AC Repair and Conversion Questions

[hawkfan]

My AC compressor is 'howling' like it has failing bearings and the air isn't getting all that cold. I'm thinking of replacing it, the accumulator, orifice tube and switching to R-134. Is this a diy type of job, or should I just but the parts I want and take it to a shop? I'm looking at this kit from Gbodyparts:

http://www.gbodyparts.com/product_info.php?products_id=745&osCsid=600f0d6c2423375e50dd8be427118136

 

[klmnla]

If I did it, anyone can. Go to Harbor freight and get a set of AC gauges and get the larger vacuum pump to properly pull the correct vacuum. Search for the step by step instructions and print them out. Flush out the lines, evaporator core and the heater core before installing the new parts. My evaporator core was too nasty, so I replaced it too. The only original parts on my system are the 2 main AC lines and the heater core. Remove the schrader valve from the new accumulator if you install the 134 adapter that has the schrader valve in it. I drained the oil out the new compressor and added 4 oz of PAG 100 to the compressor and 2 ozs into the accumulator before installing. Once you vacuum down the system to -30hg for about an hour, and then make sure you don't lose any vacuum for about an hour, run the pump again before attaching the gauges and installing the freon. Charlie on this board is a good source of info on this topic. he helped me a lot. I just replaced my 4 seasons compressor right before the 2 yr warranty ran out. Everything went in and charged up well.

 

[hawkfan]

Thanks. I found out the AC had already been converted by one of the previous owners. I charged the system hoping that would stop the groaning/howling, but no change. I went ahead and ordered all the parts. I may just take it to a pro to get it evacuated and flushed, change all the parts, and then take it back to get it pressure tested and charged. It's a shame because the AC runs fine besides the bearing noise. But I don't want to risk the compressor seizing on the road or in traffic.

 

[klmnla]

I hope it works out. I know we all try to do as much of the work ourselves to keep from going broke, but the AC system can be tricky, and it cost too much to waste 1 oz of freon.

 

[Joeld]

What KLM said, I just posted on this topic. I went from r12 to 134. I replaced the seals on the compressor. I replaced the accumulator I replaced the orifice tube. I purchased the gauge set from harbor freight, I purchased the vacuum from them for my compressor. I pulled vacuum. I charged with ester oil. I them charged with 134. My AC is ice cold and now I have the tools to do systems going forward.

 

[84BuickGNYorkPA]

Same over here, harbor freight gauge set, vacuum pump that ran off my air compressor, also took my lines to a radiator shop and they replaced the rubber and reused the aluminum fittings.

Chuck

 

[hawkfan]

Ok, so I replaced the compressor, accumulator, and orifice tube. Made sure to put Pag 100 in both the compressor and accumulator before install. I took it to a shop to get it vac tested and charged. They said everything went fine, but the 'howl' is still there and the AC started blowing warm again. I saw that my tensioner was just outside it's window of operation, so I replaced the belt and got it back within spec, but the bearing like noise is still there after the AC has been on for a while. I can't localize the noise, but it only happens after the AC has been on for a while(5-10 mins) which is why I suspected the compressor in the first place. I also noticed the compressor clutch does not cycle off and on like I would expect. It just stays on whether it's on max or norm. However, the clutch shuts right off when I pull the connector off the accumulator switch.

 

[wiseman]

This is a good reference to follow:


http://www.gnttype.org/techarea/airconditioning/R12toR134a.html

 

[klmnla]

These compressors dont cycle on and off like you see many AC systems do. However once you convert, you should adjust the low pressure cutoff switch to about the 20 or 25lb cutoff spot. I am having the same problem with my second new 4-seasons compressor. Blows cold, but is very noisy after its on a while, sounds like crap.

 

[turbodave231]

The GM R4 compressor is a fixed displacement compressor and normally cycles on and off. Under most conditions it should cycle on at 45 psi low side pressure and off at 25 psi. As you know,the pressure cycling switch on the accumulator controls the cycling. If it is really hot and humid,the compressor may stay on for extended periods and it may seem like it does not cycle. This happens because the system is working hard to remove heat from the evaporator.

The low side pressure may not be getting to the 25 psi needed to kick off the compressor. Best way to diagnose is to hook a gauge set up and watch the low side pressure. Operation in the 25-45psi on the low side is what you need. High side pressure will vary greatly based on ambient conditions......so I can't give you exact numbers.

 

[Joeld]

great reply
tough to do ac without gauge set
joel

 

[hawkfan]

Thanks for the replies. I 'tested' the AC before it officially got 'hot' here in the South and the compressor has never cycled. What's strange is the exact same noise was there even with the old Delphi compressor. But the noise and the AC getting warm happen around the same time. The noise is hard to describe and hard to localize. I'll fiddle with the switch adjustment a little and see if that helps at all.

 

[Joeld]

use a long handled screwdriver held to your ear and touch stuff with the other end. great way to find noises.
be very careful around moving parts
joel

 

[turbodave231]

If the compressor never cycles off, the high side pressure maybe climbing extremely high (over 400psi). Compressors get noisey when forced to operate under those conditions. A bad pressure cycling switch could cause the compressor to stay on.

 

[hawkfan]

If the compressor never cycles off, the high side pressure maybe climbing extremely high (over 400psi). Compressors get noisey when forced to operate under those conditions. A bad pressure cycling switch could cause the compressor to stay on.

Yep, I figured as much. I backed the adjustment screw almost all the way out and no change. The compressor stays on the whole time. I'll get another switch and see if that works.

 

[wiseman]

Does anyone have good P/N for the cycling pressure switch?

Posted from the TurboBuick.Com mobile app

 

[hawkfan]

Does anyone have good P/N for the cycling pressure switch?

Posted from the TurboBuick.Com mobile app

I just put one on a week ago. PN 15-2151. Here's a link. It's cheaper at Rockauto though:

http://shop.advanceautoparts.com/we...efrigerant-pressure-switch-acdelco_18052658-p

 

[wiseman]

I don't think that's it.....? I was looking for the low pressure cycling switch that goes onto the dryer.

Posted from the TurboBuick.Com mobile app

 

[hawkfan]

I don't think that's it.....? I was looking for the low pressure cycling switch that goes onto the dryer.

Posted from the TurboBuick.Com mobile app

That's it. I know the picture doesn't look right but this was the one I ordered. I just typed in the same PN on Rockauto.com to compare prices before I ordered it. The switch I received from Rockauto looked just like the switch I took off the dryer, plastic threads and everything. Here's an accurate pic from Amazon to compare:

http://www.amazon.com/ACDelco-15-2151-Conditioner-System-Switch/dp/B000C9C3N6

 

[wiseman]

ok, thanks for the input!