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  #1  
Old 04-21-2008, 03:27 PM
yhprum yhprum is offline
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Default 1986 AC cycling off/on

My A/C cyles off/on about every 5 seconds. Little if any cool air comes out. I used the refill can with the pressure guage on the blue filler port, shows normal then drops to low when the pump comes on. Do you think I am over serviced or under? It doesnt seem to take any additional refrigerant.
Thanks
Steve
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  #2  
Old 04-21-2008, 10:52 PM
dougs85 dougs85 is offline
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I'm assuming your A/C has been converted to R-134a, because that's all you can buy now unless you are a licensed shop. If your A/C has NOT been converted, you are putting in the wrong refrigerant. Anyway lets say you are using the right stuff, the correct pressure on the R-134a refrigerant is with the compressor running, 25-45 PSI. Turn the dash control to max, temp on low with the fan on high to keep the compressor on. The compressor will cycle much less with the proper fill.

Do you know if your A/C system has been converted to R-134a? If it has and was converted by a licensed shop there should be a label on the compressor or the A/C box stating so. Otherwise it probably has the old R-12 refrigerant.

Doug
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  #3  
Old 04-22-2008, 07:51 PM
mhamilton mhamilton is offline
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First, throw away the parts-store recharge kit. You need high and low pressures to work on an a/c system. You could be trying to feed refrigerant into a system that is about to blow the high side right off.

That said, rapid cycling usually indicates a low charge. I suggest you see what the high and low sides are reading, then if necessary add refrigerant. Your best bet is to have it all recovered, and charged back by weight.

Also, don't try any kind of magic in a can, stop leak, etc. That is guaranteed to kill a system. If you have a leak, fix it properly, then evacuate and recharge.
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Old 04-22-2008, 08:48 PM
dougs85 dougs85 is offline
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As usual Michael has given good advice. The rapid cycling gave me a clue for low charge. Did not know you could have too much pressure on the high side and at the same time too little pressure on the low side or am I misinterpreting something?

We still don't know what refrigerant is in the system, or at this point a mix?

Doug
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Old 04-23-2008, 07:25 AM
mhamilton mhamilton is offline
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It's possible, if say there is a restriction in the high side. The compressor could be ready to blow the relief valve, while the low side is going down into vacuum. Never good to charge just by the low side pressure.

I'd also guess this is an R134 system, since as you said, the part stores don't sell R12 recharge kits anymore.
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Old 04-23-2008, 10:31 PM
lsrx101 lsrx101 is offline
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+1 on what Michael has said. The issue is most likely a low system charge.

Your 86 may or may not have been converted to R134-a. If the cheapie "fill kit from the parts store" attached to the low side fitting, you can assume that someone has at least installed a Death Kit.

Because of the unknown quality of the R-134A "conversion" and the fact that the system is leaky (low charge), a total system service is needed to get you back to zero. The fact that the R-4 compressor hasn't self destructed leads me to believe that the "conversion" was done at least halfway correct

You can "recharge" the ac with R134A and it may work for a while, but the R-4 compressor in that system is basically a weak sister from day one. Improper service WILL cause it to fail catastrophically eventually. When that happens, you will be looking at replacing everything under the hood, from the evaporator outward.

Right now, you need to flush the system, reseal all of the line fittings, replace the accumulator and orifice tube, add the correct amount of the correct oil (Ester or DEC PAG for R-134A) pull a strong vacuum and recharge the the system with refrigerant.
R-4 compressors are habitual shaft seal leakers, so you might want to consider a good quality reman or New compressor also. (Cheap chain part store remans often suffer from shaft seal issues).

Not what you wanted to hear, but I hope it helps.
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  #7  
Old 04-30-2008, 10:33 AM
yhprum yhprum is offline
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Thanks for the tips, I have been away for awhile. I did get it to take a charge by jumping the low pressure switch. Now there is no cylcing and the air is cool. I did that a few days ago, will be checking to see if it lost any charge.
Steve
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  #8  
Old 05-05-2008, 03:25 PM
yhprum yhprum is offline
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Well, I'm back to cycling off and on. I think the compressor is leaking, there is a slight oil stain on the front.
What/where would be a good place to go for a new or overhauled compresssor and drier? Do I need a new expansion tube or anything else to do a proper conversion to R134? I will get the proper guages to do it right.


Thanks
Steve
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  #9  
Old 05-06-2008, 08:15 AM
mhamilton mhamilton is offline
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I suggest you buy a new R4 compressor, the quality on the reman ones is poor, and on a marginal compressor, you'd be doing the job again shortly. I installed a new R4 on a K1500, and it only cost a little more than a good reman. I highly recommend www.ackits.com

If you had a working system, it may or may not need to be flushed. That will depend if you find any junk in the lines, or trapped at the orifice tube.

If you decide the system is clean, and not to flush, then you should replace the orings, orifice tube, flush the new compressor with fresh oil of the same type as the system, and you will be good to go. Arizona Air I mentioned sells kits of orings, only a few dollars, and the orifice is 60 cents. Do you know what type of oil you have in the system?

If the system is full of debris, now is the time to take it all apart and flush everything (except compressor) with lacquer thinner or brake parts cleaner. Pretty easy to open the evaporator box and clean the coil and dirt, makes it easy to flush the evap. Then add fresh oil and put everything back together.
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