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A/C stopped working-what are "freon" options?


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I put the 1989 into storage without "recharging" the air conditioning unit. What options are there available, and how much has this cost others? I assume there is nothing major wrong with the entire system, maybe it just needs to be charged. Thank You.

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No problem not recharging the A/C for storage. R 12 is still available, however VERY expensive. Converting to R134 is the best bet (dollar-wise). If you can't do it, any COMPETENT A/C shop can do it. I did it to my '89 Riv, and can't tell the difference.<BR>Now, as to WHY the Freon is low, again if your not comfortable troubleshooting the system, a competent tech should be consulted.<BR>One hint; these vintage GM A/C systems had a history of leaking evaporators; first place I'd look. Pull the blower resistor module out of the evap case, and look inside with a light for oil and/or wet dirt. The system can be charged with a leak detection dye, and looked at with a black light.

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It depends on how bad the leak is. My 90 Reatta was down about a pound after 10 years. The dealer said it would cost over $1,000 to deal with it, as they said the seals were leaking. I had some freon left over from the days when it was a can for 99 cents. I put one can worth in last year and it works fine and the A/C light no longer comes on. So as long as the leak stays reasonable, I might get by until the end of the cars usefull life. Check ebay under freon.<p>[This message has been edited by bobwhite (edited 03-12-2001).]

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<P> The 134 refridgerent will decrease your cooling capacity and cost more HP to drive the compressor. Non metallic parts designed for R12 will also allow the 134a to migrate out, especially on a car used infrequently. If all that is required is a slight addition, ie, there is no large leak, stay with the R12.

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<P> Sorry I didn't add this earlier.<P> The higher operating pressure characteristics of the 134a are many times interpreted by the Reatta's BCM diagnostic firmware as an "AC Trouble" This comes up more often in hot climates where the system is at max capacity. There does not seem to be any way to realistically bypass the AC system diagnostics.

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Maybe I don't understand the first post; yes, by all means use R12, if you can, but I thought his system was 'out of gas'. As for R134 leaking out of the system, no more so than R12. Now you do have to purge the oil, and replace the accumulator (dryer), and a few seals and fittings (you can't use your old R12 gauges, by the way).<BR>The cooling capacity theoretically IS slightly less than R12, but if you can't get 12, or can't afford it, its the next option.

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In Jan of 2000 I began to get a message on my CRT screen "Low A/C Rferigerant-a/c system performance may be degraded. Service a/c soon." I had talked to the GM dealer that I use about a conversion since I had been reading so much at that time about doing it. He told me that he didn't know how much it would cost since they had never done a conversion before. I relayed that info here on the forum for advise. Among all the good advise that I got I distinctly remember Barney saying if they have never done a conversion before, dont you be thier first. I eventually decided just to go ahead and just have it recharged with the R12. That was my first recharge, and last summer it worked as well as did when it was new<BR>Joe

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You should have a shop leak test the system with a floresent dye and a electronic tester (heated dioed ones are the best). Large leaks tend to show up as oily spots. <P>It is good practice to replace the connection o-rings if a system is empty. If all the old freon leaked out the drier should be changed. The oriface tube should be inspected and replaced if signs of contamination. <P>A few years back it was thought that to retofit a system the compresser, hoses, and more must be changed acording to the EPA. Sence then they have revorsed there decision and have found replacing those componets unneeded. <P>I have done hundreds of retrofits. I would say the old R-12 compressors retofitted don't seem to have a leak problem like the factory R134 compressors. The hoses seem to work about the same.<P>What must be done to retrofit: <BR>1) The 3/16 and 1/4 ports must have R-134 addaptors on them.<BR>2) There must be a retro fit sticker.<BR>3) All R-12 must be evacuated from the system.<P>The system requires slightly less R134. There are formuls but myself I charge by temp/pressure not weight.<P>The compressor low cut-off switch needs to be adjusted or replaced. The problem with the Reatta is it does not use a switch like 99.9% of cars. It uses a potometer sencer. The R134 does not run at the same temps/pressures so the system sees a problem. So tec's report putting a resister in with the sencer will fix this. I don't know. But I'll be retrofitting mine this spring so I'll find out.<P>Lastly regardless of freon if the system is empty it needs to be placed under a vacuun for at least 15 minuits or you will have poor performance. A bit overcharged system will have worse performance than being a bit undercharged.<P>Tom

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<P> Just about all of the products marketed as "drop in" replacements for R-12 are propane based and extremely flammable and even explosive under collision type conditions. Stay with the R-12 or do a proper R-134a refit. Altering the sensors with external resistors renders the self-diagnostics of the BCM on the AC system useless.

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Are these systems well built and designed? Since some of our cars are in storage for most of the year, that might have something to do with the failure. I have had Mopars go 148,000+ miles with no problem whatsoever.

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Bob the BCM dignostics would still work if you installed a resister inline with the low side sencer. I'm not sure weather it needs to be in series or paralel but I do remember 2.2K ohms is recomended. I know I'll figure out which way and what size when I do mine. I just have to do the math. The idea of the resister is just to alter the sencer reading a little. Instead of the compresser kicking off in the low 30's PSI you want it to kick off in the lower 20's PSI (just above 32 degrees on the low side line temp to prevent freeze up). It would still be taking a reading and if you went into dignostics the value it would show in PSI would be off by about 10 PSI but the line temp should be close. The big yellow light would still come on if the system went empty again.<P>Tom

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Some of the quotes I've seen from others scare me. Some people mention $1,000. quotes from repair shops. Is any part of this a do it yourself job?

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Tom Walsh:<BR><B>Bob the BCM dignostics would still work if you installed a resister inline with the low side sencer. I'm not sure weather it needs to be in series or paralel but I do remember 2.2K ohms is recomended. I know I'll figure out which way and what size when I do mine. I just have to do the math. The idea of the resister is just to alter the sencer reading a little. Instead of the compresser kicking off in the low 30's PSI you want it to kick off in the lower 20's PSI (just above 32 degrees on the low side line temp to prevent freeze up). It would still be taking a reading and if you went into dignostics the value it would show in PSI would be off by about 10 PSI but the line temp should be close. The big yellow light would still come on if the system went empty again.<P>Tom</B><HR></BLOCKQUOTE><P>Tom:<P> If you install a resistor, you negate the information the sensor gives. The idea is to shift the reading the BCM sees. But by doing it with a fixed resistance, you change the gain (resistance change vs temp change) of the sensor. The diagnostics calculate the proper temperature vs pressure relationships over a relativly narrow range. If you give false information to the BCM, you eliminate the constant failure code, but give up the diagnostics. I agree that if the system were empty, the code might set. But the idea of the diagnostics is to indicate when problems are about to occur before the system is damaged.<P>

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Bob,<P>Like I said before I have not done this yet. But come spring I will have 134A in my Reatta. After doing more checking I have found this:<P>There is a low side temp sencer that turns the compresser off at 0 deg F. (thru the BCM)<BR>R-12 0 deg F = 12 PSI<P>There is a high side temp sencer that turns the compresser off at 200 deg F (thru the BCM)<BR>R-12 200 deg F = 425 PSI<P>There is a low side switch that turns off the compresser (thru relay) at 10 PSI +/- 1 PSI, sets code which disables A/C system<P>With 134A the system set up right the system still should never drop below 10 PSI. So the low pressure SWITCH is fine without any changes. This is what turns on the low A/C light and sets a code.<P>The problem is the BCM is set up to turn off the compresser at 0'F on the low side sencer which is right before the low pressure SWITCH comes on with R-12 at about 12 PSI but 0'F with R134a is 5 PSI. Below the 10 PSI minimum for the low pressure Switch witch would turn on the light and turn off the A/C. Idealy you want R-134 to be around 30-34'F on the low side which is 25-30 PSI. <P>I can't find any sencer range charts for the low or high side sencers. We want to trick the low side sencer in to thinking it is about 30'F warmer. By putting the resister in serries you increase the sencer circuit resistance. A resister is put in combination with the sencer so operating pressures and tempitures work fine. I don't see this causing any problems with system persormance. I don't think the low or high side temp sencers can set any codes or turn on any lights. The only thing that would not be right is the computer dignostic desplay of the A/C temp. It may say it's 0'F when it's realy 30'F. An A/C person does not need these computer readings just the low and high side gauge readings.<P>The high side temp is a bit high too. to turn off the compresser at 200'F with R-12 is 425 PSI. That would be a safty cut-out. Much more than that and run because something will blow. The system won't last too long at 400 PSI eather. 200'F with R-134 is 475 PSI. The system should have an aditional 134a high pressure safty cut-out switch as required by EPA for retrofits for cars that have high pressure blow off valves. I'm not sure if these cars do but I do know at that pressure something will blow. The other way to do that is to put a resister on the high side sencer to fool the BCM into thinking the temp is higher than it is so turn off the compresser in the event of a high pressure problem. <P>Tom<P>

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Guest Stan Leslie

According to the service manual 89 and 91), the AC switches/sensors work the following way.<P>Low Side Pressure Switch - Shuts system down if pressure drops below 10 PSI (low refrigerant). This is about 2 deg. F with R-12<P>Low Side Temp. Sensor - Cycles compressor clutch on at 49 deg. F and off at 30 deg. F. (doesn't care what the pressure is).<P>High Side Temp. Sensor - Turns low speed puller fan on at 122 deg.F (off at 115 deg). Turns high speed puller fan on and pusher fan on at 149 deg. F (off at 136 deg.). Turns compressor off at 199 deg. F (back on at 187 deg.), this protects system and prevents dumping refrigerant through safety valve at compressor.

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Thanks stan the low side at 30'F sounds more reasonable for the low side. I did read 0'F somewhere but it did not sound right because the evaporator would tend to freeze up and the pressure would be too low. In that case the low side sencer or switch would probibly not need anything. But for safety and to prevent the high limit valve from emptying the system in the event of a problem a high side R134a cut-off switch should be installed. Or better yet maybe put the resistor on the high side to make the BCM think the high side is hotter. This will kick on the fans sooner to lower the high pressure and turn off the system sooner. The fans turning on sooner may also inprove the A/C performance. The R134a tends to run a higher high side pressure. <P>Like I said I have not converted a Reatta yet but I'll let you know in a few weeks.<P>Tom

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Some cars the cooling fan(s) come on allways with the A/C. Other cars switch on the fans at a certain high side pressure. The Reatta and a few others use high side tempiture. The reason for not having the fans running all the time may be fuel econimy, less electrial load, better control of engine temp, faster warm up. Remember in the winter the A/C kicks on when the defroster is on to take the moisture out of the air. The car could take a lot longer to warm up.<P>Tom

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I took my Reatta to have it recharge with R-12 instead of using R-12 they converted to R-134 without my knowledge. After that the system keep telling me that A/C is low and need service. The system turn itself to low instead of auto or it doesn't work. I been taking it back and having it recharged. The last time was a couple weeks ago. Each time they can not find any leaks. I probably brought it back at least 6 - 8 times for the last two years. Must have spend almost $700 on it. I still don't know if it's going to work this time. MY ADVICE: DO NOT CHANGE TO R-134 THE SYSTEM PROBABLY DOESN'T RECOGNIZE IT.

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It sound like you have a leak they can't find. If they don't dye the system or have top quality leak detectors they may never find the leak. I don't know what they orignally did when they retrofitted. Did they replace any conponits or just fill the system not worring about leaks. A drier and reseal jop is allways a good measure for quality work in addition to replacing a bad conponit. I would try a different shop that specializes in A/C and radiators. Like I said before the sencers might need a slight tweeking with a resistor or updated to keep it working right. I would do it now but it's only 19'F here in Illinois. As for the blower not working at high speed in auto mode I would say it depends on the tempitures. It may be working corectly. I don't know all the details. It really does not have much to do with the freon. Except if it's hot out and the A/C is not working I think it is smart enough not to blow hot air on you in high mode. <P>I can't say if the shop is really required to tell you if they need to retrofit the A/C. They usually did around here to help justfy the time needed and cost. Under the Montrial Protical most industrial countries including Canida and the USA banned inportation and production of R-12. A lot of R-12 used for service is used run thru a recycle machine. Every salvage yard reclaims and sells off the freon to companies. The quality of the recycled R-12 depends on the machine (and filters) and the operator. Sometimes I did not get as good of resaults with recycled R-12. If you have the choice use virgin R-12 (or R-134a). <P>Sorry if your not happy with your A/C service. Your complaints would be the same if you used R-12 if you have a leak. These problems allways happened with R-12 too. No one cared as much when R-12 was dirt cheep. But once the A/C repair prices got to be as much as morgage payments prices up and they still have a small leak then the customer is mad.<P>Tom

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  • 2 weeks later...

Its going into the A/C shop this Tuesday morning. I will reply back about procedures, costs and performance when they are done. Who would ever think something like this could be this complex?

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this past monday I got sick of no A/C down here in florida, took it in for a 25$ diagnosis which came back as a bad compressor. Made an appointment to change the compressor (rebuilt), orifice valve, drier, flush and refill with r134a. cost would be 300$ with 1 year warranty. They opened up the system (I watched the whole thing) and the old orifice valve was completely clogged with "black death" from the compressor. The condensor was so clogged they couldn't even blow it out, so I had to get another one which was an additional 130$. Everything is working perfectly so far tho. smile.gif

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Tom I hope You do Your quickly as the weather here is getting warmer so I am going to have to get Mine going. The resister trick sounds like it could work. Let Us know.

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I have watched this topic with much interest. Currently my 89 A/C is working fine. I'm sure that the day will come when it is going to need A/C service. In the summer in my part of Texas, a 92 day is a cool summer day. I've looked at a number of "drop ins" for R12. The first thing I learned is there is no such thing as a drop in. The old R12 must be pumped out. Second those drop in all state that they are hydrocarbon based. While they state to be safe, their installation instructions make a point to say keep away from naked flame. A good idea with anything but it is something to watch out for. I did however run across a product called Freezone RB-276, <A HREF="http://www.freezonerb276.com" TARGET=_blank>http://www.freezonerb276.com</A> , that claims not to be flamable. Also it's temperture and pressure readings look very close to R12. I know nothing about this product other than what I read on the above noted website. It looks like it might be the answer to our R12 woes. Has anyone out there in Reatta land used this product?<P>Howard

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Just came back from trying to buy some Hot Shot from the local A/C supply store. They only had one can and told Us that it was being phased out and Freezone was now going to be the replacement. They did not have any info on it yet so I am not sure what it is about. They did state that it was better. We shall see. And for anyones info that is curious the Hot Shot is non flammable. The reason I was told in school to keep freon products away from open flame was because when it burns it creates phosgene gas which is highly poisonous. There are some replace gases out there that used propane as a propellant but they are being removed from the market for safety reasons. My advice would be to read the can and stay away from any that are propane propelled. Skip

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