R134a conversion to 88 F250 with all new parts

I have a 1988 F250 that I'm working on getting up and running and one of the next things I'll be working on is the air conditioning. It had factory AC but the compressor (including the brackets) and some of the lines have been removed and left open for who knows how long. So my plans are to replace nearly all of the a/c components with new stuff since what's left is questionable and new stuff is not terribly expensive.
Compressor (still have to find some used brackets)
High and low pressure lines
Condensor
Accumulator/drier
Evaporator

I want to use r134a so I can charge it myself as I have a vacuum pump and manifold gauge set to use and probably enough r134a left over from previous a/c charges to charge this one.

Ok, that was a really long explanation for my question. Do I buy all of the necessary components for an 88 f250 which are originally designed for r12 and use a conversion kit for 134a or do I buy components for a newer model f250 that were originally designed for use of r134a so that the system works better and more efficiently?

I don't plan to replace the engine accessory drive to be a serpentine drive so are there even compressors that will fit the original brackets and are designed for r134a and fit with the r134a era f250 ac lines?

superds said:

Do I buy all of the necessary components for an 88 f250 which are originally designed for r12 and use a conversion kit for 134a or do I buy components for a newer model f250 that were originally designed for use of r134a so that the system works better and more efficiently?

I don't plan to replace the engine accessory drive to be a serpentine drive so are there even compressors that will fit the original brackets and are designed for r134a and fit with the r134a era f250 ac lines?

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You can buy an FS-6 compressor (meant for a V-belt system) that's been rebuilt and prepped for R-134a.

I would strongly recommend buying a condenser and an evaporator for a '96 F-350. They will bolt in place of the condenser and evaporator in your truck, but are designed to be used with R-134a and will be more efficient. IIRC the changeover happened in '94, but I wouldn't be surprised if some early '94 trucks had R-12 systems, hence going a couple of model years up.

The pressure lines going to the compressor are different between V-belt and serpentine-belt because the compressor is in a slightly different location; other lines (i.e. the line going between the condenser and the accumulator/dryer) should be the same. I THINK that the connections are all the same, but I can't attest 100% to that. As long as the hoses are rated for air conditioning systems and they're new (i.e. not soaked with mineral oil on the inside), the hoses aren't R-134a or R-12 specific.

There are two types of oil that can be used in R-134a systems. Ester oil can mix with traces of the original R-12 mineral oil, and PAG oil requires that all vestiges of mineral oil be completely flushed out. It sounds like you're replacing enough of the system that that may not be a concern; I would recommend flushing out whatever components you're not replacing and going to the PAG oil.

You'll need a new orifice valve; there's debate on whether you should use a fixed valve meant for R-134a systems or if you should use a variable orifice valve. I'll let you look for the arguments on both sides and make your own decision.

Regardless, make sure that EVERYTHING on the inside of the system is clean-room clean and make sure you pull a good vacuum on the system so that any possible moisture is boiled out.

Hope that helps some...good luck!

{on edit} One more thing that should be replaced that you didn't mention...the compressor cycling switch. It screws into one of the Schraeder fittings on the receiver/drier. These switches do fail, and you can get a switch designed to work with R-134a systems. There are even some that have an adjustment screw so that you can set what pressure it cycles on and off at.

DO NOT buy the late condenser unless you use the late evap.. The high side fitting is different on the hose and won't fit the 88 evaporator.
All the new condensors are high efficiency to work with 134.
I prefer red variable orifice .
It's easy to do
I have a brand new fs6 , not reman if interested. Bought2 by mistake.

typ4 said:

DO NOT buy the late condenser unless you use the late evap.. The high side fitting is different on the hose and won't fit the 88 evaporator.
All the new condensors are high efficiency to work with 134.

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That's good to know...thank you! Is the high side fitting the only difference, and is it just a matter of using the correct evaporator, condenser, and that hose? Also, I've seen a late condenser, but I haven't had a chance to compare an early and a late evaporator...how different are the two?

I will look, Dan's 93 cond to evap hose would not mate with the 95 evap. I had a jump size hose made. His truck had no ac and we didn't know 95 was different.
The 95 hose would not fit the 93 cond. I would not change the original evap. Flush and use.
I'll get more info.

typ4 said:

I'll get more info.

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Sounds good I'm getting ready to do the same thing (except using a different compressor), and the more ducks I have in a row, the better. And, I want the a/c to blow ice cubes out the vents when I'm done, so anything and everything I can do to improve the efficiency of the system is a good thing (although I'm adamant about running R-134a; I will not use any blends/experimental gases...I want the system to be shop-serviceable if necessary)

Thanks for the replies. PAG oil. Check. Variable red orifice tube (I think this was the cheapest one I could find anyway and probably what I would have selected). Check. Pressure switch. Check.

So do I add the PAG oil to the compressor then seal the system then vacuum it? Doesn't the oil come out when you vacuum it?

To make sure it's clean-room clean before sealing the system how do I do that? Is this as crucial if I'm using all new components? I assume the components are clean when new, but are they clean enough?

I still plan on replacing the evaporator since this system has been open for some time and I don't know why it was disabled to begin with. I don't know the condition of the evaporator and I'm sure there's about 10 lbs of dirt in it as I'm pretty sure this truck was operated in a dirt mine or some other dirty place. It's dirty. Everywhere has dirt build up that I never thought imaginable. I can pick up an evaporator for $50 so this is probably worth avoiding the agony of cleaning all that dirt out.

So to recap what I think was recommended for buying parts:
1996: condenser, accumulator, evaporator, condenser to accumulator line and pressure switch
And for an 1988: fs6 compressor, compressor to evaporator line and compressor to condenser line

Warden, what compressor are you using?

superds said:

So do I add the PAG oil to the compressor then seal the system then vacuum it? Doesn't the oil come out when you vacuum it?

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I don't remember exactly how much should go where (I'm 400 miles away from my shop manuals ), but you want to put most of the oil in the compressor, with a little bit of the remaining oil distributed around the system. The oil's heavy enough (and designed to stay in the system when a vacuum's applied) that pulling a vacuum on the system won't suck out the oil...the system vacuum is meant to remove all air, any remaining freon (not a problem in this case ), and most importantly, lower the boiling point of any water in the system to the point where it evaporates and gets vacuumed out. By the way, how are you planning to pull a vacuum? If you have an A/C service machine, that will have a vacuum pump...if you don't, you can take a compressor motor out of a refrigerator, take the suction line, and use a flare-fitting to make an adapter to attach a hose to connect to the low pressure port on your A/C. That's what I did, and when I need to pull a vacuum, I usually set it up, plug the compressor in, and let it run overnight.

superds said:

To make sure it's clean-room clean before sealing the system how do I do that? Is this as crucial if I'm using all new components? I assume the components are clean when new, but are they clean enough?

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Since you're using all new components, you don't have to do anything to the new components to get them any cleaner than they are when they come out of the box. Just, make 100% certain that you do not get ANY contaminants in any of the components. You'll need to pour some oil into the components (see above about distributing oil in the system); just be sure that no contaminants get in the oil. If there are any used components, they'll need to be very thoroughly flushed, but it sounds like that's a moot point in your case

superds said:

I still plan on replacing the evaporator since this system has been open for some time and I don't know why it was disabled to begin with. I don't know the condition of the evaporator and I'm sure there's about 10 lbs of dirt in it as I'm pretty sure this truck was operated in a dirt mine or some other dirty place. It's dirty. Everywhere has dirt build up that I never thought imaginable. I can pick up an evaporator for $50 so this is probably worth avoiding the agony of cleaning all that dirt out.

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Yeah, for $50 and given the conditions your truck was in, I think you're on the right track that's worth it just to keep from cleaning out the fins, let alone the garbage on the inside. I would suggest shelling out the extra $$ to go OEM on this stuff...once you get the A/C buttoned up, you really don't want to have to take it back apart.

superds said:

So to recap what I think was recommended for buying parts:
1996: condenser, accumulator, evaporator, condenser to accumulator line and pressure switch
And for an 1988: fs6 compressor, compressor to evaporator line and compressor to condenser line

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I defer to Russ if he has a different opinion, but that looks right to me

superds said:

Warden, what compressor are you using?

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Unfortunately, I don't remember the model number of the compressor I'm using (I don't have access to it for the same reason I don't have access to my shop manuals at the moment), but after doing some reading, I found that it's more efficient...it uses less engine horsepower to turn it and IIRC it even moves more freon per revolution. IIRC it's OEM to 1990's Dodge trucks, but again, I'm not certain...I'm also not certain yet how I'm going to adapt it to work on my truck, but I know enough people who are good enough with fabrication that I'm sure it can be figured out

If your new compressor comes with oil, even though some say to run it, drain all of it out and use one type of oil only. 4 ounces in compressor the rest split between drier, evap and cond, maximum of 9, I use 1 8 oz container per ford system and have never had an issue, my 88 and 91 both blow very cold and are all used parts but the dryer, and comp on 88. I got used condensers at the U pull it that were near new so got lucky there.

And Tim, they make adapter parts to flare or oring and custom hoses can be made cheap up here in oregon, when we do that gear swap.lol
send me some pics when you are next to that thing again.

typ4 said:

And Tim, they make adapter parts to flare or oring and custom hoses can be made cheap up here in oregon, when we do that gear swap.lol
send me some pics when you are next to that thing again.

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Sounds good to me! Hopefully I'll be back home in a week or two...

The Warden said:

I don't remember exactly how much should go where (I'm 400 miles away from my shop manuals ), but you want to put most of the oil in the compressor, with a little bit of the remaining oil distributed around the system. The oil's heavy enough (and designed to stay in the system when a vacuum's applied) that pulling a vacuum on the system won't suck out the oil...the system vacuum is meant to remove all air, any remaining freon (not a problem in this case ), and most importantly, lower the boiling point of any water in the system to the point where it evaporates and gets vacuumed out. By the way, how are you planning to pull a vacuum? If you have an A/C service machine, that will have a vacuum pump...if you don't, you can take a compressor motor out of a refrigerator, take the suction line, and use a flare-fitting to make an adapter to attach a hose to connect to the low pressure port on your A/C. That's what I did, and when I need to pull a vacuum, I usually set it up, plug the compressor in, and let it run overnight.

Since you're using all new components, you don't have to do anything to the new components to get them any cleaner than they are when they come out of the box. Just, make 100% certain that you do not get ANY contaminants in any of the components. You'll need to pour some oil into the components (see above about distributing oil in the system); just be sure that no contaminants get in the oil. If there are any used components, they'll need to be very thoroughly flushed, but it sounds like that's a moot point in your case

Yeah, for $50 and given the conditions your truck was in, I think you're on the right track that's worth it just to keep from cleaning out the fins, let alone the garbage on the inside. I would suggest shelling out the extra $$ to go OEM on this stuff...once you get the A/C buttoned up, you really don't want to have to take it back apart.

I defer to Russ if he has a different opinion, but that looks right to me

Unfortunately, I don't remember the model number of the compressor I'm using (I don't have access to it for the same reason I don't have access to my shop manuals at the moment), but after doing some reading, I found that it's more efficient...it uses less engine horsepower to turn it and IIRC it even moves more freon per revolution. IIRC it's OEM to 1990's Dodge trucks, but again, I'm not certain...I'm also not certain yet how I'm going to adapt it to work on my truck, but I know enough people who are good enough with fabrication that I'm sure it can be figured out

Click to expand...

Lots of good info and a good explanation of vacuuming the system, thank you. I have a harbor freight ac gauge manifold and vacuum pump. I've had the manifold for a couple years but haven't used it and got the vacuum pump more recently. I have about $120 invested (after coupons) which I should recoup pretty quick since the last time I had a system filled at a mechanic after I replaced a compressor cost me a little over $100 and I have this F250 and another project on the back burner which will also need AC system charged.

I'm not sure I could cope with using Dodge parts on my Fords, I draw the line at GM 10si and 12si alternators! But if it works well, I understand using it. I'll just stick with the Ford compressor, I don't think I could handle adding any more complexity to my life!

Thanks again for the advise, you've been very helpful.

typ4 said:

If your new compressor comes with oil, even though some say to run it, drain all of it out and use one type of oil only. 4 ounces in compressor the rest split between drier, evap and cond, maximum of 9, I use 1 8 oz container per ford system and have never had an issue, my 88 and 91 both blow very cold and are all used parts but the dryer, and comp on 88. I got used condensers at the U pull it that were near new so got lucky there.

And Tim, they make adapter parts to flare or oring and custom hoses can be made cheap up here in oregon, when we do that gear swap.lol
send me some pics when you are next to that thing again.

Click to expand...

Good deal. I'll drain it for sure and pickup an 8 oz bottle of PAG. Well, I'll check my inventory before I actually buy some. I seem to do that a lot, buy too much for one project, forget I have it and buy more for the next project, in the meanwhile misplacing what I already have until I get around to doing a cleanup and organization of the shop.

Thanks for your help.

ok, had a chance to go to a wrecking yard today, scored a 50.00 core transfer case that looks brand new inside, woo hoo, .
Anyway, 87 to 93 ac condensors have #8 oring on both in and out. 94 up has one #8 and one #6, inlet,side to evap, which has the smaller "hump" for the orifice tube area. Condenser fitment may be different between 91 and OBS. Napa calls out the same one foe brick thru obs 93. gas or diesel.