Back to R12 worth it? - Page 3 - PeachParts Mercedes-Benz Forum

Mark DiSilvestro · #31 08-08-2007, 02:31 PM

Quote:

Originally Posted by rrgrassi

The aux fan kicks in when the TEMP of the freon hits a certian temp, not by pressure. Pressure is what controls the compressor. On our cars it was only if the freon pressure was too low that the compressor is shut down. I installed a hi/low switch that kills the compressor connection if the pressure is either too high (which happens w/134a) or too low (usually caused by a leak).

OK, but nevertheless, wouldn't there still be some benefit with an R12 system converted to R134a, to re-wire the aux fan to come on when the AC compressor clutch is engaged (like my '98 Nissan), or add a manual bypass so the aux fan can be operated by the driver at times other than when the drier temp switch engages?

Happy Motoring, Mark

WD8CDH · #32 08-08-2007, 03:05 PM

So far, I have had no problems with hydrocarbon refrigerants at over 100F.

There is a lot of mis-information in those links.

The flamability of hydrocarbon refrigerants is far less dangerous than the gasoline in a car.

Hydrocarbon refrigerants are used in most refrigerators in Germany and many other parts of the world.

Hydrocarbon refrigerants are use in automobiles in Australia and most european countries.

Hydrocarbon refrigerants are allowed as a replacement for R-134a in automotive A/C systems in most states in the US and can replace r-12 in older A/C systems if they are converted to R-134A first.

Hydrocarbon refrigerants are a legal replacement for R-12 in stationary refrigeration and A/C.

By the way, I am both 609 certified and Refrigeration Service Engineers Society certified and do have a stockpile of R-12 but I still prefer hydrocarbon refrigerants.

Bill Ladd · #33 08-08-2007, 03:17 PM

Here's my take on r134, now that it's about 111 degrees outside right now. Wish I had been patient and waited for my mechanic to get me some r12.

I'm lucky if I get 62 degrees out of the vents the last few days.

Pretty sure my recirc. is not working, so my system is trying to cool super hot, humid air. That doesn't help.

When I first rebuilt my system (compressor, dryer, expansion valve, flush) I was pretty happy with the results, but in this heat, forget it.

Soon as I get the time, I'm going to add a parallel flow condenser, maybe try some enviro-cool, and get my AC vacuum working properly so it'll go to recirculating cabin air.

I want this thing freezing!!

Mark DiSilvestro · #34 08-08-2007, 04:01 PM

Does someone make a parallel-flow condenser to fit an '82 W123 240D, or will I need to adapt a universal one? Reason I ask is the PO's teenager broke mine in a fender-bender. I have a new, sealed reciever/drier, and the R4 compressor still seems to be turming freely and smoothly. As the supply of R12 locally has dried up, I'm considering R134a if I can find a parallel-flow that won't be a major pain to adapt to this car.
Otherwise, I had good luck with Freeze-12 in an old Honda a few years ago.

Happy Motoring, Mark

Tymbrymi · #35 08-08-2007, 04:24 PM

Quote:

Originally Posted by Mark DiSilvestro

...will I need to adapt a universal one?

Yep. There should be pics and other documentation on the forum of other people doing exactly that.

davidmash · #36 08-08-2007, 04:46 PM

I know very little about a/c so I am just relaying my personal experience and what I was told by my shop manager at the MB dealer that I took my car too.

My 190 had a leak in the a/c and would no longer hold a charge. When it was charged last year with r12, it cooled ok, not great, just OK as it always has. I hunted around and got various opinions about what to do as I needed ac here in TX. Should I go R134 or stick with r12. I was finally swayed to go with 134. My service writer had converted 2 123 of his own and the shop manager who I have been dealing with for 7 years now and has not lied to me yet (that I know of) said to go to 134 and he promised I would not be disappointed. So I did and so far, the car cools as well as it ever did. I keep it on recirc, max temp and 2nd fan setting. It keeps me comfortable. We will be hitting 100 here this week so I might have to go to the 3rd fan setting.

One thing my shop manager undermentioned about the people who are having problems is that their systems may be over charged. Just using random numbers for example, he said that if an R12 system was designed to hold 2 lbs of refrigerant, you cannot convert to R134 and put the same amount it. He said that R134 expands more than r12 does and that for the system to function properly you need to use less R134 (I believe he said about 25% less) and that R134 is actually easier on the system because it works at a lower over all system pressure so stress on the system will be reduced.

All I can say is that on my 20 year old car, my AC cools e just fine here in the TX heat. As long as I keep the car moving, I'm fine. Stop and go it sucked with R12 and it sucks with R134.

tjohn · #37 08-08-2007, 05:09 PM

Quote:

Originally Posted by davidmash

One thing my shop manager undermentioned about the people who are having problems is that their systems may be over charged.

Yes, that's easy to do. The number I've seen is 85% R134a by weight compared to R12. However, R134a will not cool as well as R12 in an unmodified 80s MB system. Period.

Quote:

R134 is actually easier on the system because it works at a lower over all system pressure so stress on the system will be reduced.

Negative. R134a runs higher pressures compared to R12, especially on the hottest days.

Quote:

All I can say is that on my 20 year old car, my AC cools e just fine here in the TX heat. As long as I keep the car moving, I'm fine. Stop and go it sucked with R12 and it sucks with R134.

Yes, without mods the performance at idle will never be great. I still maintain a proper R12 system will do a better job.

pmckechnie · #38 08-08-2007, 07:22 PM

I am just giving my opion. I know it doesn't mean anything but here it is anyway. After not being able to get R12 in my area at a reasonable price, I replaced the dryer, flushed (including the compressor) and recharged with Freeze 12 and have not regretted it. I did the 500SEL first and it worked so well I also did the 300D the same way. Both cars are doing fine this week with temps in the high 90's to low 100's and high humidity. I had R134 in both cars and neither work very well in moderate temperatures. I can't say why Freeze 12 works better than R134 but it does if done correctly. Now please understand I would use R12 if I could get it at even 2 times the price of Freeze 12, but I can't.

tobybul · #39 08-08-2007, 07:37 PM

Have y'all read the warning label on a R134 can?

Also, I heard it will be phased out and replaced in 2 years.....

TJR300SD · #40 08-15-2007, 12:54 PM

I've been in Phoenix for five days now, and unfortunately all that money I spent on converting the AC to R134a has gone to waste.

At best I get 60's F from the vents when I'm on the freeway and it's 110 F outside. The absolute best I've gotten was 50 at night, when its 87F or so outside (ambient). Most of the time I'm sweating what seems like a gallon of water per minute. It doesn't help that the car's interior is usually 120F when it's parked.

I'll probably have to replace the dryer, the expansion valve and go back to R12, short of getting a whole new system entirely, which is not an option at this moment. R12 conversion is not cheap, but being so close to Mexico now, R12 is readily available around here, especially given the weather.

Another problem has reared it's head: my engine quickly overheats. Just ten to fifteen minutes of driving and already the temp gauge reads 110 to 115C, and sometimes the temp even spikes above that towards the 120C mark. I have to make frequent stops and pullovers to cool it off and prevent it from breaking down. The local MB shop said normal operating temperature in this climate is about 105C.

They also said the overheating problem could be AC related. In any case, I'm having them look at it tomorrow.

So there we go, I have a dual cooling problem: it's too hot inside the cabin and it's too hot inside the engine.

#41 08-15-2007, 01:08 PM

Yup, I've been down that road. I converted my 300D to R-134a when I first bought it with a bad compressor and was never happy with the performance. It was OK up to about 90F, then it just wouldn't hack it. I lived with it for a couple of years until the compressor locked up. I had the system restored to R-12 and the performance is much better. I'll never make that mistake again.

Regarding the engine cooling, everything needs to be just right to handle 110F ambient temperatures. Mine has a new radiator, and it will usually stay in the 85-95 range with 100+F ambient, but it will climb to 100C on long hills or stop and go traffic.

If you are getting to 115C, you need to do something. First, turn off the AC and see if that helps, your R-134a system is probably working pretty hard under those conditions. Make sure the exterior radiator fins are clean. Have you flushed the system yet? Does it run close to 80C in cool ambient temperatures, if not you may want to replace the thermostat? If it's hotter in traffic than on the highway, check the fan clutch.

To tell you the truth, I didn't really see a big improvement until I replace the radiator (due to a broken neck).

odie · #42 08-15-2007, 01:37 PM

there is this Freeze-12 stuff you can buy the works in R-12 systems with no conversion. Worked great in my old R-12 Datsun. It's made by Jonsens? They are a regular freon maker, not some unknown outfit.

SD Blue · #43 08-15-2007, 01:44 PM

Here are the folks I would talk to: http://www.ackits.com/ especially since you live in their neighborhood now. They also carry the parallel-flow condensors for about $150 that should improve the R134a operation.

#44 08-15-2007, 01:45 PM

Quote:

Originally Posted by odie

there is this Freeze-12 stuff you can buy the works in R-12 systems with no conversion. Worked great in my old R-12 Datsun. It's made by Jonsens? They are a regular freon maker, not some unknown outfit.

I wouldn't do it unless you know that someone will be willing to service the system.

TJR300SD · #45 08-15-2007, 03:23 PM

Quote:

Originally Posted by Craig

Yup, I've been down that road. I converted my 300D to R-134a when I first bought it with a bad compressor and was never happy with the performance. It was OK up to about 90F, then it just wouldn't hack it. I lived with it for a couple of years until the compressor locked up. I had the system restored to R-12 and the performance is much better. I'll never make that mistake again.

Regarding the engine cooling, everything needs to be just right to handle 110F ambient temperatures. Mine has a new radiator, and it will usually stay in the 85-95 range with 100+F ambient, but it will climb to 100C on long hills or stop and go traffic.

If you are getting to 115C, you need to do something. First, turn off the AC and see if that helps, your R-134a system is probably working pretty hard under those conditions. Make sure the exterior radiator fins are clean. Have you flushed the system yet? Does it run close to 80C in cool ambient temperatures, if not you may want to replace the thermostat? If it's hotter in traffic than on the highway, check the fan clutch.

To tell you the truth, I didn't really see a big improvement until I replace the radiator (due to a broken neck).

When I drive on the freeway with the AC in full blast, the coolant temp remains stable at 100C. When I pull off the freeway and go on to stop-and-go city traffic, the temp climbs dramatically and uncontrollably, forcing me to turn on the defroster at full blast in 100F+ weather (not comfortable believe me, thank god the sun roof works!). When I go back on the freeway, the temp falls and stabilizes to about 105C, and falls even further to slightly below 100C the longer I stay on the freeway. It's almost certainly the fan clutch, right?

I did replace the thermostat just a few days ago to see if that would fix it and it didn't help. The system was flushed five months ago, so I'm not sure if I need to do it again.

Right now, though, I don't have the resources to work on this stuff on my own. Before I moved here I could have, but oh well.