On Fri, 21 Jul 2006 02:21:46 +0000 (UTC), Ignoramus10329
wrote:

I agree, Bruce, but what do you think about OP's problem?

Okay, quick mind dump, I'm not going searching for every detail.

Rule Number One: You have to use the most important tool you have
in your arsenal, everyone has one and it's free - it's that ~4-pound
lump of wet wrinkly gray stuff between your ears. The "wetware
programming" takes a lot of time, but it's worth the effort.

This (Stuff) isn't Rocket Science, you just have to think. Get a
clear handle on all the signs and symptoms, and all will be revealed.
When you get the right facts clear in your head and the proverbial
"Eureka!" light bulb blinks on, you'll know it.

On to substance...

The OP mentioned something about a warranty - if the unit is only a
few years old, he needs to call the AC manufacturer or the Compressor
manufacturer and have them get someone else, someone /honest/ out
there - BEFORE dinking around on his own, which might make it worse
and void the warranty. Tell the corporate rep the names of the first
two dinks, so they don't get called back.

The bigger service companies have specialized "Hermetic Compressor
Analyzers" that measure all the nuances of the start and run coils in
the motor - inductance, ground faults, inter-winding faults, etc., and
they'll pick up most flaky compressors, and tell you WHY they failed,
without opening up the can. And they'll flag voltage or capacitor
problems. You can even kick it in reverse to free up a locked rotor.

I never bought one because I was with a small company, and I don't
drop $300 to $700 on a whim. If you don't use them often...

Could be something as stupid as burned contacts on the main
contactor - when they cheap out and use the "1-1/2-Pole" contactors,
there is a single point of failure that takes all the abuse. The
stupid things are under $20 - some under $10, if the contacts are
visibly burned and pitted, yank it.

But DO NOT change to a 2-pole contactor and modify the wiring to
match without checking the wiring diagram - they might do something
stupid like run a compressor crankcase heater using the open-circuit
voltage going across the relay. (Just like a block heater on a car -
keep the oil warm so it will flow on startup.)

I still think it's a very bad practice to use a single-pole
contactor (the "1/2" pole is just a strap between the Line and Load
lugs) and leave 120V to ground power on the motor coils - too many
things can go wrong.

It is ILLEGAL to single-phase switch the power like that on a pool
pump motor because they don't like pool service men (who didn't
properly kill the breaker, or check that it's really dead) lighting up
like neon signs, I don't see why HVAC gets a break on that rule.

Make sure there is NOT a "Break Delay" timer in the circuit, or a
delay function on one of the fancy new furnace control boards that is
messing you up - they are installed so that kiddies can't play 'Toggle
The Thermostat' and blow it up by constant locked-rotor starts against
head pressure.

Same thing with hidden "Duct Limiter" thermostats that keep people
from setting the thermostat at 45F for a week (which the AC can never
reach) and turning the evaporator core into a solid block of ice.
Been there, Thawed that.

Unless they shipped a bad capacitor, you shouldn't need to change a
run cap for several years. If you ever have to change one and it
isn't marked as "Internal Resistor" (or even if it is...) have a few
1-Meg or 2.2 Meg 1/2 watt carbons handy, and red .250 female crimp
connectors for the leads.

Shorting the terminals is very hard on the shafts of your
screwdrivers, they start getting scorch marks. And unless you leave a
bleeder on it, a charge can build back up.

You really should not need to add a "Kick-Start" kit (start
capacitor and potential relay) to a new unit. That's a dodge for
getting an old and weak compressor to fire up for a few more years,
and will probably void the warranty on a new unit.

If a new - or fairly new - compressor won't start, there may be too
much head pressure on it, or there's a voltage drop problem. If the
condenser fan isn't working right, the high side pressures will go
through the roof, and take a long time to bleed back down.

Which reminds me, check for a high-side or low-side cutoff pressure
switch opening...

-- Bruce --


--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
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