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A/C System Help!!

avr3600 on Sat September 13, 2008 8:08 PM User is offline

Year: 1971
Make: Oldsmobile
Model: Cutlass Supreme
Engine Size: 455
Refrigerant Type: R-134a
Ambient Temp: 70
Pressure Low: 26
Pressure High: 250
Country of Origin: United States

Hey Guys

I am in need of some serious A/C Help. I have a 1971 Oldsmobile Cutlass Supreme with a 455 engine. I recently had some problems with the POA Valve And Compressor. I have replaced the POA Valve and adjusted it to run 134a, also a new compressor. I vacuumed the system for one hour and checked for leaks. Then proceeded to charge. It only took 2 12oz cans and was barely cooling low was around 26- 28 high was 200. My High side line blew apart. since this happened I checked the muffler in it nothing clean as a whistle. I really am at wits end. the last two parts are the evaporator and condenser. Any input would be greatly appreciated. Thank You In Advance.

mk378 on Sat September 13, 2008 8:42 PM User is offline

Hose may have blown out just because it was old. A high pressure cutoff switch needs to be installed on all conversions to reduce the risk of blown hoses when something goes wrong like lack of condenser airflow. Along with that, how old is your fan clutch? It takes a lot more air for good A/C performance than is needed just to keep the engine at normal temperature.

You need to get a full charge for proper performance. It will continue taking R-134a as long as the low side is less than the pressure in the can, which it was.

Also consider the possibility of excessive oil. You need to change your receiver-drier (again, I hope, because R-134a must not be used in a 1971 R-12 drier) since the system was sitting open from the blown hose.

chris142 on Sat September 13, 2008 10:29 PM User is offline

Definatly sounds like a fan clutch problem for starters. If the hose blew @250psi you need to replace them all.

Chick on Sun September 14, 2008 6:43 AM User is offlineView users profile

I would pull the expansion valve, as I suspect you may have used the old drier?? And as mk378 said, you can't use an old drier, it may have come apart and clogged the expansion valve with desiccant...Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

avr3600 on Sun September 14, 2008 10:19 AM User is offline

avr3600 on Sun September 14, 2008 10:30 AM User is offline

Hey Guys
I should have mentioned That I replaced the TXV, Drier, and liquid line hose for 134a. The Only 4 old things in the system are the condenser, evaporator, highside line hose that blew and suction line hose that is still in service. There is no clutch for the fan it is direct drive to the water pump. I didn't charge it anymore because the highside was at 250psi. Thats when the line blew. What operating pressures should it be at. Also, the whole system was flushed prior to assembling and tested it. I hope this additional information will help narrow down the Problem. Please help with my costly dilemma. Thank You

P.S. Thanks to this forum I know more then the stupid guy that sold me the system. Thank You

Dougflas on Sun September 14, 2008 10:54 AM User is offline

Way back then when I used to install add-on-systems, they usually came with 5 blade fan blades to replace the 4 blade most vehicles had OEM. You needed more air across the condensers. Check that option out. I also used a 20 inch box type window fan as a tool when working on a system. Just placed it in front of the grill; usually I placed it on top of a 30 lb of R12 that was still in the shipping box.

Even though you have a new TXV, do the test for it. Place the sensing bulb in your hand and you show be able to blow thru it. Then place the bulb in crushed ice and water mix and you should not be able to blow thrru it. I do this every time before I replace a TXV ever since I had a new stuck TXV.

You have hoses that are 35 plus years old. I would have renewed them from the git-go.

avr3600 on Sun September 14, 2008 5:49 PM User is offline

What sort of operating pressures should it be at. Is it possible that the condenser has a blockage in a core that lead to blowing the hose. I will Deff. check those things out. When i pulled the high side hose it was really hot, even 5 min later it was still too hot to touch. Is That normal. Thank You

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