gen 1 R-12 vs R134a

[dmorris]

a little background 1st,

I have a 92 XLT owned since new, about 13 yrs ago I had some AC work done, this included a new everything except the evaporator and stayed with R-12 based on the techs advice.

fast forward till about 2 yrs ago, noticed AC not working very well and cycling way too much (on for only a few seconds). this was a gradual thing the 2 second cycle was recent.

I recently put in my last can of R-12 check gauges and all looked good, removed the hi side gauge and noticed I had a shrader valve leak, (it was missing the cap). I got a good cap and that seems to have solved it for now anyway.

there was some oily mess around the top of the accumulator which I assume is compressor oil maybe from the low pressure but it was not clear where of if there was a leak, I guess a sniffer would tell for sure, but I do not have one.

right now it works fine (very well actually) but I figured being 13 yrs old it will likely need service again, as I really like the truck I plan to keep it, so I would like to do it myself next time as I don't really have a good tech that I trust and would like to not bay 1500 again (it was between 1k and 1.5k IIRC).

SO

if I go with all new stuff I was planning on going 134a, I looked at 94s vs 92's and noted the following

the 94s had a rubber sheet on top of the radiator to grill junction, and sealed the trans oil cool lines in the front bottom of the radiator. It looked like a tacked on piece of material that was stranded to fit around the tubes. I presume both of these measures were to help force air thru the condenser and prevent leakage around it.

My 92 did NOT have any foam blocks along the side, however this was not orig so maybe the tech that did the work just left it out, I do not recall if the 92 I was looking at in the yard had the foam.

My 92 and the 92 in the yard had a tube and fin condenser the 94 did as well but I I think I saw one with a Parallel condenser on one of the 94's and for sure all the later models had the Parallel condenser.

I did not get a look at any of the evaporators to compare, but I did some on line searching and found several makers of after market evaps for gen1. The pics which if accurate had different numbers of sections (the premium one had the most). there were not BTU or other specs given to compare.

On mine I HOPE he put in a FS10 prob did since it still is working.

For now my only plan is to add the rubber seal on top of the grill and a seal of the trans cooler lines, and get some foam block to seal up the sides.

I am guessing a good foam would be that rubberized type stuff used in packing but not sure if its heat sensitive. I will see if I can find out the correct foam to use.

My plan for the 134a would be:

All new everything with premium evap and parallel condenser, FS10, and maybe a variable orifice with a drier rather than the accumulator and orifice tube. new hoses and green orings of course.

I will do all this myself and prob invest in a good deep vacuum pump, I like to do my own work and figure I can do as good a job of it as a random guess with a local tech.

this plan is on hold for now as the AC is working but I like to plan ahead that way I don't do anything right now (Earl to Valentine on tremors).


a little more research and I see evaps are both tube and fin as well as parallel with parallel being prefered in 134a

 

[dmorris]

http://www.homedepot.com/p/Frost-Ki...Air-Conditioner-Weather-Strip-AC42H/100059869

foam strip above link

and here is a nice primer below link

http://www.ariazone.com/manuals/Automotive Air Conditioning Training Manual.pdf

 

[Anime]

The foam stuff just fills the gaps to prevent airflow from going around the condender/radiator, and is likely missing on your 92 simply from wear and tear. The foam doesn't last forever, and exposure to weather, UV, and wind eventually wears it away to nothing. You can replace it, though it's a good idea to use flame-resistant/fire-proof material rather than just regular (flammable) foam for obvious reasons. Using rubber sheet to just make gap fillers is another option.

As for the A/C system, it's usually quite a bit of work to replace all the parts and switch the system over to R134a. If you already paid $1-1.5K, that would have been a good time to simply replace everything, as you could have bought a new A/C system for that, and just had R-134a used in it.

Given your previous investment, it may be more economical to just keep up the maintenace on the current system, and if the system leaks down again in the future, just have it evacuated and the o-rings replaced as necessary (along with the valve stems if leaking), then recharged again with R-12.

As for the leaking valve, you should get a schrader valve tool and be sure the valve stem is tight, or just take it to an A/C shop and have them check the valves. Just putting a cap on doesn't stop a valve leak, and eventually the R-12 will leak out and you'll need the system to be recharged again.

 

[dmorris]

I have the shrader valve tool will check it out.

 

[dmorris]

got the foam installed, more research on the net make the VOV orifice tube seem better than the fixed one for the type of driving I do (lot of stop and go in town low speed stuff).

looking at vac pumps, see on at harbor freight for 100$.

Revised plan:

pull orifice tube examine for junk, if clean will just replace with VOV, orings,accumulator, pull vac and recharge adding oil as needed based on what comes out reharge with R-12

if orifice tube shows evidence of compressor seal failure, well then full replacement of comp/condenser and what the heck maybe even the evap for upgraded units. Stick with R-12 since I have it, but use PAO oil so 134a can be used as well.

 

[Maniak]

A couple things. The pressure with the VOV can be quite a bit AND twice I've had the VOV blow into the evaporator. I'd take a good look at the line where the orifice tube goes and make sure it has a good crimp in the line. The last 2 evaporators barely had a crimp at all to hold the orifice tube. On the last one I used a pair of channel locks and indented/crimped the line more.


And... Here is a pic of a VOV and a VOV with black death... hopefully you don't have black death yet.

Black Death on a Variable Orifice Tube by maniak_az, on Flickr

~Mark

 

[dmorris]

so do you think the VOV is worth it? I mean is it really going to help the AC in traffic?

 

[dmorris]

I am going to have to decide what to do after I get into it. If it looks that bad I would prob just replace everything.

 

[Maniak]

I had the extreme weather one (105f+) and yes, it did increase the pressure differential to make things cooler. You will need a good fan/clutch setup to get rid of the heat from the condenser.

Since I have black death, and have had it for 5+ years (not sure if 10 yet), I am going to rebuild the entire system shortly. This time I'm going to try a red orifice tube.

If it doesn't give me enough cooling in traffic/wheeling then I'll switch to a VOV. Evacuating and charging the system isn't hard and I'm still getting r-134 cans for $6 each so I can replace what I take from my stash of over a case.


~Mark

 

[dmorris]

Your time schedule is ahead of me sounds like so please post your results.

I have a stash of R-12 so plan use that for now. I wonder of R-12 would require a different VOV orifice from a R-134a?

 

[dmorris]

hmmm reading over at the ranger forum a fellow did the VOV orifice on an R-12 and was not happy with it, thinks it was not right for R-12 but ok for 134a, looks like more research in order.

 

[pkn]

... I wonder of R-12 would require a different VOV orifice from a R-134a?

Least-Cost Aftermarket Retrofit

Many car owners may express interest in receiving a least-cost retrofit. Procedures required for a least-cost retrofit are simple and do not require major component changes. Generally, the process calls for removal of the old refrigerant, installation of new fittings and a new label, and the addition of either a polyalkylene glycol (PAG) or polyol ester (POE or ester) lubricant as well as the R-134a refrigerant. For many vehicles, this simple, least-cost retrofit should provide the vehicle owner either with a/c performance comparable to the R-12 system performance or with a/c performance that, although slightly reduced, is still sufficient to satisfy the customer. A least-cost retrofit, however, may not provide a satisfactory solution for certain vehicles.

Same page, at the end:

Refrigerant controls -- whether they are orifice tubes or expansion valves that meter refrigerant flow, or pressure cycling switches or other pressure controls designed to protect against freezing -- may have to be changed during the course of a retrofit.

So... they themselves couldn't make up their mind

 

[pkn]

hmmm reading over at the ranger forum a fellow did the VOV orifice on an R-12 and was not happy with it, thinks it was not right for R-12 but ok for 134a ...

Well, in my 1st gen I had regular orifice with R12 and was not happy about it, until the compressor died. Then I had regular orifice with R134a and was not happy about it, until another compressor died. Then I had variable orifice (105+ heat variety) with R134a and was not happy* about it until the pressure release valve blew out my freon... couple of times.

So now I'm collecting parts to install pair of electric aux fan pushers to assist the A/C at idle.

---------------
* -- Well, on highway, I must admit, the A/C was really ice cold - I have thermometer at the vent and it showed 2-4 Celsius. But it did (scratched)suck blow much hotter at idle - not enough airflow. And the VOV orifice supposed to remedy exactly this... instead, it blew up my pressure release valve. I'm still not sure which orifice - VOV or regular - I will put in now...

 

[Maniak]

<snip>
* -- Well, on highway the A/C was really ice cold - I have thermometer at the vent and it showed 2-4 Celsius. But it did suck at idle - not enough airflow.

The air flow should not have been affected by the VOV. At worst, the temp would go up at idle, but the amount of air coming through should be the same...

However, if you freeze up your evaporator you can block air flow that way but once you start moving the air flow would NOT come right back. You would have to wait for the ice to melt off the evaporator.

Also, when you switch to r-134 you should change the pop-off valve. If you don't you will pop it as you run higher pressures with r-134 and the VOV increased your idle pressure.

 

[pkn]

The air flow should not have been affected by the VOV. At worst, the temp would go up at idle, but the amount of air coming through should be the same...

However, if you freeze up your evaporator you can block air flow that way but once you start moving the air flow would NOT come right back. You would have to wait for the ice to melt off the evaporator.

I meant airflow coming thru the condenser, not airflow thru vents into the cabin, the latter does not change at idle, just becomes much wormer.

Also, when you switch to r-134 you should change the pop-off valve. If you don't you will pop it as you run higher pressures with r-134

I understand, but the retrofit from R12 to R134a was done... ahem... drat!... some 10 years ago. So it was like this:

Dark ages - 2004: R12, regular orifice, poor performance.
2004 - 2013: R134a, regular orifice, poor performance.
2013 - 2014: R134a, VOV orifice, excellent at highway, poor performance at idle.
2014 - high pressure valve pops out.

and the VOV increased your idle pressure.

Those high pressure valves is another thing I'm trying to learn about ... But places like autozone don't provide any pressure ratings for the valves...

 

[Maniak]

I know the feeling.. I did my conversion somewhere in the early 2000's and I "think" I got the pop-off valve from a 1995 explorer, but I'm not positive on that.. I do know I have a 1993 hose (runs under the TB instead of behind the plenum).

Also, I've pretty sure the pop-off valve has the pressure written on it.. At least my brain tells me I might remember seeing that.

~Mark

 

[dmorris]

And I get my new 10blade fan to go with new fan clutch with a busted blade, still in the sealed package. maybe they should have put some padding on the bottom of the box as well as the top. dopes. argh.

 

[pkn]

I know the feeling.. I did my conversion somewhere in the early 2000's and I "think" I got the pop-off valve from a 1995 explorer, but I'm not positive on that..

Good idea, to use later model, thanks... I was thinking how to get around the problem that my '92 XLT is listed in all databases as R12 and replacement parts are offered accordingly... I've even got the VOV orifice tube with BLACK (i.e. - R12) o-rings.

Also, I've pretty sure the pop-off valve has the pressure written on it.. At least my brain tells me I might remember seeing that.

Another good idea, thanks again... Time to pay a visit to Autozone on my way home, at least now I know what to ask.

 

[xploder98]

I would replace compressor, condensor, line set, and accumulator/drier and flush the heck out of your evap core. I did exactly all that on my 98 sport a couple years back and i havent been in a vehicle that gets as cold and as fast as it does. And it really didnt cost much for those parts. Thanks rockauto... That black deaths nasty stuff man. Ive been in HVAC for over 10 years and have never seen that before.

 

[xploder98]

Btw, some of you probably already know but nitrogen is great for checking for hvac leaks. In my opinon its better to check for leaks this way instead of trying to hold a vac, it simulates actual pressure in the system. Vac holds sometimes wont show a leak that a nitrogen test will. Pressurize w nitrogen to normal charge psi and spray ALL connection points with a leak test soap, if no leaks, revac and charge your system.