Rooftop Air conditioner

[larry dtimothy]

My Rooftop A/C compressor was kicking out after 3-4 seconds. While
looking it over for what I don't know, one of the leads to one of the
three capacitors broke. We found the A/C to work perfectly without that
wire attached. The capacitor was replaced and the A/C works fine whether
the wire is attached or not.
Now my question is what the wire is supposed to do. I know this is not
much information to work with, but I don't know how to identify which
capacitor does what, let alone which wire is which.
Just in case You haven't guessed by now, the extent of my knowlege of
Air Conditioning is that it's supposed to blow cold air.
Thanks for any wisdom, speculation, or whatever You might offer here
Tim Timothy

 

[larry dtimothy]

> Tim
> There are 3 capacitors you say.
Yes, Three.

> Cap 1 is a start cap for the compressor, If this one is bad compressor
> will shake and shimmy when trying to start.

Per the paperwork I have available, the start capacitor is the round
cased one of the Three. It starts normally(I think), NO shaking or
shimmying like it is having trouble getting underway.
Can't hear "click" - posssibly due to noise of compressor/fan motor

> Cap 2 is a run cap for the compressor, if this one is bad the >compressor will fire and try to run.It will sound like it is changing >speeds the pitch of the sound will go up and down. On a cool day it may >be able to run. Once head presure builds on a hot day it wont be able >to. Again out on thermal overload.

The best I can tell from the paperwork and what I understand that You're
saying, this is our culprit. It is the largest of the three.
(30uf)
The wire in question goes from here to what appears to be a relay.

> Cap 3 is a run cap for the fan motor. Again I have not looked but
> it should be the smallest of the 3. You might get things to work
> with a lead off this one. The problem is that the fan motor will not
> be operating at its design speed. This will cause head preasure
> to rise------ok on a cool day not on a hot. Everything will have to
> work harder.
The fan motor alone seems to work fine even with the old capacitor
installed and the wire hooked up.

> A word of warning here If you do not know your way around these
> things be careful-----they can hurt you. Before touching a cap
> put a screw driver accross the two connections to discharge it.
> These thing will hold a charge for a long time. Touch both
> connectors and you will be picking yourself up of the ground.
> At our ages you could do worse. Just short it out before you
> play with it.
Yessir!! Buddie!! Correctomundo on the homemade lightening!, if
I decide to learn a little about this I'll get a discharge
thingie.
> Take Care
> Arch
Thanks Arch,
And I enjoy your writings. I see no "rambling" as You say.
Tim

 

[mr.c]

I don't know for sure based on what you said, but the capacitors are
usually starting capacitors for the motors and are disconnected when the
compressor comes up to speed. It is an aid to getting them going, and they
can start by themselves but it makes them easier to start. I hope that is
what the capacitor did that you were talking about.
Al Chernoff

> My Rooftop A/C compressor was kicking out after 3-4 seconds. While
> looking it over for what I don't know, one of the leads to one of the
> three capacitors broke. We found the A/C to work perfectly without that
> wire attached. The capacitor was replaced and the A/C works fine whether
> the wire is attached or not.
> Now my question is what the wire is supposed to do. I know this is not
> much information to work with, but I don't know how to identify which
> capacitor does what, let alone which wire is which.
> Just in case You haven't guessed by now, the extent of my knowlege of
> Air Conditioning is that it's supposed to blow cold air.
> Thanks for any wisdom, speculation, or whatever You might offer here
> Tim Timothy