Attic fan quit yesterday. DIY help please.

The details- Attic fan in use yesterday and it stopped spinning at some point during the day. When discovered my first thought was it overheated and I turned it off. This unit was likely original to the construction of the house in 1995 or shortly thereafter so Its going on 30 years old. Since I was in a hurry I grabbed the power on/off stick I have in the junk drawer rather than chasing down my multimeter so this is what I can say right now. Power to the unit is there. When the switch is turned on to high or low the motor buzzes, when switched to off the motor stops buzzing. According to the stick the wire in, the motor itself and the whole frame are lighting up with power. It's bolted to the wood floor of the attic so theres no discharge felt when touching anything. when powered on high at the switch if I start spinning the stationary fan by hand it will spin by motor power but not fast enough to open the vent below to pull air up.

Does this sound like the motor is just worn out and needs replaced? or should I be looking at something else?

Edit: On the frame was written 00-01 in sharpie so it could have been installed in Jan of 2000. we bought the house in 2005.

Sounds like lack of lubrication and/or a worn motor to me. First thing to do is identify which components are causing problems. The motor is the likely suspect. 

I'm a cheap son of a gun and inclined to believe that most equipment and consumer goods were better built 30 years ago than they are now, so I would attempt to spin the motor by hand (power off) and see how stiff it feels on the assumption that the bushings ran dry of oil, then diagnose from there.

With that said, the fact that it's belt driven suggests that the motor is a separate component and can probably be replaced without tearing out the entire assembly. It's done its job.

How freely does the fan spin with the belt removed? Does it have bearings or bushings that can be checked for wear, and lubricated or replaced as necessary?

Lube.  It's pushing hot fry air through the motor every time it lights off.

Before buying another, pull it out, put it on a bench and try it.  Then blow it out, clean and lube it.  Repeat the same test.

The last thing you want is a fire in the attic.

If it is a capacitor start motor (maybe the silver box behind the motor?), the capacitor could just be shot. 

If you can do so safely, try powering on the the motor and then spinning the fan by hand.  If it runs, it is a bad capacitor. 

Edit - The silver can is a capacitor.  GE A10000AFC, 27L1113 7.5UF+/-6% 370VAC 50/60HZ DIELEKTROL V1 CAPACITOR.  $9.00 on eBay.  My bet is you replace it and all will be well

Let me get it out of there and on my workbench. When spinning the motor by hand and also when I spun the fan by hand and got it to spin under power on high, but slower than normal it felt and sounded normal. It wasn't hard to spin and didn't seem to have any play in the shaft.

A few more thoughts. This looks like a whole house fan rather than an attic ventilator. That's sort of neither here nor there in discussing the failure and the fix, but it may help when talking to repair people or hunting parts.

Speaking of hunting parts, this site may help in identifying a replacement motor: https://shop.dreisilker.com/blog/5kcp39-motors-how-to-find-a-replacement-for-5kcp39-motors/

You may find a local electric motor repair shop that can take a look. If it just needs bearings, and if those bearings can be economically replaced, that might be a viable alternative to replacement. Again, this reflects my bias against new stuff and assumption that old stuff will usually last longer.

Is this for cooling the house or venting the attic?  We went from a powered vent to a passive one that works great. But that was just to vent the attic and not to cool the house. 

In reply to CJ :

It does spin if I start it by hand when the switch is set on high but not fast enough to open the vent door below. So capacitor?

In reply to alfadriver : yes sorry.  It is for cooling the house.  Technically a whole house ventilator.

In reply to DarkMonohue : I had found that too. Home depot seems to have one similar enough it will work but I like what you say about trying to reuse this unit

In reply to gunner (Forum Supporter) :

That sounds like capacitor.

In reply to GIRTHQUAKE

Thanks! It's definitely the capacitor.

Came here to say capacitor.  That's a GE air-over motor rated for continuous duty.  It's a top-quality motor.  It wouldn't hurt to clean it up and lube it, but I'd bet money the motor is fine.  The capacitor is shot. 

In reply to gunner (Forum Supporter) :

That would be my bet and it's cheap enough to find out.

While you're in there, I'd think about replacing the brushes and springs if you can source parts.

Oil the shaft of the fan spindle while you are mucking about up there. I did a complete teardown of our house fan a few years ago. Greased everything up, oiled the motor, new belt. Moves a ton of air now.