Air conditioner temperature problems

NICKL

MEMBER
1988 OLDSMOBILE CUTLASS
2.8L
6 CYL
FWD
AUTOMATIC
79,000 MILES

Hi, I will be as brief as possible.
air conditioner was not working for a year or so. Installed R134A fittings, added Pag oil, dye and charged system. Compressor turned on and gauges read 35-40 / 200. But Dye was visible at compressor, so I replaced compressor, rec/dryer and orifice tube. Pumped down system for an hour, held vacuum overnight charged system. Could not get vent temperature below 60 degrees. Pumped down again, flushed system (all but compressor) recharged with same results. Pumped down again, hoping to remove moisture that may have been introduced with flush. No luck, added 2.8lbs of r134 again, olds calls 56oz refrig and 8 oil.
still getting 60 degrees vent temperature, condenser seems to be working okay, high pressure varies with water on condenser, fan turns on and off as expected. Evaporator had constant drip under car, almost a steam, and pressures are 45-55 / 220-260 when running 80-90 degree outside temperature and about 50% humidity. What is next? I am sure I am missing something. I work on all my cars (seven total), but I only know enough to get in trouble! Thanks fro the help.

5 Replies

HMAC300

MECHANIC
48,601 POSTS

One thing is if this is an 1988 Oldsmobile it took R12, not 134, but 134 can be adapted to r12, but it needs 80% of R12 charge not same as R12 so it should be 44 oz not 56 as you said you put in. Also if you have a thermostat with tube going into evaporator or on the out let pipe make sure it is covered with stuff to put on it to insulate it. I forget what it is called as it has been so long. Make sure all your water valves are cut off and not sending hot air in which air conditioner will try to cool as well as when on max that air door is closing and not allowing in air from outside. R134 may not get down much lower in a R12 system it may get to 50 degrees and finally how accurate is your temperature gauge. When sitting still engine should run at 1500 rpm, not idle and if ambient air is as hot as you say a fan should be put in front of condenser so it can cool the refrigerant down. Not just sitting there idling with only fan trying to pull air in.

SPONSORED LINKS

Was this

answer

helpful?

Yes

No

Monday, July 18th, 2016 AT 3:43 PM

NICKL

MEMBER
38 POSTS

Thanks, The thermometer is accurate, and I could not find a probe at evaporator or any
un-insulated lines from the orifice tubes to firewall. Sorry for the confusion, 56oz is R12 capacity, I added 45 oz of R134. I now get your point on rpm's and additional fan. Could that have been a reason it took twenty minutes to get the last 8oz of refrigerant in the system? I took the lower dash apart this morning, evaporator is mounted right behind heater core. So temperature probe may be there, but I can not see anything with the limited view. Could not find any mechanical heater core shut off, either physically or in any GM parts diagrams. Heater core does get hot, but temperature control seems to be working properly. There is no air flow through the heater core until the temperature control is moved off of the cold position. With engine at 1500 to 2000 rpm's and fan blowing on condenser, I get 55 degrees with thermometer resting on evaporator. But is 78 degrees and 45% humidity. Anything else I can do that may revel marginal parts? My very uneducated guess would be condenser if anything. Compressor, orifice tube and rec/dryer are new, evaporator is very clean nothing seemed to have any restrictions when I flushed the system. Thanks again for the help and education.

Was this

answer

helpful?

Yes

No

Tuesday, July 19th, 2016 AT 11:25 AM

HMAC300

MECHANIC
48,601 POSTS

Check both heater hoses one should be cooler than other especially if this has a water valve on it. If it does then there is no vacuum going to that valve. Also when put on max fresh air door should close and only take air in from car not outside. Also if you have one of those "bug screens" attached take that off and throw it away they are not worth anything for air conditioner they hinder it. Then check for condenser cleanliness even to inside and air draw. I cannot think of anything else at the moment. It may be the air door is staying open and allowing heat into evaporator.

Was this

answer

helpful?

Yes

No

+1

Tuesday, July 19th, 2016 AT 1:26 PM

NICKL

MEMBER
38 POSTS

I think I got it. Or should say you got it. Both heater hoses were hot, Since I can not find the shut off anywhere I added a ball valve in the heater hose line to the firewall. When driving at 30-40mph vent temp get to 48-50 degrees. Think that's as good as I can expect. This is my sons winter car, so he's gonna have to remember to open the valve when he wants heat. ONE last question, when I stop for a length of time vent temp creeps back up to close to 60, condenser fan is on. Is this normal. Thanks again for everything.

Was this

answer

helpful?

Yes

No

Wednesday, July 20th, 2016 AT 2:39 PM

HMAC300

MECHANIC
48,601 POSTS

R 134 in the r12 systems don't work really good be happy with what you have it's due to the design of one Freon system vs the other. Also i'm assuming you have a 4 cyl compressor vs todays have 5 so they pump better. Even with R12 your system would normally get 48 degrees which is considered good.