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84 mercury wagon blows cold but always cycling?

drhill on Mon June 25, 2012 2:54 PM User is offline

Year: 1984
Make: Mercury
Model: Colony Park wagon
Engine Size: 5.0
Refrigerant Type: r-12
Ambient Temp: 96
Pressure Low: 32
Pressure High: 280
Country of Origin: United States

Hello everyone,

Having a strange AC issue. Recently purchased this wagon and compressor didn't come on but had a bit of pressure in the system so I charged it a bit to see if it holds pressure. It did but was low, cool vent temps (approx 60 degrees at 101 ambient, high side 250 or less, low side 30 at idle, dropping to below low side cut off upon higher rpm (1500-2000rpm).

Today I charged with more freon figuring it's still low. Vent temps are in the low 40's at idle and pressures as you see above (taken at high idle, low side is approx 48 psi at regular idle). The system will not cut out at 1500-2000rpm stationary with the gauges hooked up but once I drove it, i could feel the compressor clutch cycling.

I'm confused because it cools so well. I don't know why the low side keeps dropping so much. I am a bit scared to add more freon because of the high side pressures! it will get above 300 if I just let it idle in the heat.

What is your advice to keep the clutch from cycling while driving?


buickwagon on Mon June 25, 2012 3:04 PM User is offline

Read more.

If your car has a CCOT system, it's behaving exactly as it is supposed to.

I've saved hundreds on service by spending thousands on tools.

mk378 on Mon June 25, 2012 3:27 PM User is offline

It's designed to cycle. If the compressor stayed on all the time, the evaporator would over-cool and freeze ice on the outside, blocking the airflow.

So quit charging, you can probably just wait for the excess to leak out. Look for leaks.

drhill on Mon June 25, 2012 3:52 PM User is offline

Thanks. I should have been more clear with my question, in addition to asking if there is an issue, I should have said: "what can I do to keep my compressor from cycling so frequently?"

I've had these cycling systems before and I never seemed to notice the cycling so much while's on and off within 5-10 seconds not the 45 sec or so I have read is normal. That's why I am inquiring. I may have put too much charge in to compensate a bit but....that's why I am asking , to get opinions from those in the know.


Edited: Mon June 25, 2012 at 3:53 PM by drhill

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