More AC stuff!! yay

[Andre]

AC in my car doesn't work. The fan does, when i have the fan turned off hot hair still blows slightly from the vents, incresses as i go faster. Is it the door that regulates where the air comes from?like the hot hair or the cold air. Is it stuck?

[mike944]

sounds like you have one of the same problems i have. except my AC works. You have 2 seperate problems there.

There is a vacuum door that controls air flow between AC and heat. when the AC is off, air flows through the heater core. The heater core should not be hot, because of a coolant valve that shuts off hot coolant flow into the heater core. Problem #1, that valve is broken. Unfortunately, it's behind the head and VERY hard to get to.

Problem #2 your AC doesn't work. That could be any number of things wrong. if the compressor does NOT come on, you're probably low on freon, but it could also be an electrical problem. If the compressor comes on, but turning the AC fan on high doesn't cause any air to come out the vents, your mixer door is probably stuck closed. If hot air blows when your AC is on, and the compressor is running, the problem is likely the air mixer door.

Mike

[scottewid]

It's hard to say. First is your car early or late? Have you confirmed the compressor is turning when the a/c is switched on?

First check that it is turning. Get a flashlight and look at the front of the compressor when the engine is running. You should be able to see that the center of the flywheel is stationary, while the clutch ring spins around it. Turn on the a/c and recheck. If it's running you should now see the whole assmembly turning. If it's not, you may have a bad clutch or even more simple, you're just low on charge.

There's a low pressure switch in the system (on the dryer/sight glass assembly) that will prevent the compressor from turning on and getting damaged if low on freon.

If it's just low on freon and if you've got your epa 609 certification, you can buy r12 freon online from www.refrigerantsales.com. You can get the 609 cert online for $19.99 at www.epatest.com. You can also get alternate r12 refrigerants like autofrost (www.autofrost.com) much cheaper, which, in my humble opinion, is better than doing a 134a conversion. Autofrost, Freeze12, etc. can be charged right into an R12 system with no changes other than evacuating the remaining old refrigerant and pulling a vacuum for 1-3 hours.

In doing a 134a conversion improperly or using one of these "quicky" conversion kits, there's a high probability your a/c will work for a while but after a few months, the compressor will seize from lack of lubrication and/or corrode the system from acids formed by mixing trace amounts of old oils and refrigerants. About half the people who do the quicky conversion get lucky and the a/c seems to work long term.

Even if the 134a conversion is done right i.e., pull compressor off and drain all the old oil out, flush the system with mineral spirits, change the expansion valve, dryer, and all o-rings, put eight ounces of esther oil into the compressor (or PAG oil, but PAG may still react with the residual chlorides in the system to creat acid, which are impossible to get completely out even with flushing) put it back together and pull a deep vacuum for at least an hour, preferably 3 hours, add another six ounces of esther oil through the charge port, and finally charge with 27 ounces of 134a (use approximately 80% of the normal 33.5oz R12 that the late cars take), you'll get vent temps anywhere from 5 to 10 degrees F warmer than if you stayed with r12. 134a just doesn't cool as well as r12, UNLESS you put in a larger parallel flow condensor, which is not really an option on these cars given the tight spaces.

Anyway, I guess I'm getting off topic: charge up the system with 33.5 ounces of R12 if low on freon. I recommend sticking with r12 because it works best. Yeah, it will be expensive, probably around $150-$200 for a shop to do it or $120 to buy it yourself, but IMO it's worth it for reliable, cold a/c.

If the compressor is turning and the low side line gets cold and the high side line gets hot, your blender door may be stuck. If you've got an early car, behind the battery under the windshield. You should see a black plastic thermos-like bottle. This is a vacuum resevoir that controls the blender door. Make sure the vacuum line is hooked up to it. On my 1984 944, it was disconnected. This caused the a/c to blow cold at idle or cruise, but anytime I hit the gas even slightly, vacuum would be cut off to the blender door causing it to close and blow warm air. When I hooked it back up, the a/c worked fine.

[pst]

Actually, for the R134a conversion you should use POE oil. This will not react with to existing oil and make acids. The street rod a/c companies also use POE oil on al of their kits. As for the condenser, the stock condenser in the 924 and 944 is plenty big enough for R134a. I know from experience from multiple conversions. My '79 924 has ALL of the origional components and I used one of the cheap kits 3 years ago. Although I also used an additive called "Quik Boost" available from JCWhitney.com. It was developed for NASA specifically to increase the cooling capacity of refrigerants. I currently have 2 cars (79 924 & 90 Eclipse) that I converted this way and the temperature is tha same as with R12. However, my Plymouth Voyager needs a larger condenser and doesn't cool very well. (the condensed is much smaller than the 924/944. I've heard many arguments about conversions but none of them were backed up by actual experience. I have converted 8 vehicles over the last 3 years and the only one that is not satisfactory is my Voyager. My 924 and my wife's Eclipse are daily drivers that are driven lots of miles with the a/c and I have had no problems in 3 years of use.

[Pinseekers]

what a pain the A/C system is!!!

[scottewid]

POE, polyol ester oil is the "esther" (spelled wrong), aka ester, oil I'm referring to.

Bottom line is a system developed for r12 will not blow as cold air when using 134a if using the same condensor. Sure it will get cold, but not as cold because 134a has a higher latent heat of vaporization and requires more surface area to reject the same amount of heat as r12. Best case scenario is it just doesn't cool as well, worst case is the condensor can't reject enough heat to keep pressures under control (134a normally runs higher pressure than r12)and you compressor burns itself out or (preferably outcome) the safety blowoff vents the refrigerant.

My dad learned the hard way with one of these quicky kits. This was 3 years ago, before I knew anything about a/c and could have advised him otherwise. He got the InterDynamics kit from Kmart and did his 1987 Oldsmobile Cutlass. First he vented the remaining r12 by sticking a golf tee in the schrader valve: highly illegal, not to mention an extraordinary waste of precious freon. By doing this, air and moisture now entered the system, further reducing the cooling capacity and longevity of the system. I bet none of the quicky kit users does it the right way, which is to have the r12 recovered then vacuum the system to get air and moisture out. My dad didn't do a vacuum. He injected the ester oil added refrigerant and presto, now converted to 134a. It cooled ok, but not as well as before because:
1)air and moisture in the system
2)r134a just isn't as good as r12 in a system designed for r12
3) he didn't adjust the low pressure cutoff switch like you're supposed to do for 134a

134a runs at much higher pressures than r12 so you must adjust or replace (if not adjustable) your low pressure cutout switch to about 19psi. R12 switches are set at 25-30psi. If you don't, the compressor will keep cycling off at 30psi, before the evaporator can get significantly cold enough to carry away the heat.

Also, he, like every other quicky converter, didn't install the EPA mandated high pressure cutout switch. This is required in any 134a conversion because, as mentioned before, 134a runs at much higher pressures. The EPA requires it to prevent the system from reaching the point at which the safety blowoff valve will vent the 134a to the atmosphere. It's illegal to vent any refrigerant, including 134a and propane to the atmosphere (go figure on the propane one, since I don't see the epa cops getting their panties up over the propane I vent everytime I turn on my barbeque grill!)

As mentioned, Dad didn't drain the old mineral oil, just added POE in hoping the mineral would find some magic low spot and stay out of the way. Turns out that low spot is the compressor.

Dad also didn't change the hoses to barrier type, also an EPA retrofit requirement.

Finally, Dad didn't replace the drier which had the old XH-5 dessicant to one with 134a compatible XH-7 or XH-9.

Regardless, he was happy with himself for two months until the system crapped out. Dad decided to take it to a "pro". Turns out all that old mineral oil plus the POE flooded the compressor and it slugged itself to death, since compressors can't compress liquid.

Also, the X5-H dessicant bag dissolved in the 134a sending lots of dessicant granules through the system. Quite a mess to clean up and flush out.

Fortunately, the pro was honest and did only the required work i.e., replacing compressor, flushing, new expansion valve, drier, orings, barrier hoses, low pressure and high pressure cutout switches. $1,000 later, Dad had a properly converted system that cools acceptably for him. Too bad he didn't take it there first and spend the $250 it would have been to convert with a working compressor and clean system.

The a/c shop said they usually see a few of these exact same situations every week during the summer.

As I previously said, if done properly and legally, a 134a conversion can provide very satisfactory results.

IMHO, the r12 cooling in 944s is marginal at best in the first place. Vent temps on a 134a conversion using the original compressor and condensor will definitely be at least 3-5 degrees warmer than r12. My preference is to hang onto every precious degree below ambient.

I've got a slow leak in my 86 951 (looses about 1lb of refrigerant every 3 months.) I had to charge it up this spring so I took it to a shop and had them evacuate the remaining r12. They're very happy to do this for free bcause I let them keep the freon that they can then sell to a recycler. I have a vacuum pump and did that my self after they took the freon out. As an experiment, I tried Autofrost(R406a) and it gives a little cooler air than r12. My vent temps with an 85F ambient with R12 were 54 and with 406a I get 50F-52F.

The 406a will leak out quicker than r12 because of the smaller r22 molecule. I'll let it all leak out and go back to r12 in a few months. I figure I'll leave it with the refrigerant it was designed for and it's really not prohibitively expesive to charge with r12 once or twice a year. By the way, it's not illegal to not fix a leak and allow the refrigerant to leak out. Some states like Wisconsin, however, impose laws stricture than federal EPA mandates and require a shop to repair leaks prior to recharging a system. A do it yourselfer does not have to fix the leaks prior to recharging, though, even under the stricter state laws.

In the end, I'd recommend staying with r12, but if one decides to convert, let a pro do it the right way, otherwise it's a crapshoot, and potentially in violation of federal law.

[Andre]

I know i'm low on freon but i dont wanna go with a $120 frean thing if i have a leak or something

i need some really cheep stuff to put in there so that i can check whats working and whats not. Any ideas?

[scottewid]

Andre, try Autofrost (r406a). It's $10 a can, still not as cheap as $5/can 134a, but a hell of a lot cheaper than r12 at anywhere from $40-$60 per can.

Autofrost is compatible with mineral oil and XH5 dessicant, so you can charge it right in with no other changes. It's what I'm using now and it works fine.

You can only get it online at www.refrigerantsales.com. You'll also need the epa 609 certification, but that's a snap to get online at www.epatest.com for $19.99. I spent an hour doint epatest's online study guide. Then took the test in 5 minutes, printed out my temporary 609 cert and then called the folks at People's Welding (www.refrigerantsales.com). They had Autofrost in the mail that same day and I got it two days later.

[lm6y]

Hmmm...... I did the conversion to an early car with a Sanden SD5 compressor, and 134A last year. Replaced all of the O-rings, reciever-drier, and left the expansion valve the way it was, and didn't replace ANY of the hoses with the barrier type.

Last weekend, the ambient temp here was 95 degrees with 60% humidity. After the A/c system stabilized, driving at 65 MPH the temp was 36 degrees at the center vent with the blower set to the #2 position. A 59 degree drop in temperature isn't too bad for a conversion that "isn't as good as R-12". I think the condensor on these cars are big enough for sufficient cooling. Now if these cars didn't have more glass surface than a greenhouse, it would be even better. The low side runs at about 30 - 32 psi, and the high side runs about 200-225 psi, and has stayed this way since the retrofit, without ANY loss of refrigerant.

Scottewid has the vacuuming process dead on. Don't even think of doing ANY A/C repairs without access to a REAL vacuum pump, and not one of those Harbor Freight cheapies. Any moisture is the enemy of your A/C system, and will kill it in due time. Also, I agree with the idea of getting rid of as much of the "old" oil as you can.

Good luck with it!

[Pinseekers]

I just charged my system with R12 in Mexico. Cost me $8 for the gas and $1.75 for the six pack. Couldn't believe how cheap.
Now my question.
Why does my heat temp gauge automatically go to a little past 3/4 when the A/C is on at high speeds, and drop to half when I come to a stop light?
When I run the car with out the A/C, the gauge never goes above 1/2!
Another question. Why does the air not really blow out of the center vents. More blows out of the defrost vent than the normal vents. With the defrost position on, it really blows hard in the defrost vent.
A note on gas mileage.
I left LA with a full tank of gas. I got to Yuma and filled her up again (to see consumption) and I used 10.46 gallons on the way down there. When I returned I refilled at Yuma and when I arrived in LA I filled up again. This time running the A/C, I used a whopping 7 gallons more. Is this typical?
Does anybody elses car seem sluggish with the A/C engaged? or is this normal as well?
Pedro

[Lawrence Coppari]

Try Fox Tool Company in Nashville, TN. They used to sell a refrigerant substitute. I have used it for 5 years in an old MB and also use it in my 944T. It does not leak as fast as F12 and works well. As there has been no seal eating in 5 years, I have to assume it is ok stuff. It is basically propane. You only need about 60% by weight to charge your system. Yes, it is flammable.

[pst]

scollewid, yes the federal EPA does not require you to repair leaks, but the law allows states to have their choise as to leak repair. As far as refit, R134a runs at higher high side pressure but a lower low side pressure. The low side pressure should be 8-12 psig. The low side switch needs replacing because of this. If a system with R134a is running with a higher low side presure, it is overcharged and will cause lower air temps. If your system does not have a large enough condenser or you are not satisfied with the outlet temp, there are new condensers on the market that are very high efficiency (aluninum multi passage tubes and parrallel plumbed) for just over $100. This will significantly improve the system. Also, it is illegal to vent to the atmosphere and to sell any chlorofluorocarbons (CFC's)to anyone who does not have EPA certification. This includes any of the R12 replacemants (all contain some amount of R22) and halon (also a CFC). Yes certain desicants will react with R134a and PAG/POE so you must be sure that the drier is compatable. POE oil did not cause the problem with your dad's car. It sounds more like the system was overcharged and liquid refrigerant entered the compressor. This, called slugging) which will destroy the compressor valves. Being that you speak of higher low side pressures with R134a this is most likely what happened.

[scottewid]

Pst, you're right about the states having the latitude to have stricter law's regarding leak repair than epa. As I mentioned, Wisconsin is such an example. I've been trying for months to figure out what NJ is. Talked to NJDEP, EPA, but jsut got the run-around. One a/c shop I went to said no, the other said yes, go figure. One of the reasons I decided to get my own 609 cert and tools to do it myself.

As for purchasing the alternatives like autofrost, yes, as I mentioned epa cert. 609 is required. This is definitely a potential deterant for some folks, even though it's easy to get. 134a and hydrocarbons don't require 609, although same as the leak issues, some states ban hydrocarbons in auto use. NJ isn't one of them yet. I know some folks are feel the HC route is safe, but as long as I can get r12 or non-flammable alternatives, I think I'll steer clear of propane.

You're right about the low side of 134a running lower pressure. Guess what I didn't say too clearly is that if you don't adjust your lowside cut out to mid to high teens, it will cycle your compressor off too soon, since r12 is usually set low to mid twenties.

Yup, a larger and/or more efficient condensor will definitely get you lower vent temps with 134a. All I'm saying is that if you have identical systems, one with r12 and the other with 134a, the 134a will definitely blow few degrees warmer. Same for r12 versus r22. R22 will always blow colder due to its physical properties. But straight r22 will also run much higher high side pressures, ice up the evaporator, and eventually kill a compressor not designed for it from the high pressures.

If you overfill a system with oil, the compressor can definitely slug itself to death, just like if liquid refrigerant were to make it to the compressor. Since Dad only added three 12oz cans for a system designed for 42 ounces, I don't think he was overcharged. Seems the most logical explanation for the compressor valves being destroyed is that since the mineral oil doesn't mix with the 134a and get evenly distributed throughout the system, it must pool at some low spot. His compressor was the low spot so it filled up with all the old mineral. Where else would the oil have gone?

[banjomike]

Rules and regulations aside, there is a moral issue here. Freon is very damaging to the ozone, and it is very persistant, which means it continues to do damage for a long time. Please don't vent your freon. Please buck up and fix leaks before recharging your a/c (even the new replacements for freon are somewhat destructive to the ozone layer). Please take a small bit of responsibility and remember that we all have to live on this planet together. Thanks I will now step down from the pulpit.

MsB

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Mike 86 944