Trane A/C -- I'm running out of ideas


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Old 05-11-24, 03:15 PM
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Trane A/C -- I'm running out of ideas

I have an older Trane system, manufactured in 1996. It's been chugging along pretty well, until a few days ago. Symptoms are: the air handler in the basement kicks on, and the outdoor unit hums gently but the compressor does not start, and no fan action at all. The contactor does engage.

Specs:
Trane series XE1200 200/230V, 60 Hz, 23 amps
Model TTP042C100A3
Dual run cap 40/12.5
Start cap 135-162


Here's what I tried:
1. Installed a new dual run capacitor
2. Installed a new start capacitor
3. Installed a new contactor

I'm trying to keep my expectations at bay, but I wonder if there's anything more I can try before calling in a technician. Ideas, please?

Thanks in advance!
 

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05-11-24, 05:51 PM
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I sure do agree.
 
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Old 05-11-24, 04:32 PM
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Did you actually check for 240vac ON the contactor ?

The hum you are hearing sounds like the contactor engaged.
Is that correct ?

If you had a capacitor problem.... the compressor and the fan will be humming quite loudly until they shut down to cool off.
 
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Old 05-11-24, 05:47 PM
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Hi PJ,

Yes, the new contactor engaged. I heard a click and then a soft barely audible hum (I had to put my ear up against the unit to hear it) which continued. The contactor engaged/pulled in just fine.

I did install new start and dual run caps, because they were old and the start cap was actually leaking white crusty stuff, although the old ones both tested OK for capacitance. I had the spares anyway so figured it couldn't hurt.

** Update: I had a thought about the fuses in the outdoor pull-out switch box. I removed them and checked them with my DMM and one of them is COMPLETELY dead. I'm suspecting that this could be the issue after all ... do you agree?
 
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Old 05-11-24, 05:51 PM
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I sure do agree.
 
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Old 05-11-24, 06:16 PM
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PJ, I guess I should have checked those fuses first, haha!

New fuses are coming from Amazon tomorrow, I'll update the results. Fingers crossed!!

Thanks again!

--Carol
 
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Old 05-11-24, 06:21 PM
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When you put the fuses in.... turn the thermostat off so that the condenser doesn't start when plugging in the fused disconnect. You don't want your hand on the fuse block if there is a possible short.
 
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Old 05-11-24, 07:06 PM
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Good thought ... will do!
 
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Old 05-12-24, 02:23 PM
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Hi PJ,

I'm feeling discouraged.

New fuses installed, still no action. Compressor not turning on, fan not turning on. Contactor pulls in and hums softly when thermostat calls for cooling.

The only other thing I can think to check is the start capacitor relay.

What do you think?
 
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Old 05-12-24, 05:32 PM
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I would check to see if the disconnect actually has power (240VAC) from the breaker or fuse panel feeding it.

The contactor can pull in and hum as the coil voltage (around 24VAC) comes from the air handler which is a separate circuit (at-least it is supposed to be) from the outside unit.
 

Last edited by CircuitBreaker; 05-12-24 at 05:41 PM. Reason: Adding information
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Old 05-16-24, 10:46 AM
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tervmommy Did you ever get this fixed yet? Just curious
 
 

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