A/C: fan spinning, compressor not kicking on. Cause?

[Beartracks]

(Cross-posted in DIY & Home Improvement Group https://www.democraticunderground.com/?com=forum&id=1158 )

My house is warming up and I realize I haven't heard the compressor kick in all afternoon. The furnace blower is still blowing, and the A/C's condenser fan motor is still working, but the compressor isn't doing it's job. For DIY yourself purposes, what might be the culprit?

- Blown fuse in the disconnect block? (Or would a blown fuse result in NOTHING working?)
- Start/Run Capacitor? (Or would capacitor failure result in the fan motor also not running?
- AC Contactor?
- Something else?

If it's the compressor itself that's actually gone bad, I might just need to get a whole new A/C since this one is already nearly 25 years old. But I'm wanting to make sure there's not something else (something cheaper) that might account for the symptoms I'm seeing.

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[WhiteTara]

1. does indeed sound like a blown fuse to the compressor

[madaboutharry]

2. 25 years is a long time in the life of an air conditioner.

Not quite dog years, but close.

[Beartracks]

3. I'm assuming it's "original equipment."

The house was 9-10 years old when I bought it, and I've been here almost 15.

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[madaboutharry]

4. I would think it is the original unit.

Wishing you the best.

[Phoenix61]

5. The energy efficiency ratings have come a long way in 25 years.

It’s been a while but when the capacitor went out on mine the fan didn’t run either. Are you sure the compressor isn’t running? If the system is short on Freon it runs but blows hot air.

[Beartracks]

6. Well, I don't *hear* the compressor running...

Doesn't it usually make a sound, separate from the sound of the fan?

Also, the system wasn't blowing *hot* air per se, but just *air* -- same as if I'd simply turned on the furnace blower but left both heat and cooling systems turned off.

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[Phoenix61]

8. Yes it does. Sounds like the capacitor or compressor. What I read says

capacitors are usually last 20 years. I have a crap system that burns through them.

[Mister Ed]

9. Aye. I hope it's the capacitor. if it's not, then it's probably the compressor. n/t

[Phoenix61]

10. Personally, I wouldn't replace a compressor in a unit that old. nt

[Mister Ed]

11. Aye, me neither. I was in the same situation last year.

I had a twenty-two-year-old unit that displayed the same symptoms described in the OP. When it proved to be the compressor and not the capacitor, I knew it was time to face the music and replace the whole system.

[Beartracks]

12. That's what I'm afraid of. But if I can make it limp along thru the summer...

... I'm already looking at some siding and fence replacement, so probably getting a home improvement loan and I can replace teh A/C then.

If oyu don't mind my asking, what did your replacement cost you?

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[Mister Ed]

14. If I recall correctly, I think replacement of the entire system cost $4,300.

That was for replacement of both the outdoor unit and the inside unit that fits in the furnace plenum.

I had hoped the problem might be with the capacitor, which stores electricity to give your compressor that brief extra boost it needs to get spinning when it starts up. You can search YouTube for instructional videos that will explain how to test your specific capacitor. If that's the issue with your system, then replacement of that relatively inexpensive part will enable your system to continue working for awhile. But, as others have said in this thread, your system is old and near the end of its service life.

[cachukis]

7. Solenoid, or something like that. Could be simple.

[Beartracks]

13. Fingers crossed.

[ProfessorGAC]

15. The Only Caution I Have...

...is that if it's a fuse, fuses blow for a reason.
That reason is most often excess power draw caused by too much resistance against the electric motor. Bearing wear on the compressor head would cause that. As in, bearings are shot.
Changing the fuse could just result in another blown fuse.
The capacitor failure could be caused by the same thing, but a bit less likely.
Your best scenario is a stuck solenoid. Solenoid failure is not directly related to a bigger problem elsewhere.