A/C repair & restoration options

[Pete_89T2]

Well after 22 years of providing ice-cold A/C, my '89T2 is having trouble cooling down the cabin. Just last week it was blowing ice cold air (better than my newer cars), but today it was blowing barely chilled air. Checked the sight glass per the FSM procedure, and I've got the bubbles showing, plus the low pressure side plumbing to the evaporator core is just slightly cooler than ambient temp (it should be ice cold when A/C is running). Compressor seems to be running fine; clutch engages, and it sounds normal as compared to how it used to sound when all was well.

This means I've lost some R12 freon, and there is most likely a leak to hunt down, fix and then properly recharge the system with R12. Since I don't have A/C service tools, looks like my options are limited to finding & bringing it to a competent shop - living without A/C is NOT an option. So here's my questions...

1. Anyone know of a reputable auto A/C shop in the northern MD/DE/PA tri-state region?

2. Fix the system & stick with R12, or bite the bullet and do the conversion to R134a? I think the R12 route makes better sense, despite the expensive cost of R12, since I've read you pretty much have to replace a good portion of the A/C system components if you switch over to R134a - true?

Makes me long for the good old days, when you can buy R12 for a few bucks a can anywhere without an EPA license and fix it yourself.

[88turboii]

Just do it yourself. buy a o-ring kit and the r134 adapters, take all the lines off in the engine bay and replace the o-rings. not too difficult at all. invest in a a/c gauge kit, hook up to low side and charge with r134 to ~40psi on the low side with a/c running full blast.

im running r134A with no problems, runs cold enough for charleston, sc

[djmtsu]

Yep. Just get an O-ring kit (many of the Ford kits have all the seals you need) and get the 134a adapters.

You would benefit from taking it to a shop and have them completely evacuate the old R12 out. It really is an easy job.

[RETed]

I would recommend going the purge and fill with R134a route.
I have a 1990 Toyota Cressida as a daily driver, and I went with the R134a as per recommendation from my AC guy.
I too read all the negatives of R134a (versus R12), but I'm pleasantly surprised how well the R134a has held up.
I got 61F (at the vents) on a calibrated thermometer when we first did the job.
(Minimum temp is 65F according to the AC guys.)

Since you gotta crack the system open to check for leaks, you might as well replace all the o-rings (to handle the R134a).
Also, you need to vacuum everything out anyways, so it's a no-brainer to go R134a.
Ask if you can slightly overfill the system with R134a - this is the key to get everything real cold enough.
The stock compressor should be able to handle an extra half pound of R134a no problem.

With all the headaches associated with R12 (i.e. licensing and PRICE), it's nice to be able to run down to the local auto parts shop and pick up a 16oz. can of R134a for $10...


-Ted

[NoDOHC]

I used stuff called Freeze-12, it is an EPA-approved alternative to R12 (uses the same lubricating oil type) I got a couple years out of it. I blew an o-ring just recently and have not got the time to fix it again (besides, I will hurt the environment if I work on my own AC in Wisconsin, so I have to drive into Michigan in order to do it...)

[tweiss3]

Try finding freeze 12, i just went through this song and dance last month, you can't find shit. Its now 134a or nothing.

[MaczPayne]

http://forums.vwvortex.com/showthrea...t-R12-to-R134a

I get my Freeze 12 on ebay, if you want to stay with an R12 type refrigerant

[jackhild59]

Originally Posted by Pete_89T2

Well after 22 years of providing ice-cold A/C, my '89T2 is having trouble cooling down the cabin. Just last week it was blowing ice cold air (better than my newer cars), but today it was blowing barely chilled air. Checked the sight glass per the FSM procedure, and I've got the bubbles showing, plus the low pressure side plumbing to the evaporator core is just slightly cooler than ambient temp (it should be ice cold when A/C is running). Compressor seems to be running fine; clutch engages, and it sounds normal as compared to how it used to sound when all was well.

This means I've lost some R12 freon, and there is most likely a leak to hunt down, fix and then properly recharge the system with R12. Since I don't have A/C service tools, looks like my options are limited to finding & bringing it to a competent shop - living without A/C is NOT an option. So here's my questions...

1. Anyone know of a reputable auto A/C shop in the northern MD/DE/PA tri-state region?

2. Fix the system & stick with R12, or bite the bullet and do the conversion to R134a? I think the R12 route makes better sense, despite the expensive cost of R12, since I've read you pretty much have to replace a good portion of the A/C system components if you switch over to R134a - true?

Makes me long for the good old days, when you can buy R12 for a few bucks a can anywhere without an EPA license and fix it yourself.

One other possibility is that your cooling fan clutch is beginning to fail. Don't neglect to check that out first.

Freeze12 is a perfectly fine replacement for R12, but you shouldn't mix it with the R12. Most shops won't work with Freeze12, so you will be on your own if you go this route. They will also encourage you to convert to R134a because they succeed with this most of the time. You will not be happy with the results. They will ultimately not be able to help you, consider that you are really on your own right now.

R134a is not a good replacement on our FC's because the FC does not have adequate condenser area. The conversion will work great if you add a larger *capacity* condenser. Other cars with large condensers would also make good candidates for conversion. Ted's Cressida falls in this category.

Before you do anything, you should find the leak. Use a soapy solution and a squirt-bottle to check all the connectors and rubber hoses. Look for bubbles.

If you don't find bubbles, you are probably just losing freon at the compressor shaft seal. Those seals leak some on all compressors, more as they age. That seal relies on oil to seal to the shaft as it rotates As the seal ages, it will leak more. One solution is to make sure to run the A/C at least weekly for 5-10 minutes to lube up that seal.

Don't take apart any connection that is not leaking just to replace the o-rings. Not necessary. If you do take a connection apart for any reason, do replace with the green oring.

Center vent temps at 50 mph, fan on high, set on recirc should be in the upper 38*/42* on a hot day-95*f+. R12 and Freeze12 can do this in the FC. R134a will likely be in the upper 40's lower 50's. This is a very big difference in capacity.


Good Luck!

-jack

[RETed]

Originally Posted by jackhild59

R134a is not a good replacement on our FC's because the FC does not have adequate condenser area. The conversion will work great if you add a larger *capacity* condenser. Other cars with large condensers would also make good candidates for conversion. Ted's Cressida falls in this category.

This is a very good and important point.

The FC is one of the very few cars that *overheat* when you turn on the A/C.
This implies the condenser core is too small.
Most times, most cars will cool down due to the A/C dedicated aux fan running on top of everything else.


-Ted

[jackhild59]

Couple of things: as macz said Freeze12 is not HC.

Next your charge is either very low or it is contaminated. You cannot tell the % charge from the pressure.

The low side pressure switch cuts the compressor out at +/- 18psi, so that 6 psi number is troubling.

I think your plan to evacuate and recharge is a good one. Put *exactly* 2-12 oz cans in. Factory charge is 26 oz. 24 is as close as you can get,'unless you find some really old 14 oz cans that sometimes show up on eBay.

Good Luck!

[Pete_89T2]

Originally Posted by jackhild59

Couple of things: as macz said Freeze12 is not HC.

My mistake, confusing Freeze12 with "envirosafe" and a few other products being sold with names similar to Freeze12 that are HC gas based. Point I wanted to make is be careful with alternatives - some may work very well, but have unintended safety risks that aren't worth it

Originally Posted by jackhild59

Next your charge is either very low or it is contaminated. You cannot tell the % charge from the pressure.

You can estimate % of charge remaining from a static pressure test, based on the ideal gas law, but it's a rough estimate. Quick ideal gas law reference:

http://en.wikipedia.org/wiki/Ideal_gas_law

The gist of it is the A/C is a sealed system, so volume is a constant, and the mass/# of gas molecules is supposed to be a constant, assuming no leaks. That leaves pressure & temp as your only variables, and these two are directly proportional. Since I was reading a high static pressure, it means I still have the majority of R12 in my system. Would need to consult with a temp vs pressure characteristic curve for R12 and know the exact mass of the original R12 charge to estimate the percentage remaining though.

Originally Posted by jackhild59

The low side pressure switch cuts the compressor out at +/- 18psi, so that 6 psi number is troubling.

This is interesting, and I probably should take a second look at the electicals... Didn't think I had an issue there since the clutch was constantly engaged while the A/C was on, turning the compressor. Does the pressure switch cut out the compressor ABOVE 18psi or does it cut out below that threshold? If it's the latter, at 6psi, my compressor shouldn't be running at all.

Originally Posted by jackhild59

I think your plan to evacuate and recharge is a good one. Put *exactly* 2-12 oz cans in. Factory charge is 26 oz. 24 is as close as you can get,'unless you find some really old 14 oz cans that sometimes show up on eBay.

Yeah, I'm crossing my fingers on a couple of ebay auctions for the R12, but I might just have to spend the bucks on a "buy it now" deal -- seems someone always outbids me at the last minute on the damned auctions!

[jackhild59]

Originally Posted by Pete_89T2

You can estimate % of charge remaining from a static pressure test, based on the ideal gas law, but it's a rough estimate. Quick ideal gas law reference:

http://en.wikipedia.org/wiki/Ideal_gas_law

The gist of it is the A/C is a sealed system, so volume is a constant, and the mass/# of gas molecules is supposed to be a constant, assuming no leaks. That leaves pressure & temp as your only variables, and these two are directly proportional. Since I was reading a high static pressure, it means I still have the majority of R12 in my system. Would need to consult with a temp vs pressure characteristic curve for R12 and know the exact mass of the original R12 charge to estimate the percentage remaining though.

I wasn't going to get all scientific on you, but since you brought up Gas Laws, understand that you are making my point. The Temperature Pressure chart says that at 85*, the pressure of R12 in a constant volume MUST be 91.7psi. This is BTW the saturated vapor pressure. We must presume there is enough liquid R12 in the system to give a saturated vapor pressure.

Practically this plays out as follows:If we add more R12, both the temperature and the pressure will rise. Then, if we let the system regain it's original 85* temp, it must settle back at exactly 91.7*. Take a little out, the temp and pressure drops. Let the temp regain 85*, you guessed it, back to 91.7. If the gas in the system is pure R12, there is only 2 ways the system can vary from the stated temp/pressure chart. One way is if there is so little in the system that there is no longer liquid available to maintain the saturated vapor pressure. In this case, the pressure will drop below the 87.5*. Or conversely, we can fill the system so completely that there is no room for vapor. The system is then filled with a non-compressible fluid. Then the pressure can exceed the 85.7*

Given the low static pressure and the very low lowside/highside pressures when running, your system is likely very close to empty. Look for leaks.

It could also be contaminated with another gas that would cause the pressure to vary from the chart. Some would cause the pressure to be lower, most would cause the pressure to be higher.

Originally Posted by Pete_89T2

This is interesting, and I probably should take a second look at the electicals... Didn't think I had an issue there since the clutch was constantly engaged while the A/C was on, turning the compressor. Does the pressure switch cut out the compressor ABOVE 18psi or does it cut out below that threshold? If it's the latter, at 6psi, my compressor shouldn't be running at all.

Ok, I oversimplified. The evaporator has a temperature control switch that keeps the coil from freezing. It switches the compressor off at about 33* and is located at a mid-point on the coil that keeps the coil from freezing up and also gives the best performance.

In a properly (or moderately low) charged system, the compressor switches off at about 18psi. and back on at about 35-40psi. If the switch does not switch the compressor off, either the switch is bad or there is not enough freon to cool the coil down to 33* to cause the compressor to switch off. I personally have never seen this occur. Usually low systems cause the compressor to rapidly cycle-on and off. If it is cycling on off in under say 30 seconds it is called short-cycling.

You are correct: The compressor should not be able to run constantly at 6psi low side.

Diagnostic of this switch is on page 44/45 on the S5 FS. S4 is identical.

I hope all this helps you solve the problem. Good Luck.

[MaczPayne]

My FC gets to around 40 with Freeze 12, in Riverside heat

Only downside is my fan isn't ducted because of the huge radiator, so cooling is a little worse when I'm stopped in traffic

[jackhild59]

Originally Posted by MaczPayne

My FC gets to around 40 with Freeze 12, in Riverside heat

Only downside is my fan isn't ducted because of the huge radiator, so cooling is a little worse when I'm stopped in traffic

Nice.

Mine is R12.

[Pete_89T2]

Here's an quick update on my A/C problem. The stock fan clutch works fine, as does the aux. e-fan for the A/C condensor, and all the ducting is in place. Picked up a loaner manifold/gauge set at my local Advance auto parts store and did a little A/C testing this past weekend per the FSM.

Before doing the FSM tests, I did a quick static pressure check (engine not running/AC off) to estimate how much freon leaked out. The high & low sides were equal at about 86 psi, and the ambient temperature was about 85*F. So that tells me I should have at least 50~75% of a full charge. If it was much lower, it would mean a greater % of the freon leaked out.

Then I did the running test, A/C on max, 1500 RPM per FSM, and my low side pressure was 6 psi, high was 110 psi. FSM states recommended action for those results is to evacuate system, check for leaks & recharge system. Since I don't have a vacuum pump or any means to recover my R12, what I'm going to do is just recharge it myself with R12 and see how long it lasts. One can should do the trick, R12 can be had easily enough on ebay, albeit it's getting pricey.

BTW, I did some research on Freeze-12 and other R12 alternatives out there, and I would not recommend using Freeze-12 or any of the similar alternatives that are based on hydrocarbon gases. Most of these are highly flammable, based on butane, propane and other HC gas blends. The idea of running a flammable gas at high pressures thru crash vulnerable areas of the car and into the passenger compartment is a bit scary.