Automotive Air Conditioning Information Forum (Archives)

NTL1991 on Fri June 22, 2012 2:21 AM

Year: 1998
Make: Oldsmobile
Model: Regency
Engine Size: 3.8L V6
Refrigerant Type: R-134a
Ambient Temp: 80*F
Pressure Low: 35 PSI
Pressure High: 215 PSI
Country of Origin: United States

Hello,

I recently replaced the original V5 compressor in my '98 Olds Regency because the clutch bearing was failing, and nobody would touch just the bearing, even though the compressor was mechanically in perfect shape. I installed a rebuilt V5, balanced the PAG oil quantity, replaced the suction/discharge hose assembly (which had a nick in the rubber foam from the pulley rubbing on it -- the hose wasn't secured properly), replaced the orifice tube and accumulator, and pulled a vacuum before charging. All per the factory service manual.

The air works exceptionally well. The last time I checked the pressures and discharge temp, I was getting spot-on high/low pressures (according to the FSM), and a colder discharge temp (39*F at 80*F ambient w/ 60% humidity). The car cools quickly and stays that way during both quick and long trips.

I noticed that I am getting a good bit of frost accumulating on the bare metal portion of the liquid line, and also the top of the accumulator. The bottom of the accumulator is usually all beads of condensation. There is no frost on the high side lines at all. The evaporator (from what I can tell) isn't freezing up or anything; I get a constant supply of cold air, even after an hour of use. I'm getting A LOT of condensation from the evaporator drain.

I'm thinking this freezing is due to the fact that the climate control almost never uses full fan speed unless I put it in manual mode (as it's programmed for the quietest operation), and once at the setpoint temperature, will bring the blower speed down to only about 15%, sometimes even mixing in heated air to keep 70-75 degrees in the cabin. I'm thinking this lack of airflow is what's causing the buildup on the line. I haven't tried operating the A/C at full cold with full fan to see if the frost buildup slows or stops.

Any ideas?

Thanks,
Nick

GM Tech on Fri June 22, 2012 6:44 AM

So what is wrong?? Frost is perfectly normal in high humidity conditions-- it is frosty underhood while you are standing there looking at it with hood up-- but chances are great that while driving with hood down, the frost is gone- due to engine heat. Lots of water condensation is great!! means it is working great- yet you don't like that....or think that is bad....As long as evap is not freezing, I would not be concerned- the system is right on the border where it can perform its best-- mechanics (and engineers) strive to "dial it in" right at the point you describe.

If the original problem was a scrapping metal on metal sound (and not a grind) then you had the low air gap issue- which is a very simple fix- many mechan ics have changed a pump for the "V-5 classic clutch drag" sound. google it for a vivid description.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

NTL1991 on Fri June 22, 2012 12:18 PM

Thanks for the reply. The reason why I posted here was to find out if the frosting was normal. If it wasn't, I'd find out from a pro like yourself what the problem was... I'm not a pro, just a car owner. I am posting my observations simply because they weren't occurring before with the old compressor. I wasn't getting as much condensation, and I wasn't getting any freezing. I never said that I didn't like all of the condensation, it's simply that it wasn't happening before... I've learned over the years that small details like that can really help out when diagnosing a problem. I'm just here to learn.

The noise was a high-pitched scraping noise and it would only happen with the compressor disengaged. I removed the belt, spun the pulley and assumed the bearing was shot from all of the resistance and noise... It was getting louder and louder and during the winter the sound was unbearable (the compressor was locked out due to low ambient temperature), so I removed the compressor and replaced it with a bypass pulley. It does make sense that the noise could be caused by the air gap being too small... Hey, at the very least, I have a spare compressor....

Nick

Edited: Fri June 22, 2012 at 12:20 PM by NTL1991

GM Tech on Fri June 22, 2012 5:47 PM

I could have fixed tha old compressor on your car for $30-- the key is that it makes the noise with a/c off.....so you had the clutch drag noise- there is not a thing wrong with the old pump- just needed and adjustment of the air gap..

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

NTL1991 on Fri June 22, 2012 9:33 PM

Yeah, I was thinking that when the compressor engaged, it was changing the amount of pressure on the bearing, causing the scraping sound to stop. Live and learn.

I'm glad I did it, though. I was really surprised at the amount of gunk on the old orifice tube... For a system with no leaks or compressor failure, it was pretty bad. (Of course, not knowing what a typical 14 year old orifice tube should look like under conditions). Now I also know the oil is new and the correct quantity...

I've got a couple of GM specific questions for you, GM Tech.

I've have a '93 Corvette Convertible which is still running R-12. No leaks, and it blows cold. I've heard of cooling issues when converting these C4's to R-134a, and most say that while the R-12 system is right on the edge of being sufficient, converting to R-134a won't keep the interior cool enough on hot summer days. Are they right? Should I just bite the bullet and keep R-12 if/when a leak occurs?

My other car is a '97 Eldorado E-body. I have a slowish leak (I'll charge it once a year, during the summer), but I've tried using UV dye and an electronic sniffer, and neither have found the leak. My fear is that it's in the evaporator core which means dropping the Northstar to remove the evaporator through the firewall. Are there any common leak points on these cars to look out for? I'd like to get the leak fixed once and for all; it's frustrating when you're trying to charge the system, and you realized that you've forgotten to reset the ACM to re-engage the compressor...

Also, why would GM use a normal cycling compressor rather than a variable displacement? It doesn't seem fitting to have a smooth, always on compressor in my Olds, yet a compressor that's cycling on and off in the Caddy...

Thanks,
Nick

GM Tech on Fri June 22, 2012 11:25 PM

Compressors always follow the engine...variable stroke are for fuel economy 3.1 and 3.8l engines (4 cyl and 6 cyl engines) etc-- big caddies (v-8 engines) Northstars - get HD series until the scrolls came along in about 2000..

V-5 classic clutch drag noise has nothing to do with the bearing-- it is the sound of the armature plate scrapping the pulley face due to the air gap being zero.(notice the iron filings on the front of the drive plate


...the rivet head stops (what the springs pull the armature drive plate back against) have corrosion built up behind them which increases the stop height and does not allow the drive plate to fully retract in the disengaged position. The issue started because the drive plate was e-coated as an assembly and there is no e-coat behind the rivet heads- it is bare metal which corrodes- rust builds up and increases the stop pad height- and soon the stops are so big, there is no longer an air gap- hence the scrapping sound. Clutch drive armature plates that were e-coated prior to assembly (early 90's era) did not have this annoying failure mode. Mechanics (with boat payments) will gladly rid you of your dragging clutch by changing out the compressor- while the easier answer is to understand the failure mode and just borrow the clutch puller tool from autone and crank the air gap out to .020"

your E-body has a compressor belly leak- you can bet- those non-painted compressors were famous for corrosion crawling in and under the o-ring sealing surfaces and causing leaks-- I reseal a couple a week...



Keep the corvette R-12--if you want it to cool right....any corvette/caddy owner can afford a little R-12


-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

NTL1991 on Sat June 23, 2012 8:09 PM

Great info, Thanks!

I'll probably rent the tool and adjust the old compressor gap so I'll have a good spare ready to go if someone with an H or C-body needs one...

I'll have to check the bottom of that HD6 for any oil residue. If it's the compressor, I'd rather bite the bullet and replace it over dropping the engine to replace the evaporator...

And I'll make sure I won't let anyone talk me into converting the Vette.

Nick

belaneni on Mon July 02, 2012 2:30 PM

Hi,
I would like to know, how can you reseal the compressor belly leak. Mine is a V-5 from a 99 pontiac bonneville.
Thanks

GM Tech on Mon July 02, 2012 7:18 PM

buy the kit online and folow instructions

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......