane. As said, properly drying the system (evacuation) is very important, whichever refrigerant is used.

[okadoc]

For what its worth we have countless auto a/c systems in Oz on HC refrigerants and never a flamability problem so its of no concern. The LEL (lower flamability limit is 2% and upper is 9% HC proportion with atmoshere. The systems simply dont hold enough charge to reach these levels in most instances and we have found many evaporators with large leaks in them on HC and theres not been an instance of combustion.To get the bang effect of course there has to be 550 deg c naked flame and as the HC is heavier than air and with fresh air intakes and ventilation of the cabins etc it just dont happen certainly not with 100 to 250 grams thats a miniscule amount.If trapped in a burning vehicle and the 134A let loose inside it would burn between 2000 and 6000 deg c causing dangerous chemical fumes to be inhaled as the old R12 gives of phosgene gas when burnt, this was the gas used in the 2nd world war to kill troops on the ground.HC burns only at 550 degc and its not hot enought to ignite the refrig oil which burns to 6000 deg in a big wooosh. If 65 % air proportion exists within these synthetic gas systems they will and have exploded causing major damage and injury under temp and pressure of compression with no need for a naked flame. I know which vehicle Id rather be in.:D

[Robyn]

A product I have used a lot is called Envirosafe. This is a low volatility hydrocarbon refrigerant, thats will work with most oils.

Mineral oil is cheap and does well.
Envirosafe takes only about 1/3 the amount of R12

The FLASH point (fire) is high and requires a large amount of the gas and the temp must be 1300F according to the maker.

This stuff has a sweet PINE scent, so if it leaks into the cab you can smell it right quick. Smells just like the pine stuff ya pour in the toilet :D

I use this stuff on any R12 systems that I get that need a fix.

R134 is some nasty $hit, with far more health concerns than R12 ever had.

The entire thing with 12 is all politics and enviro freeks.

Somebody is getting real fat on selling all these new Refrigerants.

Gawd, all the good stuff like 12,22 and such are all banned and the new materials all have far more serious safety concerns (health)

R12 was pretty benign stuff other than it displaces oxygen in a closed area.

Check out the Envirosafe "ES12A"

Missy

[DmaxMaverick]

According to the manufacturer's MSDS, M 30 has a flashpoint of -104°C, at 1.9-9.5% (LPG is 2.2-9.5%). Autoignition is 460°C (LPG is 432-470°C, depending on who you ask). Bare flame is irrelevant, all that's required is the minimum heat source.

The "Envirosafe" stuff is essentially the same. All of the above are, essentially, LPG. None of them are any more or less hazardous than any other HC refrigerant. "Low volatility" is a subjective term, and they are all the same. All of them have very similar properties, and I think the variations depend on the testing lab, and/or the publisher's observations.

[rustyk]

"Flash point" and "fire point" are different. Flash point is the temperature at which the substance will ignite in the presence od an open flame, but it will not continue to burn if the flame is removed. Fire point is the temp at which it will ignite and continue to burn if the flame is removed.

[DmaxMaverick]

I listed both, the flashpoint and the ignition (fire) point, to compare the similarities of the different HC refrigerants.

A "flashpoint" doesn't require an open flame. The "open flame" is demonstrative. Any heat source of the same temperature will "flash" a fuel the same, under the same conditions. Only heat is required, and the source of the heat is irrelevant. If only an "open flame" were required, then the description would be irrelevant. Once a fuel begins to burn, it is then an "open flame", therefore couldn't be extinguished, as the unconsumed fuel would be continually exposed to the "open flame" it becomes as it's burned. A fuel absent of oxygen won't flash, no matter the level of heat. Combine an oxidizer with the fuel, and it will flash at less than the stated heat. The "flame" is merely the observable evidence of the chemical reaction.

[trbankii]

As said, properly drying the system (evacuation) is very important, whichever refrigerant is used.

Ok, sorted through all the posts. Many thanks for the input.

As stated before, I'll be replacing the accumulator. From DMax's comment (above) and others (particularly okadoc's), sounds like I really need to take it somewhere to have it properly evacuated rather than trying to do something in my driveway.

I'll have to talk to the shop I use to see whether they are able to do this (have the equipment) or whether they recommend someone. Then have to see what refrigerant they use - and whether they'd be willing to use something like the Envirosafe if it isn't something they normally work with. Not sure if the M30 that okadoc mentions would be available in the US?

[andyh1956]

I would add one other thing to the affore well placed advice. evaporator service. these old trucks do not have cabin filters before the evap cores & over time they get to look like a cat's back with stuff on them. all this stops air flow across the evap core. without proper air flow, there is a loss of heat exchange- translate this to low cooling. you can clean the core in the truck like this- remove the fan & blower assy (now is a good time to clean the cat hair offa the blower wheel too) & lay a tarp down in the floor. get the water hose, simple green & your tooth brush & start scrubbing, it's hard to get to, & if you have clubhands you may have to go get your girlfriend to do it for you while you sit in the shade & encourage her.:D all the work under the hood is wasted without the evap being clean. oh, be sure to rinse the simple green outta your toothbrush before you use it tomorrow morning!

[trbankii]

Stopped in to talk to my mechanic. Along with the typical conversion kit, they replace the accumulator and said that if there are leaks they are typically in the condensor from road rash. He said that with kit, accumulator, condensor, materials, labor, etc, etc, etc it could easily go over $1000... :eek:

I'm sort of thinking that sweating is cheap...

[convert2diesel]

Check with your local Harbor Freight outlet. You can get all the tools you need, including the vacuum pump for less than 200 bucks. Granted I wouldn't use the equipment to make a living, but it's fine for around the house to use occasionally.

http://www.harborfreight.com/a-c-manifold-gauge-set-92649.html
http://www.harborfreight.com/25-cfm-vacuum-pump-98076.html

Everything above is good advise and the older GM systems (Harrison radial compressor) use readily available parts. I use methanol to flush out the system and have rigged up an end to my shop vac to "air" out the system after the flush (have no idea what methanol vapors would do to an AC vacuum pump).

Agree with the consensus about the propane refrigerants. Way better than CFC's. NA is the only jurisdiction left that continues to use the old stuff (guess the chemical companies have powerful lobbies). Up here I use "Duracool" but any HC refrigerant is good. Got stuck over a weekend a couple of years ago and used straight propane. Still working fine, but I do check it for leaks often.

For a 1,000 bucks you could replace the entire system :confused:. Time to find another AC shop.

Bill

[trbankii]

Ironically, I stopped in at HF over the weekend to pick up some ratchet extensions to carry in the truck and saw the display of the vacuum pump and gauges. I suppose that since the a/c is not working at all that one can pretty much assume that all of the refrigerant has already leaked out - or at least enough that capturing what remains is pretty much a moot point.

[convert2diesel]

Ironically, I stopped in at HF over the weekend to pick up some ratchet extensions to carry in the truck and saw the display of the vacuum pump and gauges. I suppose that since the a/c is not working at all that one can pretty much assume that all of the refrigerant has already leaked out - or at least enough that capturing what remains is pretty much a moot point.

You still have to find the leak and then pull a vacuum before refilling. The two tools I showed will do all of that, plus the refilling. All of my CFC's are now drilling holes in the ozone layer. With all the regs about capturing refrigerant from cars, why don't they look at commercial AC installations. If your rooftop AC unit needs servicing you can bet your bottom dollar, up to 45 gallons of the stuff is vented to the atmosphere, at least around here.

Bill

[trbankii]

I know that commercial a/c services are required to capture refrigerant around here. And to dispose of a refrigerator, window a/c unit, or anything like that you need a sticker saying that the refrigerant was reclaimed.

[ginger743]

For spotting leaks a good visual inspection of the system is a good place to start. I haven't read all of the posts on this topic but I've read a bunch of recent posts and haven't seen this mentioned.

Lube oil circulates with the refrigerant and will show up where the leak is by collecting road grime. GM also states that a , " dirty line " above the compressor pulley on the inside of the hood is normal since the shaft seal will seep a slight amount of oil which the pulley/clutch assembly will sling forming a slight , " dirty line " above the pulley area on the underside of the hood..

Every coupling uses , " O" rings which have a tendency to not seal well with age . My '96 uses an HT-6 compressor which has 3 very large , " O" rings in the body of that compressor that have a tendency to leak, the lube oil will migrate to the mount and around it when these leak. The compressor also uses , "O" rings to seal the over pressure valve and the pressure switch in the rear of the compressor.

Or you could get a charge of dye and read it with a special light that the dye shows up under.

Sooo , start with a visual inspection looking for collections of oily dirt at the connectors and around the compressor.

Jerry