Cannot get freon to add

[MatA3500]

I have the high side and low side hoses connected and the freon can connected and punctured. The AC is on max and the fan on high in my '96 ranger 3.0. When all 3 valves are opened, the ac continues to cycle on and off every few seconds. The low side pressure will go up to 70 - 80 psi and then the ac will go off and the pressure will drop. This continues to repeat, but no freon seems to be exiting the the can. I have shaken the can and put it in a pan of hot water. No luck.
The ac cools some, so I think it works.
Any idea what I am doing wrong?
Thanks,
Rich

 

[Maniak]

All 3 valves open? I hope you don't mean you have the high and low pressure line open while your trying to fill the system. You do not want that high pressure coming into the can as your trying to fill it. It will, at best, blow the bottom or top out of the can of r-134.

When you first start filling a freshly evacuated system (removed air and moisture) you should be able to get close to 1 can into the system with the vehicle off since there is a vacuum within the system. You can put it in via both the high and low side now, but I normally don't.

Once you get enough pressure into the system you can't put any more into it with the vehicle off.

At this point you you should only have the low side connection open. The high side line should be connected but the valve for the high side, at the manifold (gauges) should be closed.

Now, with the vehicle running you should be able to get more r-134 into the low side when the compressor is running. If there isn't enough pressure in there to keep the compressor running you have to use a jumper wire and jump over the low pressure switch. Once you get enough in the system the compressor will run on its own..

There is a good how to sticky at the top of the a/c section about retrofitting/charging a system for more detailed info.

I'm also moving this post into that section since its fits there better.

 

[Blee1099]

70 psi on low.. thats over double what it should be

 

[Maniak]

70 psi is right, if the system is off and its 70F oustside. Now, if the system is running and its getting 70, then yes.. thats way high.

~Mark

 

[Blee1099]

i was always told less than half of the ambient air temp

 

[Maniak]

i was always told less than half of the ambient air temp

Well, you were told wrong There was just a thread about this recently about the correct pressures. It was an r-12 pressure thread, but ambient temp (at condensor) did come up.. Also, in the how to recharge a-z thread http://www.explorerforum.com/forums/showthread.php?t=158183 you can see the equalized pressure on a non running system is about 92 in the pic.

~Mark

 

[MatA3500]

First, thank you very much for the reply.
There was very little information with the gauges that I purchases, but I did not think that opening the high side valve would do anything other than allow the pressure to be measured. Does it actually allow the pressure go to the can? If so, I am probably quite lucky, as I have had both the high and low side valves open when trying to add the freon.
When I get a chance I will try it with the truck shut off.
I let you know what the results are.

Thanks,
Rich

 

[Maniak]

There are 3 valves on the gauges themselves and 1 on the end of each hose..

The ones at the end of the hoses allow pressure from the system into the hose and up to the valve on the manifold.

The red (high side) valve on the gauge itself should not be open when the system is running as that allows pressure to go from the can to the high side hose which is connected to the high side of the system but the high side of the system is higher pressure so it would push the pressure back into the can. There is a cutout relief on the can, but when they go pop its still scary.

I think you have a handle on that part now.. When your bored, read the a-z recharge thread.. Heck, the converting threads are good too.

~Mark

 

[MatA3500]

Found the problem.

The comments caused me to look more closely at the area around the gauges. There, imprinted in the plastic, was a comment that the low side gauge would turn to open for filling or close for just checking pressure. The high side only measures pressure and does not open to allow pressure to enter the can.
So, I was missing one of the valves that need to be opened. When I turned to low side gauge to open, the system filled nicely and required a little less than a can of freon.
Although indirect, your answers were the answer. I certainly appreciate your help.
Rich