Heat Pump stops while cooling (before reaching temp set on thermostat)

My father-inlaw (82) has a heat pump that is behaving badly. If I pull the power, and replace it, after a few minutes, the unit will start to cool. It will run, sometimes for a good amount of time, before shutting down. I've replaced the capacitor for the unit, and I've replace the motor for the fan above the compressor. I've changed the batteries in the thermostat. The be havior hasn't changed. I have other symptoms. Sometimes, right after the un it stops cooling (before it reaches the set temperature on the thermostat), I will find it shaking, with only the fan, deep in the machine, running. O ther times, when the unit stops while cooling, and a deep electrical sound which sounds like the compressor still running, is happening. I have pulled the power and a huge relief of pressure occurs.
The machine is a Coleman, circa 1986, and I want to figure this out. Does a nybody have any ideas what I can do next, or what the right answer is? It's not the capacitor, it's not the batteries, and not the fan above the compr essor.
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The right answer is too replace the 32 year old piece of junk.
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On Tuesday, 17 July 2018 19:40:52 UTC-7, catalpa wrote:

I hoped comments in this forum would be helpful. I know what I'm working with, and that replacing the relic may be the best option, but I'm not considering it.
For the helpful ones, I've narrowed it down to the condenser contactor. I'm thinking I can find one locally. Thoughts?
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On 7/18/2018 9:09 AM, snipped-for-privacy@gmail.com wrote:

Please post the Launch date. Stupidity of endangering yourself and family is to be applauded.

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