Continuing AC problem

srwven on Mon June 02, 2014 9:48 PM

Year: 1989
Make: Ford
Model: Bronco
Engine Size: 5.0
Refrigerant Type: R12
Ambient Temp: 76
Pressure Low: 40
Pressure High: 150
Country of Origin: United States

Continuing from another thread, thought my AC problem was fan clutch with high pressures (may have been in addition). Anyhow AC will work then go warm after a few minutes. Was finally able to replicate it in the garage. What is happening after the initial cooling(vent temp drops to about 50F), the compressor cycles on for about 3 seconds then off for about 8-10 seconds and does this continually, with no real cooling effect( vent temp comes up to about ambient temps). The following readings are taken at 1500 RPM's. The pressure will build up to 40 on low side 120 on high side at which point the compressor kicks on, low pressure drops quickly to 20 while high side increases to 150 , compressor kicks off, pressure builds back up to 40 on low, high drops to about 120, compressor cycles on and this will continue unless I turn the AC off, allow both pressures to equilibrate (about 100), turn it back on at which point it will cool shortly then repeat this cycle.

Jag987 on Mon June 02, 2014 10:31 PM

It is most likely has a low charge. When the compressor comes on, the low side drops to 20 where the low pressure cut out switch does its job and turns off the compressor. Then the low side pressure builds back up as the system equalizes and it come back on. Recover the refrigerant and weight it. I bet it is below factory specs. Then refill it to the proper amount and your troubles should be over.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

mk378 on Tue June 03, 2014 10:48 AM

Once the refrigerant is out, open the line and check the OT for blockage. Low side pressure drops quickly then rises slowly could mean something is blocked. This can also happen with heavy water contamination in the lines, after a few minutes of normal operation, the water freezes in the expansion device and blocks it.

srwven on Tue June 03, 2014 11:16 AM

Thanks. Called four different shops today to find someone to evacuate it for me and they all state they are not setup to do R12. The low pressure comes back up quickly. It cycles on for 3 seconds off for 8 on for 3, off for 8... Shuts off at 20 on at 40. Think I may have lost some refrigerant due to HPV while I was without a properly functioning fan clutch?

Edited: Tue June 03, 2014 at 11:18 AM by srwven

Dougflas on Tue June 03, 2014 4:32 PM

where are you located? I have R12. I'm in Central west Florida.

srwven on Tue June 03, 2014 9:15 PM