I have an 8yr old Trane TTB042D100A 3 1/2 ton outdoor unit that suddenly died and will trip the breaker INSTANTLY when it starts. No hum or anything. Was working perfectly before. Wiring, low voltage, etc, checks ok.

The GE cap looks good and specs out 5/40uf.

There are no shorts to the case or lines from the terminals, but the compressor windings measure around 1 ohm or .2 ohms depending on which terminals you measure. Seems low, but I don't know the spec.

This is the tricky part, usually there is a short to the case that would cause the trip. That is why I still have hope.

Do you think a start kit can help this or its time for a new compressor? One tech said if it kills the breaker instantly its finished. Is it possible for a cap to spec out and cause this issue?

There may have been surges cause other electronic things were ruined around that time, but the A/C could be coincidental.

Did you measure the resistance across the power leads?

Did you measure the resistance across the power leads?

You mean the power to the Compressor? Yes, there are 3 terminals. - start, run and common.



S- R is 1 Ohm
S - C is 1 Ohm
R - C is .04 Ohm (close to short on the meter)

Schematic:

s - (coil) (Resistor) - R
S -(coil) (Resistor) - C
R - (coil)(overload switch) - C

I believe now the coil is shorted, the resistance seems very low.

Those readings are way too low. That's why it keeps blowing the circuit breaker.

Those readings are way too low. That's why it keeps blowing the circuit breaker.

It was an electrical surge, so its an insurance issue now.

Thanks

You could install a whole house surge supressor on the main electrical lines to help prevent things like this in the future.

You could install a whole house surge supressor on the main electrical lines to help prevent things like this in the future.

Great minds think alike, I'm off to buy one later this afternoon. I'm getting either the intermatic or the Square D.

It sounds like either you need a hardstart Capacitor or you might have a bad compressor or your compress might be on thermal lockout
Things to check if the compressor goes on thermal lock out
The compressor surges and the fan is running and the compressorwill not start.
you have to cool the compressor down with running water. And yuo have to fiind out why the compressor overheated. Most likely your fan is not running. when the compressor not on.

Things to check for a bad compressor[/B]
Check the thermal on the compressor each to ground
if they ring out you have a bad compressor
another way to check is if you disconnect the compressor harness from the compressor and you reset the breaker see if the fan comes on then then.