A/C blowing warm - questions
 

I went for a drive last week and used the A/C. It cooled quite well, but I did hear a hissing sound - it was coming and going, not constant.

Today, I took the car out, pushed the A/C button, but did not get cool air. When I got back home, I popped the hood and verified that the A/C clutch is not engaging.

Could the variable hissing sound have been an indicator of low refrigerant? I'm pretty sure it's still an R12 system. These days, how difficult is it to get an R12 refill?

Hugo

Near impossible unless you know someone who has some laying around. Most shops don't even have it anymore. Sounds like you sprung a leak. Although hoses and seals are permeable, and can seep refrigerant, the only time the system would be flat would be due to leakage. Might be a good time to convert to 134a

Some shops may still have some R12 yet, but at $70+ a pound, now would be the right time to convert to R134 since it sounds like you probably have other issues besides a simple recharge. And, you can maintain an R134 system yourself for cheap compared to what a shop charges.

the hissing is most likely a leak of the AC system.

when the freon is low, the compressor will not engage.

most likely, the freon is gone.

you should have an AC shop figure out where the leak it and fix that. could be a hose or a component of the AC system. once the leak is fixed, then charge it with R134. R134 will be cheaper and easier to find if you need to recharge in the future.

my ac shop charged $45 for diagnosis. they used a sniffer that pin point the leak.

To be clear, the hissing sound was not a leak. It sounded more like the expansion valve doing it's work.

I have the records for the car dating back to late 80's, and can't find anything related to A/C work, so there's a good chance it is/was still running on the original charge.

I'll do some testing to try to confirm if it's low refrigerant. If yes, I may still pursue the R12 route.

Hugo

R12 isn't in demand and the price isn't that outrageous anymore. Check ebay and craigslist.

If the system is overall tight and only needs a minor repair, stick with R12. 134a won't cool as well unless you change the metering device, it shouldn't be used with your existing oil and it will leak down through non barrier hoses and old style o-rings.

There are also replacements to R12 which work great. Downside is that they are azeotropic blends which shouldn't be topped off.

That said, if the system was working perfect and just stopped all of a sudden, you don't have a small leak. If it did leak out, you'll have an oil mess around the damaged area. Your refrigerant may very well be fine. If so, I'd start with pressure switches and the switch on the evaporator which cycles off the compressor to prevent freezing. Hopefully the problem is under the hood and not with the interior climate controls.

The hissing was likely a vacuum leak from one of the actuators. Check for vacuum leaks inside the cabin.
The pressure sensor switch will keep the compressor clutch from activating if there is not enough freon pressure in the system.

I had mine recharged last year with R12. The shop had it. Cost me $130 or something. That freon fiasco is a joke, a jump to conclusions on the hole in the atmosphere.

Your problem might be vacuum related. Take your air cleaner box out and see if the heater valve is closing.

Freeze 12 -
 

Check locally or on the internet for some Freeze 12. It is a blended freon that can be installed right into the older R12 automotive air conditioning systems. Some prefer to go through the R134 conversion process but I've used Freeze 12 for years in lots of cars with complete satisfaction.

The first step is to always inspect your vacuum control circuit, all the high pressure hoses, replace all your line seals, replace the dryer, make sure your A/C clutch is working (a quick test is to jumper +12 Volts to the coil and listen for the click) and then pull a good 29" vacuum on the whole system. Just for good measure, I usually leave the gauges on for an hour or so to make sure the vacuum holds. Usually a couple of pounds of Freeze 12 will keep you cool for years without the expense of the R134 conversion process.

One other check is to make sure your hot water shut off valve has closed when the A/C switch is pressed. Many 928 owners temporarily zip tie the hot water shut off valve (mounted on the firewall - back side of the air cleaner) closed each summer in the hotter locals.

Good Luck, Michael :)

I'm fairly certain all the vacuum stuff is working properly. I was getting heating in the winter and A/C cooling up to last week. I haven't had a chance to test anything yet other than to confirm the compressor clutch is not engaging. I am not getting warm or hot air when I try to run A/C, it's definitely outside air temperature. I figure if I jump the low pressure switch, I can check if the clutch engages. If it does, then low refrigerant is the likely culprit. I don't have gauges so I can't test it directly.

As for ozone hole, this isn't the right forum and I don't want to inject politics into it at all, but there is very solid science behind the issue of CFC's and ozone depletion. The Wikipedia article Ozone depletion - Wikipedia, the free encyclopedia has a good overview. That is all I will say on that subject.

Hugo

Leave this stuff up to the Ac Pros. Find a reputable AC Shop near you. The system isn't any different from other cars. Make sure to Evac that R12 legally, it's illegal to go releasing all that R12 into the atmosphere. Plus, you'll feel good not putting your future generations in jeopardy.

Mine was already empty in the Euro so I replaced all the o-rings myself and took it to the AC Shop for them to do their magic. There is a specific amount of Refrigerant (R134) and Oil that is put into your system, don't try and guess on this. I blew up a Compressor doing this, it's not worth it.

Yes, wrong place for this. But the "hole" is almost gone. As for recharge, plenty of R12 still around. But best find the leaks first.

I have used this on well over a dozen R12 German Car AC systems without incident. Fix the leak or determine the "clutch" issue first.

Enviro-Safe Refrigerants

Go out to your car and pop the hood. Find the high or low side charge port on the system, and pull one of the caps off. Press the schrader valve (Its the same thing as whats in a car tire valve stem) and see if there is pressure on it. If there is pressure on it, its not completely empty, which means there isnt a huge hole. It may have already been low, and finally got to the point where the low pressure switch cut it off. If you heard a "hissing" noise, that doesnt sould like an expansion valve.. Thats probably a hole in the system. Just hope is isnt the evaporator..

Ac systems are not that complex. Its much cheaper to buy gauges and a vacuum pump and do it all yourself. Ive been doing it for quite a while. I dont know if you can buy r12 gauges anymore, though.. The hoses on my gauges are going down hill, so ill be looking for some.

You are "supposed" to have a license to buy r12....You can still find it some places. Just pay cash so it doesn't leave a trail. I've heard the Freeze 12 is supposed to be decent, and soon im going to charge my pickup with some of it.

Anyways, if it is empty, i would just go to Freeze 12. R134a and R12's pressures are different, as a result the expansion valve needs to be adjusted, new o rings, but new hoses arent needed for 134. Ive never changed hoses when converting and havent had a leak.

If you go to freeze 12, you dont need to change o rings or adjust anything. If you put anything other than r12 in it, (and you do it yourself) Put Ester oil in it. Its compatible with r134 and r12.

Remember, if you convert, pull a vacuum on it, because r12 and r134 mixed supposedly turns to an acid and eats your system.

As for the hole in the ozone... Complete bull****, R12 had nothing to do with it. Its just government crap. They sure didnt think to check for that hole in the ozone layer 200 years ago, Did they? Sure, theres been "research" on CFC's killing the layer, but there have been just as many or more showing that it had nothing to do with it.

Hope all of that jubberish i just wrote makes sense.. Good luck!

MPDano, What is the temperature coming out of the vents on your car? 134 usually doesnt cool as well without a bit of work.

Its 20 bucks to take the 609 cert test its an easy online test EPA 609 Open Book Certification

once you pass you can buy r12 on ebay: R-12 FREON, REFRIGERANT, DU-PONT TWO (2) CANS WITH INSTALLATION HOSE. SUPER COLD | eBay

R12 manifold gauges on Amazon: Mastercool 98660 Dual 134A R-12 Aluminum Gauge Set: Amazon.com: Industrial & Scientific

I don't like the blend gases....most have to be liquid charged, which can damage the compressor if not performed properly. I don't chime in too often on AC related stuff...kinda like the computer guys who work on them all day don't touch them when they get home....

I hate the cheapo certification tests, as I feel they really don't teach the average joe anything, just a way to bypass or bend the rules (that said, I am a little hypocritical, as I took the ASE $20 test many moons ago, back when it was $15, but...I was already a certified HVAC tech). I don't oppose any DIY efforts...but I have seen many systems damaged by untrained personnell, and quite a few injuries...don't want to see anyone hurt....

Anyway did not mean to hijack the thread...just be safe messing with this stuff, it is high pressure.

Finally had a chance to poke around today. Unscrewed the protective cap on the low side port and pressed the pin for a quarter second and heard the sound of escaping gas.

Next step is to find a shop local to me that would be willing to work to find the leak (if any) and recharge with R12.

Hugo

I've become very leery of allowing any shop that doesn't know the 928 well to touch it, and I have yet to find a task simple enough an experienced non 928 mechanic can't screw up in a potentially very expensive way.

words of wisdom to live by! 100% correct:mad:

So I finally got a chance to have the car looked at by a trusted shop. They pulled a vacuum and let it sit for an hour. After confirming there were no leaks they recharged the system with R12.

Total cost was $100 for shop time, refrigerant recovery, etc plus $75 for R12 that I purchased using eBay.

Hugo