R134a A/C conversion

[rickshaw]

Ok, I feel like I'm opening up a whole can of worms with this topic. I have been through numerous posts here and on FourEyes, etc. Watched YouTube videos up the ying-yang. Realize kits like Hose Wizards sold by LMR for SVO are no longer available, new hoses not available, etc., and the HR980 compressors are becoming unavailable, even though I may have a place in FL that rebuilds them. The 86 I purchase last year without working A/C is now on my next to do list. Compressor may be perfectly good and my Ford service manual shows how to check for leaks, but it need special adapters to hook it up to pressure hoses to charge and then a sniffer to check for leaks. Figure that may be good first step. Otherwise is to reinstall the whole system (with new dryer accumulator, o-rings and condenser?) flush system, evacuate, add x lbs of R134a and then check for leaks? Then of course are the posts that R134a will leak faster from the system, etc. Don't want to think about doing a conversion with newer compressor and serpentine belts, etc. Not expecting a silver bullet, but does someone here have a known approach to this issue/problem that can offer advice? I would think most SVO owners are or will be faced with this issue at some point. PS R-12 is no longer an option.

[MIKESVO]

I've done several 134A conversions on stock systems. Just change the pressure switch before doing the evac. Add oil too.

[SVOeric]

past experience shows, if you don't change the o-rings at all the connection points, it will last about 2 years.
to be fair, most of our cars are old enough these o-rings are ready to be replaced anyway.

YES, you should 'plumb it up' and pull vac on it, to make sure it's not got any leaks, otherwise, you're just pouring money in, that's going to pour right back out.

[MIKESVO]

Yep, forgot to mention that. Change all of the O rings. Dip them in the oil too, before the install. Pull vacuum. Replace pressure switch and charge.

[rickshaw]

Roger: buy(A/C) CLUTCH CYCLING SWITCH 134A and a set of 134a compatible HNBR O-rings.

I found a replacement dryer accumulator Murry #60-6512 for $171 at OReillys! Even though its recommended to replace, if I don't, when I evacuate the system is that sufficient to pull all the moisture out?

I should also take the step to flush the evaporator, condenser and hoses with solvent to clean out residual R12 mineral oil, right?

I will need the R12 to 134a hose adapters, Ester oil. Leak detect die? If I buy a retrofit kit it will come with this. Anything else?

My car takes 2lb 10oz (2.625 lbs) of R12, according to a chart I found, I should charge with 2.1lbs of R134a, basically a little less than 3 - 12oz cans.

I did find a company in FL that sells reman HR-980 compressors for $450.

[rickshaw]

OK, down to finishing reinstall before I vacuum and charge. Can't locate a replacement accumulator/drier so will have to reuse old one which has been open for awhile, so desiccant is ineffective. Trying to figure out how much oil to add. Ford service manual says 8oz total system, but what they say by component adds up to 10 oz or more. For accumulator they want you to drain and measure first and add 1 oz more? Can't do this because had oil leak out before I could do this. Any recommendations? By the book they had compressor 4oz, condenser 1oz, evap 3oz and accumulator ? + 1oz.

[MIKESVO]

Four Seasons might have a drier? Not sure if they are still selling them or not. I did the recharge years ago but for some reason I'm thinking I did 6 oz, thinking there was residual oil still remaining in the system.

[rickshaw]

O'reillys had one listed but is out of stock (p/n 60-6512). Checking all the usual sources, many driers were listed, but none actually fit SVO. So the Ford service manual has a way to replace just what the component might be holding, e.g. evap 3oz, condenser 1 oz, etc.. Anyway, I got all 8 oz distributed inside. Concerning the dryer, there is a process to remove water from a system, but it involves charging and vacuuming three times. I guess a shop could do this, probably it's worth asking my local guy.

[rickshaw]

Ha, what a day chasing around to two OReillys to get a vacuum pump that pulled vacuum, etc, etc. After pulling vacuum for over an hour and letting it sit for over an hour, it looking good. Time to charge it. Come to find the compressor clutch was not engaging, wtf? That turns out to be engine cooling fan module. The replacement I installed comes to have no A/C circuit !?#* OK, make up a jumper to switch on the clutch and away we go. The R12 spec is for 2.65 lbs, the altered spec for R134a is 2.1 lbs (34oz). So first 12oz can only gives 7.5, same for second? So the system took 15oz and it's blowing 32degF out the dash vent, probably colder because my thermometer low limit is 32F. What's going on?

[svono50]

When your refrigerant is 'low', the pressure drop in the evap coil is greater than designed and therefore the temp drop is also greater than designed. This is what causes the eval coil to freeze up (i.e.- condensed water on the coil freezes vs running off out the condensate drain). As you continue to add refrigerant, the pressure drop decreases and the temp comes up to a proper working level where the condensate can run off. It is a balancing point of sorts to get the proper amount of charge to get the proper amount of pressure drop across the evap coil to get the condensate to drain to get you to say 'ahhhh' when you run the A/C (ha,ha!).

As for the amount of refrigerant out of the cans, that is purely temperature related. If you dip the can into a bucket of warm water, it will keep the can's pressure up high enough to extract all the charge. We used to have to do this trick on commercial system charges when working with 100 lb freon tanks, so we didn't leave anything behind. Sometimes we had to do that with the smaller 30 lb tanks on residential jobs, but would also leave them out in the sun to use some of the solar energy from the sun to 'boost' the tanks.

[gbeaird]

^^What he said! You can also turn the engine fan on and _carefully_ set the can in the air path as it runs to warm the can a bit. That's the trick I use on engines with mechanical fans.

[rickshaw]

Ah so! Well, finally read the tiny direction print on the can that said shake frequently and alternately tip can from vertical to horizontal. What is it about reading directions after the fact? Doing that I was able to get most all from the cans except an ounce and a half. So got it charged with 31oz probably less with leakages vs 34oz calculated. Your warming tip probably would have helped. We'll see how this works. I can then decide whether to fuss with it again or ask my local guy to suck out and weight the charge and refill to spec. Will get up into 80s here next week.

[rickshaw]

If you guys know pressures, let me know if how these gages look. 70degF, 80% humidity

Compressor off: approx, 39psig static both sides. Low side gage didn't zero exactly.


Final gages compressor off.jpg

Compressor on: 18psig low side (was 12psig before I packed remainder of cans, 170 psig high side
Final gages running.jpg

[gbeaird]

Yeah, the cans will always be under some pressure, so you'll never get it all out of the can. "Almost there' is good enough!